Microstructure and tribological behaviour of super-hard Ti–Si–C–N nanocomposite coatings deposited by plasma enhanced chemical vapour deposition

In this study, a series of new quaternary Ti–Si–C–N nanocomposite coatings have been deposited on HSS substrate at 550 °C using an industrial set-up of pulsed direct circuit plasma enhanced chemical vapour deposition (PECVD) equipment with a gas mixture of TiCl4/SiCl4/H2/N2/CH4/Ar. The composition of the coatings can be controlled through the adjustment of CH4 flow rate and the mixing ratio of the chlorides. Detailed structural and chemical characterisations using transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) suggest the formation of a Ti (C, N)/a-C/a-Si3N4 nanocomposite structure. Ti (C, N) films show a (200) texture, which change to random orientation of the crystallites when the silicon content reaches about 9 at.%. The tribological behaviour of these coatings was investigated at room and elevated temperature. The results show that the nanocomposite Ti–Si–C–N coatings with low Si and high C contents have a lower friction coefficient of 0.17–0.35 at room temperature. The Ti–Si–C–N nanocomposite coating containing 12 at.% Si and 30 at.% C shows excellent tribological properties with a low friction coefficient of 0.30 and a low wear rate of 4.5 × 105 mm3 N− 1m− 1 at 550 °C.