Oxidation behaviour of simple and Pt-modified aluminide coatings on IN738 at 1100 °C

The oxidation of both low and high-activity simple and Pt-modified aluminide coatings on nickel base superalloy IN738 has been studied in static air at 1100 OC up to 1000 h. For all coatings oxidation followed a parabolic law up to 400 h. The two Pt-modified coatings showed better protectiveness with lower mass gains and smaller rate constants, especially for long reaction times. The presence of Pt significantly improved the resistance to y'-~isAl formation, promoted selective oxidation of aluminium by preventing the transport of other elements outwards to A203 scale and resulted in the formation of purer, slower-growing and more adherent A1203 scales, delaying the onset of scale spalling for two types of coatings and of oxide nodules growth for the high aluminium activity coating.