Synthesis of TiC–NiCrBSi Binder Alloy Composite Powders for Cladding and Deposition of Wear-Resistant Coatings

Abstract

TiC–NiCrBSi binder metal matrix composites are fabricated by self-propagating high-temperature synthesis (SHS) in reaction powder mixtures of titanium, carbon (carbon black), and NiCrBSi alloy. It is established that stable combustion in a steady-state mode is possible with the content of a thermally inert metal binder in reaction mixtures up to 50%. Porous SHS cakes are crushed easily for subsequent separation by screening the composite-powder fraction necessary for the coating deposition. The synthesis products are studied by optical and scanning electron microscopy, X-ray diffraction (XRD), and electron probe microanalysis (EPMA). It is found that the average size of carbide inclusions in the composite structure depends on the content of thermally inert alloy powder in reaction mixtures and can be intentionally controlled in a wide range. The microhardness of granules of the composite powder formed by crushing SHS cakes decreases monotonically with an increase in the content of the metal binder softer than titanium carbide. The crystal lattice parameter of titanium carbide determined by XRD turned out considerably smaller than known values for equiatomic titanium carbide. It is established using local EPMA of carbide inclusions in the composite structure that the carbon-to-titanium weight ratio is 0.21 instead of 0.25 for equiatomic titanium carbide. Iron and silicon concentrations in carbide are negligibly low, those of oxygen and nickel are lower than 1%, and that of chromium is 2.5 wt %. It is concluded based on the analysis of the known data on the influence of all listed impurities on the titanium carbide lattice that the deficit of carbon is the main cause of a decrease in the lattice parameter.