微粒子ピーニングによるチタン系材料の窒化層形成挙動に及ぼす処理条件の影響

抄録

Friction and wear properties of titanium-based materials are improved by nitriding; however, conventional nitriding decreases their strength owing to the grain-coarsening at high temperature (approximately 900 oC). The purpose of this study is to develop the rapid nitriding for titanium-based materials at room temperature in air without heating. This approach forms the nitrided layer on titanium-based materials using the transfer of nitrided commercially pure titanium particles during fine particle peening (FPP). Plasma nitriding was performed at 600 or 700 oC to form a nitrided layer on the surface of CP-titanium particles, and FPP was performed for 1, 10, 30 s using the nitrided particles. Nitrided layer could be found on titanium alloy (Ti-6Al-4V) due to the transfer of nitrided CP-titanium particles. Nitrogen concentration tended to increase with the particle nitriding temperature. Furthermore, the thickness of nitrided layer tended to increase with the treating time. Formation rate of nitrided layer by the developed process was higher than that by the conventional nitriding. In addition, nitrogen concentration of the treated surface on CP-titanium was higher than that by Ti-6Al-4V alloy and β-type titanium alloys.