Effect of carbon content on the microstructure and mechanical properties of ultrafine WC-15Co cemented carbides using a Co-based solid solution binder phase

In this paper, a new method was proposed to improve the uniformity of the distribution of grain-growth inhibitors using a Co-based solid solution prepared with Co3O4, Cr2O3, and V2O5 as the raw materials through high-temperature hydrogen reduction. The effect of carbon content on the microstructure and mechanical properties of ultrafine WC-15Co cemented carbides using a Co-based solid solution binder phase were studied. The results demonstrated that the carbon content exerted a considerable influence on the composition of the binder phase, thereby affecting the morphology of the WC grains. With increasing the carbon content, Cr and V precipitated from the Co-based solid solution, adhering to the habit planes of WC or segregating at the WC-Co interface. This hindered the growth of WC grains, yielding an average particle size smaller than that of alloys containing 6.0 wt% carbon content. However, increased carbon content may enhance grain growth owing to the dissolution-precipitation process of WC grains during the liquid-phase sintering process. Thus, an alloy comprising 6.31 wt% carbon content and featuring trigonal prismatic-shaped WC grains with a mean particle size of 0.310 μm exhibited excellent comprehensive performance, characterized by a hardness, transverse rupture strength, and fracture toughness of 1579 kg/mm2, 2581 MPa, and 10.56 MPa·m1/2, respectively. •Ultrafine WC-15Co cemented carbides were prepared using Co-based solid solution as the binder phase.•The carbon content had a significant impact on the microstructure of the ultrafine WC-15Co cemented carbides.•The mechanism of the carbon content on the WC particle size is clarified.•High-performance WC-15Co cemented carbide with Co-based solid solution was prepared with an optimal carbon content.