Achieving combination of high hardness and toughness for WC-8Co hardmetals by creating dual scale structured plate-like WC

The dual scale structured WC-8Co hardmetals with plate-like WC grains were fabricated by sintering the mixed W-C-Co elemental composite powders prepared by plasma milling. The SEM and XRD were used to characterize the microstructure, the degree of the preferential orientation of plate-like WC and the morphology of the sintered WC-8Co hardmetals. The mechanical properties, including hardness, toughness and transverse rupture strength (TRS) of WC-8Co were measured and investigated. The result shows that by creating the dual scale plate-like WC structure, the TRS and fracture toughness of WC-8Co hardmetal can be increased distinctly while maintaining high hardness, reached to about 4000 MPa, 21.56 MPa m(1/2) and 1733 kg f/mm(2), respectively. Through investigating the cracks propagation, the toughening mechanism is proposed. It is suggested that the dual scale structure of plate-like WC not only triggers lots of crack deflection, crack bridging and crack branching, but also increases the amount of occurrence of the fracture through plate-like WC. This synergetic effect of dual scale structure and the plate-like WC morphology increase strongly the resistance to crack propagation.