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

This work reports research concerning the behaviour of cermet coatings depo sited by high velocity oxy-fuel (HVOF) spraying which are designed to exhib it resistance to abrasive wear and high-temperature oxidation. Cermet powde rs 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 ma de 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 produce d from these SHS powders contained the following phases: titanium carbide, an iron-titanium intermetallic, an iron-rich body-centred cubic binder phas e and iron-titanium oxides. The proportions of these phases varied with the initial composition of the powder. The abrasive wear resistance of the coa tings depended on both the feedstock powder composition and on the abrasive type. The coating produced from the powder mixture with titanium and carbo n in equal molar proportions was the most wear resistant to alumina abrasiv e, whereas the coating produced from the mixture with a greater molar propo rtion of titanium than carbon was the most wear resistant to silica abrasiv e. Explanations for this behaviour in terms of the expected titanium carbid e stoichiometry and the coating microstructure are proposed. The coatings p roduced in this work exhibited wear rates equivalent to or lower than a HVO F-sprayed coating produced from a commercially available blended NiCr-Cr3C2 powder. (C) 2001 Elsevier Science B.V. All rights reserved.