Environmental Barrier Coatings (EBCs) for Oxide/Oxide Composites

Kurzfassung

Ceramic matrix composites (CMC) based on alumina and mullite are candidate engineering materials for long-term high-temperature applications in oxidative atmosphere if high damage tolerance and thermal shock resistance are required. However, alumina and mullite are prone to high-temperature chemical corrosion, mainly in water vapour enriched, high-speed flowing combustion atmosphere. The application of environmental barrier coatings (EBCs) is considered the only way to overcome the water-vapor corrosion problem of all-oxide CMCs. At DLR, the development of environmental barrier coatings for porous all-oxide CMCs is currently under way. The selection of EBC materials and of coating technologies is dependent from the specific CMC application. A focused issue of all developments is the prevention of coating disintegration by application of suitable bond-coats between oxide/oxide substrates and EBCs. Depending on potential applications environmental barrier coatings with different microstructures have been deposited on WHIPOX substrates by means of thermal spraying and by gas phase deposition techniques. A review of materials and coating technologies will be presented with special regard to the performance and durability of EBC-protected all-oxide CMCs in gas turbine combustors.