Effect of Ni-xCr Binders on Microstructure and Mechanical Properties of Ti(C,N)-Based Cermets

Ti(C,N)-based cermets containing 18wt% and 38wt% Ni-xCr (x=0, 10, 20, 30, wt%) were prepared by powder metallurgy, to study the effect of the composition and content of Ni-xCr binders on microstructure and mechanical properties of Ti(C,N)-based cermets. Ni-based binder phase and Ti-based carbonitride ceramic grains are observed in the other cermets, except that high-Mo and high-Cr white microstructure is also observed in cermet containing 38wt% Ni-30Cr binder. There are often very fine white speckles in black core of ceramic grains for cermets with Cr-containing binder, especially at 38wt% binder, and grey outer rim of ceramic grains becomes thicker when Cr content is high in binders. Regardless of binder content, the hardness of cermets increases with increasing Cr content in binders, and the increment in hardness is more obvious at 38wt% binder. At 18wt% binder, transverse rupture strength and fracture toughness of cermets decrease with increasing Cr content in binders. However, at 38wt% binder, they increase firstly and then decrease with increasing Cr content in binders, and reach the peak at Ni-10Cr binder. Ceramic grains refinement lead to the increase in the probability of intergranular fracture and decrease in the probability of transgranular fracture. And the synergistic effect of ceramic grain refinement, crack deflection, crack bridging and induced microcracks can significantly improve transverse rupture strength and fracture toughness of Ti(C,N)-based cermets.