Stratified oxide scale growth on two Cr-Ni steels oxidized in high-pressure steam at 800°C

摘要: A commercial 18% Cr-11% Ni steel and a laboratory-made 21% alloy have been oxidized in steam at 50 atm pressure with approximately 0.2 ppm O2 800°C for 50–1000 hr. The oxide scales studied by optical microscopy, replica electron x-ray, selected-area-electron diffraction microprobe analysis. diffusion processes gold markers autoradiography means of the reaction18O (p, n)18F. On both materials internal oxidation combination external scale formation is observed. interface between inner internally coincides very closely original metal surface. phases present identified. fairly even thickness on grows cubic rate law. irregular thickness; areas protective Cr-oxide alternate above-mentioned structure, so-called nodules. zones nodules are frequently intersected bands compact oxide. growth mechanism discussed terms theory oxidation. reason beneficial effect increased content constant Cr briefly.