Damage evolution in EB-PVD thermal barrier coatings for turbine blades in aircraft engines under close to reality testing conditions

In advanced gas turbines for aircraft engines, internally cooled turbine blades have a ceramic thermal barrier coating (TBC) to reduce the thermal load of the metallic substrate. Exhausting the full potential of the TBC to increase the turbine inlet temperature requires reliable lifetime prediction methods, since failure of the TBC will entail the immediate failure of the blade. A lifetime prediction concept for TBCs based on lifetime analyses of close to reality tests is given. The basic idea is to ensure that failure mechanisms during testing are the same as in a turbine engine. Specimens with an electron beam physical vapour deposited (EB-PVD) TBC were tested under realistic fatigue load but drastically reduced holding times. The results exhibited that the as-coated properties of the ceramic coating are sufficient to survive the required load alternations in service. The influence of kinetic damage mechanisms on the TBC-lifetime will be determined in tests with pre-aged specimens.