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Thermal barrier coatings (TBCs) are utilized in the hot section of gas turbines primarily to increase the durability of the coated components. However, TBCs operating at the 'prime reliant' mode that permits the increase of the combustion temperature and thus the efficiency of the gas turbine have not yet been designed successfully. The demanding operating mode of a gas turbine requires a comprehensive understanding of the thermo-mechanical fatigue (TMF) behaviour of TBCs since TBC performance is essential for the integrity of the coated component. Thus, testing under near-service conditions is needed to assess durability and enable damage observations that can distinguish among potential failure mechanisms. This work presents experimental methodologies adopted for assessing the TBC behaviour and life under TMF testing. A specially designed TMF rig that allows for a realistic thermal gradient across the TBC and thus enabling the simulation of a near-service thermomechanical loading environment has been developed and validated. Using this setup, TMF tests have been conducted on a number of commercial TBC systems. The observed damage mechanisms are discussed based on the imposed TMF cycles (strain range and phase angle between thermal and mechanical loading) and the interaction between the coating and the substrate. Finally, useful conclusions on the proper design of TMF experiments are drawn.

Additional information

Authors: TZIMAS E, European Commission, Joint Research Centre, Institute for Energy, Ispra (IT);PETEVES S D, European Commission, Joint Research Centre, Institute for Energy, Ispra (IT)
Bibliographic Reference: An oral report given at: RAN 2001: Advanced Energy Conversion Technologies conference. Organised by: University of Nagoya (JP) Held at: Nagoya (JP), 15-17 December 2001
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