Parameters of an Oxide-Free Ceramic Layer on Austenitic Steel

A solid, uniform CrN coating with a thickness of 21 μm was obtained at a negative bias potential Ub = −30 V and a pressure of the nitrogen atmosphere P = 1.2*10−3 Torr on austenitic steel. The analysis showed that there is a small amount of droplet component on the surface, but it is not observed in the middle of the coating itself. The optimal indentation modes with a load of 100–500 mN were established. The hardness of the resulting ceramic layer is 23–24 GPa; the elastic modulus is 260–262 GPa. The change in surface relief ranges from −1 to +2 μm and is insignificant for materials for engineering purposes. No signs of destruction of the CrN coating during the manufacture of micro-grinding and indentation, unlike the chromium coating, were found. The obtained high characteristics of nitride ceramics are explained by its structure and non-equilibrium conditions of its production. X-ray diffraction studies showed that the coating consists of a CrN phase with a texture axis [200]. According to the analysis of substructural characteristics, the size of the crystallites is 6.0–6.7 nm.