Characterization of Isothermally Oxidized ZrO2-8wt.%Y2O3 Thermal Barrier Coatings by Electrochemical Impedance Spectroscopy

Jai Won Byeon; B. Jayaraj; Yong Ho Sohn

doi:10.4028/www.scientific.net/MSF.486-487.145

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HomeMaterials Science ForumMaterials Science Forum Vols. 486-487Characterization of Isothermally Oxidized...

Characterization of Isothermally Oxidized ZrO₂-8wt.%Y₂O₃ Thermal Barrier Coatings by Electrochemical Impedance Spectroscopy

Abstract:

Electrochemical impedance spectroscopy was employed to examine ZrO2-8wt.%Y2O3 (yttria stabilized zirconia, YSZ) thermal barrier coating (TBC) as a function of isothermal exposure time at 1121°C. Electrochemical impedance response (resistance and capacitance of YSZ and thermally grown oxide (TGO)) of TBC specimens was analyzed with an alternative current equivalent circuit based on the multi-layered micro-constituents of TBC, and the impedance response was correlated with microstructural changes attributed to isothermal oxidation. The resistance of YSZ was observed to increase initially and then decrease with thermal exposure. The initial increase was related to the high temperature sintering of YSZ, and the subsequent decrease was discussed in terms of microcrack initiation and electrolyte penetration. The TGO thickness was linearly correlated to the capacitance of TGO.

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Materials Science Forum (Volumes 486-487)

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145-148

DOI:

https://doi.org/10.4028/www.scientific.net/MSF.486-487.145

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Online since:

June 2005

Authors:

Jai Won Byeon, B. Jayaraj, Yong Ho Sohn

Keywords:

Electrochemical Impedance Spectroscopy (EIS), Isothermal Oxidation, Non-Destructive Evaluation (NDE), Thermal Barrier Coating (TBC), Thermally Grown Oxide

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[4] [8] [12] [16] [20] [24] [28] Capacitance of TGO (nF) Capacitance Summary Electrochemical impedance spectroscopy was employed to examine TBCs during isothermal oxidation. As a function of isothermal oxidation time, the evolution in resistance and capacitance determined for TBC constituents (YSZ and TGO) was related to microstructural changes such as YSZ sintering, TGO growth and crack initiation. YSZ sintering during the initial stages of thermal exposure was related to the increase in effective resistivity and resistance of YSZ coating. Metallographycally measured TGO thickness was quantitatively correlated to the capacitance of TGO. EIS technique was suggested as a feasible NDE tool for quality monitoring of thermal barrier coating in high efficiency gas turbine engine. Fig. 6. Change of TGO thickness and capacitance as a function of squire root of oxidation time at 1121 °C.

DOI: 10.3390/coatings12020107

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