Effect of partial substitution of Cr for Ni on densification behavior, microstructure evolution and mechanical properties of Ti(C,N)–Ni-based cermets

Four cermets of composition TiC–10TiN–16Mo–6.5WC–0.8C–0.6Cr3C2–(32 − x)Ni–xCr (x = 0, 3.2, 6.4 and 9.6 wt%) were prepared, to investigate the effect of the partial substitution of Cr for Ni on densification behavior, microstructure evolution and mechanical properties of Ti(C,N)–Ni-based cermets. The partial substitution of Cr for Ni decreased full densification temperature, and the higher the content of Cr additive was, the lower full densification temperature was. The partial substitution of Cr for Ni had no significant effect of the formation of Mo2C and Ti(C,N) and the dissolution of WC, and however, it had a significant effect on the dissolution of Mo2C. Cr in Ni-based binder phase diffused into undissolved Mo2C to form (Mo,Cr)2C above 1000 °C at 6.4–9.6 wt% Cr additive, and a small amount of (Mo,Cr)2C did not dissolve after sintering at 1410 °C for 1 h at 9.6 wt% Cr additive. In the final microstructure, Cr content in Ni-based binder phase increased with increasing the content of Cr additive, and however, regardless of the content of Cr additive, coarse Ti(C,N) grains generally consisted of black core, white inner rim and grey outer rim, and fine Ti(C,N) grains generally consisted of white core and grey rim. The partial substitution of Cr for Ni increased hardness and decreased transverse rupture strength (TRS). Ni-based binder phase became hard with increasing the content of Cr additive, therefore resulting in the increase of hardness and the decrease of TRS. TRS was fairly low at 9.6 wt% Cr additive, which was mainly attributed hardening of Ni-based binder phase and undissolved (Mo,Cr)2C.

Research highlights
► The partial substitution of Cr for Ni decreased full densification temperature of Ti(C,N)–Ni-based cermets.
► The partial substitution of Cr for Ni had a significant effect on the dissolution of Mo2C.
► Cr in Ni-based binder phase diffused into undissolved Mo2C to form (Mo,Cr)2C above 1000 °C at 6.4–9.6 wt% Cr additive, and (Mo,Cr)2C did not completely dissolve after liquid phase sintering at 9.6 wt% Cr additive.
► The partial substitution of Cr for Ni increased hardness and decreased transverse rupture strength.