Abstract
Hot corrosion has been considered as a serious problem in boiler tubes because of poor quality fuels which result in the presence of salt contaminants such as Na2SO4, K2SO4 and NaCl. To solve this problem, FeCrNiAlMnB/Cr3C2 coating was fabricated on AISI 1020 steel substrate by high velocity arc spray technique, and the hot corrosion behavior of the coating was investigated in the presence of Na2SO4 + 25 wt% K2SO4 and Na2SO4 + 25 wt% NaCl at 650 °C and 750 °C. Phase composition, microstructure and corrosion products of the coating were characterized by XRD and SEM/EDS techniques. The results showed that the coating exhibited much less mass gain and superior hot corrosion resistance as compared with bare AISI 1020 steel, and kinetics studies indicated parabolic characteristic for the coating under different corrosion conditions. Different morphologies attributed to corrosion products which consisted of (Fe, Cr)2O3, FeCr2O4 (Na2SO4 + 25 wt% K2SO4) and (Fe, Cr)2O3, FeO, Na2CrO4, NaFeO2 (Na2SO4 + 25 wt% NaCl) were observed after exposition to above two molten salts. The destructive effect of Na2SO4 + 25 wt% NaCl on the coating was much greater than that of Na2SO4 + 25 wt% K2SO4 due to the reaction between NaCl and protective oxide layer, which formed Cl2 and further destroyed the uncorroded coating as well as led to the formation of cracks in the protective oxide layer.
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