Thermal fatigue failure induced by delamination in thermal barrier coating |
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| Affiliation: | 1. Fracture Research Institute, Tohoku University, Sendai, 980-8579, Japan;2. Institute of Fundamental Mechanics and Material Engineering, Xiangtan University, Xiangtan, Hunan, 411105, PR China;1. Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, Hunan, China;2. Key Laboratory of Key Film Materials & Application for Equipment of Hunan province, Xiangtan University, Xiangtan 411105, Hunan, China;3. Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802, USA;1. University of South China (USC), Hunan, China;2. St.Francis Xavier University, Antigonish, Canada;1. National Base for International Science & Technology Cooperation, National Local Joint Engineering Laboratory for Key Materials of New Energy Storage Battery, Hunan Province Key Laboratory of Electrochemical Energy Storage & Conversion, School of Chemistry, Xiangtan University, Hunan 411105, China;2. School of Chemistry & Materials Engineering, Xinxiang University, Henan 453003, China;3. Hunan Provincial Key Laboratory of Flexible Electronic Materials Genome Engineering, School of Physics and Electronic Science, Changsha University of Science and Technology, Changsha, Hunan 410114, China |
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| Abstract: | The paper presents the experimental and theoretical investigation on the thermal fatigue failure induced by delamination in thermal barrier coating system. Laser heating method was used to simulate the operating state of TBC (thermal barrier coating) system. The non-destructive evaluation such as acoustic emission (AE) detect was used to study the evolution of TBC system damage. Micro-observation and AE detect both revealed that fatigue crack was in two forms: surface crack and interface delamination. It was found that interface delamination took place in the period of cooling or heating. Heating or cooling rate and temperature gradient had an important effect on interface delamination cracking propagation. A theoretical model on interface delamination cracking in TBC system at operating state is proposed. In the model, a membrane stress P and a bending moment M are designated the thermal loads of the thermal stress and temperature gradient in TBC system. In this case, the coupled effect of plastic deformation, creep of ceramic coating as well as thermal growth oxidation (TGO) and temperature gradient in TBC system was considered in the model. The thermal stress intensity factors (TSIFs) in non-FGM (functional gradient material) thermal barrier coating system is analytical obtained. The numerical results of TSIFs reveal some same results as obtained in experimental test. The model is based on fracture mechanics theory about heterogeneous materials and it gives a rigorous explanation of delaminations in TBC system loaded by thermal fatigue. Both theoretical analysis and experimental observation reveal an important fact: delaminations are fatigue cracks which grow during thermal shocks due to compressive stresses in the loading, this loads the delaminations cracks in mixed I and II mode. |
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