Effect of the combined addition of TaC and NbC on the dispersity of cubic phase in ultra-fine WC–10Co–0.5Cr cemented carbides

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TaC and NbC have different effects on the dispersity of precipitated cubic phase, which acts as an important role in regulating the mechanical properties of ultra-fine cemented carbides. In this work, the influence of the combined addition of TaC and NbC on the microstructure evolution and mechanical properties in ultra-fine WC–10Co–0.5Cr cemented carbides was systematically investigated through the thermodynamic calculations and experiments. With the guide of thermodynamic calculations, the ultra-fine WC–10Co–0.5Cr cemented carbides with the combined addition of TaC and NbC were prepared. By replacing TaC with NbC, the dispersity of cubic carbides can be improved significantly from large-size honeycombed to small-size isolated cubic particles, which is explained by thermodynamic calculations. The brittle cubic phase results in the degradation of crack propagation resistance, and thus deteriorates the mechanical properties. Therefore, both the hardness and fracture toughness increase with the improvement of dispersity of cubic phase in cemented carbides.