The Effect of cBN Additions on Densification, Microstructure and Properties of WC–Co Composites by Pulse Electric Current Sintering

Cubic boron nitride/Tungsten carbide‐cobalt ( cBN / WC – Co ) composites were fabricated at low temperature by pulse electric current sintering ( PECS ) using Ni – P as sintering additives to promote low temperature densification. Effect of c – BN addition on the densification behavior, microstructure and mechanical properties of WC – Co composites was investigated. It was found that near‐fully dense WC / Co with 0 ~ 20 vol% cBN composites could be obtained at temperatures between 1100°C and 1200°C under 50 MPa, while no phase transformation of c BN into the low‐hardness hexagonal hBN . The 20 vol% cBN / WC – Co sample sintered at 1100°C under a pressure of 50 MPa for 10 min has a combination of hardness 16.5 GPa and fracture toughness K IC 13.7 MP·m 1/2 . The homogeneously dispersed cBN particles in the WC / Co composites promoted a slight increase of hardness, but a significant improvement of fracture toughness. The cBN particle bridging or deflection and pullout contribute to the high toughness.