Effects of the counterface materials on the tribological characteristics of CNX coating deposited on plasma-nitrided Ti6Al4V

Deposition of carbon nitride (CNX) films on plasma nitrided Ti6Al4V, i.e. Duplex treatment, was prepared in order to improve the tribological properties of Ti6Al4V. Pin-on-disk wear tests with different types of counterfaces, i.e. 52 100 steel balls, alumina balls and ultrahigh molecular weight polyethylene (UHMWPE) pins, were performed to evaluate the wear and friction characteristics of the duplex-treated coatings. Wear and friction tests showed that the duplex-treated coating system sliding with different counterfaces was effective in maintaining a favorable low and stable coefficient of friction and improving the wear resistance of Ti6Al4V. For the wear tests of sliding with steel balls, the transferring of materials from the steel ball was one of the main wear events. For the wear tests of the duplex-treated coating sliding with the alumina ball, the generation, compaction and graphitization of the coating debris layer (which acted as a lubricating third body) improved the friction property and wear resistance of the coating. For the wear tests of titanium substrate sliding with UHMWPE pins, severe abrasion was found on both titanium alloy and UHMWPE pin surfaces. With the application of the duplex-treated coating system on the titanium substrate, both the coefficient of friction and wear volumes of the two counterfaces were reduced significantly.