2022/01/19 更新

写真a

サカイ ジュンイチ
酒井 潤一
所属
理工学術院
職名
名誉教授

学歴

  •  
    -
    1970年

    早稲田大学   理工学研究科   金属工学  

  •  
    -
    1970年

    早稲田大学  

  •  
    -
    1968年

    早稲田大学   理工学部   金属工学  

  •  
    -
    1968年

    早稲田大学  

学位

  • 東京大学   博士(工学)

  • 早稲田大学   工学修士

経歴

  • 1970年
    -
    1999年

    日本鋼管(株)研究員

  • 1970年
    -
    1999年

    Research Scientist of NKK

所属学協会

  •  
     
     

    (社)日本保全学会

  •  
     
     

    (一社)日本原子力学会

  •  
     
     

    (一社)表面技術協会

  •  
     
     

    (公社)化学工学会

  •  
     
     

    (一社)日本鉄鋼協会

  •  
     
     

    NACE(National Ass'n of Corrosion Engineers)

  •  
     
     

    (公社)日本鋳造工学会

  •  
     
     

    (公社)日本金属学会

  •  
     
     

    (公社)腐食防食学会

  •  
     
     

    NACE(National Ass'n of Corrosion Engineers)

▼全件表示

 

研究分野

  • 材料加工、組織制御

  • 構造材料、機能材料

  • 生体材料学

  • 生体医工学

論文

  • After-effects induced by interactions between hydrogen and the martensite transformation in Ni-Ti superelastic alloy

    Ken'ichi Yokoyama, Yuki Hirata, Jun'ichi Sakai

    PHILOSOPHICAL MAGAZINE LETTERS   97 ( 9 ) 350 - 358  2017年  [査読有り]

     概要を見る

    The effects of dynamic interactions between hydrogen and a stress-induced martensite transformation on the recovery of deteriorated tensile properties by ageing in air at room temperature have been investigated for a Ni-Ti superelastic alloy. A specimen is subjected to single stress-induced martensite and reverse transformations immediately after hydrogen charging. Upon tensile testing, brittle fracture occurs in the latter half of the elastic deformation region of the martensite phase after the stress-induced martensite transformation. Upon ageing before the tensile test, fracture occurs during the stress-induced martensite transformation. In addition, the nano- and micro-morphologies of the brittle outer part of the fracture surface of the specimen are changed by ageing. Thus, the tensile properties markedly deteriorate, rather than recover, by ageing. The present results clearly indicate that dynamic interactions between hydrogen and the stress-induced martensite transformation have serious after-effects on hydrogen embrittlement of Ni-Ti superelastic alloy.

    DOI

  • Effects of temperature, phase, elastic deformation and transformation on inhibition of localized corrosion of hydrogen-charged Ni-Ti superelastic alloy in NaCl solution

    Shigekazu Nishimoto, Ken'ichi Yokoyama, Toshiaki Inaba, Kenichiro Mutoh, Jun'ichi Sakai

    JOURNAL OF ALLOYS AND COMPOUNDS   682   22 - 28  2016年10月  [査読有り]

     概要を見る

    The effects of the solution temperature, phase, elastic deformation and the phase transformation on the inhibition of localized corrosion of a small amount of hydrogen-charged Ni-Ti superelastic alloy in 0.9% NaCl solution have been investigated by electrochemical measurements. No pitting potentials are observed in the anodic polarization curves obtained above room temperature and under static applied stress in the presence of parent or stress-induced martensite phases. In a dynamic cyclic tensile test in the elastic deformation region of the parent phase under various constant applied anodic potentials, the critical applied potential for an increase in the current density, which corresponds to the occurrence of localized corrosion, considerably shifts in the noble direction. At the stress plateau, i.e., in the superelastic region, caused by stress-induced martensite and reverse transformations, the critical applied potential for a marked increase in the current density slightly shifts in the noble direction. In the elastic deformation region of the stress-induced martensite phase, the critical applied potential for a marked increase in the current density shifts in the noble direction. The present results indicate that hydrogen charging is effective for inhibiting the localized corrosion of Ni-Ti superelastic alloy in NaCl solution at various temperatures, irrespective of the phase itself, under dynamic elastic deformation and the phase transformation. (C) 2016 Elsevier B.V. All rights reserved.

    DOI

  • Inhibition of localized corrosion of Ni-Ti superelastic alloy in NaCl solution by hydrogen charging

    Ken'ichi Yokoyama, Yuki Hirata, Toshiaki Inaba, Kenichiro Mutoh, Jun'ichi Sakai

    JOURNAL OF ALLOYS AND COMPOUNDS   639   365 - 372  2015年08月  [査読有り]

     概要を見る

    Inhibition of the localized corrosion of Ni-Ti superelastic alloy in 0.9% NaCl solution has been attempted by charging with a small amount of hydrogen, which causes negligible hydrogen embrittlement. Upon a small amount of hydrogen charging, no pitting potential is observed in anodic polarization curves. From scanning electron microscope observations, localized corrosion is inhibited on the entire side surface of charged specimens. With increasing amount of charged hydrogen, the corrosion potential shifts in the less noble direction and the current density increases under anodic applied potential. When the hydrogen charged specimens are aged in the atmosphere at room temperature, the corrosion potential becomes almost the same as that of the non-charged specimen, but the inhibition of localized corrosion remains. The present study indicates that a small amount of hydrogen charging is effective for inhibiting the localized corrosion of the alloy in NaCl solution. (C) 2015 Elsevier B. V. All rights reserved.

    DOI

  • Electrochemical study on corrosion inhibition effect of Mannich-modified phenolic resin coating on galvanized steel

    Ryosuke Sako, Jun'ichi Sakai

    Zairyo to Kankyo/ Corrosion Engineering   64 ( 10 ) 466 - 474  2015年  [査読有り]

     概要を見る

    The mechanism of corrosion inhibition of Mannich-modified phenolic resin coating which is one of the alternatives to chromate conversion coating on the electrogalvanized steel sheet was investigated by cross-section analysis and electrochemical measurements of the coating film. The 200°C cured coating film which has good corrosion inhibition has the higher charge transfer resistance (Rct) and the higher film resistance (Rf) calculated by electrochemical impedance measurement than the 80 °C cured coating film. The increase of these resistances is due to decrease of water absorption property of the film caused by crosslinking reaction. Namely the film resistance is enhanced by reduction of ionic conductivity of the film, and the charge transfer resistance is enhanced by reduction of the supply of the water containing dissolved oxygen to interface between the film and substrate. The phosphoric acid added to coating solution forms an insoluble zinc phosphate coating layer at the coating / material interface. The zinc phosphate coating layer, which is formed in close contact with the complex surface shape of the substrate by chemical interaction with the substrate surface by chemical interaction with the material surface, enhances the barrier effect to obstruct the contact of substrate with the water containing dissolved oxygen. Consequently the corrosion inhibition of the coating film is excellent. On the other hand, the 80°C cured coating film without phosphoric acid, which has no chemical interaction with the substrate, has some voids (defects) at film /substrate interface and its corrosion inhibition is inferior.

    DOI

  • Dissolution Behavior of Duplex Stainless Steels in Crevice Corrosion Growth Step

    So Aoki, Yushi Nada, Jun'Ichi Sakai

    Zairyo to Kankyo/ Corrosion Engineering   64 ( 8 ) 366 - 372  2015年  [査読有り]

     概要を見る

    The objective of this study is to clarify dissolution behavior of duplex stainless steels in crevice corrosion growth step. Crevice corrosion grew on the duplex stainless steels by holding potential at various values. After a certain period, dissolution behavior of the crevice corrosion was analyzed based on observation of corroded area. Change in crevice corrosion dissolution behavior with time was also investigated by means of in-situ observation. Four types of dissolution regions could be observed in the corrosion area from outside toward inside direction, i.e., tip of the corroded area toward initiation point, in a crevice
    they were passive region, the preferential dissolution region of γ phase, α phase and γ phase dissolution region, and the preferential dissolution region of α phase. The crevice corrosion which maintained that four dissolution regions grew toward the edge of the crevice. This dissolution behavior was given at all the potential where crevice corrosion occurred.

    DOI

  • Role of Dynamic Interactions between Hydrogen and Strain-induced Martensite Transformation in Hydrogen Embrittlement of Type 304 Stainless Steel

    Yuma Yoshioka, Ken'ichi Yokoyama, Jun'ichi Sakai

    ISIJ INTERNATIONAL   55 ( 8 ) 1772 - 1780  2015年  [査読有り]

     概要を見る

    The role of the dynamic interactions between hydrogen and the strain-induced martensite transformation in the hydrogen embrittlement of type 304 stainless steel has been investigated by fractographic observations after a modified hydrogen charging. The modified charging is cathodically conducted in 3.5% NaCl solution at 80 degrees C under aerated conditions while preventing the dissolution of chlorine and oxygen gases evolving on the platinum counter electrode, thus increasing the amount of hydrogen thermally desorbed at low temperatures. Upon tensile testing at 160 degrees C, plastic deformation of the austenite phase in the stainless steel occurs, but no strain-induced martensite transformation occurs. The fracture surface of the hydrogen-charged specimen exhibits the double-cup mode and consists of microscopic shallow dimples. Upon tensile testing at 25 degrees C, the martensite transformation and plastic deformation both occur and are intricately related; a brittle area is observed on the outer part of the fracture surface that exhibits both transgranular and intergranular fracture. At -196 degrees C, the martensite transformation increases, but the amount of plastic deformation decreases and the amount of intergranular fracture increases. It is found that, when the martensite transformation occurs before hydrogen charging, the amount of intergranular fracture decreases. Moreover, when charged hydrogen is trapped in defects in the austenite phase, the amount of intergranular fracture also decreases. The present study indicates that the dynamic interactions between hydrogen and the martensite transformation play an important role in the hydrogen embrittlement of type 304 stainless steel.

    DOI

  • Effect of curing temperature on coating structure and corrosion resistance of ammonium zirconium carbonate on galvanized steel surface

    Ryosuke Sako, Jun'ichi Sakai

    SURFACE & COATINGS TECHNOLOGY   219   42 - 49  2013年03月  [査読有り]

     概要を見る

    The effect of curing temperature on the structure and corrosion resistance of an ammonium zirconium carbonate (AZC) coating on galvanized steel was investigated as an alternative to chromate. The corrosion resistance of the AZC coating was excellent when cured at 80 degrees C, but it decreased with an increase in the curing temperature; it was significantly inferior at curing temperatures over 160 degrees C. Two endothermic events were observed at 115 degrees C and 155 degrees C. The event at 115 degrees C resulted from the elimination of the water molecule coordinated to the zirconium atom, and the event at 155 degrees C resulted from the dehydration condensation of the hydroxide group involved in the bonds between zirconium, i.e., conversion of an ol-bridge to an oxo-bridge. Furthermore, it was observed that the cathode current of the coating plate cured at 160 degrees C or 200 degrees C, whose corrosion resistance was inferior to that at 80 degrees C or 120 degrees C in the salt spray test, increased. It is supposed that the dehydration occurring at 155 degrees C promoted shrinkage of the coating volume, which in turn caused the development of fissures on the coating surface. The fissures on the coating surface reduced the corrosion resistance significantly due to the increase in cathode current, which signifies the reduction of dissolved oxygen at the coating/metal interface. (C) 2013 Elsevier B.V. All rights reserved.

    DOI

  • Hydrogen absorption behavior of titanium alloys by cathodic polarization

    Yasuhiro Ishijima, Takafumi Motooka, Fumiyoshi Ueno, Masahiro Yamamoto, Gunzo Uchiyama, Jun'ichi Sakai, Ken'ichi Yokoyama, Eiji Tada, Tooru Tsuru, Yasuo Nojima, Sachio Fujine

    International Conference on Nuclear Engineering, Proceedings, ICONE   1  2013年

     概要を見る

    Titanium and Ti-5mass%Ta alloy has been utilized in nuclear fuel reprocessing plant material because of its superior corrosion resistance in nitric acid solutions. However, Ti alloy have been known to high susceptibility of hydrogen embrittlement. To evaluate properties of hydrogen absorption and hydrogen embrittlement of Ti alloys, cathodic polarization tests and slow strain rate tests (SSRT) under cathodic polarization were carried out. Results show titanium hydrides covered on the surface of metals and hydrides thickness were within 10μm. But hydride did not observed at inner part of metals. Ti and Ti-5%Ta did not show hydrogen embrittlement by SSRT under cathodic charging. These results suggested that Ti and Ti-5%Ta could absorb hydrogen. But hydrogen did not penetrate inner portion of the metals more than 10μm in depth because titanium hydrides act as barrier of hydrogen diffusion. It is considered that retardation of hydrogen diffusion hindered hydrogen embrittlement of Ti and Ti-5%Ta alloys. Copyright © 2013 by ASME.

    DOI

▼全件表示

書籍等出版物

  • 鉄鋼便覧 第5版

    2014年

  • 社団法人 日本機械学会編 JSMEテキストシリーズ 『機械材料学』

    日本機械学会  2008年

  • 電子機器部品の腐食・防食Q&A 腐食防食協会編

    丸善  2006年

  • 改訂 4版 化学工学辞典 化学工学会編

    丸善  2005年

  • 金属の腐食防食Q&A コロージョン110番 電気化学入門編

    2003年

  • 鉄鋼便覧 第4版 日本鉄鋼協会編

    丸善  2002年

  • 金属の腐食・防食Q&A ―コロージョン110番― 電気化学入門編

    丸善  2002年

  • 腐食防食ハンドブック

    丸善  2000年

  • 防錆・防食便覧

    産業技術サービスセンター  2000年

  • 金属の腐食・防食Q&A、石油産業編 腐食防食協会編

    丸善  1999年

  • 材料環境学入門

    丸善  1993年

  • 金属の腐食・防食Q&A ―コロージョン110番―

    丸善  1988年

▼全件表示

Misc

  • ステンレス鋼の耐発銹性に及ぼす不働態被膜の安定度の影響

    富士浩行, 青木聡, 石井知洋, 酒井潤一

    材料と環境   64 ( 5 ) 178 - 182  2015年

  • 海水環境におけるステンレス鋼接触条件下での炭素鋼の腐食挙動

    佐藤弘隆, 山路徹, 酒井潤一

    材料と環境   64 ( 5 ) 183 - 187  2015年

    DOI

  • 恒温硫黄蒸気環境の銀の硫化挙動におよぼす銀表面温度の影響

    稲葉康介, 石川雄一, 酒井潤一

    材料と環境   64 ( 5 ) 188 - 192  2015年

  • Creep corrosion cracking of Sn–3.0Ag and Sn–0.5Cu solder alloys in NaCl solution

    Ken'ichi Yokoyama, Akihide Nogami, Jun'ichi Sakai

    Corrosion Science   86   142 - 148  2014年09月

    DOI

  • Risk Based Maintenance (RBM) Toward Risk Based Corrosion Engineering

    Jun’ichi Sakai

    Corrosion Engineering   63 ( 4 ) 116 - 125  2014年

  • Hydrogen Absorption into Austenitic Stainless Steels Under High-Pressure Gaseous Hydrogen and Cathodic Charge in Aqueous Solution

    Masato Enomoto, Lin Cheng, Hiroyuki Mizuno, Yoshinori Watanabe, Tomohiko Omura, Jun’ichi Sakai, Ken’ichi Yokoyama, Hiroshi Suzuki, Ryuji Okuma

    Metallurgical and Materials Transactions E   1 ( 4 ) 331 - 340  2014年

  • Risk Based Maintenance (RBM) Toward Risk Based Corrosion Engineering

    Jun’ichi Sakai

    Corrosion Engineering   63 ( 4 ) 116 - 125  2014年

  • Creep corrosion cracking of Sn-3.0Ag and Sn-0.5Cu solder alloys in NaCl solution

    Ken'ichi Yokoyama, Akihide Nogami, Jun'ichi Sakai

    Corrosion Science   86   142 - 148  2014年

     概要を見る

    The surface crack nucleation of Sn-3.0Ag and Sn-0.5Cu solder alloys has been examined by performing sustained tensile-loading tests in 0.9 mass% NaCl solution at room temperature. For Sn-3.0Ag alloy, many cracks nucleate and propagate on the side surface of the specimen, similarly to Sn-3.0Ag-0.5Cu alloy reported previously. For Sn-0.5Cu alloy, such cracks are not observed, and ordinary creep deformation occurs in the solution. The effect of sustained applied stress, i.e., creep, on the dissolution of ions is smaller for Sn-0.5Cu alloy than for Sn-3.0Ag alloy. The present results suggest that there are differences in the susceptibility to cracking under applied stress in a solution, i.e., creep corrosion cracking, among lead-free solder alloys. © 2014 Elsevier Ltd.

    DOI

  • Hydrogen Absorption into Austenitic Stainless Steels Under High-Pressure Gaseous Hydrogen and Cathodic Charge in Aqueous Solution

    Masato Enomoto, Lin Cheng, Hiroyuki Mizuno, Yoshinori Watanabe, Tomohiko Omura, Jun’ichi Sakai, Ken’ichi Yokoyama, Hiroshi Suzuki, Ryuji Okuma

    Metallurgical and Materials Transactions E   1 ( 4 ) 331 - 340  2014年

  • リスクベースメンテナンスからリスクベース防食工学へ

    酒井潤一

    材料と環境   63 ( 4 ) 138 - 144  2014年

    DOI

  • フェライトステンレス鋼におけるTi炭窒化物/素地境界すき間部起点の孔食発生

    堤口覚, 青木聡, 石井知洋, 石川伸, 酒井潤一

    材料と環境   63 ( 5 ) 325 - 328  2014年

    DOI

  • 保温材下模擬環境における炭素鋼の腐食に及ぼす温度と濡れ時間の影響

    栁瀨幸紀, 石川雄一, 酒井潤一

    材料と環境   63 ( 5 ) 329 - 332  2014年

  • 亜鉛めっき鋼板表面のマンニッヒ変性フェノール樹脂の耐食性に及ぼす焼付け温度およびリン酸の影響

    迫良輔, 酒井潤一

    Zairyo-to-Kankyo   63 ( 1 ) 17 - 24  2014年

    DOI

  • Characterisation of corrosion products formed on copper exposed at indoor and outdoor sites with high H2S concentrations

    M. Watanabe, M. Takaya, T. Handa, J. Sakai

    CORROSION ENGINEERING SCIENCE AND TECHNOLOGY   48 ( 6 ) 418 - 425  2013年09月

     概要を見る

    Corrosion products formed on copper exposed indoors and outdoors at sites with high hydrogen sulphide (H2S) concentrations were characterised using several analytical techniques. The crystalline corrosion products that formed on the copper exposed indoors were chalcocite (Cu2S) and cuprite (Cu2O), while those that formed on the copper exposed outdoors were chalcocite, cuprite and basic copper sulphates. Surface analysis by X-ray photoelectron spectroscopy revealed differences between the copper exposed indoors and outdoors that are explained by the composition, localisation and oxidation of the corrosion products. The surface morphologies of the corrosion products also differed. Elemental depth profiling by glow discharge optical emission spectroscopy revealed that the corrosion products that formed indoors were mainly chalcocite with cuprite only at and near the surface. In contrast, the corrosion products that formed outdoors were a mixture of chalcocite and cuprite. These differences in corrosion products are attributed to the differences in relative humidity during exposure.

    DOI

  • Characterisation of corrosion products formed on copper exposed at indoor and outdoor sites with high H2S concentrations

    M. Watanabe, M. Takaya, T. Handa, J. Sakai

    CORROSION ENGINEERING SCIENCE AND TECHNOLOGY   48 ( 6 ) 418 - 425  2013年09月

     概要を見る

    Corrosion products formed on copper exposed indoors and outdoors at sites with high hydrogen sulphide (H2S) concentrations were characterised using several analytical techniques. The crystalline corrosion products that formed on the copper exposed indoors were chalcocite (Cu2S) and cuprite (Cu2O), while those that formed on the copper exposed outdoors were chalcocite, cuprite and basic copper sulphates. Surface analysis by X-ray photoelectron spectroscopy revealed differences between the copper exposed indoors and outdoors that are explained by the composition, localisation and oxidation of the corrosion products. The surface morphologies of the corrosion products also differed. Elemental depth profiling by glow discharge optical emission spectroscopy revealed that the corrosion products that formed indoors were mainly chalcocite with cuprite only at and near the surface. In contrast, the corrosion products that formed outdoors were a mixture of chalcocite and cuprite. These differences in corrosion products are attributed to the differences in relative humidity during exposure.

    DOI

  • Corrosion and hydrogen absorption of commercially pure zirconium in acid fluoride solutions

    Ken'ichi Yokoyama, Daisuke Yamada, Jun'ichi Sakai

    Corrosion Science   73   375 - 381  2013年08月

     概要を見る

    The corrosion and hydrogen absorption of commercially pure zirconium have been investigated in acidulated phosphate fluoride (APF) solutions. Upon immersion in 2.0% APF solution of pH 5.0 at 25°C, a granular corrosion product (Na3ZrF7) deposits over the entire side surface of the specimen, thereby inhibiting further corrosion. In 0.2% APF solution, marked corrosion is observed from the early stage of immersion
    no deposition of the corrosion product is observed by scanning electron microscopy. A substantial amount of hydrogen absorption is confirmed in both APF solutions by hydrogen thermal desorption analysis. The amount of absorbed hydrogen of the specimen immersed in the 2.0% APF solution is smaller than that in the 0.2% APF solution in the early stage of immersion. The hydrogen absorption behavior is not always consistent with the corrosion behavior. Hydrogen thermal desorption occurs in the temperature range of 300-700°C for the specimen without the corrosion product. Under the same immersion conditions, the amount of absorbed hydrogen in commercially pure zirconium is smaller than that in commercially pure titanium as reported previously. The present results suggest that commercially pure zirconium, compared with commercially pure titanium, is highly resistant to hydrogen absorption, although corrosion occurs in fluoride solutions. © 2013 Elsevier Ltd.

    DOI

  • Corrosion and hydrogen absorption of commercially pure zirconium in acid fluoride solutions

    Ken'ichi Yokoyama, Daisuke Yamada, Jun'ichi Sakai

    CORROSION SCIENCE   73   375 - 381  2013年08月

     概要を見る

    The corrosion and hydrogen absorption of commercially pure zirconium have been investigated in acidulated phosphate fluoride (APF) solutions. Upon immersion in 2.0% APF solution of pH 5.0 at 25 degrees C, a granular corrosion product (Na3ZrF7) deposits over the entire side surface of the specimen, thereby inhibiting further corrosion. In 0.2% APF solution, marked corrosion is observed from the early stage of immersion; no deposition of the corrosion product is observed by scanning electron microscopy. A substantial amount of hydrogen absorption is confirmed in both APF solutions by hydrogen thermal desorption analysis. The amount of absorbed hydrogen of the specimen immersed in the 2.0% APF solution is smaller than that in the 0.2% APF solution in the early stage of immersion. The hydrogen absorption behavior is not always consistent with the corrosion behavior. Hydrogen thermal desorption occurs in the temperature range of 300-700 degrees C for the specimen without the corrosion product. Under the same immersion conditions, the amount of absorbed hydrogen in commercially pure zirconium is smaller than that in commercially pure titanium as reported previously. The present results suggest that commercially pure zirconium, compared with commercially pure titanium, is highly resistant to hydrogen absorption, although corrosion occurs in fluoride solutions. (C) 2013 Elsevier Ltd. All rights reserved.

    DOI

  • Effect of Galvanostatic Condition on Growth Behavior and Repassivation Potential of Crevice Corrosion of Duplex Stainless Steels

    So Aoki, Tatsuya Ehashi, Jun’ichi Sakai

    ECS Transactions   50 ( 31 ) 105 - 111  2013年

    DOI

  • The In-situ Observation of Preferential Dissolution Behaviour on Crevice Corrosion of a Duplex Stainless Steel

    So Aoki, Yushi Nada, Jun’ichi Sakai

    Proc. EUROCORR 2013   ( 1284 ) 1 - 5  2013年

  • Effect of Galvanostatic Condition on Growth Behavior and Repassivation Potential of Crevice Corrosion of Duplex Stainless Steels

    So Aoki, Tatsuya Ehashi, Jun'ichi Sakai

    CORROSION, PASSIVITY, AND ENERGY: A SYMPOSIUM IN HONOR OF DIGBY D. MACDONALD   50 ( 31 ) 105 - 111  2013年

     概要を見る

    The purpose of this study is to clarify effect of galvanostatic condition on growth behavior and repassivation potential (E-R.CREV) of crevice corrosion of duplex stainless steels. E-R.CREV measurements, microscopic observation of corroded area, and solution pH measurements inside crevice were carried out. Under the condition of large holding current in propagation step of E-R.CREV measurements, the crevice corrosion grew from the bottom to the edge of crevice. Then, it grew towards depth direction, and the sharp corroded area formed near the edge of crevice. Solution pH inside crevice lowered easily under the condition of large holding current in repassivation step, and it induced the repassivation of corroding crevice at noble potential. It was suggested that the sharp corroded area formed near the edge of crevice under the large holding current condition contributed to lowering corrosivity of solution inside corroding crevice and the repassivation of corroding crevice at the noble potential.

    DOI

  • The In-situ Observation of Preferential Dissolution Behaviour on Crevice Corrosion of a Duplex Stainless Steel

    So Aoki, Yushi Nada, Jun’ichi Sakai

    Proc. EUROCORR 2013   ( 1284 ) 1 - 5  2013年

  • Effect of Galvanostatic Condition on Growth Behavior and Repassivation Potential of Crevice Corrosion of Duplex Stainless Steels

    So Aoki, Tatsuya Ehashi, Jun'ichi Sakai

    CORROSION, PASSIVITY, AND ENERGY: A SYMPOSIUM IN HONOR OF DIGBY D. MACDONALD   50 ( 31 ) 105 - 111  2013年

     概要を見る

    The purpose of this study is to clarify effect of galvanostatic condition on growth behavior and repassivation potential (E-R.CREV) of crevice corrosion of duplex stainless steels. E-R.CREV measurements, microscopic observation of corroded area, and solution pH measurements inside crevice were carried out. Under the condition of large holding current in propagation step of E-R.CREV measurements, the crevice corrosion grew from the bottom to the edge of crevice. Then, it grew towards depth direction, and the sharp corroded area formed near the edge of crevice. Solution pH inside crevice lowered easily under the condition of large holding current in repassivation step, and it induced the repassivation of corroding crevice at noble potential. It was suggested that the sharp corroded area formed near the edge of crevice under the large holding current condition contributed to lowering corrosivity of solution inside corroding crevice and the repassivation of corroding crevice at the noble potential.

    DOI

  • Effect of Galvanostatic Condition on Growth Behavior and Repassivation Potential of Crevice Corrosion of Duplex Stainless Steels

    So Aoki, Tatsuya Ehashi, Jun’ichi Sakai

    ECS Transactions   50  2013年

    DOI

  • Fracture and corrosion behaviors of Ni-Ti superelastic alloy under sustained tensile loading in neutral fluoride solution containing hydrogen peroxide

    Atsushi Yoshida, Ken'ichi Yokoyama, Toshiaki Inaba, Kenichiro Mutoh, Jun'ichi Sakai

    JOURNAL OF ALLOYS AND COMPOUNDS   544   24 - 29  2012年12月

     概要を見る

    The fracture and corrosion behaviors of Ni-Ti superelastic alloy have been investigated by carrying out sustained tensile-loading tests in neutral 2% NaF aqueous solutions containing various H2O2 concentrations. The times to fracture in solutions with 0.001 M, 0.01 M and 1 M H2O2 are shorter than that in a solution without H2O2. In the solution with 0.1 M H2O2, however, the time to fracture becomes long and the fractographic features are markedly changed. On the basis of the polarization behavior, corrosion is enhanced with increasing H2O2 concentration. Under an applied stress above the critical stress for the stress-induced martensite transformation, the fluctuations of corrosion potential and corrosion current density become larger than those without the applied stress. The present results suggest that the fracture and corrosion behaviors of the alloy in neutral fluoride solutions are sensitively affected by the H2O2 concentration, but the relationship between fracture and corrosion does not always straightforwardly correspond to the H2O2 concentration. (C) 2012 Elsevier B.V. All rights reserved.

    DOI

  • Fracture and corrosion behaviors of Ni-Ti superelastic alloy under sustained tensile loading in neutral fluoride solution containing hydrogen peroxide

    Atsushi Yoshida, Ken'ichi Yokoyama, Toshiaki Inaba, Kenichiro Mutoh, Jun'ichi Sakai

    JOURNAL OF ALLOYS AND COMPOUNDS   544   24 - 29  2012年12月

     概要を見る

    The fracture and corrosion behaviors of Ni-Ti superelastic alloy have been investigated by carrying out sustained tensile-loading tests in neutral 2% NaF aqueous solutions containing various H2O2 concentrations. The times to fracture in solutions with 0.001 M, 0.01 M and 1 M H2O2 are shorter than that in a solution without H2O2. In the solution with 0.1 M H2O2, however, the time to fracture becomes long and the fractographic features are markedly changed. On the basis of the polarization behavior, corrosion is enhanced with increasing H2O2 concentration. Under an applied stress above the critical stress for the stress-induced martensite transformation, the fluctuations of corrosion potential and corrosion current density become larger than those without the applied stress. The present results suggest that the fracture and corrosion behaviors of the alloy in neutral fluoride solutions are sensitively affected by the H2O2 concentration, but the relationship between fracture and corrosion does not always straightforwardly correspond to the H2O2 concentration. (C) 2012 Elsevier B.V. All rights reserved.

    DOI

  • Corrosion of Carbon Steel and Alloys in Concentrated Ammonium Chloride Solutions

    K. Toba, M. Ueyama, K. Kawano, J. Sakai

    CORROSION   68 ( 11 ) 1049 - 1056  2012年11月

     概要を見る

    Corrosion resistance and the behavior of carbon steel and alloys in high concentration ammonium chloride (NH4Cl) solutions were investigated. This study was conducted to better understand material performance in severe NH4Cl corrosive environments in refineries. Immersion tests were performed under boiling 20 wt% and 40 wt% NH4Cl solutions. Sixteen materials commonly used in refineries and two new alloys were examined, including carbon steel; aluminized carbon steel; aluminum brass; Types 405, 410, 304L, 316L, and 321 stainless steels (UNS S40500, S41000, S30403, S31603, and S32100); 300-series stainless steel with 6% Mo; two types of super duplex stainless steels; Alloys 800, 625, and C-276 (UNS N08800, N06625, and N10276); Grade 2 and Grade 19 titanium (UNS R50400 and R53530); Alloy A (equivalent to a modified Type 317L [UNS S31703] stainless steel); and a modified Alloy 825 (UNS N06845). Significant corrosion was observed in carbon steel in both solutions. The corrosion rates of carbon steel were as high as 25.4 mm/y and 60.4 mm/y in 20 wt% and 40 wt% NH4Cl solutions, respectively. However, neither general corrosion nor pitting was observed on titanium alloys and alloys with a pitting resistant equivalent number (PREN) of 40 and higher. The maximum pit depth had a close relationship with the PREN. In addition, an electrochemical study was used to investigate the corrosion behavior of carbon steel. The effects of the temperature and NH4Cl concentration were determined from polarization curves and the corrosion potential.

    DOI

  • Corrosion of Carbon Steel and Alloys in Concentrated Ammonium Chloride Solutions

    K. Toba, M. Ueyama, K. Kawano, J. Sakai

    CORROSION   68 ( 11 ) 1049 - 1056  2012年11月

     概要を見る

    Corrosion resistance and the behavior of carbon steel and alloys in high concentration ammonium chloride (NH4Cl) solutions were investigated. This study was conducted to better understand material performance in severe NH4Cl corrosive environments in refineries. Immersion tests were performed under boiling 20 wt% and 40 wt% NH4Cl solutions. Sixteen materials commonly used in refineries and two new alloys were examined, including carbon steel; aluminized carbon steel; aluminum brass; Types 405, 410, 304L, 316L, and 321 stainless steels (UNS S40500, S41000, S30403, S31603, and S32100); 300-series stainless steel with 6% Mo; two types of super duplex stainless steels; Alloys 800, 625, and C-276 (UNS N08800, N06625, and N10276); Grade 2 and Grade 19 titanium (UNS R50400 and R53530); Alloy A (equivalent to a modified Type 317L [UNS S31703] stainless steel); and a modified Alloy 825 (UNS N06845). Significant corrosion was observed in carbon steel in both solutions. The corrosion rates of carbon steel were as high as 25.4 mm/y and 60.4 mm/y in 20 wt% and 40 wt% NH4Cl solutions, respectively. However, neither general corrosion nor pitting was observed on titanium alloys and alloys with a pitting resistant equivalent number (PREN) of 40 and higher. The maximum pit depth had a close relationship with the PREN. In addition, an electrochemical study was used to investigate the corrosion behavior of carbon steel. The effects of the temperature and NH4Cl concentration were determined from polarization curves and the corrosion potential.

    DOI

  • Effect of oxide formation on SCC arrest behavior at the fusion line between alloy 182 weld and low alloy steel based metal

    Ko Mizutani, Jun'ichi Sakai

    Zairyo to Kankyo/ Corrosion Engineering   61 ( 4 ) 152 - 154  2012年

     概要を見る

    This study was carried out to clarify the SCC arrest behavior at the fusion line between Alloy 182 weld and low alloy steel based metal in distilled water under high temperature and high pressure conditions. The specimen used was low alloy steel based metal overlaid with Alloy 182 weld. CBB test was conducted in the autoclave at the temperature of 288°C, the pressure of 8 MPa, the electric conductivity of introduced water with less than 10 μS/m and dissolved oxygen concentration with 8 ppm. The results of CBB test were that all cracks were arrested at the fusion line and sphere-shaped oxide on low alloy steel based metal side were found. According to the relationship between the weld thickness of Alloy 182 and the oxide size, the larger weld thickness of Alloy 182 the larger the oxides become. It suggests that the galvanic effect caused by difference of potential between Alloy 182 weld and the low alloy steel based metal may have affected the results.

    DOI

  • Electrochemical Characteristics of Alloy 182 Weld and Low Alloy Steel in High Temperature and High Pressure Water from 25 to 288ºC

    Jun'ichi Sakai

    Corrosion Engineering   61 ( 9 ) 356 - 358  2012年

    DOI

  • Effect of cure temperature and phosphoric acid on corrosion resistance of phenolic resin on galvanized steel surface

    Ryosuke Sako, Jun'Ichi Sakai

    Zairyo to Kankyo/ Corrosion Engineering   61 ( 10 ) 402 - 409  2012年

     概要を見る

    The coating film formation and the corrosion resistance of phenolic resin were examined as an alternative for chromate on the galvanizing steel sheet. The effect of cure temperature and phosphoric acid on film formation and corrosion resistance was investigated by thermogravimetry and differential thermal analysis (TG-DTA), surface energy measurement, and the coating film characterization by XPS and FT-IR analysis. The mechanism of corrosion resistance was estimated by the polarization measurement of the coating plate. The resin, which was in an aggregate state at 80°C, gradually became loose by thermal energy as temperature rose, and it self-cured above 130- 150°C to make the film that gives good corrosion resistance. Addition of phosphoric acid to the phenolic resin solution has improved the corrosion resistance even at 120°C that is below the original self-cure temperature. Though the mechanism of the effect of phosphoric acid is not always clear, it was found that phosphoric acid promotes the cure of the resin and enhances the insolubility to the salt water. Also, it was confirmed that phosphoric acid itself is incorporated into the coating film. It seems that these facts improve corrosion resistance.

    DOI

  • 二相ステンレス鋼のすき間腐食優先溶解機構

    青木聡

    まてりあ   51 ( 11 ) 516 - 520  2012年

  • Effect of oxide formation on SCC arrest behavior at the fusion line between alloy 182 weld and low alloy steel based metal

    Ko Mizutani, Jun'ichi Sakai

    Zairyo to Kankyo/ Corrosion Engineering   61 ( 4 ) 152 - 154  2012年

     概要を見る

    This study was carried out to clarify the SCC arrest behavior at the fusion line between Alloy 182 weld and low alloy steel based metal in distilled water under high temperature and high pressure conditions. The specimen used was low alloy steel based metal overlaid with Alloy 182 weld. CBB test was conducted in the autoclave at the temperature of 288°C, the pressure of 8 MPa, the electric conductivity of introduced water with less than 10 μS/m and dissolved oxygen concentration with 8 ppm. The results of CBB test were that all cracks were arrested at the fusion line and sphere-shaped oxide on low alloy steel based metal side were found. According to the relationship between the weld thickness of Alloy 182 and the oxide size, the larger weld thickness of Alloy 182 the larger the oxides become. It suggests that the galvanic effect caused by difference of potential between Alloy 182 weld and the low alloy steel based metal may have affected the results.

    DOI

  • Electrochemical Characteristics of Alloy 182 Weld and Low Alloy Steel in High Temperature and High Pressure Water from 25 to 288ºC

    Jun'ichi Sakai

    Corrosion Engineering   61 ( 9 ) 356 - 358  2012年

    DOI

  • Effect of cure temperature and phosphoric acid on corrosion resistance of phenolic resin on galvanized steel surface

    Ryosuke Sako, Jun'Ichi Sakai

    Zairyo to Kankyo/ Corrosion Engineering   61 ( 10 ) 402 - 409  2012年

     概要を見る

    The coating film formation and the corrosion resistance of phenolic resin were examined as an alternative for chromate on the galvanizing steel sheet. The effect of cure temperature and phosphoric acid on film formation and corrosion resistance was investigated by thermogravimetry and differential thermal analysis (TG-DTA), surface energy measurement, and the coating film characterization by XPS and FT-IR analysis. The mechanism of corrosion resistance was estimated by the polarization measurement of the coating plate. The resin, which was in an aggregate state at 80°C, gradually became loose by thermal energy as temperature rose, and it self-cured above 130- 150°C to make the film that gives good corrosion resistance. Addition of phosphoric acid to the phenolic resin solution has improved the corrosion resistance even at 120°C that is below the original self-cure temperature. Though the mechanism of the effect of phosphoric acid is not always clear, it was found that phosphoric acid promotes the cure of the resin and enhances the insolubility to the salt water. Also, it was confirmed that phosphoric acid itself is incorporated into the coating film. It seems that these facts improve corrosion resistance.

    DOI

  • NH4HS環境での腐食に及ぼす流れの影響

    鳥羽和宏, 阿蘇谷利光, 川野浩二, 酒井潤一

    Zairyo-to-Kankyo   61 ( 2 ) 56 - 63  2012年

    DOI CiNii

  • Effects of the Hydrogen Absorption Conditions on the Hydrogen Embrittlement Behavior of Ni–Ti Superelastic Alloy

    Ken'ichi Yokoyama, Akira Nagaoka, Jun'ichi Sakai

    ISIJ International   52 ( 2 ) 255 - 262  2012年

    DOI CiNii

  • Effects of the Hydrogen Absorption Conditions on the Hydrogen Embrittlement Behavior of Ni-Ti Superelastic Alloy

    Ken'ichi Yokoyama, Akira Nagaoka, Jun'ichi Sakai

    ISIJ INTERNATIONAL   52 ( 2 ) 255 - 262  2012年

     概要を見る

    The present study has investigated whether the hydrogen embrittlement behavior of Ni-Ti superelastic alloy can be changed by modifying the hydrogen absorption conditions. Upon immersion in H2SO4 or H3PO4 solution, the stress plateau due to the stress-induced martensite transformation becomes unclear and forms a gentle slope. In addition, the superelastic strain decreases with increasing immersion time. The peripheral part of the fracture surface of the immersed specimens is flat as usual, whereas the center part of the fracture surface is rough compared with that under other hydrogen absorption conditions reported previously. For the specimens immersed in H3PO4 solution, hydrogen thermal desorption tends to be observed at higher temperatures compared with the specimens immersed in H2SO4 solution. Moreover, for a longer immersion time, a second peak of hydrogen desorption is observed at a high temperature, indicating that the hydrogen states change with the hydrogen absorption conditions. The results of this study suggest that changing the hydrogen embrittlement behavior by modifying the hydrogen absorption conditions may enable the determination of the embrittlement mechanism of the alloy.

    DOI CiNii

  • Fracture of sustained tensile-loaded Sn–3.0Ag–0.5Cu solder alloy in NaCl solution

    Ken’ichi Yokoyama, Daisuke Tsujia, Jun’ichi Sakai

    Corrosion Science   53 ( 10 ) 3331 - 3336  2011年10月

    DOI

  • Fracture of sustained tensile-loaded Sn-3.0Ag-0.5Cu solder alloy in NaCl solution

    Ken'ichi Yokoyama, Daisuke Tsuji, Jun'ichi Sakai

    CORROSION SCIENCE   53 ( 10 ) 3331 - 3336  2011年10月

     概要を見る

    The fracture of Sn-3.0Ag-0.5Cu solder alloy has been investigated by a constant sustained tensile-loading test in 0.9 wt.% NaCl aqueous solution at room temperature. Under applied stress in the solution, many cracks nucleate and propagate on the side surface of the specimen. The fracture is not an ordinary creep rupture mode and is probably caused by the decrease in cross section of the specimen due to crack propagation. The preferential dissolution of Ag and Cu ions is clearly observed under applied stress in the solution. The time to fracture and the critical stress for fracture in the solution are lower than those in the atmosphere. The present results indicate that the reliability of lead-free solder alloys must be evaluated considering the effects of the combination of environment and applied stress. (C) 2011 Elsevier Ltd. All rights reserved.

    DOI

  • Inhibition of hydrogen embrittlement of Ni–Ti superelastic alloy in acid fluoride solution by hydrogen peroxide addition

    Ken'ichi Yokoyama, Yushin Yazaki, Jun'ichi Sakai

    Journal of Biomedical Materials Research Part A   98A ( 3 ) 404 - 411  2011年09月

    DOI

  • Inhibition of hydrogen embrittlement of Ni-Ti superelastic alloy in acid fluoride solution by hydrogen peroxide addition

    Ken'Ichi Yokoyama, Yushin Yazaki, Jun'Ichi Sakai

    Journal of Biomedical Materials Research - Part A   98 ( 3 ) 404 - 411  2011年09月

     概要を見る

    Inhibition of the hydrogen embrittlement of Ni-Ti superelastic alloy in an acidulated phosphate fluoride (APF) solution has been attempted by adding various amounts of H2O2. In a 0.2% APF solution, hydrogen absorption is markedly inhibited by adding H2O2, although corrosion is slightly enhanced by increasing the amount of added H 2O2. By adding a small amount of H2O 2 (0.001M), in the early stage of immersion, hydrogen embrittlement is inhibited and corrosion is only slightly enhanced. Upon adding H 2O2, it appears that the dominant cathodic reactions change from hydrogen evolution to H2O2 reduction reactions, or the surface conditions of the alloy are changed by H 2O2 with a high oxidation capability, thereby inhibiting hydrogen absorption. The present study clearly indicates that infinitesimal addition of H2O2 into acid fluoride solutions is effective for the inhibition of the hydrogen embrittlement of the alloy. Copyright © 2011 Wiley Periodicals, Inc.

    DOI PubMed

  • Effect of Relative Humidity on Ammonium Chloride Corrosion in Refineries

    K. Toba, T. Suzuki, K. Kawano, J. Sakai

    CORROSION   67 ( 5 ) 055005  2011年05月

     概要を見る

    Corrosion behavior and the hygroscopic properties of solid ammonium chloride (NH(4)Cl) salt were investigated. This study was conducted to determine the root cause of significant corrosion caused by NH(4)Cl salt deposition in reactor-effluent streams in hydroprocessing units. Corrosion and water absorption tests were performed under various relative humidity (RH) conditions with solid NH(4)Cl salts using a temperature and humidity control chamber. Eight types of materials commonly used in refineries were examined, including carbon steel (UNS K02702), Type 304 (UNS S30400) stainless steel, duplex (UNS S39274) stainless steel, Grade 2 titanium (UNS R50400), Alloy 400 (UNS N04400), Alloy C-276 (UNS N10276), aluminum brass (UNS C68700), and aluminized carbon steel (hot-dip aluminized UNS K02702). Significant corrosion was observed around 60% RH on all the alloys except Alloy C-276. Carbon steel corroded above 20% RH. Its highest corrosion rate was observed at 60% RH and 80 degrees C. Type 304 stainless steel and duplex stainless steel showed pitting at 50% and 60% RH. Although the metal surface on Alloy C-276 was tarnished at 50% RH, it had excellent corrosion resistance at all RH levels. It was suggested that the corrosion of NH(4)Cl is the most severe around a critical RH, above which water absorption becomes significant. In addition, based on the water absorption tests and simulation results, it was found that the critical RH of NH(4)Cl salt has a close relationship to temperature.

    DOI

  • Effect of Relative Humidity on Ammonium Chloride Corrosion in Refineries

    K. Toba, T. Suzuki, K. Kawano, J. Sakai

    CORROSION   67 ( 5 ) 055005  2011年05月

     概要を見る

    Corrosion behavior and the hygroscopic properties of solid ammonium chloride (NH(4)Cl) salt were investigated. This study was conducted to determine the root cause of significant corrosion caused by NH(4)Cl salt deposition in reactor-effluent streams in hydroprocessing units. Corrosion and water absorption tests were performed under various relative humidity (RH) conditions with solid NH(4)Cl salts using a temperature and humidity control chamber. Eight types of materials commonly used in refineries were examined, including carbon steel (UNS K02702), Type 304 (UNS S30400) stainless steel, duplex (UNS S39274) stainless steel, Grade 2 titanium (UNS R50400), Alloy 400 (UNS N04400), Alloy C-276 (UNS N10276), aluminum brass (UNS C68700), and aluminized carbon steel (hot-dip aluminized UNS K02702). Significant corrosion was observed around 60% RH on all the alloys except Alloy C-276. Carbon steel corroded above 20% RH. Its highest corrosion rate was observed at 60% RH and 80 degrees C. Type 304 stainless steel and duplex stainless steel showed pitting at 50% and 60% RH. Although the metal surface on Alloy C-276 was tarnished at 50% RH, it had excellent corrosion resistance at all RH levels. It was suggested that the corrosion of NH(4)Cl is the most severe around a critical RH, above which water absorption becomes significant. In addition, based on the water absorption tests and simulation results, it was found that the critical RH of NH(4)Cl salt has a close relationship to temperature.

    DOI

  • Effects of Cu Addition on Hydrogen Absorption and Diffusion Properties of 1 470 MPa Grade Thin-walled Steel in a Solution of HCl

    Shunsuke Toyoda, Hideto Kimura, Yoshikazu Kawabata, Yasuyoshi Yamane, Junichi Sakai

    ISIJ INTERNATIONAL   51 ( 3 ) 456 - 461  2011年

     概要を見る

    Hydrogen embrittlement is caused by the introduction of hydrogen into steel and is critical for high strength steels. To clarify the effects of the addition of Cu on the suppression of hydrogen embrittlement in a solution of HCl, hydrogen permeation tests and dynamic polarization measurements were conducted on TS 1 470 MPa grade, low-carbon martensite steels. To this end, steels containing 0.19% C, 0.2% Si, 1.3% Mn, Cr, Ti, Nb and B were prepared with and without 0.16% Cu. For comparison, ferrite and pearlite steels were also examined. The results of hydrogen permeation tests indicated that the steady-state hydrogen permeation current (J(H)) of steel containing 0.16% Cu was considerably lower than that of basic steel in 0.1 N HCl at the corrosion potential. Moreover, the J(H) of martensite steel was suppressed by the addition of Cu, and the cathode current, (i(C)) and the J(H)/i(C) were reduced. The results obtained in this study corroborated the hypothesis that the 1 or 2-mu m metallic Cu particles precipitated on the surface of the steel in a solution of HCl suppressed the cathodic reaction and the introduction of hydrogen. The hydrogen diffusion constant (D(eff)) was obtained from hydrogen permeation tests under a potential gradient. Cu addition has only small effect on D(eff) regardless of microstructure. The occupancy of trap site (n(X)) was estimated to be greater than 99% independent of Cu content and microstructure.

    DOI CiNii

  • 空冷式熱交換器伝熱管におけるNH4HSの濃縮機構解明

    鳥羽和宏, 川野浩二, 田中耕太郎, 岩脇大仁, 酒井潤一

    Zairyo-to-Kankyo   60 ( 6 ) 304 - 311  2011年

    DOI CiNii

  • Dissolution Behavior of α and γ Phases and Preferential Dissolution Mechanism of a Duplex Stainless Steel in a Simulated Crevice Solution

    So Aoki, Hiroshi Yakuwa, Katsuhiro Mitsuhashi, Jun’ichi Sakai

    Corrosion Engineering   60 ( 7 ) 328 - 332  2011年

    DOI

  • すきま内模擬溶液中における二相ステンレス鋼のα, γ各相の溶解挙動と優先溶解機構

    青木聡, 八鍬浩, 宮坂松甫, 酒井潤一

    Zairyo-to-Kankyo   60 ( 7 ) 328 - 332  2011年

    DOI CiNii

  • Potential Dependence of Preferential Dissolution Behavior of a Duplex Stainless Steel in a Simulated Solution inside a Crevice

    So Aoki, Kiyotaka Ito, Hiroshi Yakuwa, Katsuhiro Mitsuhashi, Jun’ichi Sakai

    Corrosion Engineering   60 ( 8 ) 363 - 367  2011年

    DOI

  • すきま内模擬溶液中における二相ステンレス鋼の優先溶解挙動の電位依存性

    青木聡, 伊藤淳貴, 八鍬浩, 宮坂松甫, 酒井潤一

    Zairyo-to-Kankyo   60 ( 8 ) 363 - 367  2011年

    DOI CiNii

  • Effects of Cu Addition on Hydrogen Absorption and Diffusion Properties of 1 470 MPa Grade Thin-walled Steel Tube under Atmospheric Corrosion

    Shunsuke Toyoda, Hideto Kimura, Masayasu Nagoshi, Isamu Kage, Naotake Yoshihara, Junichi Sakai

    ISIJ INTERNATIONAL   51 ( 9 ) 1516 - 1523  2011年

     概要を見る

    Hydrogen embrittlement is caused by the introduction of hydrogen into steel and is critical for high strength steels. To clarify the effects of Cu addition on hydrogen absorption and diffusion properties of steel under atmospheric condition, corrosion test was conducted on a 1 470 MPa grade thin-walled low carbon martensite steel tube. To this end, a martensite steel tube bearing 0.18% C, 0.4% Si, 1.5% Mn, 0.15% Cu, 0.01% Nb was prepared and compared with Cu free steel tube. As a result of EPMA mapping for the rust layer, Cu accumulated discretely on the rust/steel interface, especially in the bottom of pits of 0.15% Cu bearing steel tubes after the atmospheric corrosion test over 12 years. According to x-ray absorption near-edge structure (XANES) spectra, the valence of Cu in the rust layer was mainly +2 as Cu(0, OH, SO(4)). The average and maximum diffusible hydrogen content level of 0.15% Cu bearing steel was lower than that of Cu free steel after the atmospheric corrosion test. The quantity of non-diffusible hydrogen was much higher than that of diffusible hydrogen. According to diffusion calculation results, hydrogen diffusion was so rapid that the long-term corrosion hysteresis seemed to have little influence on the diffusible hydrogen content. Furthermore, the short-term corrosion hysteresis may be the main determinant of diffusible hydrogen concentration. Having regard to the fact that the valance of Cu could also be 0 as reported by Shimizu et al., an inhibition mechanism from accumulated Cu on hydrogen-induced cracking was proposed. Eluted Cu(gamma+) ions in the rust layer may precipitate as metallic Cu at the microscopic cathode during the corrosion test. As a result, the microscopic cathode becomes inactivated as an electrochemical reaction site for hydrogen. The Cu alternates between precipitates and Cu ions depending on the relative humidity, and the condensation and pH of the water in the rust layer.

    DOI CiNii

  • Effects of Cu Addition on Hydrogen Absorption and Diffusion Properties of 1 470 MPa Grade Thin-walled Steel in a Solution of HCl

    Shunsuke Toyoda, Hideto Kimura, Yoshikazu Kawabata, Yasuyoshi Yamane, Junichi Sakai

    ISIJ INTERNATIONAL   51 ( 3 ) 456 - 461  2011年

     概要を見る

    Hydrogen embrittlement is caused by the introduction of hydrogen into steel and is critical for high strength steels. To clarify the effects of the addition of Cu on the suppression of hydrogen embrittlement in a solution of HCl, hydrogen permeation tests and dynamic polarization measurements were conducted on TS 1 470 MPa grade, low-carbon martensite steels. To this end, steels containing 0.19% C, 0.2% Si, 1.3% Mn, Cr, Ti, Nb and B were prepared with and without 0.16% Cu. For comparison, ferrite and pearlite steels were also examined. The results of hydrogen permeation tests indicated that the steady-state hydrogen permeation current (J(H)) of steel containing 0.16% Cu was considerably lower than that of basic steel in 0.1 N HCl at the corrosion potential. Moreover, the J(H) of martensite steel was suppressed by the addition of Cu, and the cathode current, (i(C)) and the J(H)/i(C) were reduced. The results obtained in this study corroborated the hypothesis that the 1 or 2-mu m metallic Cu particles precipitated on the surface of the steel in a solution of HCl suppressed the cathodic reaction and the introduction of hydrogen. The hydrogen diffusion constant (D(eff)) was obtained from hydrogen permeation tests under a potential gradient. Cu addition has only small effect on D(eff) regardless of microstructure. The occupancy of trap site (n(X)) was estimated to be greater than 99% independent of Cu content and microstructure.

    DOI CiNii

  • Dissolution behavior of α and γ phases and preferential dissolution mechanism of a duplex stainless steel in a simulated crevice solution

    So Aoki, Hiroshi Yakuwa, Matsuho Miyasaka, Jun'ichi Sakai

    Zairyo to Kankyo/ Corrosion Engineering   60 ( 7 ) 328 - 332  2011年

     概要を見る

    The objectives of this study are to clarify the dissolution behavior of the ferritic phase (α phase) and the austenitic phase (γ phase) of a duplex stainless steel (DSS), and to propose a corrosion mechanism of the DSS through dissolution behavior of either the α phase or the γ phase at corrosion potential, respectively. Just a single phase specimen (α or γ phase specimen) was prepared by using selective dissolution of the DSS. The α phase showed less-noble corrosion potential compared to the γ phase, and passivated at less-noble potential. When the polarization curves of each phase are summed up, the obtained curve showed good agreement with the DSS polarization curve. The α phase of the DSS dissolved preferentially at corrosion potential. Based on these results, a preferential dissolution mechanism model of a DSS is proposed using internal polarization curves of each phase.

    DOI

  • Potential dependence of preferential dissolution behavior of a duplex stainless steel in simulated solution inside crevice

    So Aoki, Kiyotaka Ito, Hiroshi Yakuwa, Matsuho Miyasaka, Jun'ichi Sakai

    Zairyo to Kankyo/ Corrosion Engineering   60 ( 8 ) 363 - 367  2011年

     概要を見る

    Relationship between preferential dissolution behavior and the holding potential and its duration of the potentiostatic test of a duplex stainless steel in simulated solution inside corroding crevice was investigated. In the active region (-370, -300 and -260 mV vs. SCE), the current density decreased towards a certain value after the measurement started, then it stayed rather constant value until the end of the measurement, i.e., for 24 h. In the passive region (-200 and -150 mV), it decreased greatly towards certain values after the measurement started, then it stayed lower value until the end of the measurement. In all potential regions, current density values determined by potentiostatic tests showed about one order of magnitude lower than those of the dynamic anodic polarization curves. At the less noble potential (-370 mV) of the active region, ferritic phase preferentially dissolved, -while that of noble (-260 mV) of the active region, the austenitic phase dissolved preferentially. In the passive region, both phases dissolved evenly. These dissolution behavior were observed in the potentiostatic tests for 15 min as well as for 24 h. Chemical composition of dissolved metal ions after dissolution tests at certain potentials in the active region was also analyzed. Chemical composition of dissolved metal ions was almost same as chemical composition of a preferential dissolution phase of the specimen at each holding potential. It would appear that chemical composition of dissolved metal into crevice solution reflects to the preferential dissolution phase.

    DOI

  • Effects of Cu Addition on Hydrogen Absorption and Diffusion Properties of 1 470 MPa Grade Thin-walled Steel Tube under Atmospheric Corrosion

    Shunsuke Toyoda, Hideto Kimura, Masayasu Nagoshi, Isamu Kage, Naotake Yoshihara, Junichi Sakai

    ISIJ INTERNATIONAL   51 ( 9 ) 1516 - 1523  2011年

     概要を見る

    Hydrogen embrittlement is caused by the introduction of hydrogen into steel and is critical for high strength steels. To clarify the effects of Cu addition on hydrogen absorption and diffusion properties of steel under atmospheric condition, corrosion test was conducted on a 1 470 MPa grade thin-walled low carbon martensite steel tube. To this end, a martensite steel tube bearing 0.18% C, 0.4% Si, 1.5% Mn, 0.15% Cu, 0.01% Nb was prepared and compared with Cu free steel tube. As a result of EPMA mapping for the rust layer, Cu accumulated discretely on the rust/steel interface, especially in the bottom of pits of 0.15% Cu bearing steel tubes after the atmospheric corrosion test over 12 years. According to x-ray absorption near-edge structure (XANES) spectra, the valence of Cu in the rust layer was mainly +2 as Cu(0, OH, SO(4)). The average and maximum diffusible hydrogen content level of 0.15% Cu bearing steel was lower than that of Cu free steel after the atmospheric corrosion test. The quantity of non-diffusible hydrogen was much higher than that of diffusible hydrogen. According to diffusion calculation results, hydrogen diffusion was so rapid that the long-term corrosion hysteresis seemed to have little influence on the diffusible hydrogen content. Furthermore, the short-term corrosion hysteresis may be the main determinant of diffusible hydrogen concentration. Having regard to the fact that the valance of Cu could also be 0 as reported by Shimizu et al., an inhibition mechanism from accumulated Cu on hydrogen-induced cracking was proposed. Eluted Cu(gamma+) ions in the rust layer may precipitate as metallic Cu at the microscopic cathode during the corrosion test. As a result, the microscopic cathode becomes inactivated as an electrochemical reaction site for hydrogen. The Cu alternates between precipitates and Cu ions depending on the relative humidity, and the condensation and pH of the water in the rust layer.

    DOI CiNii

  • Evaluation of hydrogen absorption behaviour during acid etching for surface modification of commercial pure Ti, Ti-6Al-4V and Ni-Ti superelastic alloys

    Akira Nagaoka, Ken'ichi Yokoyama, Jun'ichi Sakai

    CORROSION SCIENCE   52 ( 4 ) 1130 - 1138  2010年04月

     概要を見る

    The hydrogen absorption behaviour during acid etching for the surface modification of commercial pure Ti, Ti-6Al-4V and Ni-Ti superelastic alloys has been investigated on the basis of the surface morphology, electrochemical behaviour and hydrogen thermal desorption analysis. To simulate the conventional acid etching for the improvement of the biocompatibility of Ti alloys, the specimens are immersed in 1 M HCl, 1 M H(2)SO(4) or 0.5 M HCl + 0.5 M H(2)SO(4) aqueous solution at 60 degrees C. Upon immersion, commercial pure Ti absorbs substantial amounts of hydrogen irrespective of the type of solution. In H(2)SO(4) or HCl + H(2)SO(4) solutions, the hydrogen absorption occurs for a short time (10 min). For Ti-6Al-4V alloy, no hydrogen absorption is observed in HCl solution, whereas hydrogen absorption occurs in other solutions. For NiTi superelastic alloy, the amount of absorbed hydrogen is large, resulting in the pronounced degradation of the mechanical properties of the alloy even for an immersion time of 10 min, irrespective of the type of solution. The hydrogen absorption behaviour is not necessarily consistent with the morphologies of the surface subjected to corrosion and the shift of the corrosion potential. The hydrogen thermal desorption behaviour of commercial pure Ti and Ni-Ti superelastic alloy are sensitively changed by acid etching conditions. The present results suggest that the evaluation of hydrogen absorption is needed for each condition of acid etching, and that the conventional acid etching often leads to hydrogen embrittlement. (C) 2010 Elsevier Ltd. All rights reserved.

    DOI CiNii

  • Evaluation of hydrogen absorption behaviour during acid etching for surface modification of commercial pure Ti, Ti-6Al-4V and Ni-Ti superelastic alloys

    Akira Nagaoka, Ken'ichi Yokoyama, Jun'ichi Sakai

    Corrosion Science   52 ( 4 ) 1130 - 1138  2010年04月

     概要を見る

    The hydrogen absorption behaviour during acid etching for the surface modification of commercial pure Ti, Ti-6Al-4V and Ni-Ti superelastic alloys has been investigated on the basis of the surface morphology, electrochemical behaviour and hydrogen thermal desorption analysis. To simulate the conventional acid etching for the improvement of the biocompatibility of Ti alloys, the specimens are immersed in 1 M HCl, 1 M H2SO4 or 0.5 M HCl + 0.5 M H2SO4 aqueous solution at 60 °C. Upon immersion, commercial pure Ti absorbs substantial amounts of hydrogen irrespective of the type of solution. In H2SO4 or HCl + H2SO4 solutions, the hydrogen absorption occurs for a short time (10 min). For Ti-6Al-4V alloy, no hydrogen absorption is observed in HCl solution, whereas hydrogen absorption occurs in other solutions. For Ni-Ti superelastic alloy, the amount of absorbed hydrogen is large, resulting in the pronounced degradation of the mechanical properties of the alloy even for an immersion time of 10 min, irrespective of the type of solution. The hydrogen absorption behaviour is not necessarily consistent with the morphologies of the surface subjected to corrosion and the shift of the corrosion potential. The hydrogen thermal desorption behaviour of commercial pure Ti and Ni-Ti superelastic alloy are sensitively changed by acid etching conditions. The present results suggest that the evaluation of hydrogen absorption is needed for each condition of acid etching, and that the conventional acid etching often leads to hydrogen embrittlement. © 2010 Elsevier Ltd. All rights reserved.

    DOI CiNii

  • 炭素鋼のボイラ水中エロージョン・コロージョンのテクニカルモジュールの作成

    伊藤慶, 酒井潤一, 木原重光

    鉄と鋼   96 ( 3 ) 117 - 122  2010年

    DOI CiNii

  • Numerical Simulation of Fatigue Crack Initiation in Thin-walled High Strength Steel as Modeled by Voronoi-polygons

    Shunsuke Toyoda, Hideto Kimura, Yoshikazu Kawabata, Shota Hashimoto, Naotake Yoshihara, Jun'ichi Sakai

    ISIJ INTERNATIONAL   50 ( 11 ) 1695 - 1701  2010年

     概要を見る

    The fatigue endurance of TS 590 MPa grade low-alloy precipitation strengthened steel was numerically and experimentally examined. The microstructure was modeled using two-dimensional Voronoi polygons. Heterogeneous stress distributions were calculated using the finite element method, taking elastic anisotropy into consideration. The number of cycles before crack initiation was estimated based on the Tanaka-Mura model. By taking into account the effects of the cyclic strain of the preceding cracks, a definable macroscopic crack initiation cycle was obtained. An actual tensile and compression fatigue test was conducted on the same steel. The stress amplitude decreased as the cycle number increased. Distinct dislocation cell structure was not observed by TEM analysis. The experimental strain fatigue limit was, to some extent, lower than that of the simulation. Surface effects, specimen homogeneity, selection of slip system, and dislocation reversibility are mentioned as the probable causes for the difference.

    DOI CiNii

  • Numerical Simulation of Fatigue Crack Initiation in Thin-walled High Strength Steel as Modeled by Voronoi-polygons

    Shunsuke Toyoda, Hideto Kimura, Yoshikazu Kawabata, Shota Hashimoto, Naotake Yoshihara, Jun'ichi Sakai

    ISIJ INTERNATIONAL   50 ( 11 ) 1695 - 1701  2010年

     概要を見る

    The fatigue endurance of TS 590 MPa grade low-alloy precipitation strengthened steel was numerically and experimentally examined. The microstructure was modeled using two-dimensional Voronoi polygons. Heterogeneous stress distributions were calculated using the finite element method, taking elastic anisotropy into consideration. The number of cycles before crack initiation was estimated based on the Tanaka-Mura model. By taking into account the effects of the cyclic strain of the preceding cracks, a definable macroscopic crack initiation cycle was obtained. An actual tensile and compression fatigue test was conducted on the same steel. The stress amplitude decreased as the cycle number increased. Distinct dislocation cell structure was not observed by TEM analysis. The experimental strain fatigue limit was, to some extent, lower than that of the simulation. Surface effects, specimen homogeneity, selection of slip system, and dislocation reversibility are mentioned as the probable causes for the difference.

    DOI CiNii

  • Improvements in fracture properties of Ni-Ti superelastic alloy in physiological saline solution containing hydrogen peroxide by surface modification

    Ken'ichi Yokoyama, Tokunori Kanemura, Jun'ichi Sakai

    Materials Science and Engineering A   513-514 ( C ) 267 - 275  2009年07月

     概要を見る

    The fracture properties of surface-modified Ni-Ti superelastic alloy are examined by a sustained tensile-loading test in physiological saline solution containing hydrogen peroxide. The surface modification of the alloy is performed by chemical etching in 35 mass% nitric acid solution at 60 °C for a long time (3 h). By modifying the surface of the specimen, many corrosion pits are formed and the surface roughness increases. When the surface-modified specimen is immersed in the test solution without applied stress, corrosion occurs over the entire specimen and the amount of dissolved nickel ions increases. Nevertheless, under applied stress, the localized corrosion leading to the fracture is inhibited and the fracture mechanism changes, thereby increasing the time to fracture. The effects of the surface modification are confirmed even under applied stress above the critical stress for martensite transformation. The present study suggests that the effectiveness of the surface modification of Ni-Ti superelastic alloy should be investigated not only without applied stress but also under applied stress. © 2009 Elsevier B.V. All rights reserved.

    DOI CiNii

  • Hydrogen Absorption and Thermal Desorption Behavior of Ni-Ti Superelastic Alloy Immersed in Neutral NaCl and NaF Solutions under Applied Potential

    Asahi Ota, Yushin Yazaki, Ken'ichi Yokoyama, Jun'ichi Sakai

    MATERIALS TRANSACTIONS   50 ( 7 ) 1843 - 1849  2009年07月

     概要を見る

    The hydrogen absorption and thermal desorption behavior of Ni-Ti superelastic alloy immersed in neutral NaCl and NaF aqueous solutions at 25 degrees C under an applied cathodic potential for 2 h have been systematically investigated by hydrogen thermal desorption analysis. The critical potential for hydrogen absorption is independent of the type and concentration of solution. The amount of absorbed hydrogen increases with decreasing applied potential, although it is only slightly changed by the type of solution. The amount of hydrogen desorbed at low temperatures, for the alloy immersed in NaF solutions, is larger than those in NaCl solutions, suggesting that the type of solution affects the hydrogen states in the alloy. The present results indicate that for Ni-Ti superelastic alloy, compared with titanium and its alloys, the critical potential for hydrogen absorption is located in a more noble direction, and the amount of absorbed hydrogen is large in NaCl and NaF solutions. Thus, the hydrogen embrittlement of Ni-Ti superelastic alloy probably occurs more readily than those of titanium and its alloys in NaCl and NaF solutions. [doi: 10.2320/matertrans.M2009078]

    DOI CiNii

  • Hydrogen Absorption and Thermal Desorption Behavior of Ni-Ti Superelastic Alloy Immersed in Neutral NaCl and NaF Solutions under Applied Potential

    Asahi Ota, Yushin Yazaki, Ken'ichi Yokoyama, Jun'ichi Sakai

    MATERIALS TRANSACTIONS   50 ( 7 ) 1843 - 1849  2009年07月

     概要を見る

    The hydrogen absorption and thermal desorption behavior of Ni-Ti superelastic alloy immersed in neutral NaCl and NaF aqueous solutions at 25 degrees C under an applied cathodic potential for 2 h have been systematically investigated by hydrogen thermal desorption analysis. The critical potential for hydrogen absorption is independent of the type and concentration of solution. The amount of absorbed hydrogen increases with decreasing applied potential, although it is only slightly changed by the type of solution. The amount of hydrogen desorbed at low temperatures, for the alloy immersed in NaF solutions, is larger than those in NaCl solutions, suggesting that the type of solution affects the hydrogen states in the alloy. The present results indicate that for Ni-Ti superelastic alloy, compared with titanium and its alloys, the critical potential for hydrogen absorption is located in a more noble direction, and the amount of absorbed hydrogen is large in NaCl and NaF solutions. Thus, the hydrogen embrittlement of Ni-Ti superelastic alloy probably occurs more readily than those of titanium and its alloys in NaCl and NaF solutions. [doi: 10.2320/matertrans.M2009078]

    DOI CiNii

  • Improvements in fracture properties of Ni-Ti superelastic alloy in physiological saline solution containing hydrogen peroxide by surface modification

    Ken'ichi Yokoyama, Tokunori Kanemura, Jun'ichi Sakai

    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING   513-14   267 - 275  2009年07月

     概要を見る

    The fracture properties of surface-modified Ni-Ti superelastic alloy are examined by a sustained tensile-loading test in physiological saline solution containing hydrogen peroxide. The surface modification of the alloy is performed by chemical etching in 35 mass% nitric acid solution at 60 degrees C for a long time (3 h). By modifying the surface of the specimen, many corrosion pits are formed and the surface roughness increases. When the surface-modified specimen is immersed in the test solution without applied stress, corrosion occurs over the entire specimen and the amount of dissolved nickel ions increases. Nevertheless, under applied stress, the localized corrosion leading to the fracture is inhibited and the fracture mechanism changes, thereby increasing the time to fracture. The effects of the surface modification are confirmed even under applied stress above the critical stress for martensite transformation. The present study suggests that the effectiveness of the surface modification of Ni-Ti superelastic alloy should be investigated not only without applied stress but also under applied stress. (c) 2009 Elsevier B.V. All rights reserved.

    DOI CiNii

  • 海水中におけるステンレス鋼表面の微生物とカソード電流との関係

    鷲頭直樹, 篠原正, 元田慎一, 酒井潤一

    材料と環境   58 ( 6 ) 234 - 240  2009年06月

    DOI CiNii

  • Relationship between Hydrogen Absorption and Corrosion Behavior of Ti-6Al-4V Alloy Immersed in Acidic Fluoride Solutions

    Atsushi Fujita, Toshio Ogawa, Ken'ichi Yokoyama, Jun'ichi Sakai

    MATERIALS TRANSACTIONS   50 ( 5 ) 1183 - 1189  2009年05月

     概要を見る

    The relationship between hydrogen absorption and the corrosion behavior of Ti-6Al-4V alloy has been examined by immersing the alloy in acidulated phosphate fluoride (APF) solution with various concentrations. Upon immersion in 0.1 mass% APF solution, no hydrogen absorption is observed despite the occurrence of general corrosion. In 0.2% APF solution, slight hydrogen absorption occurs soon after immersion, and then the surface of the specimen becomes uniformly covered with a crystalline corrosion product (Na3AlF6), thereby inhibiting further hydrogen absorption. In APF solutions with concentrations higher than 0.4%, the amount of absorbed hydrogen increases with increasing concentration of APF solution and immersion time. The type and morphology of corrosion products sensitively depend on the concentration of APF solution. Upon immersion in 0.4% APF solution, crystalline and massive Na3AlF6 are observed on the Surface of the specimen. In 1.0% and 1.5% APF solutions, Na3AlF6 with a foldlike shape and granular Na3AlF6 and Na3TiF6 are observed. In 2.0% APF solution, only granular Na3TiF6 is observed. The corrosion potentials and anodic polarization curves are analogous in all APF solutions except the 0.2% and 0.4% APF solutions. In contrast, the current density of cathodic polarization curves increases with the concentration of APF solution. The results of the present study suggest that the corrosion products play an important role in the hydrogen absorption behavior of Ti-6Al-4V alloy. [doi: 10.2320/matertrans.MRA2008481]

    DOI CiNii

  • Relationship between Hydrogen Absorption and Corrosion Behavior of Ti-6Al-4V Alloy Immersed in Acidic Fluoride Solutions

    Atsushi Fujita, Toshio Ogawa, Ken'ichi Yokoyama, Jun'ichi Sakai

    MATERIALS TRANSACTIONS   50 ( 5 ) 1183 - 1189  2009年05月

     概要を見る

    The relationship between hydrogen absorption and the corrosion behavior of Ti-6Al-4V alloy has been examined by immersing the alloy in acidulated phosphate fluoride (APF) solution with various concentrations. Upon immersion in 0.1 mass% APF solution, no hydrogen absorption is observed despite the occurrence of general corrosion. In 0.2% APF solution, slight hydrogen absorption occurs soon after immersion, and then the surface of the specimen becomes uniformly covered with a crystalline corrosion product (Na3AlF6), thereby inhibiting further hydrogen absorption. In APF solutions with concentrations higher than 0.4%, the amount of absorbed hydrogen increases with increasing concentration of APF solution and immersion time. The type and morphology of corrosion products sensitively depend on the concentration of APF solution. Upon immersion in 0.4% APF solution, crystalline and massive Na3AlF6 are observed on the Surface of the specimen. In 1.0% and 1.5% APF solutions, Na3AlF6 with a foldlike shape and granular Na3AlF6 and Na3TiF6 are observed. In 2.0% APF solution, only granular Na3TiF6 is observed. The corrosion potentials and anodic polarization curves are analogous in all APF solutions except the 0.2% and 0.4% APF solutions. In contrast, the current density of cathodic polarization curves increases with the concentration of APF solution. The results of the present study suggest that the corrosion products play an important role in the hydrogen absorption behavior of Ti-6Al-4V alloy. [doi: 10.2320/matertrans.MRA2008481]

    DOI CiNii

  • Hydrogen embrittlement behavior induced by dynamic martensite transformation of Ni-Ti superelastic alloy

    Ken'ichi Yokoyama, Miho Tomita, Jun'ichi Sakai

    Acta Materialia   57 ( 6 ) 1875 - 1885  2009年04月

     概要を見る

    The hydrogen embrittlement behavior induced by the martensite transformation of Ni-Ti superelastic alloy subjected to a dynamic cyclic tensile test with hydrogen cathodic charging has been investigated by hydrogen thermal desorption analysis. The critical stress for the martensite transformation steeply decreases with increasing number of deformation cycles, whereas the critical stress for the reverse transformation only slightly changes. The dynamic stress-induced martensite transformation markedly enhances hydrogen absorption, compared with that of the martensite phase itself. The hydrogen concentration at the surface layer of the specimen is evaluated to be above 3500 mass ppm
    nevertheless, no fracture associated with the stress-induced martensite transformation occurs. In addition, no hardening is observed at the surface layer of the specimen despite the formation of the hydride and hydrogen enrichment. The hydrogen thermally desorbed at a low temperature markedly increases, indicating that the hydrogen states are changed by the dynamic martensite transformation. Note that interactions between hydrogen and the phase transformation are probably irreversible, although the phase transformation is reversible. The present study shows, for the first time, that the hydrogen embrittlement behavior of the alloy strongly depends on the dynamic change of the hydrogen states accompanied by the martensite transformation. © 2009 Acta Materialia Inc.

    DOI CiNii

  • Hydrogen embrittlement behavior induced by dynamic martensite transformation of Ni-Ti superelastic alloy

    Ken'ichi Yokoyama, Miho Tomita, Jun'ichi Sakai

    ACTA MATERIALIA   57 ( 6 ) 1875 - 1885  2009年04月

     概要を見る

    The hydrogen embrittlement behavior induced by the martensite transformation of Ni-Ti superelastic alloy subjected to a dynamic cyclic tensile test with hydrogen cathodic charging has been investigated by hydrogen thermal desorption analysis. The critical stress for the martensite transformation steeply decreases with increasing number of deformation cycles. whereas the critical stress for the reverse transformation only slightly changes. The dynamic stress-induced martensite transformation markedly enhances hydrogen absorption. compared with that of the martensite phase itself. The hydrogen concentration at the surface layer of the specimen is evaluated to be above 3500 mass ppm; nevertheless, no fracture associated with the stress-induced martensite transformation occurs. In addition. no hardening is observed at the surface layer of the specimen despite the formation of the hydride and hydrogen enrichment. The hydrogen thermally, desorbed at a low temperature markedly increases. indicating that the hydrogen states are changed by the dynamic martensite transformation. Note that interactions between hydrogen and the phase transformation are probably irreversible, although the phase transformation is reversible. The present study shows. for the first time. that the hydrogen embrittlement behavior of the alloy strongly depends on the dynamic change of the hydrogen states accompanied by the martensite transformation. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

    DOI CiNii

  • Quartz Crystal Microbalance (QCM) study of corrosion behavior of silver and simple corrosion test using sulfur vapor

    Lisa Aoki, Keishin Osaka, Masataka Omoda, Jun'ichi Sakai, Yuichi Ishikawa

    Zairyo to Kankyo/ Corrosion Engineering   58 ( 2 ) 56 - 63  2009年02月

     概要を見る

    Quartz Crystal Microbalance (QCM) technique was employed to continuously detect extremely small mass changes during corrosion of silver by sulfur vapor originated from sulfur flower as a function of temperature, RH and distance from sulfur to the silver surface. Corrosion progressed linearly with exposure time during all the tests. The corrosion rate increased as temperature rose, while no significant dependence on RH was observed. Furthermore the corrosion rate decreased markedly with increasing distance. This suggests that diffusion of sulfur vapor to the silver controls initial sulfide formation of silver. These results have led us to propose a simple corrosion test using sulfur vapor to simulate corrosion of silver during indoor exposure of electronic equipment. The test employs the two distinct characteristics of sulfur vapor test using sulfur flower. Firstly the vapor pressure of sulfur by sulfur flower varies widely with temperature resulting a wide range of sulfur concentration. Secondly the corrosion rate of silver in sulfur vapor can be controlled by varying the distance between the sulfur flower and the silver surface. Since the corrosion by sulfur vapor follows the linear kinetics similar to those found in practice as well as to provide identical major corrosion chemistry and morphology of the corrosion product, silver sulfide as in practice, we propose it to provide a reasonably reproducible, more flexible test which is much easier to handle in the laboratory than flowing multi-component gas mixtures containing hydrogen sulfide.

    DOI

  • 水晶振動子微小天秤(QCM)を用いた銀の硫黄蒸気による腐食挙動の解析および硫黄蒸気を用いた銀の硫化腐食試験

    青木 里紗, 大坂 圭新, 面田 真孝, 酒井 潤一, 石川 雄一

    材料と環境   58 ( 2 ) 56 - 63  2009年02月

    DOI CiNii

  • Quartz Crystal Microbalance (QCM) study of corrosion behavior of silver and simple corrosion test using sulfur vapor

    Lisa Aoki, Keishin Osaka, Masataka Omoda, Jun'ichi Sakai, Yuichi Ishikawa

    Zairyo to Kankyo/ Corrosion Engineering   58 ( 2 ) 56 - 63  2009年02月

     概要を見る

    Quartz Crystal Microbalance (QCM) technique was employed to continuously detect extremely small mass changes during corrosion of silver by sulfur vapor originated from sulfur flower as a function of temperature, RH and distance from sulfur to the silver surface. Corrosion progressed linearly with exposure time during all the tests. The corrosion rate increased as temperature rose, while no significant dependence on RH was observed. Furthermore the corrosion rate decreased markedly with increasing distance. This suggests that diffusion of sulfur vapor to the silver controls initial sulfide formation of silver. These results have led us to propose a simple corrosion test using sulfur vapor to simulate corrosion of silver during indoor exposure of electronic equipment. The test employs the two distinct characteristics of sulfur vapor test using sulfur flower. Firstly the vapor pressure of sulfur by sulfur flower varies widely with temperature resulting a wide range of sulfur concentration. Secondly the corrosion rate of silver in sulfur vapor can be controlled by varying the distance between the sulfur flower and the silver surface. Since the corrosion by sulfur vapor follows the linear kinetics similar to those found in practice as well as to provide identical major corrosion chemistry and morphology of the corrosion product, silver sulfide as in practice, we propose it to provide a reasonably reproducible, more flexible test which is much easier to handle in the laboratory than flowing multi-component gas mixtures containing hydrogen sulfide.

    DOI

  • Promoting Practical Education in Corrosion Engineering Corrosion Engineering

    Jun’ichi Sakai

    Corrosion Engineering   58 ( 1 ) 21 - 28  2009年

  • 腐食工学実践教育の推進

    酒井潤一

    材料と環境   58 ( 1 ) 12 - 15  2009年

  • Effect of Microstructure on Torsional Fatigue Endurance of Martensitic Carbon Steel

    Shunsuke Toyoda, Yasuhide Ishiguro, Yoshikazu Kawabata, Kei Sakata, Akio Sato, Jun’ichi Sakai

    Journal of Solid Mechanics and Materials Engineering   3 ( 2 ) 114 - 125  2009年

    DOI CiNii

  • Characterization of patinas that formed on copper exposed in different environments for one month

    Masamitsu Watanabe, Takao Handa, Toshihiro Ichino, Nobuo Kuwaki, Jun'ichi Sakai

    Zairyo to Kankyo/ Corrosion Engineering   58 ( 4 ) 143 - 157  2009年

     概要を見る

    The early stage of copper patination, which occurs when copper is exposed to the atmosphere, was investigated by exposing copper plates for one month in urban, rural/coastal, hot springs, suburban, and volcanic areas. The exposures experiment started in summer or autumn. The patinas that formed during the one-month exposure were characterized using X-ray diffraction (XRD), X-ray fluorescence analysis, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and glow discharge optical emission spectroscopy (GDOES). The XRD patterns revealed that cuprite (Cu2O) and posnjakite (Cu 4SO4(OH)6-H2O) formed on the copper exposed in all areas, except the hot springs area. This is the first report of posnjakite forming on copper exposed for one month in benign environments. The XRD pattern revealed only cuprite on the copper exposed in the hot springs area although copper sulfide (CU2S) was found in the cathodic reduction curve. The sulfur 2p XPS spectra of copper exposed in the urban, rural/coastal, and volcanic areas mainly showed a sulfate component, whereas that of copper exposed in the hot springs area showed both sulfide and sulfate components. The former reflected the formation of posnjakite
    the latter reflected the oxidation of sulfide during exposure. In contrast, the chlorine 2p XPS spectra revealed that the chlorine existed as chloride. The SEM observation revealed that the surface morphology differed between exposure sites. GDOES depth profiling analysis revealed a difference in the distributions of sulfur and chlorine in the early stage of copper patination. The sulfur was located in the upper part of the patina, whereas the chlorine penetrated the patina. The oxidized sulfur species lowered the pH of the surface electrolyte, and this accelerated the dissolution of cuprite. They also formed posnjakite, which roughened the surface. The reduced sulfur species lowered the pH of the surface electrolyte and formed copper sulfide. The chlorine dissolved the cuprite forming copper chloride complex. This changed the chlorine depth profile.

    DOI CiNii

  • 銅の大気腐食における塩基性硫酸銅及び塩化物の生成

    渡辺正満, 松本守彦, 桑木伸夫, 酒井潤一

    材料と環境   58 ( 9 ) 328 - 334  2009年

    DOI CiNii

  • Estimating the Effects of Microscopic Stress Concentrations on the Fatigue Endurance of Thin-walled High Strength Steel

    Shunsuke Toyoda, Yoshikazu Kawabata, Kei Sakata, Akio Sato, Naotake Yoshihara, Jun'ichi Sakai

    ISIJ INTERNATIONAL   49 ( 11 ) 1806 - 1813  2009年

     概要を見る

    The effects of microscopic surface stress concentrations on the fatigue endurance of thin-walled high strength steel were systematically estimated by numerical analysis and plane-bending fatigue tests with Schenck-type specimens, using the commercially available static implicit method FEA software I-DEAS ver. 11 for the stress distribution calculations. The microscopic stress concentration factor alpha(j), from notch depth t=50 mu m and notch root radius rho=6 mu m microscopic surface ridges, monotonously increased with increases in the roughness ridge direction, theta, from 1 to 7 in the bending mode. A fitted curve was developed for deriving the calculated stress concentration, alpha(theta), from the superposition of the principal stresses. In the twisting mode, alpha(i) varied from about 4 to 7. The theta dependency of alpha(i) was smaller than that in bending mode. The empirical rule that the specimen collection direction has a lesser effect in twisting mode fatigue was supported by the ai value. It is reported that the fatigue notch factor beta increased linearly with increases in the macroscopic stress concentration factor alpha(a) of up to 3. On the other hand, beta slowly increased with increases in alpha(i) until it exceeded about 2. This marked difference might be due to differences between their respective stress gradients, which was well described by Nisitani and Endo by using a parameter rho. A plane-bending fatigue test was performed with an artificial surface micro-groove of theta=0, 90 degrees using 590 MPa class strength circumferentially flattened electric resistance welded tube. The theta=0 degrees micro-groove had little effect on the fatigue endurance in bending. On the other hand, the fatigue cracks of all the theta=90 degrees specimens initiated at the basilar part of the micro-groove without any nonpropagating cracks. The fatigue notch factor beta seems to be determined by only alpha(i) independent of rho in the microscopic stress concentration field.

    DOI CiNii

  • NH4HS環境における新防食設計手法の確立

    鳥羽和宏, 川野浩二, 酒井潤一

    材料と環境   58 ( 12 ) 441 - 447  2009年

    DOI CiNii

  • Promoting Practical Education in Corrosion Engineering Corrosion Engineering

    Jun’ichi Sakai

    Corrosion Engineering   58 ( 1 ) 21 - 28  2009年

  • Effect of Microstructure on Torsional Fatigue Endurance of Martensitic Carbon Steel

    Shunsuke Toyoda, Yasuhide Ishiguro, Yoshikazu Kawabata, Kei Sakata, Akio Sato, Jun’ichi Sakai

    Journal of Solid Mechanics and Materials Engineering   3 ( 2 ) 114 - 125  2009年

    DOI CiNii

  • Characterization of patinas that formed on copper exposed in different environments for one month

    Masamitsu Watanabe, Takao Handa, Toshihiro Ichino, Nobuo Kuwaki, Jun'ichi Sakai

    Zairyo to Kankyo/ Corrosion Engineering   58 ( 4 ) 143 - 157  2009年

     概要を見る

    The early stage of copper patination, which occurs when copper is exposed to the atmosphere, was investigated by exposing copper plates for one month in urban, rural/coastal, hot springs, suburban, and volcanic areas. The exposures experiment started in summer or autumn. The patinas that formed during the one-month exposure were characterized using X-ray diffraction (XRD), X-ray fluorescence analysis, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and glow discharge optical emission spectroscopy (GDOES). The XRD patterns revealed that cuprite (Cu2O) and posnjakite (Cu 4SO4(OH)6-H2O) formed on the copper exposed in all areas, except the hot springs area. This is the first report of posnjakite forming on copper exposed for one month in benign environments. The XRD pattern revealed only cuprite on the copper exposed in the hot springs area although copper sulfide (CU2S) was found in the cathodic reduction curve. The sulfur 2p XPS spectra of copper exposed in the urban, rural/coastal, and volcanic areas mainly showed a sulfate component, whereas that of copper exposed in the hot springs area showed both sulfide and sulfate components. The former reflected the formation of posnjakite
    the latter reflected the oxidation of sulfide during exposure. In contrast, the chlorine 2p XPS spectra revealed that the chlorine existed as chloride. The SEM observation revealed that the surface morphology differed between exposure sites. GDOES depth profiling analysis revealed a difference in the distributions of sulfur and chlorine in the early stage of copper patination. The sulfur was located in the upper part of the patina, whereas the chlorine penetrated the patina. The oxidized sulfur species lowered the pH of the surface electrolyte, and this accelerated the dissolution of cuprite. They also formed posnjakite, which roughened the surface. The reduced sulfur species lowered the pH of the surface electrolyte and formed copper sulfide. The chlorine dissolved the cuprite forming copper chloride complex. This changed the chlorine depth profile.

    DOI CiNii

  • Estimating the Effects of Microscopic Stress Concentrations on the Fatigue Endurance of Thin-walled High Strength Steel

    Shunsuke Toyoda, Yoshikazu Kawabata, Kei Sakata, Akio Sato, Naotake Yoshihara, Jun'ichi Sakai

    ISIJ INTERNATIONAL   49 ( 11 ) 1806 - 1813  2009年

     概要を見る

    The effects of microscopic surface stress concentrations on the fatigue endurance of thin-walled high strength steel were systematically estimated by numerical analysis and plane-bending fatigue tests with Schenck-type specimens, using the commercially available static implicit method FEA software I-DEAS ver. 11 for the stress distribution calculations. The microscopic stress concentration factor alpha(j), from notch depth t=50 mu m and notch root radius rho=6 mu m microscopic surface ridges, monotonously increased with increases in the roughness ridge direction, theta, from 1 to 7 in the bending mode. A fitted curve was developed for deriving the calculated stress concentration, alpha(theta), from the superposition of the principal stresses. In the twisting mode, alpha(i) varied from about 4 to 7. The theta dependency of alpha(i) was smaller than that in bending mode. The empirical rule that the specimen collection direction has a lesser effect in twisting mode fatigue was supported by the ai value. It is reported that the fatigue notch factor beta increased linearly with increases in the macroscopic stress concentration factor alpha(a) of up to 3. On the other hand, beta slowly increased with increases in alpha(i) until it exceeded about 2. This marked difference might be due to differences between their respective stress gradients, which was well described by Nisitani and Endo by using a parameter rho. A plane-bending fatigue test was performed with an artificial surface micro-groove of theta=0, 90 degrees using 590 MPa class strength circumferentially flattened electric resistance welded tube. The theta=0 degrees micro-groove had little effect on the fatigue endurance in bending. On the other hand, the fatigue cracks of all the theta=90 degrees specimens initiated at the basilar part of the micro-groove without any nonpropagating cracks. The fatigue notch factor beta seems to be determined by only alpha(i) independent of rho in the microscopic stress concentration field.

    DOI CiNii

  • Effects of acid type on corrosion and fracture behavior of Ni-Ti superelastic alloy under sustained tensile load in physiological saline solution containing hydrogen peroxide

    Tokunori Kanemura, Ken'ichi Yokoyama, Jun'ichi Sakai

    CORROSION SCIENCE   50 ( 10 ) 2785 - 2795  2008年10月

     概要を見る

    The effects of acid on the corrosion and fracture behavior of Ni-Ti superelastic alloy have been examined by sustained tensile-loading test in physiological saline solution containing hydrogen peroxide. For immersion test without applied stress at the same solution pH, although corrosion is enhanced markedly irrespective of the type of acid added, corrosion morphology depends on the type of acid added. The amount of dissolved nickel ions increases in the order of the solutions with lactic acid > phosphoric acid > acetic acid. The amount of dissolved nickel ions increases with decreasing solution pH. In contrast, under applied stress, the time to fracture in the solution with phosphoric acid becomes longer than that in the solution without acid, although the time to fracture does not increase in the solution with acetic acid or lactic acid. The time to fracture is only slightly affected by solution pH for the same type of acid added. Fractographic features change in the solution with phosphoric acid. The present study suggests that the fracture behavior of Ni-Ti superelastic alloy in physiological saline solution containing hydrogen peroxide depends on acid type rather than on solution pH; the fracture behavior is not necessarily consistent with the corrosion behavior in the case without applied stress. (c) 2008 Elsevier Ltd. All rights reserved.

    DOI CiNii

  • Effects of acid type on corrosion and fracture behavior of Ni-Ti superelastic alloy under sustained tensile load in physiological saline solution containing hydrogen peroxide

    Tokunori Kanemura, Ken'ichi Yokoyama, Jun'ichi Sakai

    CORROSION SCIENCE   50 ( 10 ) 2785 - 2795  2008年10月

     概要を見る

    The effects of acid on the corrosion and fracture behavior of Ni-Ti superelastic alloy have been examined by sustained tensile-loading test in physiological saline solution containing hydrogen peroxide. For immersion test without applied stress at the same solution pH, although corrosion is enhanced markedly irrespective of the type of acid added, corrosion morphology depends on the type of acid added. The amount of dissolved nickel ions increases in the order of the solutions with lactic acid > phosphoric acid > acetic acid. The amount of dissolved nickel ions increases with decreasing solution pH. In contrast, under applied stress, the time to fracture in the solution with phosphoric acid becomes longer than that in the solution without acid, although the time to fracture does not increase in the solution with acetic acid or lactic acid. The time to fracture is only slightly affected by solution pH for the same type of acid added. Fractographic features change in the solution with phosphoric acid. The present study suggests that the fracture behavior of Ni-Ti superelastic alloy in physiological saline solution containing hydrogen peroxide depends on acid type rather than on solution pH; the fracture behavior is not necessarily consistent with the corrosion behavior in the case without applied stress. (c) 2008 Elsevier Ltd. All rights reserved.

    DOI CiNii

  • Corrosion behavior of silver by outgassed sulfur species from vulcanized rubber (1) - Examination of corrosion factors -

    Masataka Omoda, Oshika Taizo, Jun'ichi Sakai, Yuichi Ishikawa

    Zairyo to Kankyo/ Corrosion Engineering   57 ( 8 ) 358 - 365  2008年08月

     概要を見る

    Corrosion factors which influence the corrosion of silver by outgassed sulfur species from vulcanized rubber have been investigated by means of quartz crystal microbalance technique (QCM) and cathodic reduction technique. Silver sulfide was the only corrosion product identified during all the tests. Corrosion progressed linearly with time and the corrosion rate did not depend on humidity, but depended markedly on the temperature and the volume of rubber contained, In addition, it is clarified that the corrosion rate varies according to the types of rubber and even among various chroloprene products. Thus it is considered that the corrosion behavior of silver with vulcanized rubber is determined by the concentration of the sulfur gas species outgassed from the rubber. The free sulfur in the rubber is assumed to be the source. It may be suggested that the outgassing of sulfur gas is determined by diffusion of sulfur molecule Sx (x = 2-8) in the rubber and this diffusion process determined the corrosion rate of silver.

    DOI

  • ゴムからのアウトガスによる銀の微小腐食挙動解析(第1報)-腐食要因の解明-

    面田真孝, 大鹿泰三, 酒井潤一, 石川雄一

    材料と環境   57 ( 8 ) 358 - 365  2008年08月

    DOI CiNii

  • Corrosion behavior of silver by outgassed sulfur species from vulcanized rubber (1) - Examination of corrosion factors -

    Masataka Omoda, Oshika Taizo, Jun'ichi Sakai, Yuichi Ishikawa

    Zairyo to Kankyo/ Corrosion Engineering   57 ( 8 ) 358 - 365  2008年08月

     概要を見る

    Corrosion factors which influence the corrosion of silver by outgassed sulfur species from vulcanized rubber have been investigated by means of quartz crystal microbalance technique (QCM) and cathodic reduction technique. Silver sulfide was the only corrosion product identified during all the tests. Corrosion progressed linearly with time and the corrosion rate did not depend on humidity, but depended markedly on the temperature and the volume of rubber contained, In addition, it is clarified that the corrosion rate varies according to the types of rubber and even among various chroloprene products. Thus it is considered that the corrosion behavior of silver with vulcanized rubber is determined by the concentration of the sulfur gas species outgassed from the rubber. The free sulfur in the rubber is assumed to be the source. It may be suggested that the outgassing of sulfur gas is determined by diffusion of sulfur molecule Sx (x = 2-8) in the rubber and this diffusion process determined the corrosion rate of silver.

    DOI

  • Susceptibility to hydrogen absorption and hydrogen thermal desorption of titanium alloys immersed in neutral fluoride solution under applied potential

    Ken'ichi Yokoyama, Katsutoshi Takashima, Jun'ichi Sakai

    MATERIALS TRANSACTIONS   49 ( 7 ) 1661 - 1666  2008年07月

     概要を見る

    The susceptibility to hydrogen absorption and hydrogen thermal desorption of titanium alloys has been investigated in a neutral 2.0% NaF solution at 37 degrees C under various applied cathodic potentials. Ti-0.2Pd, Ti-6Al-4V and Ti-11.3Mo-6.6Zr-4.3Sn alloys absorb hydrogen under less noble potentials than -1.5 V, -1.9V and -1.4V versus it saturated calomel electrode, respectively. The amounts of absorbed hydrogen of Ti-0.2Pd, Ti-6Al-4V and Ti-11.3Mo-6.6Zr-4.3Sn alloys under an applied potential of -2.0 V for 24 h are approximately 1200, 100 and 1100 mass ppm, respectively. Upon immersion in the 2.0% NaF solution under an applied potential, the hydrogen thermal desorption behavior of Ti-0.2Pd alloy differs from those immersed in acid fluoride Solutions, whereas the hydrogen thermal desorption behaviors of Ti-6Al-4V and Ti-11.3Mo-6.6Zr-4.3Sn alloys are similar to those immersed in acid fluoride solutions. The present results indicate that in a neutral fluoride solution. the effects of an applied potential on the hydrogen absorption and desorption behaviors of Ti-6Al-4V alloy are considerably smaller than those of commercial pure titanium reported previously, Ti-0.2Pd and Ti-11.3Mo-6.6Zr-4.3Sn alloys.

    DOI CiNii

  • Effects of potential, temperature and pH on hydrogen absorption and thermal desorption behaviors of Ni-Ti superelastic alloy in 0.9% NaCl solution

    Miho Tomita, Ken'ichi Yokoyama, Jun'ichi Sakai

    CORROSION SCIENCE   50 ( 7 ) 2061 - 2069  2008年07月

     概要を見る

    The effects of electrochemical potential, solution temperature and pH on the hydrogen absorption and desorption behaviors of Ni-Ti superelastic alloy immersed in 0.9% NaCl solution for 2 h have been investigated systematically by hydrogen thermal desorption analysis. For hydrogen cathodic charging under constant applied potential, upon increasing solution temperature, the critical potential for the hydrogen absorption very slightly shifts to a noble direction. As solution pH decreases, the critical potential for the hydrogen absorption shifts markedly to a noble direction and approaches to the corrosion potential; the critical current density for the hydrogen absorption slightly decreases. At a less noble potential than the critical potential for the hydrogen absorption, the amount of absorbed hydrogen increases markedly with decreasing applied potential. For hydrogen cathodic charging under constant current density, the amount of absorbed hydrogen increases with increasing Solution temperature and decreasing solution pH. The basic hydrogen desorption behavior only slightly depends on solution temperature or pH. Nevertheless, hydrogen desorption at low temperatures for specimens subjected to cathodic charging under constant Current density is observed distinctly as compared with that under constant applied potential. (C) 2008 Elsevier Ltd. All rights reserved.

    DOI CiNii

  • Susceptibility to hydrogen absorption and hydrogen thermal desorption of titanium alloys immersed in neutral fluoride solution under applied potential

    Ken'ichi Yokoyama, Katsutoshi Takashima, Jun'ichi Sakai

    Materials Transactions   49 ( 7 ) 1661 - 1666  2008年07月

     概要を見る

    The susceptibility to hydrogen absorption and hydrogen thermal desorption of titanium alloys has been investigated in a neutral 2.0% NaF solution at 37°C under various applied cathodic potentials. Ti-0.2Pd, Ti-6A1-4V and Ti-11.3Mo-6.6Zr-4.3Sn alloys absorb hydrogen under less noble potentials than -1.5 V, -1.9 V and -1.4 V versus a saturated calomel electrode, respectively. The amounts of absorbed hydrogen of Ti-0.2Pd, Ti-6A14V and Ti-11.3Mo-6.6Zr-4.3Sn alloys under an applied potential of -2.0V for 24h are approximately 1200, 100 and 1100 mass ppm, respectively. Upon immersion in the 2.0% NaF solution under an applied potential, the hydrogen thermal desorption behavior of Ti-0.2Pd alloy differs from those immersed in acid fluoride solutions, whereas the hydrogen thermal desorption behaviors of Ti-6A1-4V and Ti-11.3Mo-6.6Zr-4.3Sn alloys are similar to those immersed in acid fluoride solutions. The present results indicate that in a neutral fluoride solution, the effects of an applied potential on the hydrogen absorption and desorption behaviors of Ti-6A1-4V alloy are considerably smaller than those of commercial pure titanium reported previously, Ti-0.2Pd and Ti-11.3Mo-6.6Zr-4.3Sn alloys. © 2008 The Japan Institute of Metals.

    DOI CiNii

  • Effects of potential, temperature and pH on hydrogen absorption and thermal desorption behaviors of Ni-Ti superelastic alloy in 0.9% NaCl solution

    Miho Tomita, Ken'ichi Yokoyama, Jun'ichi Sakai

    CORROSION SCIENCE   50 ( 7 ) 2061 - 2069  2008年07月

     概要を見る

    The effects of electrochemical potential, solution temperature and pH on the hydrogen absorption and desorption behaviors of Ni-Ti superelastic alloy immersed in 0.9% NaCl solution for 2 h have been investigated systematically by hydrogen thermal desorption analysis. For hydrogen cathodic charging under constant applied potential, upon increasing solution temperature, the critical potential for the hydrogen absorption very slightly shifts to a noble direction. As solution pH decreases, the critical potential for the hydrogen absorption shifts markedly to a noble direction and approaches to the corrosion potential; the critical current density for the hydrogen absorption slightly decreases. At a less noble potential than the critical potential for the hydrogen absorption, the amount of absorbed hydrogen increases markedly with decreasing applied potential. For hydrogen cathodic charging under constant current density, the amount of absorbed hydrogen increases with increasing Solution temperature and decreasing solution pH. The basic hydrogen desorption behavior only slightly depends on solution temperature or pH. Nevertheless, hydrogen desorption at low temperatures for specimens subjected to cathodic charging under constant Current density is observed distinctly as compared with that under constant applied potential. (C) 2008 Elsevier Ltd. All rights reserved.

    DOI CiNii

  • Technical module of erosion-corrosion

    Jun'ichi Sakai, Kei Ito, Shigemitsu Kihara

    Zairyo to Kankyo/ Corrosion Engineering   57 ( 5 ) 211 - 217  2008年05月

     概要を見る

    RBM (Risk Based Maintenance) is a promising method of maintenance for aged plants. The Risk is defined as the product of likelihood and consequence of failure. The likelihood of failure is evaluated by prediction of residual life or sensitivity of failure and degradation. Technical module is a tool to evaluate the likelihood of failure. In this paper development of technical module for erosion-corrosion which is one of the most likely mechanism of failure in aged plants is introduced.

    DOI

  • エロージョン・コロージョンのテクニカルモジュール

    酒井潤一, 伊藤慶, 木原重光

    Zairyo-to-Kankyo   57 ( 5 ) 211 - 217  2008年05月

    DOI CiNii

  • Technical module of erosion-corrosion

    Jun'ichi Sakai, Kei Ito, Shigemitsu Kihara

    Zairyo to Kankyo/ Corrosion Engineering   57 ( 5 ) 211 - 217  2008年05月

     概要を見る

    RBM (Risk Based Maintenance) is a promising method of maintenance for aged plants. The Risk is defined as the product of likelihood and consequence of failure. The likelihood of failure is evaluated by prediction of residual life or sensitivity of failure and degradation. Technical module is a tool to evaluate the likelihood of failure. In this paper development of technical module for erosion-corrosion which is one of the most likely mechanism of failure in aged plants is introduced.

    DOI

  • Hydrogen thermal desorption behavior of Ni-Ti superelastic alloy subjected to tensile deformation after hydrogen charging

    Miho Tomita, Kenichi Yokoyama, Kenzo Asaoka, Junichi Sakai

    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING   476 ( 1-2 ) 308 - 315  2008年03月

     概要を見る

    The hydrogen thermal desorption behavior of Ni-Ti superelastic alloy subjected to tensile deformation after hydrogen charging has been investioated. Cathodic hydrogen charging is performed with a current density of 10A/m(2) in a 0.9% NaCl aqueous solution for 2h at room temperature (25 degrees C). In this case, hydrogen desorption is observed from room temperature to 400 degrees C. For the specimen immediately after hydrogen charging. upon tensile loading covering the stress plateau region caused by stress-induced martensite transformation followed by unloading, hydrogen that desorbs at low temperatures (approximately 150 degrees C) is observed markedly. In contrast, for the specimen aged for 240h at room temperature in air after hydrogen charging, most hydrogen that desorbs at low temperatures shifts to a higher-temperature region and diffuses toward the center of the specimen, although the charged hydrogen does not diffuse out. Variation in hydrogen desorption behavior is rarely observed, even upon tensile loading in the plastic deformation region of the martensite phase followed by unloading. The present results suggest that dynamic processes such as stress-induced martensite and reverse transformations affect hydrogen desorption behavior at low temperatures of hydrogen-charged Ni-Ti superelastic alloy. (c) 2007 Elsevier B.V. All rights reserved.

    DOI CiNii

  • Hydrogen thermal desorption behavior of Ni-Ti superelastic alloy subjected to tensile deformation after hydrogen charging

    Miho Tomita, Kenichi Yokoyama, Kenzo Asaoka, Junichi Sakai

    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING   476 ( 1-2 ) 308 - 315  2008年03月

     概要を見る

    The hydrogen thermal desorption behavior of Ni-Ti superelastic alloy subjected to tensile deformation after hydrogen charging has been investioated. Cathodic hydrogen charging is performed with a current density of 10A/m(2) in a 0.9% NaCl aqueous solution for 2h at room temperature (25 degrees C). In this case, hydrogen desorption is observed from room temperature to 400 degrees C. For the specimen immediately after hydrogen charging. upon tensile loading covering the stress plateau region caused by stress-induced martensite transformation followed by unloading, hydrogen that desorbs at low temperatures (approximately 150 degrees C) is observed markedly. In contrast, for the specimen aged for 240h at room temperature in air after hydrogen charging, most hydrogen that desorbs at low temperatures shifts to a higher-temperature region and diffuses toward the center of the specimen, although the charged hydrogen does not diffuse out. Variation in hydrogen desorption behavior is rarely observed, even upon tensile loading in the plastic deformation region of the martensite phase followed by unloading. The present results suggest that dynamic processes such as stress-induced martensite and reverse transformations affect hydrogen desorption behavior at low temperatures of hydrogen-charged Ni-Ti superelastic alloy. (c) 2007 Elsevier B.V. All rights reserved.

    DOI CiNii

  • Activities of 180th Committee for Risk Based Plant Management

    Sakai,J

    Korea-Japan Special Seminar for RBI/RBM, Seoul, Korea(CSSK)     46  2008年

  • 上位r個のデータを用いる極値統計による土壌埋設鋼管の最大腐食深さ推定および最大孔食速度の予測

    小向茂, 酒井潤一

    統計数理研究所共同研究リポート 212、極値理論の工学への応用(5)     118 - 134  2008年

  • Effect of Cu addition on delayed fracture resistance of low carbon steel for 1470 MPa grade electric resistance welded tube

    Shunsuke Toyoda, Yasuhide Ishiguro, Yoshikazu Kawabata, Kei Sakata, Akio Sato, Jun'ichi Sakai

    ISIJ INTERNATIONAL   48 ( 5 ) 640 - 648  2008年

     概要を見る

    The effect of chemical composition on delayed fracture resistance, taking into consideration the application of a 1470 MPa grade thin-wall as-rolled electric resistance welded (ERW) tube to automotive structural parts, was investigated. Chemical composition of the base steel alloy was 0.18%C-0.4%Si-1.8%Mn-0.015% Nb-0.01%P-0.001%S. Cu, Ni, Cr, B and Mo were individually added to the base steel. A 4-point bending test in 1 N-hydrocrolic acid was conducted for quench and tempered specimens. Cu added steel showed the best delayed fracture resistance. After the immersion, a metallic Cu layer was formed on the steel surface. Based on the results of the 4-point bending test, several kinds of 1470 MPa grade ERW steel tubes were prepared and evaluated for their delayed fracture resistance. Cu added steel tubes showed excellent delayed fracture resistance in a cyclic corrosion condition with salt water spray, as well as in hydrocrolic acid. Cu accumulation on the rust-steel interface was observed by electron probe microanalysis (EPMA). An atmospheric corrosion test lasting 12 years was also conducted. Delayed fracture resistance as evaluated by (a) an immersion test in hydrochloric acid, (b) a cyclic corrosion test with salt water spray, and (c) an atmospheric corrosion test, showed good correlation with each other. Based on the results above, two models are proposed for the mechanism of delayed fracture suppression by Cu addition: (1) Cu suppressed cathodic reaction and hydrogen entry at sulfide inclusion, and (2) Cu suppressed hydrogen entry by stabilization of sulfuric-ions as an insoluble compound.

    DOI CiNii

  • Activities of 180th Committee for Risk Based Plant Management

    Sakai,J

    Korea-Japan Special Seminar for RBI/RBM, Seoul, Korea(CSSK)     46  2008年

  • Effect of Cu addition on delayed fracture resistance of low carbon steel for 1470 MPa grade electric resistance welded tube

    Shunsuke Toyoda, Yasuhide Ishiguro, Yoshikazu Kawabata, Kei Sakata, Akio Sato, Jun'ichi Sakai

    ISIJ INTERNATIONAL   48 ( 5 ) 640 - 648  2008年

     概要を見る

    The effect of chemical composition on delayed fracture resistance, taking into consideration the application of a 1470 MPa grade thin-wall as-rolled electric resistance welded (ERW) tube to automotive structural parts, was investigated. Chemical composition of the base steel alloy was 0.18%C-0.4%Si-1.8%Mn-0.015% Nb-0.01%P-0.001%S. Cu, Ni, Cr, B and Mo were individually added to the base steel. A 4-point bending test in 1 N-hydrocrolic acid was conducted for quench and tempered specimens. Cu added steel showed the best delayed fracture resistance. After the immersion, a metallic Cu layer was formed on the steel surface. Based on the results of the 4-point bending test, several kinds of 1470 MPa grade ERW steel tubes were prepared and evaluated for their delayed fracture resistance. Cu added steel tubes showed excellent delayed fracture resistance in a cyclic corrosion condition with salt water spray, as well as in hydrocrolic acid. Cu accumulation on the rust-steel interface was observed by electron probe microanalysis (EPMA). An atmospheric corrosion test lasting 12 years was also conducted. Delayed fracture resistance as evaluated by (a) an immersion test in hydrochloric acid, (b) a cyclic corrosion test with salt water spray, and (c) an atmospheric corrosion test, showed good correlation with each other. Based on the results above, two models are proposed for the mechanism of delayed fracture suppression by Cu addition: (1) Cu suppressed cathodic reaction and hydrogen entry at sulfide inclusion, and (2) Cu suppressed hydrogen entry by stabilization of sulfuric-ions as an insoluble compound.

    DOI CiNii

  • カソード電流に及ぼす海洋微生物とバイオフィルムの影響

    鷲頭直樹, 篠原正, 元田慎一, 酒井潤一

    Zairyo-to-Kankyo   56 ( 10 ) 472 - 479  2007年10月

    DOI CiNii

  • Hydrogen embrittlement of Ni-Ti superelastic alloy aged at room temperature after hydrogen charging

    Ken'ichi Yokoyama, Toshio Ogawa, Katsutoshi Takashima, Kenzo Asaoka, Jun'ichi Sakai

    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING   466 ( 1-2 ) 106 - 113  2007年09月

     概要を見る

    The hydrogen embrittlement of a Ni-Ti superelastic alloy aged at room temperature (25 degrees C) in air after hydrogen charging is examined using tensile test and hydrogen thermal desorption analysis (TDA). Cathodic hydrogen charging is performed at a current density of 10 A/m(2) for 6h in 0.9% NaCl aqueous solution at room temperature. For the specimen immediately after hydrogen charging, tensile fracture occurs near the critical stress for martensite transformation without stress-induced martensite transformation. Hydrogen thermal desorption is observed from room temperature to 400 degrees C. Charged hydrogen exists within approximately 50 mu m from the surface of the specimen. Hydride formation is confirmed by X-ray diffraction (XRD) analysis. In contrast, the specimens aged at room temperature after hydrogen charging fracture during or after stress-induced martensite transformation. The amount of hydrogen desorbed at low temperatures (room temperature to 200 degrees C) decreases. Charged hydrogen diffuses toward the center part of the specimen, and some charged hydrogen diffuses out in the early stage of aging at room temperature. In addition, no XRD peaks corresponding to hydrides are detected. The present results suggest that aging at room temperature in air after hydrogen charging changes the distribution and state of hydrogen in Ni-Ti superelastic alloy, thereby leading to a partial recovery of the tensile properties of the alloy. (c) 2007 Elsevier B.V. All rights reserved.

    DOI CiNii

  • Fracture of Ni-Ti superelastic alloy under sustained tensile load in physiological saline solution containing hydrogen peroxide

    Ken'ichi Yokoyama, Toshio Ogawa, Atsushi Fujita, Kenzo Asaoka, Jun'ichi Sakai

    JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A   82A ( 3 ) 558 - 567  2007年09月

     概要を見る

    The fracture of Ni-Ti superelastic alloy has been investigated by a sustained tensile-loading test in physiological saline solution containing hydrogen peroxide (0.15M NaCI + 0.3M H2O2). The fracture always occurs when the applied stress exceeds the critical stress for martensite transformation. In contrast, under a low applied stress, the fracture does not always occur within 1000 h. The fracture is probably mainly caused by localized corrosion associated with the preferential dissolution of nickel ions. In 0.3M H2O2 solution without NaCl, the fracture does not occur even under a high applied stress. The results of the present study imply that one reason for the fracture of the Ni-Ti super-elastic alloy in vivo is localized corrosion due to the synergistic effects of hydrogen peroxide and sodium chloride under applied stress. (C) 2007 Wiley Periodicals, Inc.

    DOI

  • Hydrogen embrittlement of Ni-Ti superelastic alloy aged at room temperature after hydrogen charging

    Ken'ichi Yokoyama, Toshio Ogawa, Katsutoshi Takashima, Kenzo Asaoka, Jun'ichi Sakai

    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING   466 ( 1-2 ) 106 - 113  2007年09月

     概要を見る

    The hydrogen embrittlement of a Ni-Ti superelastic alloy aged at room temperature (25 degrees C) in air after hydrogen charging is examined using tensile test and hydrogen thermal desorption analysis (TDA). Cathodic hydrogen charging is performed at a current density of 10 A/m(2) for 6h in 0.9% NaCl aqueous solution at room temperature. For the specimen immediately after hydrogen charging, tensile fracture occurs near the critical stress for martensite transformation without stress-induced martensite transformation. Hydrogen thermal desorption is observed from room temperature to 400 degrees C. Charged hydrogen exists within approximately 50 mu m from the surface of the specimen. Hydride formation is confirmed by X-ray diffraction (XRD) analysis. In contrast, the specimens aged at room temperature after hydrogen charging fracture during or after stress-induced martensite transformation. The amount of hydrogen desorbed at low temperatures (room temperature to 200 degrees C) decreases. Charged hydrogen diffuses toward the center part of the specimen, and some charged hydrogen diffuses out in the early stage of aging at room temperature. In addition, no XRD peaks corresponding to hydrides are detected. The present results suggest that aging at room temperature in air after hydrogen charging changes the distribution and state of hydrogen in Ni-Ti superelastic alloy, thereby leading to a partial recovery of the tensile properties of the alloy. (c) 2007 Elsevier B.V. All rights reserved.

    DOI CiNii

  • Fracture of Ni-Ti superelastic alloy under sustained tensile load in physiological saline solution containing hydrogen peroxide

    Ken'ichi Yokoyama, Toshio Ogawa, Atsushi Fujita, Kenzo Asaoka, Jun'ichi Sakai

    Journal of Biomedical Materials Research - Part A   82 ( 3 ) 558 - 567  2007年09月

     概要を見る

    The fracture of Ni-Ti superelastic alloy has been investigated by a sustained tensile-loading test in physiological saline solution containing hydrogen peroxide (0.15M NaCl + 0.3M H2O2). The fracture always occurs when the applied stress exceeds the critical stress for martensite transformation. In contrast, under a low applied stress, the fracture does not always occur within 1000 h. The fracture is probably mainly caused by localized corrosion associated with the preferential dissolution of nickel ions. In 0.3M H2O2 solution without NaCl, the fracture does not occur even under a high applied stress. The results of the present study imply that one reason for the fracture of the Ni-Ti superelastic alloy in vivo is localized corrosion due to the synergistic effects of hydrogen peroxide and sodium chloride under applied stress. © 2007 Wiley Periodicals, Inc.

    DOI PubMed

  • Hydrogen absorption and thermal desorption behaviors of Ni-Ti superelastic alloy subjected to sustained tensile-straining test with hydrogen charging

    Ken'ichi Yokoyama, Miho Tomita, Kenzo Asaoka, Jun'ichi Sakai

    SCRIPTA MATERIALIA   57 ( 5 ) 393 - 396  2007年09月

     概要を見る

    The hydrogen absorption and thermal desorption behaviors of Ni-Ti superelastic alloy subjected to a sustained tensile-straining test with cathodic hydrogen charging have been investigated. Under an applied strain in the presence of the martensite phase, hydrogen absorption is markedly enhanced and the amount of desorbed hydrogen, particularly at low temperatures, is increased. In addition, the hydrogen diffusion distance in the specimen increases. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

    DOI CiNii

  • Effects of potential on hydrogen absorption and desorption behaviors of titanium in neutral fluoride solutions

    Katsutoshi Takashima, Ken'ichi Yokoyama, Kenzo Asaoka, Jun'ichi Sakai

    JOURNAL OF ALLOYS AND COMPOUNDS   431 ( 1-2 ) 203 - 207  2007年04月

     概要を見る

    The effects of potential on the hydrogen absorption and desorption of commercial pure titanium immersed in neutral 2.0% and 0.2% NaF solutions for 24 h have been investigated by hydrogen thermal desorption analysis. Hydrogen absorption occurs in both solutions under less noble potentials than -1.2 V versus a saturated calomel electrode. The amount of absorbed hydrogen increases with decreasing applied potential. Under the same applied potential, the amount of hydrogen absorbed in the 2.0% NaF solution is larger than that in the 0.2% NaF solution. Hydrogen thermal desorption is observed in the temperature range from 250-300 to 700 degrees C. For the 2.0% NaF solution, compared with the 0.2% NaF solution, the amount of hydrogen desorbed in the high temperature range is large. The hydrogen desorption behavior for neutral NaF solutions under the applied potential is not necessarily consistent with that for acidulated phosphate fluoride solutions without the applied potential reported previously. (c) 2006 Elsevier B.V. All rights reserved.

    DOI CiNii

  • Effects of potential on hydrogen absorption and desorption behaviors of titanium in neutral fluoride solutions

    Katsutoshi Takashima, Ken'ichi Yokoyama, Kenzo Asaoka, Jun'ichi Sakai

    JOURNAL OF ALLOYS AND COMPOUNDS   431 ( 1-2 ) 203 - 207  2007年04月

     概要を見る

    The effects of potential on the hydrogen absorption and desorption of commercial pure titanium immersed in neutral 2.0% and 0.2% NaF solutions for 24 h have been investigated by hydrogen thermal desorption analysis. Hydrogen absorption occurs in both solutions under less noble potentials than -1.2 V versus a saturated calomel electrode. The amount of absorbed hydrogen increases with decreasing applied potential. Under the same applied potential, the amount of hydrogen absorbed in the 2.0% NaF solution is larger than that in the 0.2% NaF solution. Hydrogen thermal desorption is observed in the temperature range from 250-300 to 700 degrees C. For the 2.0% NaF solution, compared with the 0.2% NaF solution, the amount of hydrogen desorbed in the high temperature range is large. The hydrogen desorption behavior for neutral NaF solutions under the applied potential is not necessarily consistent with that for acidulated phosphate fluoride solutions without the applied potential reported previously. (c) 2006 Elsevier B.V. All rights reserved.

    DOI CiNii

  • Hydrogen absorption and thermal desorption behaviors of Ni-Ti superelastic alloy subjected to sustained tensile-straining test with hydrogen absorption

    Ken’ichi Yokoyama, Miho Tomita, Kenzo Asaoka, Jun’ichi Sakai

    Scripta Materialia   57 ( 5 ) 393 - 396  2007年

    DOI CiNii

  • Hydrogen absorption of titanium and nickel-titanium alloys during long-term immersion in neutral fluoride solution

    Ken'ichi Yokoyama, Toshio Ogawa, Kenzo Asaoka, JuN'Ichi Sakai

    Journal of Biomedical Materials Research - Part B Applied Biomaterials   78 ( 1 ) 204 - 210  2006年07月

     概要を見る

    Hydrogen absorption of biomedical titanium and Ni-Ti alloys in a neutral fluoride (2.0% NaF) solution for up to 10,000 h at 37°C has been evaluated by means of hydrogen thermal desorption analysis. For α titanium (commercial pure titanium), the amount of absorbed hydrogen was, at most, 10-30 mass ppm, and the corrosion product and hydride formation were revealed on the surface of the specimen by X-ray diffraction analysis. Ni-Ti superelastic alloy absorbed ∼150 mass ppm of hydrogen, which was probably sufficient to result in the pronounced degradation of the mechanical properties, although corrosion was hardly observed. In contrast, hydrogen absorption of α-β titanium (Ti-6Al-4V) and β titanium (Ti-11.3Mo-6.6Zr-4.3Sn) alloys was negligible, although general corrosion was observed. The results of the present study indicate that the susceptibility of titanium and Ni-Ti alloys to hydrogen absorption in the neutral fluoride solution is different from that in the acidic fluoride solution reported previously. © 2005 Wiley Periodicals, Inc.

    DOI PubMed

  • Hydrogen absorption of titanium and nickel-titanium alloys during long-term immersion in neutral fluoride solution

    K Yokoyama, T Ogawa, K Asaoka, J Sakai

    JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART B-APPLIED BIOMATERIALS   78B ( 1 ) 204 - 210  2006年07月

     概要を見る

    Hydrogen absorption of biomedical titanium and Ni-Ti alloys in a neutral fluoride (2.0% NaF) solution for up to 10,000 h at 37 degrees C has been evaluated by means of hydrogen thermal desorption analysis. For a titanium (commercial pure titanium), the amount of absorbed hydrogen was, at most, 10-30 mass ppm, and the corrosion product and hydride formation were revealed on the surface of the specimen by X-ray diffraction analysis. Ni-Ti superelastic alloy absorbed similar to 150 mass ppm of hydrogen, which was probably sufficient to result in the pronounced degradation of the mechanical properties, although corrosion was hardly observed. In contrast, hydrogen absorption of alpha-beta titanium (Ti-6Al-4V) and beta titanium (Ti-11.3Mo-6.6Zr-4.3Sn) alloys was negligible, although general corrosion was observed. The results of the present study indicate that the susceptibility of titanium and Ni-Ti alloys to hydrogen absorption in the neutral fluoride solution is different from that in the acidic fluoride solution reported previously. (c) 2005 Wiley Periodicals, Inc.

    DOI

  • Effects of moisture and dissolved oxygen in methanol and ethanol solutions containing hydrochloric acid on hydrogen absorption and desorption behaviors of Ni-Ti superelastic alloy

    T Ogawa, K Yokoyama, K Asaoka, J Sakai

    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING   422 ( 1-2 ) 218 - 226  2006年04月

     概要を見る

    The effects of moisture (H2O concentration) and dissolved oxygen in methanol and ethanol solutions containing 0.1% hydrochloric acid (HCl) on hydrogen absorption and desorption behaviors of the Ni-Ti superelastic alloy have been examined by hydrogen thermal desorption analysis. In the methanol solution, the amount of absorbed hydrogen decreases with increasing H2O concentration. For 5% H2O, the thermal desorption peak of hydrogen gradually shifts from 400 to 250 degrees C with immersion time. When the H2O concentration is higher than 10%, the hydrogen absorption is not observed. Under a deaerated condition, significant dissolution of the specimen due to corrosion is observed; however, the increment in the amount of desorbed hydrogen is not observed. In the ethanol solution, the critical H2O concentration for hydrogen absorption is approximately 0.8%. For 2% H2O, the hydrogen absorption is not exhibited, although slight corrosion is observed. The amount of absorbed hydrogen under the deaerated condition is ten times more than that under the aerated condition. The dissolved oxygen varies the hydrogen desorption behavior. (c) 2006 Elsevier B.V. All rights reserved.

    DOI

  • Effects of moisture and dissolved oxygen in methanol and ethanol solutions containing hydrochloric acid on hydrogen absorption and desorption behaviors of Ni-Ti superelastic alloy

    T Ogawa, K Yokoyama, K Asaoka, J Sakai

    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING   422 ( 1-2 ) 218 - 226  2006年04月

     概要を見る

    The effects of moisture (H2O concentration) and dissolved oxygen in methanol and ethanol solutions containing 0.1% hydrochloric acid (HCl) on hydrogen absorption and desorption behaviors of the Ni-Ti superelastic alloy have been examined by hydrogen thermal desorption analysis. In the methanol solution, the amount of absorbed hydrogen decreases with increasing H2O concentration. For 5% H2O, the thermal desorption peak of hydrogen gradually shifts from 400 to 250 degrees C with immersion time. When the H2O concentration is higher than 10%, the hydrogen absorption is not observed. Under a deaerated condition, significant dissolution of the specimen due to corrosion is observed; however, the increment in the amount of desorbed hydrogen is not observed. In the ethanol solution, the critical H2O concentration for hydrogen absorption is approximately 0.8%. For 2% H2O, the hydrogen absorption is not exhibited, although slight corrosion is observed. The amount of absorbed hydrogen under the deaerated condition is ten times more than that under the aerated condition. The dissolved oxygen varies the hydrogen desorption behavior. (c) 2006 Elsevier B.V. All rights reserved.

    DOI

  • Fracture of sustained tensile-loaded Ti-0.2% Pd alloy in acid and neutral fluoride solutions

    K Yokoyama, T Ogawa, K Asaoka, J Sakai

    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING   419 ( 1-2 ) 122 - 130  2006年03月

     概要を見る

    The fracturing of Ti-0.2 mass% Pd (Ti-0.2Pd) alloy in acid and neutral fluoride solutions has been investigated by a sustained tensile-loading test. In 2.0% acidulated phosphate fluoride (APF) and neutral 2.0% NaF solution, the time to fracture of the Ti-0.2Pd alloy is shorter than that of commercial pure titanium for the same applied stress. In 2.0 and 0.2% APF solutions, fractures are characterized by a cup-cone mode irrespective of applied stress. In 2.0 and 0.2% NaF solutions, transitions from cup-cone to shear modes of the fractures are observed with decreasing applied stress. The results of the present study suggest that the susceptibility to fracturing of the Ti-0.2Pd alloy is higher than that of commercial pure titanium. (c) 2005 Elsevier B.V. All rights reserved.

    DOI CiNii

  • Fracture of sustained tensile-loaded Ti-0.2% Pd alloy in acid and neutral fluoride solutions

    K Yokoyama, T Ogawa, K Asaoka, J Sakai

    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING   419 ( 1-2 ) 122 - 130  2006年03月

     概要を見る

    The fracturing of Ti-0.2 mass% Pd (Ti-0.2Pd) alloy in acid and neutral fluoride solutions has been investigated by a sustained tensile-loading test. In 2.0% acidulated phosphate fluoride (APF) and neutral 2.0% NaF solution, the time to fracture of the Ti-0.2Pd alloy is shorter than that of commercial pure titanium for the same applied stress. In 2.0 and 0.2% APF solutions, fractures are characterized by a cup-cone mode irrespective of applied stress. In 2.0 and 0.2% NaF solutions, transitions from cup-cone to shear modes of the fractures are observed with decreasing applied stress. The results of the present study suggest that the susceptibility to fracturing of the Ti-0.2Pd alloy is higher than that of commercial pure titanium. (c) 2005 Elsevier B.V. All rights reserved.

    DOI CiNii

  • Evaluation of hydrogen absorption properties of Ti-0.2 mass% Pd alloy in fluoride solutions

    K Yokoyama, T Ogawa, K Asaoka, J Sakai

    JOURNAL OF ALLOYS AND COMPOUNDS   400 ( 1-2 ) 227 - 233  2005年09月

     概要を見る

    The hydrogen absorption properties of Ti-0.2 mass% pd (Ti-0.2Pd) alloy in 2.0% and 0.2% acidulated phosphate fluoride (APF) and neutral 2.0% NaF solutions (25 degrees C) has been evaluated by hydrogen thermal desorption analysis. During the early stage of immersion (120 h) in the 2.0% APF solution, the amount of absorbed hydrogen was lower than 500 mass ppm. A thermal desorption of hydrogen primary appearing with a peak at 500-600 degrees C and a broad desorption ranging from 100 to 400 degrees C were observed. In the 0.2% APF solution, the amount of absorbed hydrogen saturated at 100-200 mass ppm; the thermal desorption of hydrogen appeared with a single peak at 550 degrees C. In the 2.0% NaF solution, hydrogen absorption was negligible even after 1000 It of immersion, although corrosion pits were observed. The results of the present study suggest that the hydrogen absorption of Ti-0.2Pd alloy, as compared with commercial pure titanium, is suppressed in fluoride solutions. (c) 2005 Elsevier B.V. All rights reserved.

    DOI CiNii

  • Susceptibility to delayed fracture of alpha-beta titanium alloy in fluoride solutions

    K Yokoyama, T Ogawa, K Asaoka, J Sakai

    CORROSION SCIENCE   47 ( 7 ) 1778 - 1793  2005年07月

     概要を見る

    The susceptibility to delayed fracture of the alpha-beta titanium alloy Ti-6Al-4V has been investigated in acidic and neutral fluoride solutions at room temperature. The time to fracture decreased with increasing applied stress in 2.0% and 0.2% acidulated phosphate fluoride (APF) solutions at pH 5.0. The time to fracture in the 2.0% APF solution was shorter than that in the 0.2% APF solution, although at an applied stress higher than 1000 MPa, the times to fracture were almost the same in both the solutions. For immersion in the 0.2% APF solution, when the applied stress was lower than 700 MPa, delayed fracture did not occur within 1000 h. The fracture surface of specimens immersed in the 2.0% APF solution exhibited brittleness associated with hydrogen absorption, while that in the 0.2% APF solution was ductile and characterized macroscopically as having a cup-cone morphology. The amounts of hydrogen absorbed in 2.0% and 0.2% APF solutions for 24 h were approximately 200 and 30 mass ppm, respectively. As the immersion time increased, the amount of hydrogen absorbed in the 2.0% APF solution increased, whereas that in the 0.2% APF solution hardly increased. In neutral 2.0% and 0.2% NaF solutions, the delayed fracture did not occur within 1000 h, although general corrosion was observed. These results indicate that the susceptibility to delayed fracture of alpha-beta titanium alloy, compared with those of the alpha titanium and beta titanium alloy reported previously, is low in acidic and neutral fluoride solutions. (c) 2004 Elsevier Ltd. All rights reserved.

    DOI CiNii

  • Susceptibility to delayed fracture of alpha-beta titanium alloy in fluoride solutions

    Ken'Ichi Yokoyama, Toshio Ogawa, Kenzo Asaoka, Jun'Ichi Sakai

    Corrosion Science   47 ( 7 ) 1778 - 1793  2005年07月

     概要を見る

    The susceptibility to delayed fracture of the alpha-beta titanium alloy Ti-6Al-4V has been investigated in acidic and neutral fluoride solutions at room temperature. The time to fracture decreased with increasing applied stress in 2.0% and 0.2% acidulated phosphate fluoride (APF) solutions at pH 5.0. The time to fracture in the 2.0% APF solution was shorter than that in the 0.2% APF solution, although at an applied stress higher than 1000 MPa, the times to fracture were almost the same in both the solutions. For immersion in the 0.2% APF solution, when the applied stress was lower than 700 MPa, delayed fracture did not occur within 1000 h. The fracture surface of specimens immersed in the 2.0% APF solution exhibited brittleness associated with hydrogen absorption, while that in the 0.2% APF solution was ductile and characterized macroscopically as having a cup-cone morphology. The amounts of hydrogen absorbed in 2.0% and 0.2% APF solutions for 24 h were approximately 200 and 30 mass ppm, respectively. As the immersion time increased, the amount of hydrogen absorbed in the 2.0% APF solution increased, whereas that in the 0.2% APF solution hardly increased. In neutral 2.0% and 0.2% NaF solutions, the delayed fracture did not occur within 1000 h, although general corrosion was observed. These results indicate that the susceptibility to delayed fracture of alpha-beta titanium alloy, compared with those of the alpha titanium and beta titanium alloy reported previously, is low in acidic and neutral fluoride solutions. © 2004 Elsevier Ltd. All rights reserved.

    DOI CiNii

  • Distribution and thermal desorption behavior of hydrogen in titanium alloys immersed in acidic fluoride solutions

    T Ogawa, K Yokoyama, K Asaoka, J Sakai

    JOURNAL OF ALLOYS AND COMPOUNDS   396 ( 1-2 ) 269 - 274  2005年06月

     概要を見る

    The distribution and thermal desorption behavior of hydrogen in alpha titanium (commercial pure titanium) and beta titanium alloy (Ti-11.3Mo-6.6Zr-4.3Sn) immersed in acidic fluoride solutions (pH 5.0 +/- 25 2 degrees C) have been investigated. For alpha titanium, most of the hydrogen absorbed in the fluoride solution existed as titanium hydride within approximately 50 mu m from the surface of the specimen. The local hydrogen concentration in the vicinity of the surface was evaluated above 5000 mass ppm. Hydrogen thermal desorption was observed in the temperature range from 200 to 700 degrees C. It is likely that the desorption at a low temperature resulted from the dissociation of the hydride, whereas that at a high temperature was caused by hydrogen strongly trapped in matrix defects induced by hydride formation. For the beta titanium alloy, the absorbed hydrogen diffused toward the center of the specimen without hydride forming. Hydrogen was almost uniformly distributed over the whole cross-section of the specimen, although hydrogen content was high at the surface layer of the specimen. Hydrogen desorption appeared in the range from 400 to 600 degrees C, implying that the absorbed hydrogen was mostly hydrogen in solution. The corrosion product (TiF3) on the surface of the specimen caused the desorption temperature to rise more than 100 degrees C, suggesting the origin of the scatter of desorption behavior. (c) 2005 Elsevier B.V. All rights reserved.

    DOI CiNii

  • Distribution and thermal desorption behavior of hydrogen in titanium alloys immersed in acidic fluoride solutions

    T Ogawa, K Yokoyama, K Asaoka, J Sakai

    JOURNAL OF ALLOYS AND COMPOUNDS   396 ( 1-2 ) 269 - 274  2005年06月

     概要を見る

    The distribution and thermal desorption behavior of hydrogen in alpha titanium (commercial pure titanium) and beta titanium alloy (Ti-11.3Mo-6.6Zr-4.3Sn) immersed in acidic fluoride solutions (pH 5.0 +/- 25 2 degrees C) have been investigated. For alpha titanium, most of the hydrogen absorbed in the fluoride solution existed as titanium hydride within approximately 50 mu m from the surface of the specimen. The local hydrogen concentration in the vicinity of the surface was evaluated above 5000 mass ppm. Hydrogen thermal desorption was observed in the temperature range from 200 to 700 degrees C. It is likely that the desorption at a low temperature resulted from the dissociation of the hydride, whereas that at a high temperature was caused by hydrogen strongly trapped in matrix defects induced by hydride formation. For the beta titanium alloy, the absorbed hydrogen diffused toward the center of the specimen without hydride forming. Hydrogen was almost uniformly distributed over the whole cross-section of the specimen, although hydrogen content was high at the surface layer of the specimen. Hydrogen desorption appeared in the range from 400 to 600 degrees C, implying that the absorbed hydrogen was mostly hydrogen in solution. The corrosion product (TiF3) on the surface of the specimen caused the desorption temperature to rise more than 100 degrees C, suggesting the origin of the scatter of desorption behavior. (c) 2005 Elsevier B.V. All rights reserved.

    DOI CiNii

  • Hydrogen embrittlement of Ni-Ti superelastic alloy in ethanol solution containing hydrochloric acid

    T Ogawa, K Yokoyama, K Asaoka, J Sakai

    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING   393 ( 1-2 ) 239 - 246  2005年02月

     概要を見る

    The hydrogen embrittlement of the Ni-Ti superelastic alloy in ethanol solution containing 0.1 mass% hydrochloric acid (HCl) has been investigated using a tensile test (after immersion) and hydrogen thermal desorption analysis (TDA). Upon immersion, the alloy absorbed substantial amounts of hydrogen associated with localized corrosion. The maximum amounts of absorbed hydrogen after immersion for 120 and 600 h were 260 and 1200 mass ppm, respectively. The hydrogen thermal desorption of the immersed specimens appeared as two peaks at approximately 150 and 350 degreesC. As immersion time increased, the amount of desorbed hydrogen at the lower temperatures increased markedly. When the amount of absorbed hydrogen exceeded 200-400 mass ppm, a marked reduction in tensile strength occurred. The fracture mode of specimens that absorbed hydrogen changed from ductile behavior to brittle behavior; the peripheral parts of the fracture surface exhibited a quasi-cleavage-like topography. The hydrogen embrittlement characteristic of the Ni-Ti superelastic alloy in ethanol solution containing 0.1% HCl was not always in accordance with those of the same alloy in other solutions such as the methanol solution containing 0.1% HCl reported previously. (C) 2004 Elsevier B.V. All rights reserved.

    DOI

  • Japanese Type Risk Based Maintenance Technology for Chemical Plant.

    Sakai. J, Kubouchi. M

    Chemical Engineering of Japan   69 ( 11 ) 629 - 632  2005年

  • 化学プラントに望まれる日本型リスクベース保全技術の確立

    酒井 潤一, 久保内 昌敏

    化学工学   69 ( 11 ) 629 - 632  2005年

  • Hydrogen embrittlement of work-hardened Ni-Ti alloy in fluoride solutions

    K Yokoyama, K Kaneko, T Ogawa, K Moriyama, K Asaoka, J Sakai

    BIOMATERIALS   26 ( 1 ) 101 - 108  2005年01月

     概要を見る

    Hydrogen embrittlement of work-hardened Ni-Ti alloy has been examined in acidulated phosphate fluoride (APF) solutions. Upon immersion in a 2.0% APE solution with a pH of 5.0, tensile strength decreased markedly with immersion time. Moreover, the fracture mode changed from ductile to brittle due to brittle layer formation at the peripheral part of the cross section of the specimen. The amount of absorbed hydrogen increased linearly with immersion time, and it reached above 5000 mass ppm after 24 h. The hydrogen desorption temperature of the immersed specimens shifted from 450degreesC to a lower temperature with immersion time. As the amount of absorbed hydrogen was larger than 500 mass ppm, the degradation of mechanical properties was recognized. Although the tensile properties and fracture mode scarcely change in a 0.2% APF solution, the slight reduction in hardness and hydrogen absorption of several hundreds mass ppm were observed. The results of the present study imply that work-hardened Ni-Ti alloy is less sensitive to hydrogen embrittlement compared with Ni-Ti superelastic alloy. (C) 2004 Elsevier Ltd. All rights reserved.

    DOI PubMed CiNii

  • Japanese Type Risk Based Maintenance Technology for Chemical Plant.

    Sakai. J, Kubouchi. M

    Chemical Engineering of Japan   69 ( 11 ) 629 - 632  2005年

  • Evaluation of Hydrogen Absorption Properties of Ti-0.2mass% Pd alloy in Fluoride Solutions

    Ogawa T, Yokoyama K, Asaoka K, Sakai J

    J.Alloys and Compounds   400 ( 1-2 ) 227 - 233  2005年

    DOI CiNii

  • Hydrogen Embrittlement of Ni-Ti Superelastic Alloy in Ethanol Solution Containing Hydrochloric Acid

    Ogawa T, Yokoyama K, Asaoka K, Sakai J

    Mater. Sci. Eng. A   393   239 - 246  2005年

    DOI

  • Hydrogen embrittlement of work-hardened Ni-Ti alloy in fluoride solutions

    K Yokoyama, K Kaneko, T Ogawa, K Moriyama, K Asaoka, J Sakai

    BIOMATERIALS   26 ( 1 ) 101 - 108  2005年01月

     概要を見る

    Hydrogen embrittlement of work-hardened Ni-Ti alloy has been examined in acidulated phosphate fluoride (APF) solutions. Upon immersion in a 2.0% APE solution with a pH of 5.0, tensile strength decreased markedly with immersion time. Moreover, the fracture mode changed from ductile to brittle due to brittle layer formation at the peripheral part of the cross section of the specimen. The amount of absorbed hydrogen increased linearly with immersion time, and it reached above 5000 mass ppm after 24 h. The hydrogen desorption temperature of the immersed specimens shifted from 450degreesC to a lower temperature with immersion time. As the amount of absorbed hydrogen was larger than 500 mass ppm, the degradation of mechanical properties was recognized. Although the tensile properties and fracture mode scarcely change in a 0.2% APF solution, the slight reduction in hardness and hydrogen absorption of several hundreds mass ppm were observed. The results of the present study imply that work-hardened Ni-Ti alloy is less sensitive to hydrogen embrittlement compared with Ni-Ti superelastic alloy. (C) 2004 Elsevier Ltd. All rights reserved.

    DOI PubMed CiNii

  • Hydrogen absorption of titanium in acidic fluoride solutions

    K Yokoyama, T Ogawa, K Asaoka, J Sakai

    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING   384 ( 1-2 ) 19 - 25  2004年10月

     概要を見る

    Hydrogen absorption of commercial pure titanium in acidulated phosphate fluoride (APF) solutions of various concentrations has been examined by hydrogen thermal-desorption analysis. In immersion in the 2.0% APF solution of pH 5.0 at 25degreesC, the amount of absorbed hydrogen increased with immersion time and then saturated at approximately 800-900 mass ppm. During the early stage of the 24 h immersion, the amount of hydrogen absorbed in the 0.2% APF solution was almost the same as that in the 2.0% APF solution, i.e., 200 mass ppm, whereas it saturated at 300 mass ppm with longer immersion time. For the specimen immersed in the 2.0% APF solution for 24 h, hydrogen desorption was observed with a peak at approximately 550degreesC. As the immersion time increased, the second desorption appeared in the range from 150 to 400degreesC. In contrast, for the specimens immersed in the 0.2% APF solution, the desorption peak temperature tended to shift from 550 to 450degreesC with immersion time. Hydrogen absorption was hardly observed in the specimen immersed in the 0.02% APF solution. The concentration of the APF solutions also affected the type of corrosion product and the surface topography of the immersed specimens. The results of the present study clearly indicate that the degradation of the mechanical properties or fracture of titanium caused by hydrogen absorption occurs in acidic fluoride solutions. (C) 2004 Elsevier B.V. All rights reserved.

    DOI

  • Degradation in performance of orthodontic wires caused by hydrogen absorption during short-term immersion in 2.0% acidulated phosphate fluoride solution

    K Kaneko, K Yokoyama, K Moriyama, K Asaoka, J Sakai

    ANGLE ORTHODONTIST   74 ( 4 ) 487 - 495  2004年08月

     概要を見る

    The purpose of this study was to investigate the degradation in performance of four major alloys of orthodontic wires, namely nickel-titanium, beta titanium, stainless steel, and cobalt-chromium-nickel, caused by hydrogen absorption during short-term immersion in an acid flouride solutions. The hydrogen-related degradation of orthodontic wires after immersion in 2.0% acidulated phosphate fluoride solution at 37degreesC for 60 minutes was evaluated by a tensile test, scanning electron microscope observation, and hydrogen thermal desorption analysis. Upon immersion, the tensile strengths of the nickel-titanium and beta titanium wires decreased. Particularly, the nickel-titanium wire fractured before yielding, and the fracture mode changed from ductile to brittle. The amounts of absorbed hydrogen in the nickel-titanium and beta titanium wires were 200 and 100 mass ppm, respectively. On the other hand, the tensile strengths of the stainless steel and cobalt-chromium-nickel wires were only slightly affected by immersion. The results of this study suggest that degradation in performance of orthodontic wires of titanium alloys occurs because of hydrogen absorption even after a short-term immersion in fluoride solutions.

  • Hydrogen absorption behavior of beta titanium alloy in acid fluoride solutions

    T Ogawa, K Yokoyama, K Asaoka, J Sakai

    BIOMATERIALS   25 ( 12 ) 2419 - 2425  2004年05月

     概要を見る

    Hydrogen absorption behavior of a beta titanium alloy in acid fluoride solutions has been analyzed by hydrogen thermal desorption. The amount of absorbed hydrogen increased with immersion time in a 2.0% acidulated. phosphate fluoride (APF) solution. In the case of an immersion time of 60 h, the amount of absorbed hydrogen exceeded 10000 mass ppm. In contrast, the amount of hydrogen absorbed in the 0.2% APF solution was several times smaller than that in the 2.0% APF solution for the same immersion time. For immersion in a 0.2% APF solution, hydrogen absorption saturated after 48 h. The surface topography and corrosion products on the surface of the specimen immersed in the 2.0% APF solution were different from those in the 0.2% APF solution. During the later stage of immersion, the amount of absorbed hydrogen markedly increased under higher applied stress, although the applied stress did not enhance hydrogen absorption during the early stage of immersion. These results of hydrogen absorption behavior are consistent with the delayed fracture characteristics of the beta titanium alloy. (C) 2003 Elsevier Ltd. All rights reserved.

    DOI PubMed CiNii

  • Hydrogen absorption behavior of beta titanium alloy in acid fluoride solutions

    T Ogawa, K Yokoyama, K Asaoka, J Sakai

    BIOMATERIALS   25 ( 12 ) 2419 - 2425  2004年05月

     概要を見る

    Hydrogen absorption behavior of a beta titanium alloy in acid fluoride solutions has been analyzed by hydrogen thermal desorption. The amount of absorbed hydrogen increased with immersion time in a 2.0% acidulated. phosphate fluoride (APF) solution. In the case of an immersion time of 60 h, the amount of absorbed hydrogen exceeded 10000 mass ppm. In contrast, the amount of hydrogen absorbed in the 0.2% APF solution was several times smaller than that in the 2.0% APF solution for the same immersion time. For immersion in a 0.2% APF solution, hydrogen absorption saturated after 48 h. The surface topography and corrosion products on the surface of the specimen immersed in the 2.0% APF solution were different from those in the 0.2% APF solution. During the later stage of immersion, the amount of absorbed hydrogen markedly increased under higher applied stress, although the applied stress did not enhance hydrogen absorption during the early stage of immersion. These results of hydrogen absorption behavior are consistent with the delayed fracture characteristics of the beta titanium alloy. (C) 2003 Elsevier Ltd. All rights reserved.

    DOI PubMed CiNii

  • The effect of reduction on the mechanical properties of CeO2 doped tetragonal zirconia ceramics

    M Matsuzawa, M Abe, S Horibe, J Sakai

    ACTA MATERIALIA   52 ( 6 ) 1675 - 1682  2004年04月

     概要を見る

    Four types of zirconia ceramic, Ce-TZP, 3Y-TZP. 8Y-FSZ and Mg-PSZ, were heat treated in hydrogen gas. Only Ce-TZP was very effectively reduced after the heat treatment. The drastic weight loss and the increase of internal friction, which were observed in the reduced Ce-TZP, were due to the high number of oxygen vacancies introduced into the matrix. The various mechanical properties of Ce-TZP before and after the heat treatment were investigated. Sufficient reduction effectively increased the hardness but unfortunately also embrittled the sample. The serious increase in embrittlement could not be attributed to the hydrogen introduced into the matrix, but was due principally to the low transformability of the reduced Ce-TZP. On the other hand, the anelastic property of the reduced Ce-TZP was considerably improved by the increase in oxygen vacancies and, furthermore, the tensile fracture strength was influenced due to the fact that anelasticity occurs instead of phase transformation. (C) 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

    DOI CiNii

  • Delayed fracture of Ni-Ti superelastic alloys in acidic and neutral fluoride solutions

    K Yokoyama, K Kaneko, K Moriyama, K Asaoka, J Sakai, M Nagumo

    JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A   69A ( 1 ) 105 - 113  2004年04月

     概要を見る

    Hydrogen-related degradation of the mechanical properties of a Ni-Ti superelastic alloy has been examined by means of delayed fracture tests in acidic and neutral fluoride solutions and hydrogen thermal desorption analysis. Delayed fracture took place in both solutions; the time to fracture was shorter in the acidic solutions than in the neutral solutions with the same fluoride concentration. The time to fracture was reduced in both solutions when applied stress exceeded the critical stress for martensite transformation. In the acidic solutions, Ni-Ti superelastic alloy underwent general corrosion and absorbed substantial amounts of hydrogen. Fractographic features suggested that the delayed fracture in the acidic solutions was attributable to hydrogen embrittlement, whereas in the neutral solutions, a different fracture mode appeared associated with localized corrosion only in the vicinity of the fracture initiation area. In the neutral solutions, the amount of absorbed hydrogen was much less than that in the acidic solutions, and the delayed fracture was likely to be induced by active path corrosion accompanying hydrogen absorption. The results of the present study imply that the hydrogen-related degradation of performance of Ni-Ti superelastic alloys occurs in the presence of fluoride. (C) 2004 Wiley Periodicals, Inc.

    DOI

  • The effect of reduction on the mechanical properties of CeO2 doped tetragonal zirconia ceramics

    M Matsuzawa, M Abe, S Horibe, J Sakai

    ACTA MATERIALIA   52 ( 6 ) 1675 - 1682  2004年04月

     概要を見る

    Four types of zirconia ceramic, Ce-TZP, 3Y-TZP. 8Y-FSZ and Mg-PSZ, were heat treated in hydrogen gas. Only Ce-TZP was very effectively reduced after the heat treatment. The drastic weight loss and the increase of internal friction, which were observed in the reduced Ce-TZP, were due to the high number of oxygen vacancies introduced into the matrix. The various mechanical properties of Ce-TZP before and after the heat treatment were investigated. Sufficient reduction effectively increased the hardness but unfortunately also embrittled the sample. The serious increase in embrittlement could not be attributed to the hydrogen introduced into the matrix, but was due principally to the low transformability of the reduced Ce-TZP. On the other hand, the anelastic property of the reduced Ce-TZP was considerably improved by the increase in oxygen vacancies and, furthermore, the tensile fracture strength was influenced due to the fact that anelasticity occurs instead of phase transformation. (C) 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

    DOI CiNii

  • Fracture of nickel-titanium superelastic alloy in sodium hypochlorite solution

    K Yokoyama, K Kaneko, E Yabuta, K Asaoka, J Sakai

    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING   369 ( 1-2 ) 43 - 48  2004年03月

     概要を見る

    Fracture of the Ni-Ti superelastic alloy for endodontic instruments such as files was investigated with a sustained tensile-loading test in sodium hypochlorite (NaOCl) solution of various concentrations. It was found that the time to fracture was reduced when the applied stress exceeded the critical stress for martensite transformation. When the applied stress was higher than the critical stress, the 0.3 mm diameter wires of the Ni-Ti superelastic alloy sometimes fractured within 60 min. From the results of observations of the fracture surface using a scanning electron microscope, it was revealed that the fracture of the Ni-Ti superelastic alloy is significantly influenced by corrosion when the applied stress was higher than the critical stress for martensite transformation. The results of the present study suggest that one of the causes of the fracture of Ni-Ti files during clinical use is corrosion under the applied stress above the critical stress for martensite transformation in NaOCI solution. (C) 2003 Elsevier B.V. All rights reserved.

    DOI

  • Fracture of nickel-titanium superelastic alloy in sodium hypochlorite solution

    K Yokoyama, K Kaneko, E Yabuta, K Asaoka, J Sakai

    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING   369 ( 1-2 ) 43 - 48  2004年03月

     概要を見る

    Fracture of the Ni-Ti superelastic alloy for endodontic instruments such as files was investigated with a sustained tensile-loading test in sodium hypochlorite (NaOCl) solution of various concentrations. It was found that the time to fracture was reduced when the applied stress exceeded the critical stress for martensite transformation. When the applied stress was higher than the critical stress, the 0.3 mm diameter wires of the Ni-Ti superelastic alloy sometimes fractured within 60 min. From the results of observations of the fracture surface using a scanning electron microscope, it was revealed that the fracture of the Ni-Ti superelastic alloy is significantly influenced by corrosion when the applied stress was higher than the critical stress for martensite transformation. The results of the present study suggest that one of the causes of the fracture of Ni-Ti files during clinical use is corrosion under the applied stress above the critical stress for martensite transformation in NaOCI solution. (C) 2003 Elsevier B.V. All rights reserved.

    DOI

  • Fracture associated with hydrogen absorption of sustained tensile-loaded titanium in acid and neutral fluoride solutions

    Ken'ichi Yokoyama, Kazuyuki Kaneko, Youji Miyamoto, Kenzo Asaoka, Jun'ichi Sakai, Michihiko Nagumo

    Journal of Biomedical Materials Research - Part A   68 ( 1 ) 150 - 158  2004年01月

     概要を見る

    The fracture of commercial pure titanium in acid and neutral fluoride solutions has been examined by a sustained tensile-loading test and hydrogen thermal desorption analysis. It was found that the fracture of titanium occurred in neutral 2.0% NaF solution as well as in 2.0% acidulated phosphate fluoride (APF) solution. The time to fracture decreased with increasing applied stress in both 2.0% APF and 2.0% NaF solutions. In the case of the same applied stress, the time to fracture in the 2.0% APF solution was shorter than that in the 2.0% NaF solution. General corrosion was exhibited on the side surface of the tested specimens. The formation of sodium titanium fluoride was observed on the surface of the immersed specimens in the 2.0% APF solution. Hydrogen desorption of the tested specimen in the 2.0% APF solution was observed with a peak at approximately 600°C. The amount of absorbed hydrogen was &gt
    300 mass ppm in the 2.0% APF solution under an applied stress for 24 h. The results of the present study imply that applying stress to titanium by immersing in fluoride solutions leads to the degradation of its mechanical properties. © 2003 Wiley Periodicals, Inc.

    DOI PubMed CiNii

  • Fracture associated with hydrogen absorption of sustained tensile-loaded titanium in acid and neutral fluoride solutions

    K Yokoyama, K Kaneko, Y Miyamoto, K Asaoka, J Sakai, M Nagumo

    JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A   68A ( 1 ) 150 - 158  2004年01月

     概要を見る

    The fracture of commercial pure titanium in acid and neutral fluoride solutions has been examined by a sustained tensile-loading test and hydrogen thermal desorption analysis. It was found that the fracture of titanium occurred in neutral 2.0% NaF solution as well as in 2.0% acidulated phosphate fluoride (APF) solution. The time to fracture decreased with increasing applied stress in both 2.0% APF and 2.0% NaF solutions. In the case of the same applied stress, the time to fracture in the 2.0% APF solution was shorter than that in the 2.0% NaF solution. General corrosion was exhibited on the side surface of the tested specimens. The formation of sodium titanium fluoride was observed on the surface of the immersed specimens in the 2.0% APF solution. Hydrogen desorption of the tested specimen in the 2.0% APF solution was observed with a peak at approximately 600degreesC. The amount of absorbed hydrogen was >300 mass ppm in the 2.0% APF solution under an applied stress for 24 h. The results of the present study imply that applying stress to titanium by immersing in fluoride solutions leads to the degradation of its mechanical properties. (C) 2003 Wiley Periodicals, Inc.

    DOI PubMed CiNii

  • Fracture associated with hydrogen absorption of sustained tensile-loaded titanium in acid and neutral fluoride solutions

    Ken'ichi Yokoyama, Kazuyuki Kaneko, Youji Miyamoto, Kenzo Asaoka, Jun'ichi Sakai, Michihiko Nagumo

    Journal of Biomedical Materials Research - Part A   68 ( 1 ) 150 - 158  2004年01月

     概要を見る

    The fracture of commercial pure titanium in acid and neutral fluoride solutions has been examined by a sustained tensile-loading test and hydrogen thermal desorption analysis. It was found that the fracture of titanium occurred in neutral 2.0% NaF solution as well as in 2.0% acidulated phosphate fluoride (APF) solution. The time to fracture decreased with increasing applied stress in both 2.0% APF and 2.0% NaF solutions. In the case of the same applied stress, the time to fracture in the 2.0% APF solution was shorter than that in the 2.0% NaF solution. General corrosion was exhibited on the side surface of the tested specimens. The formation of sodium titanium fluoride was observed on the surface of the immersed specimens in the 2.0% APF solution. Hydrogen desorption of the tested specimen in the 2.0% APF solution was observed with a peak at approximately 600°C. The amount of absorbed hydrogen was &gt
    300 mass ppm in the 2.0% APF solution under an applied stress for 24 h. The results of the present study imply that applying stress to titanium by immersing in fluoride solutions leads to the degradation of its mechanical properties. © 2003 Wiley Periodicals, Inc.

    DOI PubMed CiNii

  • Fracture associated with hydrogen absorption of sustained tensile-loaded titanium in acid and neutral fluoride solutions

    K Yokoyama, K Kaneko, Y Miyamoto, K Asaoka, J Sakai, M Nagumo

    JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A   68A ( 1 ) 150 - 158  2004年01月

     概要を見る

    The fracture of commercial pure titanium in acid and neutral fluoride solutions has been examined by a sustained tensile-loading test and hydrogen thermal desorption analysis. It was found that the fracture of titanium occurred in neutral 2.0% NaF solution as well as in 2.0% acidulated phosphate fluoride (APF) solution. The time to fracture decreased with increasing applied stress in both 2.0% APF and 2.0% NaF solutions. In the case of the same applied stress, the time to fracture in the 2.0% APF solution was shorter than that in the 2.0% NaF solution. General corrosion was exhibited on the side surface of the tested specimens. The formation of sodium titanium fluoride was observed on the surface of the immersed specimens in the 2.0% APF solution. Hydrogen desorption of the tested specimen in the 2.0% APF solution was observed with a peak at approximately 600degreesC. The amount of absorbed hydrogen was >300 mass ppm in the 2.0% APF solution under an applied stress for 24 h. The results of the present study imply that applying stress to titanium by immersing in fluoride solutions leads to the degradation of its mechanical properties. (C) 2003 Wiley Periodicals, Inc.

    DOI PubMed CiNii

  • Degradation in performance of orthodontic wires due to hydrogen absorption in 2.0% acidulated phosphate fluoride solution

    Kaneko K, Yokoyama K, Moriyama K, Asaoka K, Sakai J

    Angle Orthod.   74   487 - 495  2004年

  • Delayed fracture of Ni-Ti superelastic alloys in acidic and neutral fluoride solutions

    Yokoyama K, Kaneko K, Moriyama K, Asaoka K, Sakai J, Nagumo M

    J. Biomed. Mater. Res.   69A   105 - 113  2004年

  • Hydrogen absorption of titanium in acidic fluoride solutions

    Yokoyama K, Ogawa T, Asaoka K, Sakai J

    Mater. Sci. Eng. A   384   19 - 25  2004年

    DOI

  • Degradation of tensile strength of Ni-Ti superelastic alloy due to hydrogen absorption in methanol solution containing hydrochloric acid

    K Yokoyama, T Ogawa, K Asaoka, J Sakai, M Nagumo

    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING   360 ( 1-2 ) 153 - 159  2003年11月

     概要を見る

    Degradation of tensile strength of a Ni-Ti superelastic alloy due to hydrogen absorption has been studied in methanol solution containing 0.1 mass % hydrochloric acid (HCl). The amount of absorbed hydrogen from the solution was measured by thermal desorption analysis (TDA). Hydrogen desorption of immersed specimens appeared in the temperature range from 100 to 600 degreesC. The amounts of absorbed hydrogen of immersed specimens were in the range of 50-500 mass ppm when immersed in the solution for 8-120 h. Tensile strength of immersed specimens decreased abruptly up to immersion time of 24 h. In the immersion time range from 24 to 120 h, the tensile strength was coincident with the critical stress for martensite transformation. It was concluded that the degradation of tensile strength of a Ni-Ti superelastic alloy is caused by hydrogen absorption in methanol solution containing HCl. (C) 2003 Elsevier B.V. All rights reserved.

    DOI

  • Degradation of tensile strength of Ni-Ti superelastic alloy due to hydrogen absorption in methanol solution containing hydrochloric acid

    K Yokoyama, T Ogawa, K Asaoka, J Sakai, M Nagumo

    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING   360 ( 1-2 ) 153 - 159  2003年11月

     概要を見る

    Degradation of tensile strength of a Ni-Ti superelastic alloy due to hydrogen absorption has been studied in methanol solution containing 0.1 mass % hydrochloric acid (HCl). The amount of absorbed hydrogen from the solution was measured by thermal desorption analysis (TDA). Hydrogen desorption of immersed specimens appeared in the temperature range from 100 to 600 degreesC. The amounts of absorbed hydrogen of immersed specimens were in the range of 50-500 mass ppm when immersed in the solution for 8-120 h. Tensile strength of immersed specimens decreased abruptly up to immersion time of 24 h. In the immersion time range from 24 to 120 h, the tensile strength was coincident with the critical stress for martensite transformation. It was concluded that the degradation of tensile strength of a Ni-Ti superelastic alloy is caused by hydrogen absorption in methanol solution containing HCl. (C) 2003 Elsevier B.V. All rights reserved.

    DOI

  • Hydrogen embrittlement of Ni-Ti superelastic alloy in fluoride solution

    Ken'Ichi Yokoyama, Kazuyuki Kaneko, Keiji Moriyama, Kenzo Asaoka, Jun'Ichi Sakai, Michihiko Nagumo

    Journal of Biomedical Materials Research - Part A   65 ( 2 ) 182 - 187  2003年05月

     概要を見る

    Hydrogen embrittlement of Ni-Ti superelastic alloy in a fluoride solution (0.2% APF) has been investigated by means of a tensile test (after immersion) and hydrogen thermal desorption analysis. Upon immersion, the tensile strength of the alloy decreased to the critical stress level of martensite transformation. Hydrogen desorption of the immersed specimens appeared with a peak at around 500°C. The amount of absorbed hydrogen in the alloy ranged from 100 to 1000 mass ppm when immersed in the fluoride solution for 2 to 24 h. The immersion in the fluoride solution led to the degradation of mechanical properties due to hydrogen embrittlement. The results of the present study imply that one reason that Ti and its alloys fracture in the oral cavity is the fact that hydrogen is absorbed in a fluoride solution, such as prophylactic agents. © 2003 Wiley Periodicals, Inc.

    DOI PubMed CiNii

  • Delayed fracture of beta titanium orthodontic wire in fluoride aqueous solutions

    K Kaneko, K Yokoyama, K Moriyama, K Asaoka, J Sakai, M Nagumo

    BIOMATERIALS   24 ( 12 ) 2113 - 2120  2003年05月

     概要を見る

    Hydrogen embrittlement of a beta titanium orthodontic wire has been examined by means of a delayed-fracture test in acid and neutral fluoride aqueous solutions and hydrogen thermal desorption analysis. The time to fracture increased with decreasing applied stress in 2.0% and 0.2% acidulated phosphate fluoride (APF) solutions. The fracture mode changed from ductile to brittle when the applied stress was lower than 500 MPa in 2.0% APE solution. On the other hand, the delayed fracture did not occur within 1000 h in neutral NaF solutions, although general corrosion was also observed similar to that in APE Solutions. Hydrogen desorption of the delayed-fracture-tested specimens was observed with a peak at approximately 500degreesC. The amount of absorbed hydrogen was 5000-6500 mass ppm under an applied stress in 2.0% APF solution for 24 h. It is concluded that the immersion in fluoride solutions leads to the degradation of the mechanical properties and fracture of beta titanium alloy associated with hydrogen absorption. (C) 2003 Elsevier Science Ltd. All rights reserved.

    DOI PubMed CiNii

  • Hydrogen embrittlement of Ni-Ti superelastic alloy in fluoride solution

    Ken'Ichi Yokoyama, Kazuyuki Kaneko, Keiji Moriyama, Kenzo Asaoka, Jun'Ichi Sakai, Michihiko Nagumo

    Journal of Biomedical Materials Research - Part A   65 ( 2 ) 182 - 187  2003年05月

     概要を見る

    Hydrogen embrittlement of Ni-Ti superelastic alloy in a fluoride solution (0.2% APF) has been investigated by means of a tensile test (after immersion) and hydrogen thermal desorption analysis. Upon immersion, the tensile strength of the alloy decreased to the critical stress level of martensite transformation. Hydrogen desorption of the immersed specimens appeared with a peak at around 500°C. The amount of absorbed hydrogen in the alloy ranged from 100 to 1000 mass ppm when immersed in the fluoride solution for 2 to 24 h. The immersion in the fluoride solution led to the degradation of mechanical properties due to hydrogen embrittlement. The results of the present study imply that one reason that Ti and its alloys fracture in the oral cavity is the fact that hydrogen is absorbed in a fluoride solution, such as prophylactic agents. © 2003 Wiley Periodicals, Inc.

    DOI PubMed CiNii

  • Susceptibility to delayed fracture of Ni-Ti superelastic alloy

    Ken'Ichi Yokoyama, Shiyozo Watabe, Kenichi Hamada, Jun'Ichi Sakai, Kenzo Asaoka, Michihiko Nagumo

    Materials Science and Engineering A   341 ( 1-2 ) 91 - 97  2003年01月

     概要を見る

    The susceptibility of Ni-Ti superelastic alloys to hydrogen embrittlement has been examined by means of a delayed-fracture test and hydrogen thermal desorption analysis. It was found that the time to fracture was drastically reduced when the applied stress exceeded the critical stress for martensite transformation. In the applied stress range lower than the critical stress, the time to fracture lessened in the order of instability of the alloys to undergo reversible martensite transformation. Hydrogen thermal desorption of specimens subjected to delayed-fracture test is classified into two types according to the applied stress level. The amount of desorbed hydrogen was markedly increased when the applied stress was higher than the critical stress. It was concluded that Ni-Ti superelastic alloys transformed to martensite are sensitive to environmental conditions accompanying accelerated hydrogen embrittlement. © 2002 Elsevier Science B.V. All rights reserved.

    DOI

  • Effects of martensite phase of Ni-Ti shape memory alloy on corrosion behavior in sodium hypochlorite solutions

    Jun’ichi Sakai, Eiji Yabuta, Ken’ichi Yokoyama

    13th APCCC (Japan)    2003年

  • EFFECTS OF HYPOCHLORITE AND FLUORIDE ON CORROSION BEHAVIOR OF Ti-Ni ALLOY

    Jun’ichi Sakai, Eiji Yabuta, Ken’ichi Yokoyama

    5th Latincorr. NACE (Chili)    2003年

  • Delayed fracture of beta titanium orthodontic wire in fluoride aqueous solutions

    Kazuyuki Kaneko, Ken'ichi Yokoyama, Keiji Moriyama, Kenzo Asaoka, Jun'ichi Sakai, Michihiko Nagumo

    Biomaterials   24 ( 12 ) 2113 - 2120  2003年

     概要を見る

    Hydrogen embrittlement of a beta titanium orthodontic wire has been examined by means of a delayed-fracture test in acid and neutral fluoride aqueous solutions and hydrogen thermal desorption analysis. The time to fracture increased with decreasing applied stress in 2.0% and 0.2% acidulated phosphate fluoride (APF) solutions. The fracture mode changed from ductile to brittle when the applied stress was lower than 500MPa in 2.0% APF solution. On the other hand, the delayed fracture did not occur within 1000h in neutral NaF solutions, although general corrosion was also observed similar to that in APF solutions. Hydrogen desorption of the delayed-fracture-tested specimens was observed with a peak at approximately 500°C. The amount of absorbed hydrogen was 5000-6500 mass ppm under an applied stress in 2.0% APF solution for 24h. It is concluded that the immersion in fluoride solutions leads to the degradation of the mechanical properties and fracture of beta titanium alloy associated with hydrogen absorption. © 2003 Elsevier Science Ltd. All rights reserved.

    DOI PubMed CiNii

  • Susceptibitty to Delayed Fracture of Ni-Ti Superelastic Alloy

    Yokoyama K, Watabe S, Hamada K, Sakai J, Asaoka K, Nagumo M

    Mat'l Sci. & Eng'g. A   A341   91 - 97  2003年

    DOI

  • Effects of martensite phase of Ni-Ti shape memory alloy on corrosion behavior in sodium hypochlorite solutions

    Jun’ichi Sakai, Eiji Yabuta, Ken’ichi Yokoyama

    13th APCCC (Japan)    2003年

  • EFFECTS OF HYPOCHLORITE AND FLUORIDE ON CORROSION BEHAVIOR OF Ti-Ni ALLOY

    Jun’ichi Sakai, Eiji Yabuta, Ken’ichi Yokoyama

    5th Latincorr. NACE (Chili)    2003年

  • Delayed Fracture and Hydrogen Absorption of Ni-Ti alloy

       2001年

  • Materials Performance in SCW.

      48   191  2001年

  • CORROSION BEHAVIOR OF SEVERAL COMMERCIAL ALLOYS IN SUPERCRITICAL WATER INCLUDING HIGH CONCENTRATION OF CHLORIDE IONS

    CORROSION 2001   /,#01363  2001年

  • Corrosion Behavior of Several Commercial Alloys in Supercritical Water including high Concentration of Chlovide ions

    NACE   01363  2001年

  • Delayed Fracture and Hydrogen Absorption of Ni-Ti alloy

       2001年

  • Materials Performance in SCW.

      48   191  2001年

  • CORROSION BEHAVIOR OF SEVERAL COMMERCIAL ALLOYS IN SUPERCRITICAL WATER INCLUDING HIGH CONCENTRATION OF CHLORIDE IONS

    CORROSION 2001   /,#01363  2001年

  • 塩化物飛来環境における対候性鋼のさびの保護性

    材料と環境/腐食防食協会   49: 2  2000年

  • Experience Survey of Chloride Resistant Steels in Process Plants

    Int'l Corr. Forum CORROSION'99, NACE   #385  1999年

  • SCC of Stailess Steel Heat Exchanger

    Proc. of 1st Int'l Symp. On Innovative Approaches for Improving Heat Exchanger Reliability, NACE, MTI    1998年

▼全件表示

受賞

  • 腐食防食学会 技術賞

    2014年  

  • 腐食防食協会 技術賞

    2008年  

  • 腐食防食協会 協会賞

    2008年  

  • 腐食防食協会 岡本剛記念講演者

    2006年  

共同研究・競争的資金等の研究課題

  • 電子材料の腐食

  • リスクベース保全技術

  • 高温損傷

  • Tiの耐環境特性

  • 生体材料・口腔材料

  • 鉄鋼錆の酸化還元機構

  • ガルバニック腐食解析

  • 微小損傷検出

  • 腐食機構

  • 機能材料に関する研究

  • 腐食機構に関する研究

  • 耐食材料に関する研究

  • Study on Functional Materials

  • Study on Corrosion Mechanism

  • Study on Corrosion Resistant Materials

▼全件表示

講演・口頭発表等

  • ステンレス鋼の耐発銹性に及ぼす不働態皮膜の安定度の影響

    腐食防食学会 関東支部技術交流会  

    発表年月: 2015年

  • カソード水素チャージによる純Zrの表層剥離発生挙動の解明

    腐食防食学会 関東支部技術交流会  

    発表年月: 2015年

  • 硫黄蒸気環境の銀の硫化挙動におよぼす風速の影響

    日本金属学会 2015年 春期講演大会  

    発表年月: 2015年

  • 水素化物の析出形態を変化させた純Tiの変形組織観察

    日本金属学会 2015年 春期講演大会  

    発表年月: 2015年

  • ステンレス鋼の耐発銹性に及ぼす塩化物による不働態皮膜の破壊の影響

    日本鉄鋼協会 第169回春季講演大会  

    発表年月: 2015年

  • SUS304 ステンレス鋼におけるマルテンサイト変態と水素との相互作用-粒界破面に及ぼす変態量及び水素の存在状態の影響

    日本金属学会 2014年春期(第154回)講演大会  

    発表年月: 2014年

  • FIP試験環境での初期水素吸蔵の検討

    腐食防食学会 材料と環境2014  

    発表年月: 2014年

  • FIP試験溶液での電解による腐食反応挙動の検討

    腐食防食学会 材料と環境2014  

    発表年月: 2014年

  • 腐食防食学会規格『20%チオシアン酸アンモニウム溶液中でのPC鋼材の水素脆化試験方法』JSCE S1201

    腐食防食学会 材料と環境2014  

    発表年月: 2014年

  • ジルコニウムの硝酸中におけるγ線照射環境下での放射線分解水素吸収挙動

    原子力学会 2014年秋の大会  

    発表年月: 2014年

  • Ni-Ti超弾性合金の水素脆性に及ぼすマルテンサイトバリアントの再配列と水素との相互作用

    日本金属学会 2014年秋期(第155回)講演大会  

    発表年月: 2014年

  • 水素チャージによる純Zrの表面剥離挙動に及ぼす定荷重及び定ひずみの影響

    日本金属学会 2014年秋期(第155回)講演大会  

    発表年月: 2014年

  • リン酸酸性フッ化物水溶液中における純Tiの腐食と水素吸収に及ぼす過酸化水素添加の影響

    日本金属学会 2014年秋期(第155回)講演大会  

    発表年月: 2014年

  • カソード電解水素チャージによる純Zr表面の剥離挙動の観察

    日本金属学会 2014年秋期(第155回)講演大会  

    発表年月: 2014年

  • ステンレス鋼の耐発銹性に及ぼす不働態皮膜の安定度の影響

    腐食防食学会 第61回材料と環境討論会(秋期)  

    発表年月: 2014年

  • API-X65 の水素侵入挙動に及ぼす電析Ca 皮膜の影響

    腐食防食学会 第61回材料と環境討論会(秋期)  

    発表年月: 2014年

  • 二相ステンレス鋼のすき間腐食発生,成長時におけるすき間内pH の経時変化

    腐食防食学会 第61回材料と環境討論会(秋期)  

    発表年月: 2014年

  • 海水環境におけるステンレス鋼接触条件下での普通鋼の腐食挙動(2)

    腐食防食学会 第61回材料と環境討論会(秋期)  

    発表年月: 2014年

  • 炭素鋼の腐食に及ぼす希薄ギ酸の影響

    腐食防食学会 第61回材料と環境討論会(秋期)  

    発表年月: 2014年

  • 恒温硫黄蒸気環境の銀の硫化挙動におよぼす銀表面温度の影響

    腐食防食学会 第61回材料と環境討論会(秋期)  

    発表年月: 2014年

  • 硫黄蒸気環境の銀の硫化挙動におよぼす反応表面温度の影響

    早稲田大学各務記念材料技術研究所 第一回材研フェスタ  

    発表年月: 2014年

  • カソード水素チャージによる純Zrの表層剥離発生挙動の解明

    早稲田大学各務記念材料技術研究所 第一回材研フェスタ  

    発表年月: 2014年

  • Role of Mo on Corrosion Resistance of 13%Cr Steels in CO2 Environments

    15th Middle East Corrosion Conference  

    発表年月: 2014年

  • Corrosion of Carbon Steel and Alloys in Ammonium Chloride Salt

    NACE CORROSION2014  

    発表年月: 2014年

  • A study of a reproduction method of ennoblement of spontaneous potential of stainless steels in seawater by laboratory testing

    Gordon Research Conferences, Corrosion – Aqueous  

    発表年月: 2014年

  • Effect of residual chlorine on the spontaneous potential of stainless steels in seawater

    EUROCORR2014  

    発表年月: 2014年

  • 水素吸収させたSUS304へのひずみ付与がその水素除去後の機械的性質に及ぼす影響

    腐食防食学会 関東支部技術交流会  

    発表年月: 2013年

  • 銀の硫化挙動に及ぼすパラジウム添加の影響

    腐食防食学会 関東支部技術交流会  

    発表年月: 2013年

  • 応力及び熱誘起変態によるトレーニングを施した Ni-Ti 超弾性合金の水素脆化挙動

    日本金属学会 春期(第152回)講演大会  

    発表年月: 2013年

  • 銀の硫化挙動に及ぼすパラジウム添加の影響

    日本金属学会 春期(第152回)講演大会  

    発表年月: 2013年

  • SUS304ステンレス鋼の水素脆性破面形態に及ぼす加工誘起マルテンサイト変態の影響

    日本鉄鋼協会 第165回春季講演大会  

    発表年月: 2013年

  • NaCl水溶液中におけるSn-9.0Zn鉛フリーはんだのき裂発生挙動

    日本金属学会 秋期(第153回)講演大会  

    発表年月: 2013年

  • 水素添加によるNi-ち超弾性合金の局部腐食抑制に及ぼす相と変態の影響

    日本金属学会 秋期(第153回)講演大会  

    発表年月: 2013年

  • 純Tiの引張特性に及ぼす水素化物の分布状態の影響

    日本金属学会 秋期(第153回)講演大会  

    発表年月: 2013年

  • 溶接金属におけるδフェライトの耐食性への寄与(溶接部腐食2)

    腐食防食学会 第60回材料と環境討論会(秋期)  

    発表年月: 2013年

  • 二相ステンレス鋼の腐食電位における優先溶解メカニズム

    腐食防食学会 第60回材料と環境討論会(秋期)  

    発表年月: 2013年

  • アルカリ性環境下における炭素鋼の脱不働態化に及ぼすpH低下の影響

    腐食防食学会 第60回材料と環境討論会(秋期)  

    発表年月: 2013年

  • フェライトステンレス鋼におけるTi炭窒素化物起点の孔食発生

    腐食防食学会 第60回材料と環境討論会(秋期)  

    発表年月: 2013年

  • チオシアン酸アンモニウム溶液中の鋼材初期腐食挙動

    腐食防食学会 第60回材料と環境討論会(秋期)  

    発表年月: 2013年

  • 保温材下模擬環境における炭素鋼の腐食に及ぼす温度と濡れ時間の影響

    腐食防食学会 第60回材料と環境討論会(秋期)  

    発表年月: 2013年

  • Effect of Alloying Palladium on Sulfurization behavior of Silver

    Gordon Research Conference -High Temperature Corrosion  

    発表年月: 2013年

  • The In-situ Observation of Preferential Dissolution Behaviour on Crevice Corrosion of a Duplex Stainless Steel

    European Federation of Corrosion EUROCORR 2013  

    発表年月: 2013年

  • 時効による水素脆化の回復と促進 : 水素化物の分解による影響

    日本鉄鋼協会第164回秋季大会 シンポジウム「水素脆化研究の基盤構築 中間成果報告会」  

    発表年月: 2012年

  • SUS310Sステンレス鋼の水素脆化:粒界破壊に及ぼす水素チャージ法と鋭敏化の影響

    日本金属学会 秋期(第151回)講演大会  

    発表年月: 2012年

  • Sn-3.0Ag鉛フリーはんだのクリープ腐食割れに及ぼす粒界方位差の影響

    日本金属学会 秋期(第151回)講演大会  

    発表年月: 2012年

  • Ni-Ti超弾性合金の水素脆化に及ぼす熱誘起マルテンサイト変態と水素との動的相互作用

    日本金属学会 秋期(第151回)講演大会  

    発表年月: 2012年

  • 純Ti及びTi-5Ta合金の水素脆化に及ぼす時効の影響

    日本金属学会 秋期(第151回)講演大会  

    発表年月: 2012年

  • 二相ステンレス鋼のすき間腐食成長挙動

    腐食防食学会 第59回材料と環境討論会(秋期)  

    発表年月: 2012年

  • API-X65の水素脆化特性に及ぼすアルカリ溶液の影響

    腐食防食学会 第59回材料と環境討論会(秋期)  

    発表年月: 2012年

  • マンニッヒ変性フェノール樹脂皮膜の耐食性に及ぼすリン酸の影響

    腐食防食学会 第59回材料と環境討論会(秋期)  

    発表年月: 2012年

  • Role of Mo on Corrosion Resistance of 13%Cr Steels In Sweet Environment

    European Federation of Corrosion, EUROCORR 2012 The European Corrosion Congress  

    発表年月: 2012年

  • Effect of Galvanostatic Condition on Growth Behavior and Repassivation Potential of Crevice Corrosion of Duplex Stainless Steels

    216th the Electrochem. Soc, (Honolulu)  

    発表年月: 2012年

  • Role of Sulfur Dioxide and Particulate Sulfate in the Formation of Basic Copper Sulfate on Copper Exposed in Tokyo

    16th Asian Pacific Corrosion Control Conference  

    発表年月: 2012年

  • 純Tiの水素吸収挙動に及ぼす溶存酸素の影響

    腐食防食協会 関東支部技術交流会  

    発表年月: 2011年

  • チオシアン酸アンモニウム水溶液中における鋼材の腐食挙動

    腐食防食協会 2011年度春期講演大会 材料と環境2011  

    発表年月: 2011年

  • ステンレス鋼の水素脆化に及ぼす電解溶液の影響

    日本金属学会関東支部 学生講演会  

    発表年月: 2011年

  • 再処理施設における経年変化研究―(8) 放射線照射下での硝酸塩溶液における水素発生とチタンの水素吸収―

    日本原子力学会 2011年秋の大会  

    発表年月: 2011年

  • 二相系ステンレス鋼の腐食すきま再不働態化電位に及ぼす成長過程の影響

    日本鉄鋼協会 第162回秋季講演大会  

    発表年月: 2011年

  • 水素研究会 A グループ中間報告:水素添加法と水素状態分析ラウンドロビンテスト

    日本鉄鋼協会 第162回秋季講演大会  

    発表年月: 2011年

  • 定荷重試験による純Ti及びTi-5Ta合金の水素脆化特製の評価

    腐食防食協会 第58回材料と環境討論会(秋期)  

    発表年月: 2011年

  • 純Ti及びTi-5Taの放射線照射環境下での硝酸溶液における水素吸収挙動

    腐食防食協会 第58回材料と環境討論会(秋期)  

    発表年月: 2011年

  • チオシアン酸アンモニウム水溶液中における鋼材の腐食挙動 その2

    腐食防食協会 第58回材料と環境討論会(秋期)  

    発表年月: 2011年

  • Sweet環境における13%Crマルテンサイト系ステンレス鋼の耐食性に及ぼすMoの役割

    腐食防食協会 第58回材料と環境討論会(秋期)  

    発表年月: 2011年

  • Alloy 182 / 低合金鋼溶接境界部のき裂停留挙動に関する材料, 環境因子からの検討

    腐食防食協会 第58回材料と環境討論会(秋期)  

    発表年月: 2011年

  • 水素添加によるNi-Ti超弾性合金のNaCl水溶液中における局部腐食抑制

    腐食防食協会 第58回材料と環境討論会(秋期)  

    発表年月: 2011年

  • SUS304鋼の水素脆化挙動に及ぼすNaCl水溶液中の電解水素チャージ条件

    腐食防食協会 第58回材料と環境討論会(秋期)  

    発表年月: 2011年

  • NaCl水溶液中において定荷重負荷したSn-3.0Ag及びSn-0.5Cu鉛フリーはんだの破壊挙動

    腐食防食協会 第58回材料と環境討論会(秋期)  

    発表年月: 2011年

  • ラインパイプ鋼の塑性変形特性に及ぼす侵入水素量の影響評価

    腐食防食協会 第58回材料と環境討論会(秋期)  

    発表年月: 2011年

  • 酸素を含む中性水溶液中におけるFe3O4による炭素鋼の腐食促進

    腐食防食協会 第58回材料と環境討論会(秋期)  

    発表年月: 2011年

  • Ni基合金 / 低合金鋼 異材溶接継手界面における 200℃での酸化物形成挙動

    腐食防食協会 第58回材料と環境討論会(秋期)  

    発表年月: 2011年

  • 二相系ステンレス鋼すき間腐食初期成長挙動

    腐食防食協会 第58回材料と環境討論会(秋期)  

    発表年月: 2011年

  • すき間腐食挙動に及ぼすすき間間隙の影響

    腐食防食協会 第58回材料と環境討論会(秋期)  

    発表年月: 2011年

  • E_R,CREV測定の成長過程中の腐食挙動

    腐食防食協会 第58回材料と環境討論会(秋期)  

    発表年月: 2011年

  • フェノール樹脂皮膜の耐食性におよぼす焼付け温度の影響

    腐食防食協会 第58回材料と環境討論会(秋期)  

    発表年月: 2011年

  • Crevice Corrosion Behavior of a Duplex Stainless Steel in a Simulated Crevice Solution

    ACA, 18th International Corrosion Congress  

    発表年月: 2011年

  • 高温高湿環境下での炭素鋼の腐食促進に及ぼす塩化物の影響

    腐食防食協会 関東支部技術交流会  

    発表年月: 2010年

  • 水素吸収させた純 Ti の過酸化水素含有生理食塩水中における腐食挙動

    日本金属学会 2010年春期(第146回)大会  

    発表年月: 2010年

  • 二相系ステンレス鋼のすきま腐食における優先溶解挙動

    日本鉄鋼協会 第159回春季講演大会  

    発表年月: 2010年

  • 高温高湿環境下での炭素鋼の腐食促進に及ぼす塩化物の影響

    腐食防食協会 材料と環境2010  

    発表年月: 2010年

  • Ni-Ti 超弾性合金の水素脆性―マルテンサイト変態に伴う転位の影響―

    日本金属学会 2010年秋期(第147回)大会  

    発表年月: 2010年

  • ステンレス鋼の水素脆性に及ぼすマルテンサイト変態の影響

    日本金属学会 2010年秋期(第147回)大会  

    発表年月: 2010年

  • NaCl 水溶液中で定荷重負荷した鉛フリーはんだの材質劣化挙動

    日本金属学会 2010年秋期(第147回)大会  

    発表年月: 2010年

  • 水素吸収させた Ti-6Al-4V 合金表面でのリン酸カルシウムの析出挙動

    日本金属学会 2010年秋期(第147回)大会  

    発表年月: 2010年

  • Ni-Ti超弾性合金の応力誘起マルテンサイト変態と水素との相互作用

    日本鉄鋼協会 第160回秋季講演大会  

    発表年月: 2010年

  • Ni 基合金/低合金鋼 境界部のき裂停留挙動に関する材料,環境因子からの検討

    腐食防食協会 第57回材料と環境討論会  

    発表年月: 2010年

  • 常圧沸騰NH4Cl 水溶液環境における耐食材料の評価

    腐食防食協会 第57回材料と環境討論会  

    発表年月: 2010年

  • 二相系ステンレス鋼の定電位すきま腐食試験におけるすきま内環境測定

    腐食防食協会 第57回材料と環境討論会  

    発表年月: 2010年

  • Improvement of the Water Injection System to Mitigate NH4Cl Salt Corrosion

    Joint NACE/JSCE Workshop  

    発表年月: 2010年

  • Preferential dissolution of crevice corrosion of a duplex stainless steel

    Gordon Research Conference: Corrosion – Aqueous  

    発表年月: 2010年

  • Evaluation of Degradation of Ni-Ti Alloy as Biomaterial

    International Corrosion Engineering Conference 2010  

    発表年月: 2010年

  • 二相系ステンレス鋼の腐食反応に伴い発生する水素のSECM観察

    腐食防食協会 関東支部講演大会  

    発表年月: 2009年

  • 純Ti表面のリン酸カルシウム析出に及ぼす水素化物の影響

    日本金属学会 2009年春期(第144回)大会  

    発表年月: 2009年

  • NaCl 及び NaF 水溶液中における Ni-Ti 超弾性合金の水素吸収挙動

    日本金属学会 2009年春期(第144回)大会  

    発表年月: 2009年

  • Ni-Ti超弾性合金の昇温水素放出挙動-水素添加法の組み合わせによる影響-

    日本金属学会 2009年春期(第144回)大会  

    発表年月: 2009年

  • エロージョン・コロージョンのテクニカルモジュール作成におけるボイラー水中FACの減肉速度予測モデル

    日本鉄鋼協会 第157回春季講演大会  

    発表年月: 2009年

  • 18Crフェライト系ステンレス鋼の耐すき間腐食性に及ぼすMo添加の影響

    日本鉄鋼協会 第157回春季講演大会  

    発表年月: 2009年

  • 二相系ステンレス鋼の腐食反応に伴い発生する水素のSECM観察

    日本鉄鋼協会 第157回春季講演大会  

    発表年月: 2009年

  • 社会・産業インフラの安心・安全、信頼性向上のためのメンテナンス

    (社)日本鉄鋼連盟 亜鉛鉄板委員会 第26回技術情報交換会  

    発表年月: 2009年

  • 硫化銀針状結晶成長挙動の極値統計解析

    腐食防食協会 材料と環境2009  

    発表年月: 2009年

  • 二相系ステンレス鋼のa,g各相の溶解挙動

    腐食防食協会 材料と環境2009  

    発表年月: 2009年

  • 銅の大気腐食における塩基性硫酸銅の析出に関する一考察

    腐食防食協会 材料と環境2009  

    発表年月: 2009年

  • 塩水環境下における高耐食性合金の水素吸収挙動の定量評価

    財団法人ソルト・サイエンス研究財団 第21回平成20年度助成研究発表会  

    発表年月: 2009年

  • FIP試験環境での鋼材腐食の電気化学的評価

    腐食防食協会 第56回材料と環境討論会  

    発表年月: 2009年

  • 原子力用316L配管溶接部における溶解挙動のin situ観察

    腐食防食協会 第56回材料と環境討論会  

    発表年月: 2009年

  • 銀のパラジウム添加による硫化抑制のメカニズムの検討

    腐食防食協会 第56回材料と環境討論会  

    発表年月: 2009年

  • サワー環境におけるチタン製空冷式熱交換器チューブの腐食解析

    腐食防食協会 第56回材料と環境討論会  

    発表年月: 2009年

  • 二相系ステンレス鋼のa,g各相の溶解挙動の時間依存性

    腐食防食協会 第56回材料と環境討論会  

    発表年月: 2009年

  • 中性NaF水溶液中におけるNi-Ti超弾性合金の破壊挙動に及ぼすH2O2濃度の影響

    日本金属学会 2009年秋期(第145回)大会  

    発表年月: 2009年

  • 二相系ステンレス鋼の優先溶解機構の検討

    日本鉄鋼協会 第158回秋季講演大会  

    発表年月: 2009年

  • Ni-Ti超弾性合金の昇温水素放出挙動に及ぼす水素添加法の影響

    日本鉄鋼協会 第158回秋季講演大会  

    発表年月: 2009年

  • Dissolution Behavior of a and g phases of a Duplex Stainless Steel in a Simulated Crevice Solution

    216th ECS Meeting, the Electrochemical Society  

    発表年月: 2009年

  • Activities of JSPS 180th Risk Based Plant Management Committee and a Situation on RBI/RBM in Japan

    15th Asian-Pacific Corrosion Control Conference  

    発表年月: 2009年

  • Activities of JSPS 180th Risk Based Plant Management Committee and a Situation on RBI/RBM in Japan

    2009 Joint KGS - JSPS 180 Committee International Meeting on RBI/RBM  

    発表年月: 2009年

  • 物理的水処理による給水管の防食機構解明

    腐食防食協会 関東支部講演会  

    発表年月: 2008年

  • 水素吸収環境によるNi-Ti超弾性合金の脆化挙動の変化

    日本金属学会春期(第142回)大会  

    発表年月: 2008年

  • 過酸化水素添加によるフッ化物水溶液中におけるNi-Ti超弾性合金の水素脆化抑制

    日本金属学会春期(第142回)大会  

    発表年月: 2008年

  • Ti-Pd合金の塩酸含有アルコール溶液中における環境脆化感受性

    日本金属学会春期(第142回)大会  

    発表年月: 2008年

  • 腐食工学実践教育の推進 (協会賞受賞講演)

    腐食防食協会 材料と環境2008  

    発表年月: 2008年

  • すき間内模擬溶液中における二相系ステンレス鋼の腐食生成物電位依存性

    腐食防食協会 材料と環境2008  

    発表年月: 2008年

  • 「危険物施設の鋼製地下貯蔵タンクおよび鋼製地下配管の電気防食」制定と啓蒙・普及 (技術賞受賞講演)

    腐食防食協会 材料と環境2008  

    発表年月: 2008年

  • 海水環境における腐食と微生物との相互作用に対する電気化学的検討

    腐食防食協会 材料と環境2008  

    発表年月: 2008年

  • 交流レジストメトリーを用いた腐食モニタリング

    第55回材料と環境討論会  

    発表年月: 2008年

  • ラインパイプ鋼の中性付近pHSCC発生の定歪試験による評価

    第55回材料と環境討論会  

    発表年月: 2008年

  • 二相系ステンレス鋼の腐食挙動のAFM観察

    第55回材料と環境討論会  

    発表年月: 2008年

  • 銅の大気腐食に対する二酸化硫黄と硫化水素の影響

    第55回材料と環境討論会  

    発表年月: 2008年

  • Ni-Ti超弾性合金の水素脆性と応力誘起変態

    日本金属学会2008年秋期(第143回)大会  

    発表年月: 2008年

  • 過酸化水素添加による酸処理中のTiおよびNi-Ti合金の水素吸収抑制

    日本金属学会2008年秋期(第143回)大会  

    発表年月: 2008年

  • (独)日本学術振興会 産学協力委員会「リスクベース設備管理第180委員会」の活動

    日本高圧力技術協会 第7回リスクベースメンテナンスセミナー  

    発表年月: 2008年

  • Activities of 180th Committee for Risk Based Plant Management

    Korea-Japan Special Seminar for RBI/RBM  

    発表年月: 2008年

  • Effect of Microstructure on Torsional Fatigue Endurance of Martensitic Carbon Steel

    the 3rd JSME/ASME International Conference on Materials and Processing 2008 (ICM&P2008)  

    発表年月: 2008年

  • Development of technical module for erosion-corrosion

    4th International Workshop on Risk-Based Engineering  

    発表年月: 2008年

  • Activities of JSPS’s 180th Committee for Risk Based Plant Management

    4th International Workshop on Risk-Based Engineering  

    発表年月: 2008年

  • CORROSION BEHAVIOR OF A DUPLEX STAINLESS STEELIN A SIMULATED CREVICE SOLUTION

    16thICC  

    発表年月: 2008年

  • Atmospheric Corrosion of Copper in an Indoor Environment with a High H2S Concentration

    16thICC  

    発表年月: 2008年

  • Crの過不働態溶解挙動

    腐食防食協会 関東支部講演会  

    発表年月: 2007年

  • 極値統計による最大ウイスカ長さの推定

    発表年月: 2007年

  • 装置材料のリスク評価に基づく設備の信頼性維持プロセス

    化学工学会 第72年会  

    発表年月: 2007年

  • 酸添加した過酸化水素水含有生理食塩水中におけるNi-Ti超弾性合金の破壊特性

    日本金属学会春期(第140回)大会  

    発表年月: 2007年

  • 定ひずみ下におけるNi-Ti超弾性合金の水素吸収特性

    日本金属学会春期(第140回)大会  

    発表年月: 2007年

  • 0.9% NaCl水溶液中におけるNi-Ti超弾性合金の水素吸収挙動に及ぼす環境因子の影響

    腐食防食協会 材料と環境2007  

    発表年月: 2007年

  • 酸添加過酸化水素含有生理食塩水中におけるNi-Ti超弾性合金の腐食挙動

    腐食防食協会 材料と環境2007  

    発表年月: 2007年

  • Ni-Ti超弾性合金の水素脆化に及ぼす相変態の影響

    日本鉄鋼協会シンポジウム「水素状態分析標準化の基盤研究」  

    発表年月: 2007年

  • 炭素鋼エロージョン・コロージョンのテクニカルモジュール作成

    日本鉄鋼協会 第154回秋季講演大会  

    発表年月: 2007年

  • Ni-Ti超弾性合金の水素吸収と昇温放出挙動に及ぼす繰返し変形の影響

    日本金属学会秋期(第141回)大会  

    発表年月: 2007年

  • 過酸化水素含有生理食塩水中におけるNi-Ti超弾性合金の耐食性の向上-硝酸浸漬による表面改質-

    日本金属学会秋期(第141回)大会  

    発表年月: 2007年

  • Ti及びNi-Ti合金の表面改質に伴う水素吸収の評価

    日本金属学会秋期(第141回)大会  

    発表年月: 2007年

  • 交流レジストメトリーを用いた腐食モニタリングの検討

    第54回材料と環境討論会  

    発表年月: 2007年

  • 隙間内模擬溶液中におけるニ相ステンレス鋼の腐食挙動

    第54回材料と環境討論会  

    発表年月: 2007年

  • カソード部に特有な海洋微生物の存在とカソード電流の関係

    第54回材料と環境討論会  

    発表年月: 2007年

  • 炭素鋼エロージョン・コロージョンのテクニカルモジュール作成

    JSPS リスクベース設備管理第180委員会 第4回研究会  

    発表年月: 2007年

  • Hydrogen absorption behavior of Ti-6Al-4V alloy in acidic fluoride solutions

    The Society for Titanium Alloys in Dentistry  

    発表年月: 2007年

  • バイオフィルムによるカソード反応の加速について

    腐食防食協会関東支部講演会  

    発表年月: 2006年

  • 電気化学的陽極酸化法によるTiの表面改質

    腐食防食協会 関東支部講演会  

    発表年月: 2006年

  • 極値統計による最大ウイスカ長さの

    溶接学会マイクロ接合研究会  

    発表年月: 2006年

  • 二相系ステンレス鋼の反応活性の

    日本金属学会春期(第138回)大会  

    発表年月: 2006年

  • Ni-Ti超弾性合金の水素脆化―大気中放置による水素濃度分布の変化―

    日本金属学会春期(第138回)大会  

    発表年月: 2006年

  • 環境材料学への今日的期待

    腐食防食協会 材料と環境2006  

    発表年月: 2006年

  • 自然海水中におけるバイオフィルムの

    腐食防食協会 材料と環境2006  

    発表年月: 2006年

  • Ni-Ti超弾性合金の水素放出挙動

    日本金属学会秋期(第139回)大会  

    発表年月: 2006年

  • 加硫ゴムによる銀の微小腐食

    腐食防食協会 第53回材料と環境討論会  

    発表年月: 2006年

  • Susceptibility to Hydrogen Embrittlement of Ti-0.2Pd Alloy in Fluoride Solutions

    Journal of Dental Research vol. 85 (IADR Abstracts) , Brisbane, Australia  

    発表年月: 2006年

  • ritical Hardness for HSC in Deposit Welding on Steel Line Pipes under Cathodic Protection

    International Pipeline Conference, #IPC2006-10227,Calgary, Canada  

    発表年月: 2006年

  • A Simple Indoor Corrosion Test for Silver

    14th Asia-Pacific Corrosion Control Congress, #03-08,Shanghai  

    発表年月: 2006年

  • 純Tiのフレッティング腐食疲労におよぼすハイドロキシアパタイトの影響

    腐食防食協会 関東支部 講演会  

    発表年月: 2005年

  • 過酸化水素を含有した生理食塩水中におけるNi-Ti超弾性合金の破壊

    日本金属学会春期(第136回)大会  

    発表年月: 2005年

  • フッ化ナトリウム水溶液中におけるNi-Ti超弾性合金の水素吸収抑制―硝酸浸漬による表面処理―

    日本金属学会春期(第136回)大会  

    発表年月: 2005年

  • 硫黄ガス環境下における銀の微小腐食の律速過程解析

    腐食防食協会 材料と環境2005  

    発表年月: 2005年

  • 純Tiのフレッティング疲労におぼすハイドロキシアパタイトの影響

    日本金属学会秋期(第137回)大会  

    発表年月: 2005年

  • 過酸化水素を含有した生理食塩水中におけるNi-Ti超弾性合金の腐食挙動

    日本金属学会秋期(第137回)大会  

    発表年月: 2005年

  • 海水中での亜鉛めっき鋼の電位に及ぼす大気中で生成した腐食性生物の影響

    日本鉄鋼協会 第150回秋季講演大会  

    発表年月: 2005年

  • 硫黄ガス環境下での銀の微小腐食に対する添加元素の影響

    腐食防食協会 第52回材料と環境討論会  

    発表年月: 2005年

  • 海水中におけるステンレス鋼電位貴化現象の実験室的再現

    腐食防食協会 第52回材料と環境討論会  

    発表年月: 2005年

  • 海水中におけるステンレス鋼表面のカソード反応に及ぼす生物皮膜の影響

    腐食防食協会 第52回材料と環境討論会  

    発表年月: 2005年

  • SUB-MICROMETER ORDER CORROSION OF SILVER BY SULFUR VAPOR IN AIR STUDIED BY MEANS OF QUARTZ CRYSTAL MICROBALANCE

    16th International Corrosion Congress  

    発表年月: 2005年

  • 塩酸を含むエタノール溶液中におけるNi-Ti超弾性合金の水素脆化

    日本金属学会春期(第134回)大会  

    発表年月: 2004年

  • フッ化ナトリウム水溶液中におけるチタンおよびチタン合金の遅れ破壊特性

    日本金属学会春期(第134回)大会  

    発表年月: 2004年

  • 廃棄物からの浸出水環境下における鋼の腐食挙動

    腐食防食協会 材料と環境2004  

    発表年月: 2004年

  • 塩酸を含むアルコール溶液中におけるNi-Ti擬弾性合金の水素脆化特性

    腐食防食協会 材料と環境2004  

    発表年月: 2004年

  • CaCO3析出に及ぼす流速と磁場の影響

    腐食防食協会 材料と環境2004  

    発表年月: 2004年

  • 海水中におけるステンレス鋼の自然浸漬電位におよぼす残留塩素の影響

    腐食防食協会 材料と環境2004  

    発表年月: 2004年

  • 硫黄ガス環境下での銀の微小腐食速度影響因子についての一考察

    日本金属学会秋期(第135回)大会  

    発表年月: 2004年

  • 酸性フッ化ナトリウム水溶液中におけるTi-6Al-4V合金の水素吸収特性と腐食挙動

    日本金属学会秋期(第135回)大会  

    発表年月: 2004年

  • フッ化ナトリウム水溶液中でTi合金が吸収した水素の昇温放出分析による特徴付け

    日本金属学会秋期(第135回)大会  

    発表年月: 2004年

  • フッ化ナトリウム水溶液中で遅れ破壊したTi合金の表面および破面観察

    腐食防食協会 第51回材料と環境討論会  

    発表年月: 2004年

  • SUS304とSUS430におけるメタルダスティングの発生と成長

    腐食防食協会 第51回材料と環境討論会  

    発表年月: 2004年

  • Introduction of a JSPS Research Project “Development of Risk Based Maintenance Technology in Chemical Process Industries”

    The Korea-China-Japan joint symposium on 「Social Demands for Corrosion Engineering in Chemical Process Industries」at 2004 CSSK Meeting  

    発表年月: 2004年

  • フッ化ナトリウム水溶液中における歯科矯正用ベータチタン合金の遅れ破壊

    日本金属学会春期講演大会  

    発表年月: 2003年

  • 二相ステンレス鋼のクロム欠乏領域の計算

    日本鉄鋼協会 第146回秋季講演大会  

    発表年月: 2003年

  • 海岸地域における飛来海塩量の推定

    日本鉄鋼協会 第146回秋季講演大会  

    発表年月: 2003年

  • Ce-TZPセラミックスの機械的特性に及ぼす構造欠陥の影響

    日本金属学会秋期講演大会  

    発表年月: 2003年

  • 次亜塩素酸ナトリウム水溶液におけるNi-Ti超弾性合金の腐食破壊

    日本金属学会秋期講演大会  

    発表年月: 2003年

  • フッ化ナトリウム水溶液中におけるベータチタンの水素吸収特性

    日本金属学会秋期講演大会  

    発表年月: 2003年

  • 硫黄ガス環境下における銀の微小腐食

    腐食防食協会 第50回材料と環境討論会  

    発表年月: 2003年

  • SUS304とSUS430のメタルダスティング感受性の比較評価

    腐食防食協会 第50回材料と環境討論会  

    発表年月: 2003年

  • 物理的水処理の給水配管腐食に及ぼす効果の一考察

    腐食防食協会 第50回材料と環境討論会  

    発表年月: 2003年

  • 生体適合性に優れたTiの陽極酸化皮膜の生成・制御とその耐食性評価

    腐食防食協会 第50回材料と環境討論会  

    発表年月: 2003年

  • 次亜塩素酸ナトリウム水溶液中におけるNi-Ti超弾性合金の腐食挙動

    腐食防食協会 第50回材料と環境討論会  

    発表年月: 2003年

  • Effects of martensite phase of Ni-Ti shape memory alloy on corrosion behavior in sodium hypochlorite solutions

    13th APCCC  

    発表年月: 2003年

  • EFFECTS OF HYPOCHLORITE AND FLUORIDE ON CORROSION BEHAVIOR OF Ti-Ni ALLOY

    5th Latincorr. NACE  

    発表年月: 2003年

  • Ni-Ti超弾性合金のフッ化ナトリウム水溶液中における水素脆化

    春期日本金属学会  

    発表年月: 2002年

  • 酸性および中性フッ化ナトリウム水溶液中におけるNi-Ti超弾性合金の遅れ破壊

    春期日本金属学会  

    発表年月: 2002年

  • 超臨界水試験装置 給水加熱器割れ発生事例

    腐食防食協会 第49回材料と環境討論会  

    発表年月: 2002年

  • 口腔内環境におけるチタンの破壊-フッ化ナトリウム水溶液の影響

    秋期日本金属学会  

    発表年月: 2002年

  • Ni-Ti超弾性合金の遅れ破壊特性と水素吸収特性

    日本金属学会2001年春期講演大会  

    発表年月: 2001年

  • 超臨界および亜臨界状態の都市ごみ飛灰抽出水における各種金属材料の腐食調査

    腐食防食協会 第48回材料と環境討論会  

    発表年月: 2001年

▼全件表示

特定課題研究

  • 耐食材料の電気化学的評価に関する予備的調査研究

    2000年  

     概要を見る

     Ni-Ti超弾性合金は優れた耐食性、生体適合性を有しており、医療分野でも利用される機会が多くなっている。しかし、生体内環境や、口腔内環境は金属材料にとって苛酷な環境であり、損傷事例も報告されている。歯科矯正用ワイヤーも期待寿命より短期間で破損している。このような現象を例に予備調査を進めた。Ti合金は環境因子の感受性が高いが、口腔内での腐食現象に影響を与える環境因子は十分には解明されていない。環境因子として腐食現象の結果として生体液から発生し、合金内に侵入する水素イオンに着目し、その材質劣化への影響を検討した。Ni-Tiワイヤーに応力負荷条件下で水素イオンを陰極チャージし、材料履歴とチャージ量とを因子として水素脆性感受性を調査した。水素添加定荷重試験において破断までの時間はマルテンサイト変態誘起応力に依存する事が明らかとなった。応力誘起変態後は環境因子の影響を受けやすく材質の劣化が促進される事が考えられる。超弾性特性に着目した材質的変化と環境因子との相関に着目した研究を進める必要があろう。

 

委員歴

  • 2009年
    -
     

    (公社)腐食防食学会  会長

  • 2004年
    -
     

    (公社)日本鋳造工学会  評議員

  • 2003年
    -
     

    (公社)日本金属学会  評議員