High temperature oxidation behavior of micro/nanostructured WC-Co coatings deposited from Ni-coated powders using high velocity oxygen fuel spraying

Abstract

High temperature oxidation of WC-based cermet coatings deposited from electroless Ni-coated micro- and nano-structured WC-Co powders (Ni/mc-WC and Ni/nc-WC) was studied. High velocity oxygen fuel (HVOF) spraying was employed for coating deposition, and thermo-gravimetry analysis (TGA) was carried out to examine the oxidation kinetics at 600-800 degrees C. For comparison, the same experiments were performed on conventional micro/nanostructured WC-Co coatings (mc-WC and nc-WC). Oxidation resistance of Ni/mc-WC and Ni/nc-WC coatings at 800 degrees C was improved by 88.5% and 893% compared to me-WC and nc-WC coatings, respectively. Linear kinetics with activation energies of 90.4 and 78.9 kJ/mol were obtained for me-WC and nc-WC, respectively, while oxidation kinetics of Ni/mc-WC and Ni/nc-WC coatings obeyed the parabolic law with greater activation energies of 212 and 197.5 kymol. (C) 2016 Elsevier B.V. All rights reserved.