Effect of spark plasma sintering temperature on microstructure and mechanical properties of mullite - WC composites

In this paper, the influences of variation of spark plasma sintering (SPS) temperature on the microstructure and mechanical properties of mullite-(10 wt%)WC composites were investigated. It was found that the increment of the SPS temperature from 1300 degrees C to 1400 degrees C improves the densification behaviour and mechanical properties of this composite. However, with the further increasing of the SPS temperature to 1450 degrees C, the grain size of mullite matrix considerably increased and tungsten carbide reinforcements partially decomposed to W2C phase. Due to inferior mechanical properties of W2C in comparison with WC and grain growth of mullite matrix, mechanical properties of this sample were deteriorated. As a consequence, the SPS temperature of 1400 degrees C was chosen as the optimum consolidation condition for this composite. The comparison of microhardness, fracture toughness and strength of mullite-(10 wt%)WC composite (15.89 GPa, 4.07 MPa.m(1/2) and 298 MPa, respectively) with the monolithic mullite samples SPS-processed at the temperature of 1400 degrees C confirms the positive effect of WC addition to mullite matrix.