Abstract: 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 exhibite better resistance to not only oxidation but also hot-corrosion. A dense Al2O3 layer in the GTBCs effectively prohibites inward diffusion of O and S and outward diffusion of Al and Cr during the tests. On the other hand, an "inlaid" interface, resulting from oxidation of the Al along the columnar grains of the bond coat, enhances the adherence of Al2O3 layer. Failure of the GTBC finally occurred by cracking at the interface between the bond coat and Al2O3 layer, due to the combined effect of sulfidation of the bond coat and thermal cycling.

Key words: Gradient thermal barrier coating (GTBC), Electron beam physical vapor deposition (EB-PVD)