Corrosion-Resistant Thermal Barrier Coatings

The corrosion resistance of the zirconia-based thermal barrier coatings to combustion products, such as vanadate and sulfate salts generated in fuel-fired gas turbines, was examined. Investigations have been conducted on the quaternary oxide system ZrO{sub 2}-Y{sub 2}O{sub 3}-SiO{sub 2}-Al{sub 2}O{sub 3}. In this oxide mixture, the ZrO{sub 2} (Y{sub 2}O{sub 3}) crystallites were enveloped by zirconium and aluminum silicates, which had formed during the sintering process and were precipitated preferentially on the ZrO{sub 2} (Y{sub 2}O{sub 3}) grain boundaries. By this method, it was possible to reduce leaching away of the yttria contained in the ZrO{sub 2} crystallite and to enhance the corrosion resistance of the thermal barrier coatings.