Abstract

A thermal cycling test was designed in order to predict thermal barrier coatings (TBC) life of combustion chambers. The thermal cycle is produced by two 2kW halogen lamps highly focused on the TBC. A 25X100 mm TBC is plasma sprayed centered onto a substrate 25X300 mm. The thermal cycling can be done either under argon atmosphere or air in order to be able to discriminate the oxidation induced acoustic emissions from the expansion mismatch. Two transducers located at each end of the substrate monitor the acoustic signals emitted by crack initiation and/or propagation. The advantage of using two transducers is that with a time of flight approach cracking phenomena can be located along the TBC. This process allows the study of welded substrates coated with TBC, TBC coated around holes and to check for the presence of cracks by using metallography preparation. The challenge of the test is to use the early cycles emission signatures in order to predict the long term durability of the TBC.

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