High Temperature Scaling of Binary Fe-Y Alloys in Pure Oxygen

The scaling of two iron-based alloys containing 15 and 30wt% yttrium as well as of pure yttrium has been studied at 600-800°C in 1 atm of pure 0 2 .Both alloys formed external scales containing a mixture of iron and yttrium oxides plus double Fe-Y oxides followed by a region of internal oxidation of yttrium, so that the oxidation of iron could not be prevented.Corrosion of the two alloys was generally irregular and occurred at rates not very different from those of oxidation of pure iron.No yttrium depletion was observed in the alloys beneath the region of internal oxidation, in spite of the much larger stability of Y2O3 with respect to iron oxides.The scaling behavior of the two alloys is interpreted by taking into account the limited solubility of yttrium in iron.