プラズマ放電改質チタンの耐摩耗性と耐食性の評価

抄録

Titanium alloys is widely used as biomedical implant materials due to its high strength and biocompatibility. However, poor wear resistance has prohibited its application as bearing materials for artificial joints. In order to improve the wear resistance of titanium alloys, much research has been done on surface modification of titanium. Plasma discharge modification (PDM) is one of the promising surface modification methods of titanium. In this study, wear and corrosion resistance of PDM treated titanium, TiC processing and Si processing, was evaluated. The result of ball on disk wear test showed that PDM greatly improves the wear resistance of titanium. This is attributed to the hard TiC layer formed by PDM both on TiC processing and Si processing. The result of anodic polarization tests revealed that the PDM layer shows equal or superior passive current density compared to titanium substrate. However, the pitting potential decreased compared to titanium substrate. Observation of the tested samples show that the corrosion started from the dimple and the interface of the PDM shots created during modification. Therefore, the early pitting potential may be caused by the galvanic coupling of the substrate and the PDM layer at the dimple and PDM shot interface.