Microstructure and cyclic oxidation behaviour of low-Pt/Dy co-doped β-NiAl coatings on single crystal (SC) superalloy

The low-Pt/0.1 at.% Dy co-doped β-NiAlCrSi coating was produced on single crystal (SC) superalloy IC21 by electro-plating of a ~ 3 μm thick Pt film followed by electron beam physical vapour deposition (EB-PVD) of a β-NiAlDyCrSi over layer. For comparison, the single low-Pt doped and single Dy-doped β-NiAlCrSi coatings were also prepared, respectively. The cyclic oxidation behaviour of the above coatings at 1200 °C was investigated. Minor Dy-doping led to refinement of grains of the as-deposited coating. The addition of Pt effectively suppressed precipitation of topologically close-packed phase (TCP) in the interdiffusion zone (IDZ) during heat-treatment. The coupled effects of Pt/Dy co-doping led to lower oxidation rate, less scale rumpling and improved scale adherence than the single-doping cases and the related mechanisms were discussed.