Microstructure and mechanical properties of WC–Co-based cemented carbide with bimodal WC grain size distribution

In order to improve the wear resistance of coarse-grained WC–Co cemented carbides, the fine WC powder were used to reinforce the metallic binder. These WC–Co-based cemented carbides having bimodal WC grain size distributions were synthesized by liquid phase sintering. For comparison, the cemented carbides having unimodal WC grain size distributions were synthesized. The microstructure, hardness, fracture toughness and wear resistance of these cemented carbides were investigated. The results show that adding fine WC powder is an effective method to improve the wear resistance of coarse-grained WC–Co cemented carbides. The WC size, mean free path and fracture toughness decrease with the addition of fine WC powder, while the hardness exhibits an opposite trend. The impact-wear coefficient of bimodal distribution cemented carbides is noticeably lower than that of the unimodal one with the same hardness, which means that the cemented carbides with bimodal grain structure have better combination of hardness and impact-abrasive wear resistance. The impact-abrasive wear mechanism of the bimodal cemented carbides is that the fine WC grains prevent abrasive wear and the coarse WC grains prevent impact wear.