PREPARATION AND DIFFUSION RESISTANCE OF GRADIENT PtAl COATINGS WITH RE-BASE DIFFUSION BARRIERS

It is critical to mitigate the problem of elemental interdiffusion between the traditional PtAl coatings and the alloy substrate under severe high-temperature service environments. In this work, gradient PtAl coatings containing Re-based diffusion barriers were prepared by sequentially electroplating Ni–Re, Ni, and Pt layers between traditional PtAl coatings and Ni-based single-crystal superalloys, followed by final vapor-phase deposition of infiltration. It is shown that the chemical composition of the lower part of the coating is similar to that of the single-crystal superalloy, and the presence of Re-based diffusion barriers leads to lower elemental diffusion fluxes between the coating and the substrate, thus mitigating the precipitation of TCP phases from the substrate during the high-temperature oxidation process. Gradient PtAl coatings containing Re-based diffusion barriers have excellent mechanical properties due to the precipitation of a small amount of TCP phase from the matrix, while generating an Al 2 O 3 film with good oxidation resistance.