Structure and mechanical properties of Ni and Cr binary doped amorphous carbon coatings deposited by magnetron sputtering and pulse cathodic arc

This paper studies the structure and mechanical properties of amorphous carbon coatings (a-C) modified by Ni and Cr binary doping. The a-C:(Ni-x+Cr-y) coatings were deposited using pulsed cathodic carbon arc technique with direct current magnetron sputtering. Microstructure, surface morphology and chemical composition of the a-C:(Ni-x+Cr-y) coatings were analyzed via Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy. Friction parameters of the coating were studied under the condition of dry sliding using a "sphere-plane method. It has been established that the structure of binary doped coatings mainly consists of an amorphous carbon matrix, primarily with sp(2) bonds, chromium carbide and nickel metal clusters. The dependence of the Csp(3)/Csp(2) ratio and microhardness on the composition in the coating has been specified. The Ni/Cr ratio in the coating with the optimal content of Csp(2) and C-Cr carbide phases resulting in a decrease in the wear rate of the counterbody has been determined. At the same time, binary doping of carbon coatings substantially changes in both the phase compositions and surface morphology, which leads to the stabilization of the friction coefficient and reduces the counterbody wear rate.