Evolution of microstructure, mechanical and tribological properties of vanadium carbonitride coatings sputtered at different nitrogen partial pressures

Abstract

Vanadium carbide coatings were deposited by R.F. reactive magnetron sputtering at different nitrogen partial pressures. The structures and the mechanical and tribological behaviour of these coatings were studied. By using a combined approach of EDS and WDS, it has been shown that increasing nitrogen concentration from 0 to 27 at.% led to decrease the carbon content from 48.50 to 30.50 at.%. All coatings exhibited a dominant fcc-VC structure with additional fractions of vanadium nitrides, as determined by XRD. Nanoindentation measurements showed that the highest hardness of 26.1 GPa was obtained for the coating with a (N + C) / (V) ratio equal to 1.44. The transition in brittleness-ductile failure mode was noticed with increasing nitrogen content. This adhesive feature can prevent phase separation and improves the wear resistance of the coatings. Moreover, the nitrogen partial pressure showed a significant influence on the friction coefficient because of film density and residual stress effects.