Journal of Inorganic Materials ›› 2019, Vol. 34 ›› Issue (12): 1265-1271.DOI: 10.15541/jim20190135

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Defect Evolution and Microcracks of 8YSZ Double-layer Thermal Barrier Coatings by Water Immersion Ultrasound Macroscopic Detection

WANG Lin1,DING Kun-Ying2,LIN Xiao-Ping1,3(),LI Ze3,ZHENG Run-Guo3,YANG Lian-Wei3   

  1. 1. School of Materials Science and Engineering, Northeastern University, Shenyang 110819, China
    2. School of Science, Civil Aviation University of China, Tianjin 300300, China
    3. School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004, China
  • Received:2019-04-02 Revised:2019-05-01 Published:2019-12-20 Online:2019-05-22
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  • Supported by:
    Civil Aviation Administration Science and Technology Program Subsidized Project(MHRD20160106);National Natural Science Foundation of China(51501222)


Evolution of internal structure of 8wt% Y2O3-ZrO2 (8YSZ) thermal barrier coatings during thermal shock was detected by PASCAN-64 water immersion ultrasonic equipment and scanning electron microscopy. The results show that echo signal obtained by reflection of the ultrasonic wave which is incident from vertical top coating to the bond coating mainly reflect evolution of the structure of top coating, and the echo signal obtained by reflection of ultrasonic wave which is incident from vertical basement to interface between bond coating and top coating mainly reflect evolution of structure of TGO layer, while the microstructure evolution of the whole coating is reflected by transimission signal obtained by transimission of the ultrasonic wave from vertical top coating to substrate. When porosity of the coating top coating is less than 11%, the maximum transverse size of the coating top coating is less than 50 μm and the TGO layer is mainly dense α-Al2O3, the amplitude of the echo signal dB is less than 0. Uniform distribution of signals can be observed from corresponding images, indicating that the coating is in good condition. When the porosity of top coating is more than 44%, the maximum transverse size is more than 100 μm, and the TGO layer is mainly composed of oxides of Cr and Co with sparse structure and thickness of more than 5.2 μm. From the image, the area whose amplitude dB is greater than 0 is connected into pieces, which indicates the imminent failure of the coating. Water immersion ultrasound technology can accurately reflect the evolution of internal structure of thermal barrier coatings, and it is a good nondestructive testing method for internal defects of thermal barrier coatings.

Key words: thermal barrier coatings, thermally grown oxide, structure evolution, water-immersion ultrasonic, macroscopic examination

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