The tribological characteristics of titanium nitride, titanium carbonitride and titanium carbide coatings

The tribological behaviors of TiN, TiC and Ti(C,N) coatings prepared by differing mass flow rates of nitrogen and acetylene during the coating process are studied in this work. The lower specimens were coated with titanium film as the underlayer and with TiN, TiC or Ti(C,N) film as the top layer. They were deposited by the cathodic are ion plating process. The chemical compositions of eight types of ceramic coatings were determined by the wavelength-dispersive X-ray analysis. The influence by changing the mass flow rate ratio of N-2 and C2H2 gases on specimens tribological behavior, microhardness, coating morphology, and adhesive strength was investigated. The three-body abrasive wear more often appeared at the temperatures that the ceramic coating was not yet softened by the frictional heat. Increasing the mass flow rate ratio of the acetylene gas in the coating process is favorable for more ions to react with the titanium, thus resulting in noticeable rises of the C/Ti atomic ratio; conversely, it is disadvantageous for nitrogen ions to react with the titanium. The wear rate of the lower specimen with the TiN film is the lowest of the three kinds of ceramic coatings; however, its friction coefficient is relatively higher than that of the TiC film. (C) 1997 Elsevier Science S.A.