Local and microstructure-related effects affecting the high temperature oxidation of alumina formers: a brief survey

摘要

Local effects such as precipitation of alloyed additions, segregation of impurities and scale mechanical failure through its cracking and/or spallation often play an important role in oxidation-induced degradation of high temperature materials. This paper reviews a number of effects and processes which either are entirely local or exhibit different extents or rates in various regions in the scale, at the scale-substrate interface and/or at the substrate surface. Special attention is paid to the implications of the starting material inhomogeneity, various types of mechanical failure in the oxide layer, oxidant penetration towards and into the substrate and finishing of component edges. The experimental evidence was obtained using commercial and synthetic alumina formers oxidised under isothermal and thermal cycling conditions. The observed effects are discussed in terms of their influence on the oxidation and degradation rate and mechanisms at temperature range relevant to the application of alumina formers, i.e. exceeding 1070 K.