Microstructure and mechanical properties of (Nb,W,Ti)(C,N)-Ni solid solution cermets with 6 to 20 wt% Ni

Ni bonded (Nb,W,Ti)(C,N) solution cermets with overall compositions of NbC-(6–20)Ni-18WC-14 Ti(C0.7N0.3) (wt%) were prepared by pressureless vacuum sintering of compacted NbC, Ni, WC and Ti(C0.7N0.3) mixtures. The microstructure, phase constitution, room temperature mechanical properties were investigated and the phase composition in the cermets sintered at 1450 °C was simulated by thermodynamic modelling. The sintered cermets exhibited a microstructure of a cubic Ni alloy binder dispersed in the matrix of core-rim structured (Nb,W,Ti)(C,N) complete solid solution grains. The average ceramic grain size was in the range of 1.5–2.1 μm and increased with increasing binder content and sintering temperature. The hardness decreased whereas the fracture toughness and flexural strength increased with increasing Ni content. For the cermets sintered at 1450 °C, the 6 wt% Ni cermet had a hardness of 1627 kg/mm2, a toughness of 7.8 MPa.m1/2 and a flexural strength of 1478 MPa. The toughness and strength were improved to 13.1 MPa.m1/2 and 2446 MPa in the cermet with 20 wt% Ni.