Effect of WC on microstructure and mechanical properties of silicon nitride nano-composites

Silicon nitride nano-composites were fabricated by hot-pressing nano-sized Si3N4 powders and sub-micrometer WC powders. The effect of WC particles on microstructure and mechanical properties of silicon nitride ceramics was analyzed and discussed. SEM micrographs showed that WC particles have little effect on the microstructure morphology of silicon nitride nano-composites consisting of spherical grains. The addition of WC particles could improve the fracture toughness and the flexural strength. The maximum values of the fracture toughness and the flexural strength could be obtained when the amount of WC particles was 4 wt.% and 8 wt.%, respectively. However, the Vickers hardness (HV) values of silicon nitride ceramics containing WC particles were lower than that of monolithic silicon nitride ceramic, and the value was minimum when the WC amount was 4 wt.%.