三次元窒素拡散制御した工業用純チタンの創製とその4点曲げ疲労特性

抄録

Titanium has been widely used in biomaterial fields owing to its excellent corrosion resistance, superior tissue compatibility; however, titanium shows poor resistance. Conventional nitriding can improve the tribological properties, but decreased the strength and corrosion resistance. The purpose of this study is to improve various properties of commercially pure titanium with high corrosion resistance by the formation of three-dimensional nitrogen diffusion phases using powder metallurgy. Gas nitriding was performed at 550 or 600 oC to form a nitrided layer at the surface of powders, and nitrided powders were consolidated by spark plasma sintering at 800, 1000, 1200 and 1400 oC. Nitrogen concentration of sintered compacts tended to increase with the nitriding temperature. Grain size of sintered compacts became large as the nitriding and sintering temperature increased. Tensile tests were performed for sintered compacts fabricated from nitrided powder in air. Ultimate tensile strength of CP titanium with three-dimensional nitrogen diffused phase was higher than that of the un-nitrided one. Furthermore, the ultimate tensile strength and ductility of sintered compacts tended to increase with decreasing the nitriding temperature. Fatigue tests were also performed in air under four-point bending. Fatigue properties of sintered compact fabricated from nitrided powder tended to be improved with decreasing the nitriding temperature.