Tribological Properties of nc-TiC/a-C:H Coatings Prepared by Magnetron Sputtering at Low and High Ion Bombardment of the Growing Film

摘要

Two series of nc-TiC/a-C:H coatings were deposited by a hybrid PVD-PECVD process of titanium sputtering in argon/acetylene atmosphere at two configurations of magnetic field resulting in different impinging ion fluxes on the growing film. The composition of the coatings is varied by changing the acetylene gas flow during the depositions. Tribological test were performed in conditions emulating dry machining of metals using 100Cr6 steel ball and silicon nitride ball as the counterpart. High temperature tribo-tests at 300°C and 500°C were performed with silicon nitride ball counterpart to examine the thermal stability of the coatings deposited at 320°C. Special focus was given on coatings with optimal chemical composition for high hardness. The coefficient of friction (CoF) and wear as functions of C/Ti are presented and compared between the series. It is observed that in the range of 1 < C/Ti < 2 the CoF is largely independent on the ion flux during the deposition and is ～0.2 - 0.3. The CoF then decreases with increasing carbon content up to a certain limit. Highest carbon-containing coating shows an increased CoF and wear. The CoF for coatings in the high hardness region is stable around 0.3 for the whole test at 300°C, the CoF at 500°C was stable at ～0.2 for the first half of the test, then the coating failed. The wear tracks were mostly delaminated. The coatings were strongly oxidized after the test.