Thermal Exposure Testing of a Multilayer Oxidation Protection System for Gamma-TiAl

Gamma Titanium-Aluminides are lightweight intermetallic materials, which show attractive mechanical properties. Therefore Gamma Titanium-Aluminides find application as blade material for jet engines in Aerospace Industry. However due to the sensitivity against (high temperature) oxidation the usage is limited to colder parts, such as low pressure turbine stages. In order to improve the efficiency of aircraft engines, an extended implementation of Gamma Titanium-Aluminides is an important strategy, which demands for novel oxidation protection solutions. In this study a thermally sprayed multilayer coating system, based on ZrO2/Y2O3 and an MCrAlY top coat for oxidation protection of Gamma Titanium-Aluminides is evaluated and current developments are presented. One of the main focuses of the work is to understand the involved failure mechanisms and to improve the coating lifetime by lowering residual stresses. These measures are achieved by varying the coating parameters regarding the results of long time thermal exposure tests and microstructural investigations.