Formation of perovskite type phases during the high temperature oxidation of stainless steels coated with reactive element oxides

Abstract The beneficial effects of reactive elements (RE) on the high temperature (HT) oxidation behavior of stainless steels have previously been attributed to the formation of perovskite compounds on oxide grain boundaries. In order to verify the ability of Cr 2 O 3 to form perovskite compounds with reactive element oxides RE 2 O 3 (RE=La, Nd, Sm, Gd, Yb, Y), mixtures of Cr 2 O 3 and RE 2 O 3 powders were oxidized at 1000 °C in air, and characterized by X-ray diffraction. Results were compared to those obtained on RE 2 O 3 -coated Fe-30Cr samples (RE=Y, Nd, Sm, Yb) oxidized at 1000 °C under the same conditions. It was found that the most efficient reactive element oxide, Y 2 O 3 , was not this which was completely converted into perovskite structure. So, it is assumed that it is not the reaction rate of the perovskite formation, or the ability of the RE oxide to form a perovskite structure, but rather the intrinsic properties of the perovskite, which is the origin of the RE effect.