Densification, microstructure and mechanical properties of SiO2–cBN composites by spark plasma sintering

SiO2–cBN composites were consolidated by spark plasma sintering at 1473–1973 K. The effects of cBN content and sintering temperature on the relative density, phase transformation, microstructure and mechanical properties of the SiO2–cBN composites were investigated. The relative density of the SiO2–cBN composites increased with increasing SiO2 content. The phase transformation of cBN to hBN in SiO2–cBN composites was identified at 1973 K, showing the highest transformation temperature in cBN-containing composites. The SiO2–20 vol% cBN composites sintered at 1673 K showed the highest hardness and fracture toughness of 12.5 GPa and 1.5 MPa m1/2, respectively.