Microstructure and characterization of WC-2.8 wt% Al2O3-6.8 wt% ZrO2 composites produced by spark plasma sintering

Abstract WC-Al2O3 and WC-ZrO2 composites in previous research suffered a trade-off between hardness and fracture toughness. Herein, it is found that combining 2.8 wt% Al2O3 and 6.8 wt% ZrO2 together in a WC composite, via spark plasma sintering, can produce both high hardness and high fracture toughness. The new composite was sintered at temperatures ranging from 1350 to 1600 °C, and the densification, phase constitution, microstructure, and mechanical properties of it were investigated. Surprisingly, the WC-2.8 wt% Al2O3-6.8 wt% ZrO2 composite achieved full densification at a low sintering temperature of 1400 °C. With a sintering temperature of 1450 °C, the optima hardness and fracture toughness were produced, 21.0 GPa and 8.5 MPa m1/2, respectively. The mechanisms driving the low sintering temperature and well-combined mechanical properties of the composite were identified and explored.