Structure and phase composition of SHS products in titanium, carbon and aluminum reactive mixtures

Abstract

The TiC + Al binder metal matrix composites were obtained by self-propagating high-temperature synthesis (SHS) in the reactive powder mixtures of titanium, carbon (carbon black) and aluminum. It was found that a steady-state wave combustion occurs when the aluminum powder content in reactive mixtures does not exceed 50 wt.%. Loose SHS cakes obtained during synthesis were crashed and screened to get lumpy, nearly equlaxial composite powders favorable to good flowability necessary for powder application in cladding and spraying of wear-resistant coatings. The synthesis products were studied by scanning electron microscopy, X-ray diffraction (XRD) and local energy-dispersive X-ray spectroscopy (EDX). It was found that the average size of carbide inclusions in the composite structure depends on the content of thermally inert aluminum powder in the reaction mixtures. The titanium carbide lattice parameter determined by XRD turned out to be slightly below the known values for equiatomic titanium carbide. However, no any dependence of the lattice parameter on the aluminum content in composites was found. TiC inclusions in the composite structure were investigated by EDX spectroscopy. Titanium content in the carbide was close to that in equiatomic titanium carbide. Titanium carbide contains up to 2.5 wt.% aluminum in addition to titanium and carbon. Aluminum dissolution in the carbide lattice can influence the lattice parameter.