High pressure synthesis of tungsten carbide-cubic boron nitride (WC-cBN) composites: Effect of thermodynamic condition and cBN volume fraction on their microstructure and properties

Tungsten carbide (WC) with different amounts of Cubic boron nitride (cBN) were synthesized by High Pressure-High Temperature (HPHT) method. The mapping correlation between thermodynamic condition, cBN addition, and microstructure, mechanical properties of WC-cBN composites was established and analyzed by response surface methodology. The main factors affecting the properties of composites were identified by ANOVA. The optimum thermodynamic condition was calculated. It was found that a minor phase transformation of cBN into the low-hardness hBN occurred at a temperature of 1300 degrees C and intensified at 1500 degrees C. The homogeneously dispersed cBN particles in the WC matrix promoted an improvement of hardness and fracture toughness, but the phase transition of cBN and its truss effect can dramatically reduce the mechanical properties. The Vickers hardness and fracture toughness of the well-sintered WC-cBN bulks reached a high value of 34 GPa and 13.6 MPa.m(1/2), which are improved by 17% and 52% respectively compared with the pure WC samples sintered under similar high-pressure level.

Automated summary

Tungsten carbide (WC) with different amounts of Cubic boron nitride (cBN) were synthesized using High Pressure-High Temperature (HPHT) method. The correlation between thermodynamic condition, cBN addition, microstructure, and mechanical properties of WC-cBN composites was analyzed. It was found that the phase transition of cBN at a certain temperature had a significant impact on the hardness and fracture toughness of the materials. The well-sintered WC-cBN composites exhibited improved hardness and fracture toughness compared to pure WC samples sintered under similar high-pressure levels.