Oxidation Behaviour of MCrAlY Bond Coats Manufactured by Plasma, HVOF and Cold Gas Dynamic Spraying

摘要

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.