Understanding the potential of microwave sintering on WC - Co

Tungsten-rich cemented carbides are known for their excellent features in terms of balancing strength, durability, wear resistance and fracture toughness. Conventional sintering has been widely used to manufacture these strong and hard materials, even with its shortcomings in manufacturing time, energy requirement and strength threshold, paving way for a number of new and enhanced processing techniques aimed at developing high performance carbide tools. Microwave sintering has been successfully applied to a range of materials, including ceramics and a broad series of refractory metals. This study used microwave sintering to manufacture high-strength WC-Co alloys requiring significantly less time and processing steps, and without grain growth inhibitors as part of the composition. Particles, sized between 100 and 500 nm, were compacted using a conventional, unidirectional press at room temperature to create loosely bonded green samples that were later microwave sintered. The effect of sintering temperature and initial particle size, and how each of these influences the microwave behaviour for such range of materials, are also discussed. The maximum demonstrated hardness in submicron samples was 1800 HV, which is 20% larger than most industrial cutting tools manufactured using conventional routes. Fracture toughness was calculated from combining the hardness results and crack length measurements. Submicron particles exhibited great fracture toughness with a maximum of 14 MPa root m, which is impressive considering the high hardness achieved in these samples. The samples with enhanced mechanical behaviour, including hardness and fracture toughness, demonstrated homogeneity in grain size, grain growth and WC-Co bonding.