Microstructure and mechanical properties of ultrafine WC–Ni–VC–TaC–cBN cemented carbides fabricated by spark plasma sintering

Ultrafine WC–Ni–VC–TaC cemented carbides with different amounts of cubic boron nitride (cBN) were fabricated by spark plasma sintering, and the microstructure and mechanical properties of the as-prepared cermets were investigated. Scanning electron microscopy observations showed that the size of WC grains in the cermet samples was 0.2–0.4 μm. After the addition of cBN, the samples were still quite dense with the highest relative density of almost 98% when the addition fraction of cBN was 50 vol.%, although some micropores might exist in the samples. X-ray diffraction results indicated that no phase transformation of cBN was detected. The relative density and hardness of the cemented carbides increased with the addition fraction of cBN, but their strength decreased. When the fraction of cBN increased from 0 up to 50 vol.%, the hardness of the samples increased from 2100 to 3200 HV, but the flexural strength decreased from 1950 to 1250 MPa.