Thermal barrier coatings typically incorporate a YSZ topcoat and a metallic bond coat. During service, a reaction zone consisting of different thermally grown oxides forms at the interface. Although most such oxides are detrimental, one (α-Al2O3) improves service life due to its barrier effect on oxygen diffusion. In this study, Al and AlOx films are deposited on metallic bond coats by dc magnetron sputtering prior to topcoat deposition. The resulting TBCs were thermally cycled to determine the effect of the interlayer films on service life and TGO formation. It is shown that the Al films transform in situ into dense Al2O3 layers that act as oxygen diffusion barriers. TBCs with interlayer alumina, whether deposited directly or formed in situ, showed less cracking and were more mechanically stable during thermal cycle tests.

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