Pt-modified Ni aluminides and MCrAlY coatings (where M = Ni and/or Co) are widely used on turbine blades and vanes for protection against oxidation and corrosion and as bond coatings in thermal barrier coating (TBC) systems. The present work shows the ability of a new fabrication technique, the Spark Plasma Sintering, to develop rapidly new coating compositions and microstructures. This technique allows combining powders and metallic foils on a superalloy substrate in order to obtain multilayered coatings in a single short experiment. Fabrication of MCrAlY overlays with local Pt and/or Al enrichment is shown, as well as fabrication of coatings made of ζ-PtAl 2 , ε-PtAl, α-AlNiPt 2 , martensitic β-(Ni,Pt)Al or Pt-rich γ/γ′ phases. The realization of a complete TBC system with a porous and adherent Yttria Stabilized Zirconia (YSZ) layer on a γ/γ′ low mass bond coating is also demonstrated. Difficulties of fabrication are reviewed and discussed, such as Y segregation, risks of carburization, local overheating, or difficulty to coat complex shape parts. Finally, some first results of cyclic oxidation are given.
Cyclic and isothermal oxidation behaviors of first and fourth-generation superalloys AM1 and MCNG were investigated to evaluate the ability of the scratch test to quantify the adhesion of multi-layered oxide scales. Effects of sulfur content and of scale thickness were studied independently. Available models lead to large discrepancies in the calculated work of adhesion values with the evaluation of the residual stress being the largest source of error. Nevertheless, models can assess the effect of sulfur content and the scratch test can be used to correlate the long-term cyclic oxidation behavior and the adhesion of oxide scales.
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