TGO formation and failure mode of TBC systems comprising PVD-Al interlayers

The physical characteristics and volume growth of TGO in TBC systems lead to TBC failure. It is proved that enriching the BC/TC interface with α-Al₂O₃ is conducive to an extended operational time by prolonging the steady-state growth stage of the TGO. The basing phase reactions in TBC systems with heightened Al activity, however, are not studied yet.

In this work, the stage formation of TGO layers and the failure mode of TBC systems with PVD-Al interlayers are described. The study uses thermal cycling tests with maximum temperatures of 1,150 °C. The phases and thickness of the TGOs are investigated by SEM/EDS and Raman after 1, 5, 10, 20, 40, 80 and 130 thermo cycles. The results plot the interface change and crack formation as a function of the thermal cycle number, which allows a correlation between TGO growth and maximum crack length.