A study on hot corrosion behaviour of Ni-5Al coatings on Ni- and Fe-based superalloys in an aggressive environment at 900 °C

Ni-5Al coating was deposited on Ni- and Fe-based superalloys by high velocity oxy fuel (HVOF) process to enhance their high-temperature corrosion resistance. Hot corrosion studies were conducted on bare as well as HVOF-coated superalloy specimens after exposure to a molten salt environment at 900 degrees C under cyclic conditions. Each cycles consisted of I h heating in the silicon carbide tube furnace followed by 20 min cooling in air. Thermogravimetric technique was used to approximate the kinetics of corrosion. Techniques like X-ray diffraction (XRD), scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDAX) were used to characterize the corrosion products. The coatings and the oxide scale formed on the exposed surface were found to be intact with the superalloys. Superfer 800 with Ni-5Al coating has provided a good protection to the superalloys in the given molten salt environment. (C) 2007 Elsevier B.V. All rights reserved.