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| Abstract No.: |
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Scheduled at:
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Wednesday, June 04, 2008, Room 05 12:20 PM
Characterization 2
Modern characterization offers a good possibility for proofing the reliability and the performance of thermal sprayed coatings
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| Title: |
Residual interfacial strength in an APSed TBC after the thermal cycle fatigue
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| Authors: |
Yasuhiro Yamazaki* / Niigata Institute of Technology, Japan
Toshihiko Yoshida / Niigata Institute of Technology, Niigata
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| Abstract: |
The durability of a industrial gas turbine is principally limited by those components operating at high temperatures in the turbine sections because those are exposed to hot gas. Air plasma sprayed thermal barrier coatings, which reduce the temperature in the underlying substrate material, are an essential requirement for the hot section components. To take full advantage of the potential of the TBC system, the evaluation and the prediction of the lifetime of itself become important. Therefore, experimental and analytical investigations in TBC systems have been performed. As a result of such energetic studies, it has clearly been shown that the adherence of the top coating is one of the most important parameter for the durability of TBC system.
In this work, the thermal fatigue tests of 400-1000 deg.C thermal cycle wave with 1 hour hold at maximum temperature have been carried out. In addition, the residual interfacial strength was also evaluated. The relationship between the thermal cycle fatigue and the interfacial strength was discussed. From the measurement of the AE signals during the thermal fatigue tests, the primary fatigue damage occurred in each cooling stage of the thermal fatigue cycles. And it can be considered that the thermal stress was related to such damage caused by the mismatch in the thermal expansion coefficient between the ceramic top coating and the metal substrate. The residual interfacial strength was significantly decreased by the thermal cycle fatigue due to the initiation of the micro-cracks near the interface. The degradation mechanism of the adherence was discussed based on the analysis of the thermal stress distribution as well as the experimental results.
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