Oxidation and hot corrosion of gradient thermal barrier coatings prepared by EB-PVD

The performances of gradient thermal barrier coatings (GTBCs) produced by EB-PVD were evaluated by isothermal oxidation and cyclic hot corrosion (HTHC) tests. Compared with conventional two-layered TBCs, the GTBCs exhibit better resistance to oxidation and hot-corrosion. A dense Al2O3 layer in the GTBCs effectively prohibits the 0 and S inward diffusion and the Al and Cr outward diffusion during the tests. On the other hand, an inlaid interface, resulting from the oxidation of the Al along the columnar grains of the bond coat, enhances the adherence of the Al2O3 layer. The failure of the GTBC can finally occur by cracking at the interface between the bond coat and the Al2O3 layer, due to the combined effect of sulfidation of the bond coat and thermal cycling.