Preparation and properties of the VC/Cr3C2/TaC doped ultrafine WC-Co tool material by spark plasma sintering

This work is focused on the preparation and properties of ultrafine WC-Co cemented carbides. Samples were prepared by spark plasma sintering technology using WC and Co nanopowders and different inhibitors such as VC, Cr3C2 and TaC. The influence of inhibitors on the microstructure and mechanical properties of cemented carbides was investigated by using separate addition of VC/Cr3C2/TaC (0, 0.4 and 0.8 wt%) and pairwise addition (VC-Cr3C2, VC-TaC and Cr3C2-TaC). The results showed that with the addition of VC/Cr3C2/TaC, the average WC grain size decreased and VC led to smaller grain size than Cr3C2 and TaC. WC grain morphologies of cemented carbides with VC were triangular prisms with multi-step structure, whereas tended to be round and blunt in cemented carbides with Cr3C2/TaC. Moreover, the addition of inhibitors caused hardness to increase and fracture toughness to decrease in various degrees. Transverse rupture strength (TRS) was affected by changes in grain size and WC/Co interfacial energy caused by inhibitors. The sample with 0.4 wt% VC-0.4 wt% Cr3C2 sintered at 1250 °C had comprehensive mechanical properties. Its relative density, average grain size, hardness, fracture toughness and TRS were 98.9%, 200 nm, 2110 kg/mm2, 10.4 MPa⋅m1/2 and 1990 MPa, respectively.