Hot Corrosion and Protection of a Cast Nickel-Base Superalloy for Gas Turbine

The corrosion products on both corroded blades and corroded specimens as made of cast nickel-base superalloy and coated with alumlnide are eximined by optical microscope, x-ray diffraction, SEM, EDXA and chemical analyses to explore failure mechanism. It is shown that sulphurization and hot corrosion caused by molten salt and it is suggested that the mechanism of hot corrosion of low-chromium, refractory metal-rich superalloy is the synergism of sulphidation, basic fluxing and acidic fluxing. A diffusion-type slurry coating and a sintered slurry coating based on aluminium-silicon exhibit a much better hot corrosion resistance than conventional pack aluminide coating.