Short-time Oxidation of Cast γ/γ′-Ni–Cr–Al–Ta–Re Alloys at 1,000 °C

Cast Ni–Cr–Al base alloys with two Cr ranges, 7–9.5 at.% and 3–4 at.%, respectively, and with Re + Ta refractory element contents of up to 7.5 at.% were subjected to oxidation experiments in air. The oxidation conditions were 100 h continuously at 1,000 °C and discontinuously for 500 h at temperature by cycling between room temperature and 1,000 °C. The times at temperature to the onset of scale spallation were monitored. Scale formation was investigated by SEM, EDS and XRD. The thermal expansion of the alloys and the lattice parameter of their γ-Ni phases were determined to assess their effect on the oxidation performance. Scale adhesion appears to be affected by mechanical interlocking at the alloy/scale interface.