Phase Composition, Microstructural Evolution and Mechanical Properties of (TiZrHfCr)C– x Ni Multi‐Phase Cermets

ABSTRACT

(TiZrHfCr)C– x Ni multi‐phase multi‐component carbide‐based cermets with varying Ni contents were fabricated by spark plasma sintering (SPS) using carbide powders prepared by carbothermal reduction reaction. The effects of sintering temperature and Ni addition on phase composition, microstructural evolution, and mechanical properties were systematically investigated. The incorporation of Ni significantly lowers the densification temperature, enabling near‐full densification of the cermets at 1450°C. Influenced by the substantial atomic size mismatch between Cr and Zr/Hf, the (TiZrHfCr)C carbide matrix does not form a single‐phase solid solution; instead, a multi‐phase microstructure is detected, comprising (ZrHf)C‐rich, (TiCr)C‐rich and Cr ₃ C ₂ phases. As the Ni content increases, the dissolution of Ti into (ZrHf)C‐rich phase is enhanced, accompanied by a decrease in Cr content within (TiCr)C‐rich phase. Under sintering conditions of 1650°C for 10 min, (TiZrHfCr)C‐10 wt% Ni sample exhibits the optimal mechanical properties, achieving a Vickers hardness of 19.0 GPa and fracture toughness of 7.4 MPa·m ^1/2 . Furthermore, the crack bridging and deflection mechanism associated with ductile Ni phase during crack propagation synergistically enhance the fracture toughness.