Formation of a continuous β-NiAl layer near the interface in a γ+β MCrAlY

MCrAlY alloys are widely used as oxidation/corrosion protective coatings and TBC bond coats to protect superalloys in gas turbines. Recently, a thermal cycling test was carried out in an EB-PVD MCrAlY – superalloy system, the result of which showed that a continuous β-NiAl layer formed in a MCrAlY coating near the MCrAlY – superalloy interface. Since β phase can be as a container of Al, the formation of the β layer is probably beneficial to prolong the coating life. The composition profiles of alloying elements indicate that the formation of the β layer was a result of outward diffusion of Al from the substrate into the coating. An oxidation-diffusion model was also adapted to simulate the development of the microstructures in the materials. The current work shows the possibility of developing MCrAlY coatings with in-situ formation of β layer.