Damage Detection of Thermal Barrier Coatings by Electrochemical Impedance Spectroscopy

2008 ◽  
pp. 129-136 ◽  
Author(s):  
B. Jayaraj ◽  
S. Vishweswaraiah ◽  
V. H. Desai ◽  
Y. H. Sohn
Keyword(s):  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Damage Detection ◽  
Thermal Barrier Coatings ◽  
Electrochemical Impedance ◽  
Thermal Barrier ◽  
Barrier Coatings

Post-Exposure Evaluation of Thermal Barrier Coatings by Electrochemical Impedance Spectroscopy

2000 ◽  
Vol 645 ◽  
Author(s):  
Jianqi Zhang ◽  
Vimal Desai
Keyword(s):  
High Temperature ◽  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Thermal Barrier Coatings ◽  
Electrochemical Impedance ◽  
Morphological Properties ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Functional Relationships

ABSTRACTHigh temperature behavior of air plasma sprayed (APS) thermal barrier coatings (TBC) was investigated in this study by electrochemical impedance spectroscopy (EIS). Scanning electron microscope (SEM) was used to examine cross-sectional morphology of exposed TBC. It was found that characteristic EIS spectra were obtained effectively to differentiate variant post-exposed TBC such as isothermal oxidation and cyclic oxidation. In addition, the type and length of high temperature exposure were qualitatively discernible from the EIS data. A model of an EIS alternative current (AC) equivalent circuit was proposed quantitatively to relate the EIS parameters to the morphological properties of the exposed TBC and functional relationships have been established between them. From the results, EIS has been identified capable of monitoring the microstructure of post-exposed TBC and evaluating TBC damage.

Quality Assurance Evaluation of Thermal Barrier Coatings by Electrochemical Impedance Spectroscopy

2000 ◽  
Vol 645 ◽  
Author(s):  
Jianqi Zhang ◽  
Danyash Tamboli ◽  
Vimal Desai
Keyword(s):  
Quality Assurance ◽  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Linear Relationship ◽  
Thermal Barrier Coatings ◽  
Electrical Impedance ◽  
Electrochemical Impedance ◽  
Thermal Barrier ◽  
Morphological Examination ◽  
Barrier Coatings

ABSTRACTThe technique of electrochemical impedance spectroscopy (EIS) was used to examine the behavior of intact thermal barrier coatings (TBC) at ambient temperature. Cross-sectional morphological examination of TBC was conducted by scanning electron microscope (SEM). By correlating the SEM visual examination with EIS data, TBC was characterized non-destructively. A model of EIS alternative current (AC) equivalent circuit was proposed to establish the relationship between the EIS elemental parameters in the circuit and the microstructural characteristics of TBC. A linear relationship was found to exist between the electrical impedance of TBC topcoat and the thickness of the topcoat. The porosity of TBC top coat showed a linear relationship with the capacitance of ceramic TBC, and the pore shape in the TBC topcoat was represented by the value of the electrical impedance of the pore. The result in the study has demonstrated that EIS can be used as a non-destructive evaluation (NDE) technique for quality assurance of TBC.

NONDESTRUCTIVE IMPEDANCE SPECTROSCOPY EVALUATION OF THE BOND COAT OXIDATION IN THERMAL BARRIER COATINGS

2007 ◽  
Vol 14 (05) ◽  
pp. 935-943 ◽  
Author(s):  
L. YANG ◽  
Y. C. ZHOU ◽  
W. G. MAO ◽  
Q. X. LIU
Keyword(s):  
Impedance Spectroscopy ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Equivalent Circuit Model ◽  
Isothermal Oxidation ◽  
Thermally Grown Oxide ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Plasma Sprayed

In this paper, the impedance spectroscopy technique was employed to examine nondestructively the isothermal oxidation of air plasma sprayed (APS) thermal barrier coatings (TBCs) in air at 800°C. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were also used to characterize the microstructure evolution of TBCs. After oxidation, the thermally grown oxide (TGO), which was mainly composed of alumina as confirmed by EDX, formed at the upper ceramic coat/bond coat interface, the lower bond coat/substrate interface, and the bond coat. Impedance diagrams obtained from impedance measurements at room temperature were analyzed according to the equivalent circuit model proposed for the TBCs. Various observed electrical responses relating to the growth of oxides and the sintering of YSZ were explained by simulating the impedance spectra of the TBCs.

Non-Destructive Characterisation of Thermal Barrier Coatings Using Impedance Spectroscopy

2000 ◽  
Vol 645 ◽  
Author(s):  
Junfa Mei ◽  
Xin Wang ◽  
Ping Xiao
Keyword(s):  
Electrical Properties ◽  
Impedance Spectroscopy ◽  
Oxide Layer ◽  
Thermal Barrier Coatings ◽  
Thermal Barrier ◽  
Thermal Treatments ◽  
Barrier Coatings ◽  
Non Destructive ◽  
Clear Change ◽  
Composition Changes

ABSTRACTImpedance spectroscopy (IS) has been used to characterise the degradation of thermal barrier coatings (TBCs) due to thermal treatments at 1100°C for a period up to 200 hrs. The growth of the oxide layer at the yttria stabilised zirconia (YSZ)/bond coat interface in TBCs can be examined by measuring the impedance diagrams. From the analysis of the impedance diagrams of TBCs, the electrical properties of YSZ were found to be nearly constant during the thermal treatments, indicating there was little change in the microstructure and composition of YSZ. However, there was a clear change in the electrical properties of the oxide layer in the TBCs after thermal treatments, suggesting both microstructural and composition changes occurred in the oxide layer. These studies indicate that the IS is a very useful method in non-destructive characterisation of the degradation of TBCs.

The Impedance Spectroscopy Study of the Oxides Layer in Thermal Barrier Coatings

2018 ◽  
Vol 281 ◽  
pp. 510-515
Author(s):  
Zi Yuan Wang ◽  
Min Wang ◽  
Ya Jie Yuan ◽  
Wei Pan
Keyword(s):  
Impedance Spectroscopy ◽  
Thermal Barrier Coatings ◽  
Thermally Grown Oxide ◽  
Thermal Barrier ◽  
Relaxation Processes ◽  
Impedance Spectra ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Different Temperatures ◽  
Plasma Sprayed

Air-plasma-sprayed (APS) thermal barrier coatings (TBCs) were oxidized in air at different temperatures for 1000h and sequentially investigated by impedance spectroscopy (IS) and scanning electron microscopy (SEM). After oxidation at temperatures higher than 900°C, a thermally grown oxide (TGO) layer was formed at the bond coat/topcoat interface in TBCs. The impedance spectra of oxidized TBCs typically contains two relaxation processes that stem from the yttria-stabilized zirconia (YSZ) topcoat of TBCs and the TGO layer. The TGO resistivity that obtained by simulating the impedance spectra increased with the increasing of annealing temperature, demonstrating the growth and the densification of TGO layer.

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