The selective oxidation of Ni-5Cr and Ni-4Al alloys is evaluated during high (800°C) and low (420°C) temperature exposures with the oxygen partial pressure moderated by a Ni/NiO powder buffer. Internal oxidation of Cr and Al is observed throughout the matrix and at grain boundaries at 800°C accompanied by the ejection of Ni onto the surface for both. At 420°C, matrix internal oxidation was eliminated and only Ni-4Al exhibited intergranular (IG) oxidation. Surprisingly, a protective surface oxide rapidly formed for Ni-5Cr blocking IG oxidation. This is contradictory to results in 330–360°C hydrogenated water environments where both alloys show IG oxidation.
Revised: May 29, 2019 |
Published: July 15, 2018
Citation
Kruska K., D.K. Schreiber, M.J. Olszta, B.J. Riley, and S.M. Bruemmer. 2018.Temperature-dependent selective oxidation processes for Ni-5Cr and Ni-4Al.Corrosion Science 139.PNNL-SA-129585.doi:10.1016/j.corsci.2018.04.037