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.