Hot corrosion of glass coating on nickel base superalloy

Hot corrosion behaviour of BaO–MgO–SiO2 based glass coating on nickel base superalloy was studied using 80 wt.% Na2SO4 + 20 wt.% NaCl salt mixture, which melts at about 700 °C. In one set of experiments the glass coated superalloy substrates were immersed in the molten salt wherein in the other samples were suspended in the salt vapour at 1000 °C. During the test, mass loss per unit surface area was observed to be higher for specimens suspended in the salt vapour. The phase composition and microstructure of the corroded coating were investigated by X-ray diffraction (XRD), optical microscopy and scanning electron microscopy (SEM) in association with energy dispersive X-ray (EDX) analysis.