Oxidation of duplex coatings with different thickness ratio of the inner nanocrystalline layer to the outer NiCrAlY one

Oxidation behavior of three duplex coatings with different thickness ratio of the inner nanocrystalline layer to the outer NiCrAlY one (1:2, 1:1 and 2:1) on N5 single-crystal superalloy is investigated. Results indicate that Ta in the inner layer can transport through the NiCrAlY one to the outer surface and to be oxidized there, which accelerates oxidation. Meanwhile, Cr and Al will diffuse from the NiCrAlY layer through the inner one to the alloy substrate, resulting in precipitation of TCP phases. Layer thickness ratio plays an important role in oxidation of the duplex coatings by affecting such elements interdiffusion.