Effect of Platinum Pre-Coating on Isothermal Oxidation Behavior of MCrAIY Coating by Plasma Spray Process

In this work we have evaluated the effect of platinum (Pt) pre-coating on microstructure evolution of MCrAIY coating during isothermal oxidation, to improve high temperature oxidation and corrosion resistance of the nickel-based superalloy MAR M247-DS. Pt was deposited on the superalloy by electroplating before the MCrAIY coating by a vacuum plasma spray, which was compared to the superalloy without Pt pre-coating. The samples were subjected to isothermal oxidation in a box furnace at 1100 deg C for 25-150 hrs. The weight gain and loss caused by the oxidation of samples was recorded, and the variation of surface layer and interface morphology were observed before and after the oxidation tests. The length decrement of cross section is remarkably low on according to the precipitation of (Ni,Pt)Al phase by Pt pre-coating. Also, the amount of voids at interface between the coating and the superalloy, which would be introduced as a processing defect, is reduced by Pt pre-coating.