Abstract
The effects of the active element yttrium (0.5 wt.%) on hot-corrosion resistance of sputtered Co30Cr6Al coatings (where the composition is in approximate weight per cent) on superalloy IN-738 have been studied. The results showed that the addition of yttrium obviously enhanced the resistance against the hot corrosion of the CoCrAl coating. The Cr 2O 3 scale formed on yttrium-free coating was prone to spalling in NaCl-containing molten salts. On the contrary, the Al 2O 3 scale formed on the CoCrAlY coating was very resistant to hot corrosion. It was suggested that the yttrium may promote the initial process of Al 2O 3 nucleation to form a protective Al 2O 3 scale on the CoCrAlY coating. It was shown that the active element yttrium can improve the Al 2O 3 film adherence remarkably.
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