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In this work we have evaluated the effect of platinum (Pt) pre-coating on microstructure evolution of MCrAlY 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 MCrAlY 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°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.

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Bond coatings, CoNiCrAlY, are prepared on Inconel 738 substrate by vacuum plasma spray (VPS). Mechanical properties of VPSed CoNiCrAlY coatings are investigated via Taguchi method and L18(21×37)orthogonal arrays to determine the optimal setting and the relationship of experimental variables. Seven parameters were considered as follows: (A) arc current; (B) primary gas flow rate; (C) secondary gas flow rate; (D) stand-off distance; (E) working pressure; (F) carrier gas flow rate (Ar); and (G) powder feeding rate.The effect of carrier gas flow rate on the porosity is determined to be the highest among the parameters investigated. Higher microhardness values are observed for the VPSed coatings as compared to the coatings prepared by conventional high velocity oxygen fuel probably due to low amount of the porosity.