表面改質処理を施したTiNi形状記憶合金の腐食疲労特性

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  • Corrosion Fatigue Property of Surface-Modified TiNi Shape Memory Alloy

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<p>TiNi shape memory alloys have been using in medical devices such as self-expanding stents which expand narrow parts of blood vessels. However, if Ni ions in the TiNi shape memory alloy dissolve in the blood through a corrosion reaction, this may cause an allergy. Furthermore, fatigue fracture is expected to occur in the early stage because stents are placed in blood vessels for a prolonged amount of time. This study aims to improve the corrosion resistance and corrosion fatigue life by surface modification on TiNi shape memory alloy wires. To improve the corrosion resistance of the TiNi shape memory alloy wires, a passive layer was generated to its surface by thermal nitridation treatment. And then, we revealed that the corrosion resistance and corrosion fatigue life of the surface-modified TiNi shape memory alloy wire by an anodic polarization test and a rotating bending fatigue test in NaCl water solution. The results obtained in this study are summarized as follows: (1) The corrosion resistance of the thermal nitrided material is much better than those of the normal heat treated and the polished material. (2) The electrolytic polishing before the thermal nitridation treatment has little contribution to the corrosion fatigue life. (3) The corrosion fatigue life of the electrolytically-polished material is much higher than those of the any other materials prepared in this study.</p>

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