Influence of WC addition on mechanical properties of (HfNbTaZrTiMo)C-Co cermet

(HfNbTaZrTiMo)C-Co high entropy carbide cermet was fabricated by conventional vacuum sintering. The effect of WC addition on the mechanical properties of cermets was also investigated. For cermets without WC addition, with the extension of sintering time, the hardness of cermets first rose and then fell, while the fracture toughness showed a decreasing trend. The increase in sintering temperature led to a decline in hardness and an enhancement of fracture toughness. The (HfNbTaZrTiMo)C-15 wt. % Co cermet sintered at 1450 degrees C for 2 h had the best comprehensive properties, with the hardness and fracture toughness of 16.36 +/- 0.17 GPa and 7.19 MPa center dot m1/2, respectively. After adding WC, there was a typical black core (undissolved (HfNbTaZrTiMo)C phase)-gray rim (seven-component (HfNbTaZrTiMoW)C solid solutions) structure in the cermets. Meanwhile, Mo diffused into WC to form (Mo, W)C solid solutions. The formations of (HfTaZrNbMoTiW)C and (Mo, W)C solid solutions resulted in an improvement in hardness. In addition, since the addition of WC enhanced the wettability between carbides phase and Co phase, the comprehensive properties of cermets were improved. The hardness and fracture toughness of the (HfNbTaZrTiMo)C-42.5 wt. % WC-15 wt.% Co cermet sintered at 1450 degrees C for 2 h were 17.42 +/- 0.06 GPa and 8.22 MPa center dot m1/2, respectively.