Oxidation resistance of aluminum-coated Fe-20Cr alloys containing rare earths or yttrium

Aluminum-coated Fe-20Cr-(rare earth or yttrium) alloy foils were developed with oxidation resistance equivalent or superior to Fe-20Cr-5Al-(rare earth or yttrium) alloy foils. The coated foils were made by dipping Fe-20Cr sheet into a salt-covered aluminum bath and then rolling the sheet to foil. Oxidation resistance of the coated foil was enhanced by adding rare earths or yttrium to the Fe-20Cr substrate alloys to insure oxide adherence. Test results indicate that only sufficient addition to tie up sulfur as a stable sulfide is needed in the Fe-20Cr alloy. Aluminum-coated foils show lower oxide growth rates than similar Fe-Cr-Al alloys, most likely the result of fewer impurities (particularly Fe) is the coated foils' growing oxide scale.