Effect of Mo2C addition on the microstructures and mechanical properties of WC-SiC ceramics

Mo2C was added to WC-4.85 mol% SiC ceramics and sintered at 1600 °C using a resistance-heated hot-pressing machine. Dense ceramics containing 0-3 mol% Mo2C were obtained. The reaction products (W, Mo)5Si3 and (W, Mo)Si2 were produced during sintering. The relative amounts of (W, Mo)Si2 decreased and (W, Mo)5Si3 increased with increasing Mo2C amount. The abnormally-grown plate-like WC grains formed for WC-4.85 mol% SiC ceramics below 1.5 mol% Mo2C. Above 2 mol% Mo2C, the ceramics had a fine, equiaxed granular structure. The average WC grain size decreased from 0.77 μm without Mo2C, to 0.50 μm above 2 mol% Mo2C. The Vickers hardness increased with increasing Mo2C amount, reaching 21.4 GPa at 2 mol% Mo2C. The hardness of the WC-4.85 mol% SiC ceramics correlated with the inverse square root of the WC grain size. The fracture toughness for the Mo2C-added WC-4.85 mol% SiC ceramics ranged from 7.1 to 7.8 MPa m0.5.