Investigation of surface properties of high temperature ion nitrided titanium alloys

The aim of this study is surface hardening of Ti6Al4V titanium alloy by plasma nitriding technique.Titanium and titanium alloys are very attractive materials because of their excellent properties like a good corrosion resistance and biocompatibility for many industries. But using of titanium and its alloys are very low in mechanical engineering applications because of poor surface hardness and wear resistance. These problems can be overcome using such surface engineering technologies as thermochemical treatments to obtain desirable properties. Applications of titanium and its alloys supply very wide applications with forming high hardness surface layers by plasma nitriding. In the research stage of this thesis surface modification of Ti6Al4V titanium alloy were observed. According to the results of the questionnaire that plasma nitriding treatment has been performed in constant gas mixture, for different times at various temperatures.The study presents the results of the examinations of microstructures, microhardnesses, thicknesses, X-Ray difraction analyses, wear behaviours of surface layers formed on the Ti6Al4V titanium alloy by plasma nitriding. By optic inspection two layers were determined on the samples that called compound and diffusion layers. Compound layer contain titanium nitrides, XRD results support in this formations. XRD analysis showed that increasing the nitriding temperature resulted in the increase of the growth of these phases. By microhardness measurements investigations, the surface hardness were found to increase with increasing process temprature and time. Also the case depth were found to increase with increasing process temprature and time. The result of wear tests which was carried out using ball-on-disc machine is wear resistance of Ti6Al4V alloy increases as the time and temperature of plasma nitridig increase.