Entwicklung von Schutzschichten gegen Hochtemperaturoxidation für Titanaluminid-Legierungen

Titanium aluminide alloys have attractive properties for structural applications at high-temperatures. Therefore research has been focused on the improvement of intermetallic TiAl alloys for a few decades. The use of such alloys in aircraft engines allows the reduction of fuel consumption as well as the reduction of noise and NOx emissions. Engine manufacturers aim at improving the efficiency of the next generation engines. Although TiAl alloys look promising for reducing the weight in the low pressure turbine, the use of TiAl alloys remains limited to the coldest stages (up to 700°C) due to mechanical and environmental limitations of this type of material above this temperature. TiAl alloys suffer from ductility loss at room temperature after an exposure at high temperature. This seems to be linked to the up-take of oxygen and nitrogen into the substrate subsurface zone which changes the mechanical properties. The aims of the current development are to extend the use of TiAl alloys to areas with higher temperatures in the engine. For this purpose the high-temperature resistance of TiAl alloys for low pressure blades has to be improved.

This project is a collaborative work between Dechema-Forschungsinstitut, Safran Group, and the French laboratory CIRIMAT. The aim of the project is the development of protective coatings that will allow the use of intermetallic TiAl components at elevated temperatures (up to 800°C) by providing improved oxidation resistance. The concept is based on the application of a pre-coating, serving as a reservoir for controlled surface enrichment. As a second step the halogen effect will be applied to the coated surface in order to achieve maximum oxidation resistance.