Microstructure, mechanical properties and tribological performance of TiSiN-WS2 hard-lubricant coatings

TiSiN-WS2 hard-lubricant coatings were deposited on WC/TiC/Co cemented carbides by arc ion plating and middle-frequency magnetron sputtering. The microstructure, mechanical properties and tribological performance were examined. Results showed that WS2 layer had (0 0 2) and (1 0 1) multi-orientation structure and TiN grains of TiSiN layer became bigger due to the annealing effect in deposition of WS2 layer. As the thickness of WS2 layer increased, hardness of TiSiN-WS2 coatings decreased largely while the adhesive strength increased, which is mainly beneficial from the release of residual stress of TiSiN layer in deposition process of WS2 layer and the low tensile stress caused by the lubricant effect of WS2 in scratch test. The deposition of WS2 layer on top of TiSiN layer significantly improved coatings' tribological performance with lower friction coefficient, less adhesive materials and smaller wear rate of steel ball. Even after WS2 layer was worn out, the friction coefficient was still lower than TiSiN coating, which is attributed to that WS2 remaining in wear track still worked.