Thermal ageing of a multilayer oxidation protection coating system for Gamma-titanium aluminides

Gamma-titanium aluminides are intermetallic materials which are characterized by low densities and attractive mechanical properties. For this reason, Gamma-titanium aluminides are applied as a material for turbine blades in aviation. However, because of the high affinity to oxidation in high-temperature conditions, the use is limited to colder parts, such as the low-pressure turbine stages. In order to increase the efficiency of aircraft engines, the increased utilisation of ?-titanium aluminides is one important approach which requires the development of new oxidation protection systems. A thermally sprayed multilayer coating system, based on ZrO2/Y2O3 and an MCrAlY top layer, for the oxidation protection of ?-titanium aluminides was investigated in this study. The paper focuses on understanding the involved failure mechanisms and improving the service life of the coating system. These analyses are made on the basis of long-time ageing tests and microstructural investigations.