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 degrees 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. (C) 2015 Elsevier B.V. All rights reserved.