Comparative Study on Microstructure and Mechanical Properties of Coarse-grained WC-based Cemented Carbides Sintered with Ultrafine WC or (W+C) as Additives

The effects of ultrafine WC(WCUF,0.5μm) or W(1μm) and C(0.3μm)(W+C)UFadditives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared systematically.Overall,the cemented carbides with WCUF/(W+C)UFadditives are almost fully densification to be higher than 99%,and the average grain size is kept above 2.8μm.The WCUFadditive assists grains to(truncated)trigonal prism shape by two dimensional(2D) growth,whereas the(W+C)UFadditive assists grains to rounded shape by three dimensional(3D) growth,lowers WC contiguity and increases face-centered-cubic Co.The hardness and bending strength of(75WCC-15WCUF)-10Co are 86.6 HRA and 2 272 MPa,respectively,both higher than those of(75WCC-15(W+C)UF)-10Co,which could be ascribed to the enhanced densification and unblemished grains.However,the fracture toughness of the(75WCC-15(W+C)UF)-10Co is 23.5 MPa·m1/2,higher than that of the(75WCC-15WCUF)-10Co due to the uniform WC-Co structure and flexible binder phase.