The present investigation aims to evaluate the high-temperature oxidation and hot corrosion behaviour of Ni-based superalloy (Superni 75) and Fe-based superalloy (Superfer 800H). The superalloy specimens were exposed to air and molten salt (Na2SO4-25%NaCl) environment at 800 °C under cyclic conditions. The thermogravimetric technique was used to establish the kinetics of corrosion. X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe micro analyser (EPMA) techniques were used to characterize the corrosion products. The hot corrosion resistance of Ni-based superalloys was found to be better than that of Fe-based superalloys. The formation of scale rich in Cr2O3, NiO and spinel NiCr2O4 has contributed for the better oxidation and hot corrosion resistance of Superni 75, whereas relatively lesser hot corrosion resistance of Superfer 800H is due to the formation of non-protective oxide of iron, and sulphides of iron and nickel.
Key Words: Superalloys, Hot corrosion, Oxidation, Molten salt environment
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