Abstract
This paper examines the oxidation behaviour of CoNiCrAlY coatings manufactured by APS, HVOF and CGDS deposition techniques when subjected to isothermal heat treatments. Comparison of the as-deposited coating microstructures is achieved by means of scanning electron microscopy (SEM). Investigation of the oxide compositions and growth dynamics is achieved by SEM, X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). Oxide growth rates were determined by a series of mass gain measurements. Results from this study demonstrate that lower coating porosity and oxide contents lead to lower oxide growth rates. Results also demonstrate that low-temperature processing of CoNiCrAlY bond coats is beneficial to their oxidation behaviour as it favours the formation of alumina in preference to other detrimental fast-growing mixed oxides.
