Vol.:(0123456789) Oxidation of Metals https://doi.org/10.1007/s11085-019-09918-w 1 3 ORIGINAL PAPER Oxidation Behavior of γ′‑Ni 3 Al‑Based Ni–20Al–5Cr Alloys With and Without Reactive Elements Under Diferent Heating Conditions Wei‑Ting Chen 1,2  · Brian Gleeson 3  · Arthur Heuer 1 Received: 21 October 2018 / Revised: 24 April 2019 © Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract High-temperature oxidation of a model γ′-Ni 3 Al-based Ni–20Al–5Cr alloy and ver- sions of this alloy doped with Y, Hf, or Si, or some combination of these, was inves- tigated. Oxide scale evolution was characterized using SEM, TEM, and TOF–SIMS. The resulting scale microstructures depended quite sensitively on the heating rate to the oxidation temperature of 1100 °C. However, whatever the heating rate, the dopant additions improved the oxidation resistance of the base alloy. The reactive elements Y and Hf, if segregated to the surface during preheating under conditions where appreciable oxidation was not possible, suppressed transient oxidation and facilitated the exclusive growth of the thermodynamically stable α-Al 2 O 3 scale. Keywords NiAlCr alloy · Oxidation · Reactive element efect · Si efect · Scale microstructure Background Aluminum-containing Ni-based alloys and coatings fnd extensive use in gas tur- bine engines owing to their excellent high-temperature strength and outstanding thermal stability at temperatures as high as 1200 °C [1–3]. However, the service lifetimes of turbine components are frequently limited by oxidation resistance. Ideally, the oxidation of such alloys and coatings results in the exclusive forma- tion of a slow-growing α-Al 2 O 3 scale, which acts to signifcantly reduce further * Arthur Heuer ahh@cwru.edu 1 Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106, USA 2 Present Address: Materials Research Center, Missouri University of Science and Technology, Rolla, MO 65409, USA 3 Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15261, USA