Development of hot gas corrosion-resistant protective coating systems on non-oxide Si-based ceramics for turbine applications

Project description: A significant increase in the efficiency of gas turbines using superalloys cannot be expected, even with complex cooling concepts. However, non-oxide Si-based ceramics such as Si3N4, SiC and also ceramic fiber composites such as SiC/SiC are suitable for this purpose. These ceramics allow a considerable increase in operating temperatures, have a low density and are very stable to oxidation due to a passivating SiO2 protective layer. However, the formation of the oxide layer proves to be a major disadvantage under hot gas corrosion conditions, since reaction with water vapor from the turbine combustion gases leads to the formation of volatile silanols, which does not ensure the required long-term stability of the components. Protective coatings based on ytterbium disilicate show great potential for this purpose, as they have excellent hot gas corrosion stability and the appropriate thermal expansion coefficient for the ceramics mentioned. Within the DFG project two strategies will be investigated to develop sufficiently thick (> 100 µm) protective coatings based on ytterbium disilicate, which protect Si3N4, SiC and SiC/SiC against hot gas corrosion up to 1400 °C in the long term and can be applied by simple coating processes such as dipping and spraying.

Duration: 04/2021 - 03/2024

Funding body: DFG

Contact: PD Dr. Günter Motz