Effect of surface modification on surface properties and tribological behaviours of titanium alloys

Abstract

Nitrogen ion implantation and carburization technology were chosen to modify the surface properties of titanium alloys. The surface components and element concentration distribution profile of the modified titanium alloy were characterized with X-ray photoelectron spectroscopy (XPS). The surface hardness and contact angle of the modified titanium alloys were measured to analyse the improvement of the mechanical properties and wettability. Friction and wear tests were performed between the modified titanium alloy plate against a ZrO2 ball on a universal multi-functional tester. Then the tribological behaviours of the modified titanium alloys were investigated by means of scanning electron microscopy and a laser granularity ana-lyser. The XPS analysis results indicated that titanium nitride and titanium carbide were formed on the titanium alloy surface. In addition, the surface hardness of nitrogen-ion-implanted titanium increased from 335±7.4 HV ( n=6) to 357±9.8 HV ( n=6), whereas the surface hardness of carburized titanium increased to 750±25.3 HV ( n=6). The contact angles of nitrogen-ion-implanted and carburized titanium alloys were decreased from 83 to 80 and 71.5°, respectively, indicating an improvement of surface wettability. In addition, the wear results indicated that both nitrogen ion implantation and carburization greatly improved the wear resistance of the titanium alloys and decreased the size of the wear debris. Finally, an attempt was made to explain the wear mechanisms of the modified titanium alloys.