Plasma-Sprayed TiC-Based Cermets

The microstructure and microhardness of eleven volumetric cermets based on TiC carbide with nickel- and cobalt-based matrices after liquid-phase sintering at a temperature of 1400°C were studied. It is proposed to use the research results for the subsequent production of powders for plasma spraying of coatings. The compositions of the matrices and the contents of additional hardening phases and carbon were selected taking into account the specific features of the formation of plasma coatings: a decrease in the carbon content and high solidification rates of the sprayed particles with the formation of additional nanosized carbides and an increase in the volume fraction of carbides from 70 to 88%. The traditional composition for cermets with TiC carbide, NiCr–Mo, and industrial powders such as PG-SR2 grade (PN-CrNi80Si2B2) with the composition (wt %) Ni, 13.5 Cr, 2.7 Si, 4.5 Fe, 0.37 C, 1.65 B and TAFA 1241F grade with the composition (wt %) Co, 32 Ni, 21 Cr, 8 Al, 0.5 Y were used as the matrix. The ring zone on TiC carbide is formed by sintering with the participation of WC, Cr3C2, TiN, matrix phases, and 1–2.8 wt % of additional carbon in the composition of cermets. As a result, the initial volume fraction of TiC carbide increases from 70 to 88%. Additional carbon is also consumed to decrease the oxygen content at the sintering stage (the reduction of oxides). Upon sintering, the cermets have high microhardness values of 1940–3210 kgf/mm2 at an indentation load of 20 G and lower values at an indentation load of 200 G, which can be explained by the scale factor. The calculated maximum contribution of the hardness of the hardening phases to the hardness of the cermet was assessed for cermets with a Co matrix at 3681 kgf/mm2.