On Deviations from Parabolic Growth Kinetics in High Temperature Oxidation

摘要

For high temperature oxidation of industrial alumina forming alloys, deviations from parabolic oxide growth kinetics are generally observed, even in systems where spallation is not (yet) occurring. The major published approaches, e. g. microstructural changes, stress-induced defect concentration changes in the scale and diffusional transport in the substrate are assessed. While these mechanisms are primarily operative for scales on 'thick' substrates, depletion of aluminium (and chromium)determines the behaviour of thin foils and of other geometries prone to localized depletion. For thin foils, the resulting growth law is presented in a parametric study. This shows that for technical FeCrAl(RE)alloys the effect of the successive depletion of aluminium and chromium on the growth law may be generally masked by microstructural relaxation processes in the alumina subscale and in the chromin subscale, respectively, of the observed duplex oxide scale.