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

Abstract

The effects of ultrafine WC (WC_UF, 0.5 µm) or W (1 µm) and C (0.3 µm) (W+C)_UF additives on the densification, microstructure and mechanical properties of coarse-grained cemented carbides were compared systematically. Overall, the cemented carbides with WC_UF/(W+C)_UF additives are almost fully densification to be higher than 99%, and the average grain size is kept above 2.8 µm. The WC_UF additive assists grains to (truncated) trigonal prism shape by two dimensional (2D) growth, whereas the (W+C)_UF additive 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 (75WC_C-15WC_UF)-10Co are 86.6 HRA and 2 272 MPa, respectively, both higher than those of (75WC_C-15(W+C)_UF)-10Co, which could be ascribed to the enhanced densification and unblemished grains. However, the fracture toughness of the (75WC_C-15(W+C)_UF)-10Co is 23.5 MPa·m^1/2, higher than that of the (75WC_C-15WC_UF)-10Co due to the uniform WC-Co structure and flexible binder phase.

Keywords

coarse-grained WC-based cemented carbide / ultrafine WC / ultrafine (W+C) / microstructure / mechanical properties

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