Entwicklung eines mechanismenbasierten Lebensdauermodells für Bi-Layer-Wärmedämmschichtsysteme

Thermal barrier coatings (TBCs) have been used successfully for several decades to protect the metallic components of stationary gas turbines or aero engines and have helped to increase the efficiency of turbines, lowering their CO₂ emissions significantly. Nevertheless, the demand for even higher temperatures is persisting and consequently the search for advanced materials is still ongoing. Especially materials with high melting point and low thermal conductivity are in the focus of research for advanced thermal barrier coating materials. Two possible candidates discussed in literature are La₂Zr₂O₇ and Gd₂Zr₂O₇, however, both materials have a lower coefficient of thermal expansion than standard yttria stabilized zirconia (YSZ). This may lead to higher stresses in single-layer coatings and can - in combination with the lower fracture toughness of La₂Zr₂O₇ and Gd₂Zr₂O₇ - induce earlier failure of the TBC especially in cyclic exposure conditions. Bi-layer thermal barrier systems consisting of a lower YSZ layer covered by a second layer of Gd₂Zr₂O₇ on top are a promising approach to overcome the limitations of single layered coatings. The aims of this project are therefore to (i) establish production routes for reproducible coating manufacture of bi-layer Gd₂Zr₂O₇-YSZ thermal barrier coatings, (ii) investigate the mechanical properties of bi-layer TBCs, and (iii) establish a mechanism-based lifetime model for the novel bi-layer TBCs.