The mechanical properties of surface scales on nickel-base superalloys

The effect of both sodium chloride and sodium sulphate contaminant corrosion on the same range of nickel based alloys as tested in oxidation is reported over the temperature range 650 to 9500C. It is shown that the onset of corrosion by both NaCl and Na2SO4 is determined by the surface oxide integrity and that the ranking order for corrosion initiation by both these species is identical to that observed with respect to the mechanical stability of the surface oxide scales measured during isothermal oxidation. This correlation is shown to be significant in terms of the fundamental mechanisms of hot corrosion initiation. (author)