Wear behavior of the surface of Ti-6Al-4V alloy modified by treating with a pulsed d.c. plasma-duplex process

Ti-6Al-4V alloy has been used with some success in orthopedic devices and other engineering components due to several beneficial properties. However, inadequate wear behavior of Ti-6Al-4V alloy has largely restricted fields of application for this material. In this paper, a new method of plasma nitriding and plasma-enhanced chemical vapor deposition (plasma-duplex process) was conducted on Ti-6Al-4V alloy in order to modify its wear performance. The results indicate that the plasma nitriding processing temperature plays a dominant role in nitrided layer formation when compared to other nitriding parameters (e.g. treatment time, gas flow ratio of H₂/N₂ etc.). It is also shown that plasma nitriding and TiN coatings produced by plasma-duplex processing provide a marked improvement in the wear performance of the modified Ti-6Al-4V alloy surface. However, the friction coefficients of plasma-duplex treated samples increased significantly compared to the substrate. There is also a negative effect on the wear behavior if the TiN coating adhesion is poor.