Study of cyclic hot corrosion of nanostructured Cr/Co–Al coatings on superalloy

Nanostructured Cr/Co–Al coatings were deposited on Superni-718 substrate by DC/RF magnetron sputtering in the present work. Hot corrosion studies were conducted on bare substrate and the Cr/Co–Al coated Superni-718 after exposure to a molten salt environment of Na2SO4–60%V2O5 at 900 °C under cyclic conditions. The weight change measurements were made to calculate the cyclic hot corrosion kinetics of the coatings at 900 °C. The microstructural features of the as deposited coatings were characterized by FE-SEM, AFM and XRD. It was observed that the corrosion rate of Cr/Co–Al coated superalloy is lower than that of the uncoated superalloy due to the formation of continuous, dense, adherent and protective oxide scale over the surface of the coatings. The protective oxide scales are basically the thin layer of Cr2O3, Al2O3, and CoCr2O4 which has formed over the Cr/Co–Al coated superalloy substrate exposed to molten salt environment at temperature, 900 °C.