Formation of superhard coatings during treatment of titanium films with low-temperature nitrogen plasma in open atmosphere

The processes of formation of superhard coatings by treating titanium films on sapphire substrates with a low-temperature nitrogen plasma flow in open atmosphere have been studied. It is shown that a coating of nitrogen-containing TiO$_2$ with a rutile structure, the microhardness of which is twice as high as that of rutile TiO$_2$ (up to 27 GPa), is formed during plasma treatment. Deposition of this coating hardens the surface of sapphire plates by 22–23%. High yield and synthesis in open atmosphere make the proposed technique promising for preparing superhard coatings with a high oxygen resistance.