Grain growth behaviour and mechanical properties of coarse-grained cemented carbides with bimodal grain size distributions

The WC grain growth behaviour and mechanical properties of coarse-grained cemented carbides with bimodal grain size distributions were investigated using WC-5Co composite powders with accurately controlled WC grain size distribution. The composite powders were prepared by a Sol-Gel process and ultrafine WC (UF-WC, 300 nm) was added to coarse WC (C-WC, 6.0 mu m) to adjust the WC grain size distribution. It indicated that the WC grains undergo 2-D nucleation with 2-D growth at low OF-WC addition (<= 6 wt%), resulting in a truncated trigonal prisms shape, whereas the WC grains grow up through 2-D nucleation with 3-D growth at high OF-WC addition (>= 9 wt%), leading to a pyramid-like shape with a layer-by-layer structure of WC grains. Vickers hardness and fracture toughness tests indicated that the cemented carbide containing 6 wt% OF-WC present significant improvements in the hardness (1281.7 +/- 1.6 HV10) and the fracture toughness (25.4 +/- 0.2 MPa m(1/2)).

Automated summary

The study reveals that adjusting the WC grain size distribution by adding ultrafine WC and coarse WC can significantly impact the grain growth morphology of cemented carbides. Hardness and fracture toughness tests demonstrate that alloys containing 6 wt% ultrafine WC exhibit the best mechanical properties.