THE HOT CORROSION OF 2 FE-AL INTERMETALLICS AT 600-DEGREES-C

The hot corrosion of Fe3Al and FeAl has been studied at 600-degrees-C in combustion gases and in the presence of Na2SO4-NaCl and Na2SO4-V2O5 mixtures with some additional measurements with pure Na2SO4. Under all conditions the alloys underwent significant attack with formation of scales containing both Fe and Al. However corrosion in Na2SO4 pure or mixed with NaCl slowed down significantly with time, while corrosion in Na2SO4-V2O5 mixtures was more severe, irregular and long-lasting. Except for the Na2SO4-NaCl mixture, Fe3Al corroded more than FeAl. The scales consisted always of an outer layer rich in iron oxide and an inner layer containing mostly Al but also Fe and S whose actual composition differed for the two salt mixtures. The corrosion mechanism involved to a different extent mixed oxidation-sulfidation and scale fluxing.