Effect of temperature and deposition technology on the microstructure, chemistry and tribo-mechanical characteristics of Ti-B based thin films by magnetron sputtering

This study deals with a deep investigation on chemical, structural, mechanical and tribological properties of TiBx coatings produced by means of PVD techniques, i.e. Direct Current (DC-MS) and High Power Impulse Magnetron Sputtering (HiPIMS). TiBx coatings were deposited onto Si wafer, at different substrate temperatures (200, 300 and 400 °C). DC-MS products were strongly overstoichiometric (B at.%/Ti at.% up to 2.86 ± 0.01 at 200 °C), while HiPIMS ones showed a B/Ti atomic ratio closed to 2, particularly at high temperature. Moreover, HiPIMS films exhibited a dense and almost featureless morphology. All the deposited films were constituted of one crystalline TiB2 phase with hexagonal structure, but in HiPIMS mode, a completely dominant (001) texture was developed, which could be responsible of superior mechanical properties and low wear rates, compared to DC-MS products. Different wear mechanisms, i.e. micro-peeling vs direct ploughing at low abrasion rate have been speculated for the two coating types.