Wear behaviour of nitrogen-implanted and nitrided Ti6Al4V alloy

Abstract

The comparison between the wear behaviour of nitrogen-implanted Ti6Al4V alloy (where the alloy composition is given in approximate weight per cent) and that of nitrided Ti6Al4V alloy is reported. Both treatments were carried out at temperatures from 573 to 973 K on lapped surfaces (arithmetic average roughness R a ≈ 0.01 μm); in order to compare roughness effects, nitriding was also carried out on rougher samples (R a ≈ 0.25 μm). An improvement in wear resistance for lapped surfaces was noted after implantation at 573 K or higher temperatures and after nitriding at temperatures over 773 K only; however, at 873 K, nitriding was more effective than implantation. Rough nitrided surfaces showed better wear resistance than lapped nitrided surfaces or lapped implanted surfaces. Most probably the improvement in wear resistance on implanted samples is due to a reduction in friction induced by chemical modification of the surface as a result of oxide and TiN. Scanning electron microscopy observations which show subsurface voids and coalescence are in good agreement with a wear model previously reported. As implantation preserves the surface finish, a possible application is suggested.