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

Abstract: 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/cm² 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/cm² 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.[Figure not available: see fulltext.]