Influence of nano-Ni on the microstructure of multicarbide-based alloys

Abstract

Titanium carbide alloys are used for manufacturing of cutting tools, dies, wear-resistant parts. Significant advantages of such materials are high hardness, wear resistance, resistance to build up edge, but they possess low strength and crack resistance. Since the mechanical properties are structurally sensitive, it is important to establish size of the starting powders effect on the alloy’s microstructure formation and the morphology of carbide grains. In this paper TiC-5NbC-5WC-x (NiCr) alloys have been investigated, where x is 10, 18, 24% (wt.) at the ratio Ni:Cr = 3:1. Fine and nano nickel were used as starting powders. The alloys were obtained by powder metallurgy technology, which included homogenization of carbide powders and binder metals, pressing, sintering at the temperature 1350 ̊C during 40 minutes. The microstructure of the alloys was examined by scanning electron microscopy using ZEISS EVO 40 XVP microscope and energy dispersive X-ray spectrometry. In all alloys, regardless of the chemical composition and size of the starting nickel powders, the core/rim structure of carbide grains specifying titanium carbide-based alloys, however, of different size and shape, were found. Comparison of alloys, containing 13.5% (wt.) of fine or nano nickel, revealed that the diffusion of carbide metals in the binder is more intense in alloys with nano nickel, which could result in its maximum alloying and strengthening.