African Journal of Physics ISSN 9821-5213 Vol. 8 (4), pp. 001-007, April, 2021. © International Scholars Journals

Full Length Research Paper

Cyclic oxidation behavior of Ni- and Fe-based superalloys in air and Na₂SO₄-25%NaCl molten salt environment at 800 ^oC

T.S. Sidhu^*, Ajay Malik, S. Prakash_, R.D. Agrawal

Metallurgical and Materials Engineering Department, Indian Institute of Technology Roorkee, Roorkee-247667 (UA) India

Accepted 20 September 2020

Abstract

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 Cr₂O_3, 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