Surface modification of Ti-6Al-4V alloy by nitrogen ion implantation

Surface modification of titanium alloy (Ti-6Al-4V) by nitrogen implantation at the energy 120 keV with doses ranging from 1 × 1016 to 1 × 1018 N+/cm2 have been investigated from the tribological point of view. Implantation of nitrogen ions was performed in two different ways: (a) when no carbon deposition on the samples (produced from the oil diffusion pump and using a liquid nitrogen trap) took place and (b) when carbon atoms were doped into the nitrogen implanted layer (due to recoiling implantation). The depth distribution of the nitrogen implanted atoms was performed by using the RBS technique. The surface characterization of the implanted samples was carried out by means of XRD. It was shown that recoiling implantation reduces significantly the friction coefficient and the wear rates. The maximum decrease in these parameters was pronounced in the nitrogen implanted layer doped with carbon at the dose 1 × 1018 N+/cm2. In this case, TiC, or Ti(C, N) layers could be produced. On the other hand, the hardness measurements have shown an improvement at the surface layer of the titanium sample dependent on the nitrogen dose compared with the unimplanted sample.