Hot Corrosion Behavior of Si-Y-Co-Modified Aluminide Coating Exposed to NaCl + Na2SO4 Salt at 1173 K

The microstructure and hot corrosion behavior of a Si-Y-Co-modified aluminide coating prepared on a nickel base superalloy DZ125 by the pack cementation process was studied. The Co-Al-Si-Y coated specimen had a mass gain of only 0.25 mg/cm(2) after being exposed to NaCl + Na2SO4 salt for 100 h at 1173 K. Thus the addition of Si to a Y-Co-modified aluminide coating increased its hot corrosion resistance by 40 %. The improved hot corrosion resistance of the Co-Al-Si-Y coating was mainly attributed to the formation of an Al2O3 scale with SiO2 on the surface of the coating during the hot corrosion test. SiO2 can prohibit the high fluxing rate of dissolution of the protective Al2O3 scale and prevent rapid corrosion attack owing to its low solubility over a wide range of salt acidity and its weak oxygen permeability. Graphical Abstract The Co-Al-Si-Y coated specimen had a mass gain of only 0.25 mg/cm(2) after being exposed to NaCl + Na2SO4 salt for 100 h at 1173 K. The addition of Si to a Y-Co-modified aluminide coating improved its hot corrosion resistance. [GRAPHICS]