Alloying effects on oxidation mechanisms in polycrystalline Co–Ni base superalloys

Ismail, F.B. and Vorontsov, V.A. and Lindley, T.C. and Hardy, M.C. and Dye, D. and Shollock, B.A. (2017) Alloying effects on oxidation mechanisms in polycrystalline Co–Ni base superalloys. Corrosion Science, 116. pp. 44-52. ISSN 0010-938X (https://doi.org/10.1016/j.corsci.2016.12.009)

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Abstract

Oxidation mechanisms in polycrystalline Co–Ni–Cr–Al–W–Ta alloys were investigated using 16O/18O isotopic tracer analysis in the focused ion-beam secondary ion mass spectrometer (FIB-SIMS). It was found that Al additions favour the formation of a continuous alumina-rich layer, that Cr indirectly improved oxidation resistance and that increasing the Co fraction resulted in poorer oxidation performance. In the alloy containing 15 at.% Cr and 10 at.% Al, the outer scale formed after 200 h oxidation at 800 °C comprised oxides less than 1 μm thick. It is concluded that protective oxide scales can be formed in Co–Ni base superalloys.

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