Effect of the Cr content on the sintering behaviour of TiCN–WC–Ni–Cr3C2 powder mixtures

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In TiCN–W–Cr–Ni cermets produced by liquid phase sintering melting occurs at lower temperatures as their Cr content increases. For low Cr additions (up to 4wt.%) eutectic temperatures are close to those found in the TiC–WC–Ni system. For 8wt.% Cr and above, temperatures are similar to those found in the Cr–Ni–C system. The precipitation of M7C3 carbides is observed to start at 8wt.% Cr in samples sintered at 1425°C for 1h. This sets a limit for the Cr solubility in the binder phase of these cermets around 18wt.%. The dissolution of WC and Cr3C2 particles starts at temperatures as low as 1150°C, but that the homogenization of the binder phase is only achieved after melting. The carbonitride phase exhibits the typical precipitation of inner and outer rims onto Ti(C,N) cores. However, a fine precipitation of Ni-rich particles is found inside Ti(C,N) cores, likely related to coalescence phenomena.