Preparation and oxidation behavior of NiCrAlY coatings with Re-base diffusion barrier on a nickel-based single-crystal superalloy

Four Pt-modified NiCrAlY coatings with different thicknesses and Re contents diffusion barrier (DB) were prepared on a single crystal superalloy by sequential treatments of Ni-Re co-electrodeposition, arc ion plating and Pt electrodeposition. To explore the effect of different forms of the Re-base DB on the oxidation resistance and interdiffusion behavior in Pt-modified NiCrAlY coating, the isothermal oxidation behavior of the four coatings at 1050 °C was investigated. The results indicated that Re-base DB can effectively improve the high-temperature oxidation resistance of Pt-modified NiCrAlY coating by inhibiting the internal diffusion of Al as well as the external diffusion of refractory elements. The coating samples of 5 µm Ni-45Re (at%) DB exhibited the lowest interdiffusion extent and the best long-term stability. Higher Re content DB tended to form layered σ-(Cr,Re) phase, while DB with lower content could only form granular σ-(Cr,Re) phase. The influence of different micromorphologies of the σ-phase on the long-term stability of DB was discussed.