Abstract
Operating temperatures above 700°C are desired to improve the efficiency of power generation systems such as microturbines. Therefore, the use of creep-resistant Ni-based or Fe-based alloys, which can form protective Cr2O3 and Al2O3 scales, is required. In this paper, Fe- and Ni-based alloy foils were oxidized in air + 10 % H2O for up to 3,000 h at 850°C to identify the most promising alloys. The thickness and chemical composition of the spinel oxide formed on top of the Cr2O3 scale varied between S3100, N08120 and N06230 alloy foils. In addition, the rate of Cr and Mn loss (spinel and Cr2O3 oxidation and volatilization) or Al loss (oxidation) and the dissolution of strengthening precipitates, were found to be a function of the nature of the formed oxide (Fe or Ni-rich spinel, Cr2O3, Al2O3). Alloys N06230 and alumina-forming austenitic (AFA) steels were found to be well-suited for the applications as microturbine recuperator foil materials up to 850°C.
