N. Maier (Sp), Eberhard-Karls-Universität Tübingen (Germany); G. Rixecker, Max-Planck-Institute for Metals Research, Stuttgart (Germany); K.G. Nickel, Eberhard-Karls-Universität Tübingen (Germany)
Rare Earth silicates are candidates for environmental barriers for the protection of silicon-based ceramics in turbine environments. Mono-silicates may have a superior initial protective power, but the di-silicates are most promising for coating by simple pre-oxidation treatments. Therefore we concentrated on the latter.
The literature data on the corrosion of monolithic silicates in hot wet air are not uniform. For this reason we investigated the corrosion behaviour of several rare earth disilicate materials in flowing air with 30% water vapour at 1500°C. Besides the pure silicates Y2Si2O7, Yb2Si2O7 and Lu2Si2O7 several solid solutions were tested and will be compared. We will also present new results on the stability and kinetics of formation of the polytypes of the silicates and discuss corrosion mechanisms and models with regard to predictions for long-term use.
