Mechanical properties and microstructure of spark plasma sintered WC-8 wt.%Co-VC-cBN ultrafine grained cemented carbide

Abstract WC-Co cemented carbide tools offer better cutting performance when cutting difficult-to-machine materials, such as high-temperature alloys, titanium alloys, and high-strength steels. In this paper, high performance WC-8 wt.% Co cemented carbide materials with cBN and VC were prepared by spark plasma sintering. The effects of cBN and VC content on mechanical properties and microstructure of WC-8 wt.% Co-VC-cBN cemented carbide materials were studied. The results show that the relative density, Vickers hardness, and fracture toughness of WC-based cemented carbide materials decreased significantly as the content of cBN and VC increased. WC-8 wt.% Co-0.2 wt%VC-1 wt.% cBN (named as YG8V2B10) cemented carbide material had the optimal properties when sintered at 1250 °C. Its Vickers hardness, fracture toughness, and flexural strength are 20.81 GPa, 13.01 MPa m1/2, and 1630 MPa, respectively. High-temperature flexural strength of YG8V2B10 was also investigated. The flexural strength of YG8V2B10 cemented carbide materials decreased as the temperature increased. When the temperature of YG8V2B10 cemented carbide material exceeded 400 °C in air, matrix at the surface of YG8V2B10 was oxidized, which leads to a significant decrease in the flexural strength.