Abstract
The microstructures and properties of VC+Cr3C2 doped WC-2, 4mass%Co submicro-grained hardmetals that were prepared from WC powder of 0.12μm by hybrid sintering (a combination method of directly electrifying hot-press sintering with normal sintering, i.e., external heating pressureless sintering) and normal sintering were investigated, following the previous study on 10 mass% Co hardmetal.
The lowest densification sintering temperature for almost full density (≥99% of theoretical density) in hybrid sintering, e.g., for 2 mass% Co alloy, was lower by 40 K than in normal sintering, which was larger than that (30 K) for 10 mass% Co hardmetal. The minimum WC mean grain size and the maximum hardness HV of hybrid-sintered hardmetal were 0.19μm and 2650, respectively. These values were smaller and larger than those (0.22μm and 2460) of normal-sintered hardmetal, differing from 10 mass% Co hardmetal. The fracture toughness (Kc) at a definite hardness of hybrid hardmetal was superior with that of normal-sintered hardmetal in the same way as 10 mass% Co hardmetal. Thus, it was concluded that hybrid sintering has merits in the densification sintering temperature, grain size, hardness and fracture toughness, compared with normal sintering, particularly for low Co hardmetals.
