Effects of Ni and Cu additions on microstructures, mechanical properties and wear resistances of ultra-coarse grained WC-6Co cemented carbides

Ultra-coarse grained WC-6Co cemented carbides with 1.2 wt% (Ni and/or Cu) additions were investigated and compared with a focus on microstructure, mechanical properties and wear resistance using scanning electron microscope, X-ray diffraction, mechanical properties tests and wear test. The results reveal that Ni and/or Cu play a definite role in inhibiting the growth of WC grain and stabilizing fcc-Co. Moreover, Cu exhibits a stronger inhibition effect on the WC grain growth compared to Ni. In addition, Ni promotes WC grains to evolve towards the plate-like shape, while Cu retards the evolution of WC grains from round shape to facetted shape. Therefore, the addition of 1.2 wt% Ni can improve simultaneously hardness and fracture toughness, resulting in an approximate 50% improvement in wear resistance. However, Cu is proven to improve hardness at the expense of fracture toughness, and deteriorate wear resistance. Instead of Cu, in this regard, Ni is a promising addition to strength ultra-coarse grained WC-Co cemented carbides used for rock-drilling applications.