Effects of nano WC and Cr3C2 on grain growth, microstructure and mechanical properties of ultra-coarse cemented carbides

Ultra-coarse cemented carbide is widely used in construction and mining fields, but it is difficult to achieve good coordination between WC grain size and mechanical properties by traditional technology. In this paper, ultra-coarse cemented carbide was successfully prepared by the synergies of nano-powder activation and Cr ₃C ₂ grain growth inhibition. The specific effects of nano WC powder and Cr ₃C ₂ on WC grain growth at various stages and the microstructure and performances for ultra-coarse cemented carbide were investigated. The result shows that nano WC powder had no significant effect at the solid phase sintering stage, but could promote the WC grain growth at the liquid phase sintering stage. Cr ₃C ₂ was able to inhibit the WC grain growth at both the solid phase and liquid phase sintering stages, the WC grain size distribution of the alloy was more uniform. But excessive Cr ₃C ₂ would lead to the appearance of pores, weakening the mechanical properties of the alloy. The most suitable addition amount of Cr ₃C ₂ was 0.5 wt%. The simultaneous addition of nano WC and Cr ₃C ₂ guaranteed the ultra-coarse cemented carbide with uniform microstructure and excellent mechanical properties, its TRS, hardness, and average WC grain size were 2753 MPa, 1047 kg/mm ², and 6.63 μm.