Fabrication of WC-Graphene-Al Composites by Rapid Sintering and Their Mechanical Properties

Abstract

Tungsten carbides are very attractive because of their superior properties, e.g., high thermal and electrical conductivities, high melting point, high hardness, and relatively high chemical stability. Tungsten carbides with a binder metal, for example Ni or Co, are mainly used to fabricate nozzles, molds and cutting tools in the composite form. Al has been reported as an alternative binder in Tungsten carbide since Al shows a higher oxidation resistance than Ni or Co and is less expensive. Nanostructured WC-Graphene-Al composites were sintered rapidly using pulsed current activated sintering (PCAS). The mechanical properties (hardness and fracture toughness) and microstructure were investigated using scanning electron microscopy and Vickers hardness tester. The PCAS method successfully obstructed grain growth, resulting in nanostructured materials, and induced a very fast consolidation nearly at the level of theoretical density. The grain size of WC in WC-Graphene-Al composite decreased with the addition of Al content. The fracture toughness and hardness of the WC-5vol.% graphene-x vol.% Al (x=0, 5, 10, 15) were 4.7, 5.5, 5.9, 7.9 MPa·m1/2 and 2008, 1961, 1883, 1731 kg/mm2, respectively. The fracture toughness was improved without remarkable decrease of hardness due to the small dimensions of the WC grain and the consolidation facilitated by adding Al to WC-Graphene matrix.