Effect of molybdenum on high-temperature corrosion of Fe–Al intermetallics

Fe41Al4Mo and Fe32Al19Mo (at.%) intermetallics were prepared by self-propagating high-temperature synthesis (SHS) combined with arc melting (AM) and vacuum annealing. Corrosion resistance was evaluated on the basis of sulphidation and oxidation tests. Sulphidation experiments were carried out in the flowing H2/H2S mixtures mainly at a temperature of 1273 K and at sulphur pressures 10−3–0.3 Pa. Reaction progress was followed thermogravimetrically. The extent of corrosion attack increased with sulphur pressure, temperature and molybdenum concentration. Oxidation tests were carried out in air in isothermal (at 1073 and 1273 K) and thermal cycling conditions (24-h cycles at 1223 K). The results of kinetic studies, metallographic observations as well as phase and chemical analysis of corrosion products indicated limited resistance of the investigated FeAlMo alloys to sulphidation or oxidation at elevated temperatures.