Sulfidation resistance of CeO2-modified HVOF sprayed FeAl coatings at 700 °C

FeAl based coatings containing various amounts of CeO2 ranging from 0 to 8 wt.% CeO2 were deposited onto carbon steel by high-velocity oxygen fuel spraying, and were tested at 700 °C for 300 h in a gas mixture of H2S–H2–O2–Ar with a high partial pressure of S− 2 and low partial pressure of O− 2. Sulfidation resistance of FeAl coating was improved by the addition of 2–5 wt.% CeO2, which inhibits the outward diffusion of Fe, acts as traps for sulphur in splat boundaries, and slows down the depletion of Al in the coating. The corrosion products were found to consist of FeS and Fe1−XS on the pure FeAl coatings, but primarily Fe1−XS on FeAl coatings with 2–8% CeO2. The addition of 8 wt.% CeO2 induced thermal cracks and hence decreased sulfidation resistance. The optimum amount of CeO2 addition in FeAl in terms of sulfidation resistance is suggested to be 2–5 wt.%.