Microstructure and mechanical properties of (Ti,W)C-Ni cermet prepared using a nano-sized TiC-WC powder mixture

The microstructure and mechanical properties of a (Ti,W)C-Ni cermet, which was prepared from a mixture of nano-sized TiC-WC powder, were investigated in comparison with those of a (Ti,W)(CN)-Ni cermet, which was also prepared from a mixture of nano-sized powder, and previously reported to have high toughness values. The mixture of nano-sized powders was prepared by milling commercial Ti and W powders at various molar ratios (9:1, 8:2, 7:3, 6:4), with graphite. The mixture was isothermally sintered with Ni powder at 1500°C for 1 h. EDS analysis revealed that the solid-solution phase in the (Ti,W)C-Ni cermet contained considerably more W (44.6 at%) than in the (Ti,W)(CN)-Ni cermet (30.6 at%). This was attributed to the higher affinity between TiC and WC, than between Ti(CN) and WC. The fracture toughness (max. 15.2 MPa m^1/2) of the (Ti,W)C-Ni cermet was superior to that of the (Ti,W)(CN)-Ni cermet (max. 12.1 MPa m^1/2). The toughness enhancement is attributed to the increase of W content in the solid-solution phase, together with the higher volume fraction of Ni-binder phase.