Effect of temperature on hot corrosion of nickel-based alloys for 700 °C A-USC power plants

Nickel-based alloys were exposed to a synthetic flue gas at varying temperatures from 700 °C to 800 °C. Two main damage mechanisms were revealed, including general surface oxidation caused by eutectic melting of sulfates and internal cracking caused by sulfur diffusion. The damage level of the alloys did not monotonically increase with temperature. Significant weight losses due to molten sulfate corrosion were found at 700–760 °C, and the minimum damage was at 780 °C. Nimonic 263 with the highest cobalt, titanium contents and the lowest aluminum content exhibited the best resistance to both molten sulfate corrosion and sulfur invasion.