Enhancement of the mechanical properties of ultrafine-grained WC-Co cemented carbides via the in-situ generation of VC

WC-12Co-xVC cemented carbides were synthesized using an in-situ synthesis method consisting of precursor formation, deoxidization and carbonization-sintering steps. The experimental results showed the mean grain size of the WC in the sintered alloys decreased from 1.05 to 0.46 and 2.13–0.57 µm, corresponding to the VC content from 0 to 2 wt% at 1350 °C and 0–6 wt% at 1400 °C. V4WC5 thin-layer was generated in the final sintered sample with low VC addition. As the VC content increased to more than 2 wt%, the V4WC5 with larger particles size were generated except the V4WC5 thin-layer, which would effectively enhance the hardness of WC-12Co-VC cemented carbides. The fracture toughness reached the maximum value of 16.45 MPa·m1/2 for WC-12Co-2VC sintered at 1350 °C for 2 h; while the Vickers hardness reached the maximum value of 2124 HV for WC-12Co-6VC sintered at 1400 °C for 2 h, respectively.