医療用Co-Cr合金の表面性状と組織に及ぼすショットピーニングの効果

抄録

Co-Cr alloy is widely used as implant materials. In artificial joints, wear and fatigue fracture are one of the concerns. In order to improve the service life of artificial joints, it is necessary to improve the wear resistance and fatigue strength of Co-Cr alloy. Shot peening (SP) is one of the methods to improve these parameters. However, no previous study has been done on evaluating the SP treated Co-Cr alloy. In this study, the surface morphology and crystalline structure of shot peened Co-Cr alloy were evaluated. The result of roughness test showed that the roughness increases by SP treatment. This effect was remarkable among specimens using large particle size and high hardness projection materials. Large surface roughness may cause wear debris and become a starting point of fatigue fracture in actual implant usage. Therefore, projection materials that increase the surface roughness are incompatible for improving wear and fatigue properties. Increase of hardness was observed of specimens that showed high ratio of strain-induced martensitic transformation (SIMT) and refinement of crystal grains which was confirmed by EBSD analysis.