Effect of Aluminising on the Hot Corrosion Resistance of Nickel-Chromium Alloys

The effects of aluminising on the hot corrosion resistance of two nickel-chromium alloys containing 10 and 30 weight percent chromium, respectively, were examined. The Ni/Cr specimens were aluminised by pack cementation in Ar and underwent cyclic hot corrosion testing in Na2SO4- NaCl molten salt. XRD analysis indicated that a NiAl phase formed between the coating layer and substrate. Cyclic hot corrosion test results indicated that the effects of aluminising are more pronounced in the case of the 10 % Cr than in the case of 30 % Cr. The ductile NiAl phase suppressed the potential for crack initiation during thermal cycling of the 10 % Cr specimens, and reinforced the hot cyclic corrosion resistance in molten salt for the 30 % Cr specimens.