Variation of Contents of Carbon, Nitrogen, and Oxygen upon Formation of Plasma Cermet Coatings with Steel Matrix Reinforced with Titanium Carbide

Abstract

This article describes comparative studies of a coating made of high-speed steel and cermet powder on its basis with 50 vol % of TiC strengthening carbide phase. Coatings are formed by Ar–N₂ plasma with local protection by powders with particle sizes from 25 to 55 μm. It is demonstrated that the TiC content in the coating is retained, but the lattice constant of this phase decreases from 0.43212 nm for powder to 0.43035 nm in the coating because of variation of contents of carbon, oxygen, and nitrogen. After plasma coating of 50 vol % TiC–R6M5 powder, the average carbon content in the coating decreases from 7.83 to 6.74 wt %. The oxygen content in the cermet coating increases to 2.8 wt % in comparison with 0.8 wt % in the initial powder. The nitrogen content also increases from 0.05 to 0.89 wt %. The microhardness of particles of initial powders of high-speed steel is 8.91 GPa, and that of 50 vol % TiC–R6M5 cermet is 9.5 GPa. The microhardness of the cermet coating, 11.0 GPa, corresponds to the calculated value obtained by the mixture rule at microhardness of the R6M5 steel coating equal to 6.64 GPa.