Preparation of (W, Mo)C-SiC ceramics and their mechanical properties

Binderless cemented carbides consisting of a (W,Mo)C solid solution and SiC were synthesized and consolidated by resistance-heated hot pressing of WC-Mo2C-C-SiC powder mixtures in the temperature range of 1600 to 1800 °C. The microstructures and reaction products of the ceramics were examined, and their density and mechanical properties were measured. The solid-state reaction for synthesizing (W,Mo)C solid solutions is (l-x)WC + x/2 Mo2C + x/2C → W1-xMo2C. Without the addition of SiC, Mo2C remained after hot pressing. However, for (W,Mo)C-SiC ceramics obtained from the powder mixtures with SiC content ±5 mol% and x ±0.2, very little residual Mo2C was observed. Each (W,Mo)C grain was composed of a W-rich core phase and a W-deficient phase on the core's periphery, suggesting a two-phase separation during cooling. The (W,Mo)C-SiC ceramics with x± 0.2 were densely sintered, and their Young's modulus changed with the SiC content according to the Voigt mixture rule. The (W,Mo)C-SiC ceramics sintered at 1600°C had high hardness above 23 GPa and a fracture toughness of ∼ 5.8 MPa m 1/2.