Microstructural Evolution and Mechanical Properties of Multi‐Phase (ZrHf x NbVMoW)–Co Cermets

ABSTRACT A series of novel multi‐phase (ZrHf x NbVMoW)C–Co multi‐component carbide‐based cermets with varying Hf contents was successfully fabricated by spark plasma sintering (SPS) at 1350°C–1650°C under an interval of 100°C using carbide powders prepared by the carbothermal reduction reaction. It is revealed that the addition of Hf leads to preferential formation of (ZrHfNb)C‐rich phase rather than the original (ZrNb)C‐rich phase for (ZrNbVMoW)C–Co cermet. This leads to improved driving force of formation for the other (VMoW)C‐rich phase, facilitating WC dissolution into (VMo)C‐matrix and promoting intermediate‐phase solid solution, which results in the multi‐phase microstructure composing of (ZrHfNb)C‐ and (VMoW)C‐rich phase while simultaneously improving the densification behavior. Notably, the induced lattice distortion and solid solution strengthening from Hf addition significantly enhance the overall mechanical properties of multi‐phase (ZrHf x NbVMoW)C–Co cermets. The optimal comprehensive performance is achieved at Hf content of 1/6, exhibiting superior Vickers hardness (20.3 GPa) and fracture toughness (6.8 MPa·m 1/2 ).