Fabrication, mechanical properties, and oxidation resistance of (Nb,Ti)CN-Ni cermets with different TiC_0.7N_0.3 contents

NbCN-Ni cermets with various TiC_0.7N_0.3 contents (0–17.6 wt%) were fabricated via powder metallurgy method. The addition of TiC_0.7N_0.3 resulted in the formation of (Nb,Ti)CN grains with Ti-rich boundaries and Nb-rich cores. The average (Nb,Ti)CN grain sizes decreased with the an increase in the TiC_0.7N_0.3 content. However, an excessive amount of TiC_0.7N_0.3 exacerbated the formation of the graphite phase within the cermets. The (Nb,Ti)CN-Ni cermets underwent liquid-phase sintering at 1311.5 ℃ and reached full densification at a sintering temperature of 1480 ℃. TiC_0.7N_0.3 fully dissolved into NbCN grains at a temperature of 1350 ℃. The (Nb,Ti)CN-Ni cermets exhibited a semicoherent (Nb,Ti)CN₍₁₁₁₎/Ni₍₁₁₁₎ interface, and an increase in the Ti content reduced the misfits between the (Nb,Ti)CN and Ni. Owing to the reduction in average grain size and the formation of (Nb,Ti)CN grains, the HV₁₀ and oxidation resistance of the (Nb,Ti)CN-Ni cermets increased with the increases of TiC_0.7N_0.3 content. The transverse rupture strength (TRS) and fracture toughness first increased and then decreased, which was attributed to the formation of the graphite phase.