Microstructure and mechanical properties of dual-grain structured WC-Co cemented carbides

In this study, the dual-grain structured WC-Co cemented carbides were fabricated by in situ reaction using carbon, fine W powders, Co powders, and coarse WC powders as starting materials. The phase formation, microstructure, and mechanical properties of the prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that the cemented carbides with both coarse and fine WC grains which were evenly distributed within the continuous Co binder phase could be obtained. A WC1-x phase of 5-6 atomic layers was observed between fine WC grain and Co binder phase. The hardness of the present cemented carbides was nearly similar to the ones prepared with the mixture of coarse WC, fine WC and cobalt powders. The fracture toughness of the present cemented carbides was greatly improved owing to crack deflection and transgranular fracture. The present dual-grain structured cemented carbides presented good comprehensive mechanical properties with a Vickers hardness of 1360 +/- 37 HV30, a transverse rupture strength of 3304 +/- 105 MPa, and a fracture toughness of 14.78 +/- 0.45 MPa m(1/2), respectively.