High temperature scaling of binary Fe-Y alloys in pure oxygen

The scaling of two iron-based alloys containing 15 and 30wt% yttrium as wel l as of pure yttrium has been studied at 600-800 degrees C in 1 atm of pure O-2. Both alloys formed external scales containing a mixture of iron and y ttrium oxides plus double Fe-Y oxides followed by a region of internal oxid ation of yttrium, so that the oxidation of iron could not be prevented. Cor rosion of the two alloys was generally irregular and occurred at rates not very different from those of oxidation of pure iron. No yttrium depletion w as observed in the alloys beneath the region of internal oxidation, in spit e of the much larger stability of Y2O3 with respect to iron oxides. The sca ling behavior of the two alloys is interpreted by taking into account the l imited solubility of yttrium in iron.