In this work, the high temperature oxidation behavior of selected MCrAlY overlay coatings has been compared using the integral layer profile analysis. Emphasis is placed upon the influence of chemical composition on the oxidation. Commercial MCrAlY coatings are oxidized isothermally at a 1000°C for different time periods in order to form the thermally grown oxide layer. The results show that the oxide scale formation on coatings is considerably influenced by a composition of base metal, M, as well as CrAlY. Ni in coating leads to decrease of mixed oxide scale formation. As the oxidation time increases, transient oxidation stage is represented. Then protective alumina oxide layer formation, Al-depletion, Ni or Co outward diffusion and solid state reaction with pre-existing alumina to form spinel phase, and Cr{sub}2O{sub}3 oxide formation at the oxide-to-metal interface occur; these processes highly depend on the oxidation temperature and microstructures of MCrAlY coatings. In this study, under the high temperature oxidizing condition, Ni-including CoNiCrAlYs, NiCrAlYs and NiCoCrAlYs outperform the cobalt-based systems.
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