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

• DOI: 10.1016/j.corsci.2016.12.009
• Publication Date: 2016-12-23T22:17:48Z
• Authors: F.B. Ismail; V.A. Vorontsov; T.C. Lindley; M.C. Hardy; D. Dye; B.A. Shollock
• Keywords: Technology; Multidisciplinary; Science & Technology; Energy; Materials Science; NICKEL; TN; Materials Science, Multidisciplinary; HIGH-TEMPERATURE ALLOYS; 02 engineering and technology; STEM; 0905 Civil Engineering; Chemistry; Oxidation; Metallurgy & Metallurgical Engineering; QD; 0912 Materials Engineering; 0210 nano-technology; SIMS; Superalloys; 0913 Mechanical Engineering

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.