Study of the thermal dependence of mechanical properties, chemical composition and structure of nanocomposite TiC/a-C:H coatings

•Two nc-TiC/a-C:H coatings were prepared using unbalanced magnetron sputtering.•The hardness and elastic modulus did not change substantially up to 700 °C.•The decrease of fracture toughness after annealing was indicated.•Decrease in H content after annealing has been proven.•Increase in mean crystallite size was observed.

This work is aimed at the study of thermal stability of nc-TiC/a-C:H coatings deposited on steel substrates by unbalanced reactive magnetron sputtering of titanium in an acetylene containing atmosphere. The as-deposited coatings show high hardness and elastic modulus together with low wear and low friction coefficients. The coating properties were investigated as a function of annealing temperature using thermal desorption spectroscopy under UHV conditions. The hardness and elastic modulus did not change substantially up to 700 °C compared to the properties of the as-deposited coatings. The most significant changes were observed in case of their fracture toughness, which decreased due to the hydrogen loss from amorphous carbon matrix.