Microstructure and abrasive wear behaviour of FeCr–TiC coatings deposited by HVOF spraying of SHS powders

Abstract

This work reports research concerning the behaviour of cermet coatings deposited by high velocity oxy-fuel (HVOF) spraying which are designed to exhibit resistance to abrasive wear and high-temperature oxidation. Cermet powders have been produced by self-propagating high-temperature synthesis (SHS) reaction of elemental powder mixtures of Fe, Cr, Ti and C. The Fe and Cr made up 30 wt.% of the powders with a chromium to iron ratio of 1:4 by weight and the Ti and C were present in varying proportions. The coatings produced from these SHS powders contained the following phases: titanium carbide, an iron–titanium intermetallic, an iron-rich body-centred cubic binder phase and iron–titanium oxides. The proportions of these phases varied with the initial composition of the powder. The abrasive wear resistance of the coatings depended on both the feedstock powder composition and on the abrasive type. The coating produced from the powder mixture with titanium and carbon in equal molar proportions was the most wear resistant to alumina abrasive, whereas the coating produced from the mixture with a greater molar proportion of titanium than carbon was the most wear resistant to silica abrasive. Explanations for this behaviour in terms of the expected titanium carbide stoichiometry and the coating microstructure are proposed. The coatings produced in this work exhibited wear rates equivalent to or lower than a HVOF-sprayed coating produced from a commercially available blended NiCr–Cr 3C 2 powder.