The preparation, preparation mechanism and properties of extra coarse-grained WC–Co hardmetals

Extra coarse-grained hardmetals with WC linear-intercept grain size of more than 6.5 μm were prepared by adding activated sub-micrometer WC powders during ball milling. Metallographic examination shows that the grain boundaries of WC with narrow size distribution are straight. Thermal conductivity, fracture toughness, oxidation resistance and corrosion resistance of these hardmetals were measured also. The results indicate the thermal conductivities and fracture toughness are more than two times of 0.8 μm WC hardmetals’ with the same cobalt content. The excellence of the fracture toughness is thanks to the plastic deformation of extra coarse-grained hardmetals. The oxidation resistance of the hardmetal with addition of nickel is not significantly improved, but adding nickel can improve the corrosion resistance.