Rapid densification and mechanical properties of ultra-high-pressure sintered transition metal carbide ceramics

Densifying transition metal carbide (TMC) ceramics is challenging due to their low diffusion coefficient and strong covalent bonding. Ultra-high-pressure sintering (UHPS) is a promising technique for preparing dense ceramic materials at low temperatures, but it is underutilized in TMC ceramics. Herein, we report the successful employment of UHPS at 1500 °C for 3 min with an auxiliary pressure of 7 GPa, yielding TaC, NbC, TiC, and ZrC ceramics with relative densities of 99.3%, 98.9%, 98.2%, and 96.4%, respectively. We demonstrate that the densification mechanism of the TMC ceramic in this investigation encompasses plastic deformation and high-pressure assisted atomic diffusion. Furthermore, we determine the Vickers hardness and fracture toughness of TaC, NbC, TiC, and ZrC ceramics to be 16.5, 15.9, 24.0, and 17.7 GPa and 2.5, 2.9, 2.8, and 1.8 MPa m 1/2 , respectively. Moreover, with increasing temperature from room temperature to 500 °C, the hardness and elastic modulus of all four TMC ceramics gradually decrease, with the hardness declining by approximately 17–25%.