Laser ultrasonic evaluation of bonding layer in thermal barrier coating

Yang Zhao; Jianwei Chen; Zhenzhen Zhang

doi:10.1117/12.2084309

23 March 2015 Laser ultrasonic evaluation of bonding layer in thermal barrier coating

Yang Zhao, Jianwei Chen, Zhenzhen Zhang

Proceedings Volume 9438, Health Monitoring of Structural and Biological Systems 2015; 943809 (2015) https://doi.org/10.1117/12.2084309
Event: SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring, 2015, San Diego, California, United States

Abstract

A noncontact laser ultrasonic method is provided for nondestructive characterization of bonding layer (BL) in thermal barrier coating (TBC). A physical mode of thin multi-layered structure is established for the case of received ultrasonic waveform consisting of reverberant overlapping echoes. Then, the transmission coefficient of the mode was derived in this work. Experiments have been performed on TBC specimens using the proposed method. The specimens are produced by electronic beam physical vapor deposition (EBPVD) method. A pulsed laser with width of 10 ns was used to generate ultrasonic while a two wave mixing (TWM) interferometer was employed to receive the ultrasonic signals. Wavelet soft-threshold method (WSTM) was introduce to improve the signal to noise ratio of laser ultrasonic testing TBC. The transmission coefficient spectrum of TBC was obtained to measure the longitudinal velocity of BL. Further, the numerical fitting method is used to determine the attenuation of BL. The proposed method is used to evaluate TBC after 1, 10 and 100 times, and the experimental results are in according with the SEM observations. This method is able to nondestructively characterize BL in TBC system, and is important to practical engineering application.

Citation Download Citation

Yang Zhao, Jianwei Chen, and Zhenzhen Zhang "Laser ultrasonic evaluation of bonding layer in thermal barrier coating", Proc. SPIE 9438, Health Monitoring of Structural and Biological Systems 2015, 943809 (23 March 2015); https://doi.org/10.1117/12.2084309

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