Rare earth oxide coatings to decrease high temperature degradation of chromia forming alloys

The influence of surface coatings of Ce, La, Pr, and Y oxide gels on the oxidation behaviour of an Fe-20Cr alloy at 1000 C is described. The morphology of the rare earth (RE) oxide coatings varied with the nature of RE. The oxidation rate of RE oxide coated Fe-20Cr was significantly less than that of the uncoated alloy. The extent of influence the RE oxide coating exercised on the oxidation rate decreased in the following order: La, Ce, Pr, Y. The scale formed in the presence of RE oxide was very thin, fine grained and adherent chromia. A direct correlation between rare earth ion radius and the extent of influence on chromia growth rate at 1000 C was observed. 20 refs.