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. •Full densification of Ni bonded NbC-18WC-14Ti(C0.7N0.3) cermets with 6 to 20 wt% Ni was achieved by pressureless sinte¬ring in vacuum for 90 min at 1390 or 1450°C. Both WC and Ti(C0.7N0.3) completely dissolved in the NbC and binder phases. Core-rim NbC solution grains with a Nb and W-rich core and a Ti-rich rim were formed.•The variation in Ni resulted in a clear effect on the hardness and toughness of the cermets. The hardness of the cermets decreased, whereas the toughness increased with increasing binder content. The trend is in agreement with the correlation in WC-Co and other ceramic-metal composites.•With increasing Ni content from 6 to 20 wt%, the hardness decreased from 1627 to 1128 kg/mm2, whereas the toughness increased from 7.8 to 13.1 MPa.m1/2 and the strength increased from 1478 to 2446 MPa for the cermets sintered at 1450°C.