Ultrasonic characterization of thermally grown oxide in thermal barrier coating by reflection coefficient amplitude spectrum

Zhiyuan Ma; Yang Zhao; Zhongbing Luo; Li Lin

doi:10.1016/j.ultras.2013.11.012

Ultrasonic characterization of thermally grown oxide in thermal barrier coating by reflection coefficient amplitude spectrum

Ultrasonics. 2014 Apr;54(4):1005-9. doi: 10.1016/j.ultras.2013.11.012. Epub 2013 Dec 7.

Authors

Zhiyuan Ma¹, Yang Zhao², Zhongbing Luo¹, Li Lin³

Affiliations

¹ NDT & E Laboratory, Dalian University of Technology, Dalian 116085, China.
² NDT & E Laboratory, Laser Institute of Shandong Academy of Sciences, Jinan 250014, China.
³ NDT & E Laboratory, Dalian University of Technology, Dalian 116085, China. Electronic address: linli@dlut.edu.cn.

PMID: 24359869
DOI: 10.1016/j.ultras.2013.11.012

Abstract

The thermally grown oxide (TGO) growth at the interface of ceramic coating/bond coating in thermal barrier coatings (TBCs) was evaluated by ultrasonic reflection coefficient amplitude spectrum (URCAS). A theoretical analysis was performed about the influence of acoustic impedance match relationship between the ceramic coating and its adjacent media on URCAS. The immersion ultrasonic narrow pulse echo method was carried out on the TBC specimen before and after oxidation under 1050°C×1h for 15cycles. The resonant peaks of URCAS obtained before and after oxidation showed that TGO which generated between the ceramic coating and bond coating due to the oxidation, changed the acoustic impedance match between the ceramic coating and its adjacent media. This method is able to nondestructively characterize the generation of TGO in TBCs, and is important to practical engineering application.

Keywords: Acoustic impedance; Reflection coefficient amplitude spectrum; TGO; Thermal barrier coating; Ultrasonic.