The Effect of Cracking of Thermally Grown Oxide Layers in Thermal Barrier Coatings Examined Using FIB Tomography and Inverse Modelling

As a thermal barrier coating (TBC) is exposed to elevated temperatures, oxidation proceeds at the interface between the top coat of the TBC and the bond coat/substrate. This aluminium-rich layer, in the case of the TBC studied in this work, produces an alumina thermally grown oxide (TGO) at the interface. This layer continues to grow as the exposure time increases and is prone to cracking. Failure of the TGO creates a debond which will affect the heat transfer through the system and lead to localised overheating. Samples of an IN6203DS substrate with a CoNiCrAlY bond coat and YSZ top coat have been thermally aged and a selection of these used to determine the morphology of cracking within the TGO. This quantitative information has subsequently been used to determine the effect on the heat transfer performance of the TBC system using a process of inverse modelling.