Microstructure and mechanical properties of Mo-free Ti(C,N)-based cermets with Ni–xCr binders

Abstract

TiC–9.0TiN–19.5WC–0.5Cr3C2–0.3C–38.0(Ni–xCr) (x=0, 10, 20 and 30wt.%) cermets were prepared, to investigate microstructure and mechanical properties of Mo-free Ti(C,N)-based cermets with Ni–xCr binders. 20–30wt.% Cr in binders led to the obvious increase of the dissolution rate of WC, which was mainly attributed to the decease of the solid/liquid transition temperature of Ni-based binder phase. In the final microstructure, Ti(C,N) grains exhibited two kinds of the core/rim structure: one consisted of black core, white inner rim and grey outer rim, and the other consisted of white core and grey rim. Ti(C,N) grains with black core were on the whole larger in size, independently of Cr content in binders, and their grey outer rim increased in thickness with the increase of Cr content in binders. More often than not, white inner rims were thin and incomplete in shape, and there were fine white speckles in black cores, when Cr content in binders reached 20–30wt.%. Lattice parameter of Ni-based binder phase increased with the increase of Cr content in binders, which was attributed to that the total amount of such alloying elements as Ti, W and Cr in this phase increased with the increase of Cr content in binders, and however, it increased slightly when Cr content in binders was in the range of 10–20wt.%. Transverse rupture strength reached a peak value when Cr content in binders was 20wt.%, and hardness increased with the increase of Cr content in binders.