Development of a mechanism-based lifetime model for bi-layer thermal barrier coating systems

DFG: SCHU729/25-1, FVV: 1108

Bild Forschungsprojekt

Hochtemperaturofen in Betrieb

Period: 2012-07-01 to 2014-06-30
Funder: DFG/FVV-EM
Project Manager: Dr. Mario Rudolphi
Research Group: High Temperature Materials

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.

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