A comparison of the high-temperature oxidation of 17Cr-2Ni and 18Cr-8Ni austenitic stainless steels at 973 K

The oxidation behavior in air at 973 K of the austenitic stainless steels 18Cr-8Ni and 17Cr-2.5Ni-10.5Mn-2Cu-0.17N (low-nickel content), was studied in a thermobalance. The steels were heated from room temperature up to 973 K at 10 K min(-1), oxidized for 80 hr and then cooled to room temperature at 80 K min(-1). The two steels had the same weight gains, 0.18 mg cm(-2), which is equivalent to oxidation layers about 1.15 mu m theoretical thickness. In both cases, the general shapes of the Delta W S-1 (mg cm(-2)) curves vs. t (hours) were parabolic, but X-ray diffraction of the oxidized surfaces, surface and cross-section optical microscopy and SEM observations and EDS microanalysis show important differences between them.