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

• Melting in TiCN–W–Cr–Ni cermets occurs at lower temperatures as the Cr content increases.
• Eutectics change from those of the TiC–WC–Ni system to the ones found in the Cr–Ni–C system.
• Precipitation of M7C3 carbides sets a limit for the Cr solubility in the binder phase.
• The homogenization of the binder phase composition is only achieved after melting.
• A fine precipitation of Ni-rich particles is found inside Ti(C,N) cores.

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 4 wt.%) eutectic temperatures are close to those found in the TiC–WC–Ni system. For 8 wt.% 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 8 wt.% Cr in samples sintered at 1425 °C for 1 h. This sets a limit for the Cr solubility in the binder phase of these cermets around 18 wt.%. 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.

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