RFプラズマで窒化したチタンの特性と窒化層の破壊強さ

抄録

We attempted to nitride titanium using radio frequency plasma. We studied the relationship between nitriding conditions and characteristics of the nitrided layer have been investigated, then tested stationary fracture strength and the fracture mechanism of the nitrided layer using inverse acoustic emission (AE) analysis. We obtained the following results.
1) The composition of the nitrided layer depends greatly on the substrate temperature. Stoichiometric TiN were maintained as long as temperature was high enough. Nitriding was governed by the internal diffusion of nitrogen. The hardness of the nitrided layer decreases exponentially with depth. The nitriding rate showed the activating dominance of temperature dependence.
2) Fracture mode and dynamics under stationary loaded conditions was evaluated by inverse AE signal analysis. A nitrided layer dominated by Ti₂N, which is treated at high temperatures, has more excellent mechanical properties than that of TiN-dominated layers treated at high temperatures.
3) The wear loss in the nitrided layer, which has considerable hardness and is dominated by TiN, is small compared to that of Ti₂N. Nevertheless, cracks occurred in the TiN layer under sliding wear. Exfoliation and fracture of the nitrided layer under sliding wear could be evaluated by AE source wave analysis if an exact analysis of stress in the nitrided layer could be conducted..