Effects of Sintering Pressure and Co Content on the Microstructure and Mechanical Performance of WC–Co Cemented Carbides

The fabrication of WC-based cemented carbides faced challenges including inhomogeneous composition and grain coarsening. To solve these problems, WC–Co cemented carbides were fabricated via spark plasma sintering (SPS) using core–shell WC–Co powders prepared by an electroless plating method. The effects of sintering pressure and Co content on the microstructure and mechanical properties of the cemented carbides were investigated. The results showed that, with increasing sintering pressure, the relative density of the sintered samples was improved (98.4–99.6%) while the grains were coarsened (0.94–1.07 μm). The optimal properties (fracture toughness 11.11 MPa·m1/2, and hardness 2100.3 HV30) were obtained when sintered with a pressure of 20 MPa. Grain coarsening at higher pressure (30 MPa) reduced the toughness of the cemented carbides. When the Co content was increased from 3 wt.% to 8 wt.%, fracture toughness was improved while the hardness of the cemented carbides was reduced, attributed to the intrinsic high toughness and low hardness of the Co phase. The WC–8 wt.% Co cemented carbides exhibited optimized synergic mechanical performance (hardness of 1874.2 HV30 and fracture toughness of 13.77 MPa·m1/2). This work elucidated the relationship between the key sintering parameters (pressure and Co content) and the microstructure and mechanical properties of the cemented carbides. The achievements obtained provide a theoretical foundation for high-quality fabrication of the WC–Co cemented carbides.