Detection of Thermally Grown Oxides in Thermal Barrier Coatings by Nondestructive Evaluation

Fahr, A.; Rogé, B.; Thornton, J. A.

doi:10.1361/105996306x92587

Cited by 23 publications

(5 citation statements)

References 9 publications

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“…The simple structure of the TBC system consists of the ceramic top coat, bond coat and superalloy substrate. During service life, a thermally grown oxide (TGO) layer (mostly α-Al2O3) forms on the bond coat surface and reduces the rate of oxidation [7]. The objective of the top ceramic coating is to reduce the metal temperature.…”

Section: Introductionmentioning

confidence: 99%

Modelling Thermal Conductivity Of Porous Thermal Barrier Coatings For High-Temperature Aero Engines Using Five Phase Model

Ghai¹,

Chen²,

Baddour³

2018

Progress in Canadian Mechanical Engineering

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Thermal Barrier Coatings (TBC) are used to shield hot sections of gas turbine engines, helping to prevent the melting of metallic surfaces. This paper proposes a Five-phase model to calculate the effective thermal conductivity of a TBC, taking into consideration the effect of various defects. By comparing the predicted values with experimental results, it was shown that the proposed five-phase model can predict the thermal conductivity of ceramic coatings closer to the actual values.

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Section: Introductionmentioning

confidence: 99%

Modelling Thermal Conductivity Of Porous Thermal Barrier Coatings For High-Temperature Aero Engines Using Five Phase Model

Ghai¹,

Chen²,

Baddour³

2018

Progress in Canadian Mechanical Engineering

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“…Nondestructive inspection techniques that can be applied to TGO detection include ultrasound , eddy current testing (ECT) , OCT , electrochemical impedance , and THz waves . However, these methods have limitations.…”

Section: Thermally Grown Oxide Layer Detectionmentioning

confidence: 99%

Nondestructive inspection of thermal barrier coating of gas turbine high temperature components

Fukuchi

Ozeki

Okada

et al. 2016

IEEJ Transactions Elec Engng

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A thermal barrier coating (TBC) is applied to high-temperature components in gas turbines, and consists of a ceramic topcoat and a metallic bondcoat. Various kinds of TBC degradation and damage occur in high-temperature components during service, such as topcoat thinning, topcoat delamination, and formation of a thermally grown oxide (TGO) layer below the topcoat, each of which can be examined using a suitable nondestructive inspection technique. Topcoat thinning can be detected by topcoat thickness measurement using terahertz waves, which are electromagnetic waves in the frequency region between optical and radio waves. The measurement resolution is about 10 μm, which is comparable to microscopic observation of the cross section in destructive inspection. Topcoat delamination can be detected by active thermography, in which the topcoat surface is scanned by a heating laser and the surface temperature distribution is measured by a thermal infrared camera. The combination of temperature peak and residual thermal image detection is effective in eliminating false detection. The TGO layer can be detected using photoluminescence, in which the Cr 3+ ions included as an impurity in Al 2 O 3 are detected. Since delamination tends to occur at locations at which the TGO layer has grown, TGO layer detection provides an effective method to select regions where delamination has occurred or is likely to occur. An inspection flow based on these techniques is proposed, which is expected to aid the establishment of condition-based maintenance strategies of high-temperature components.

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“…Khan [ 19 ] and Sabbagh [ 20 ] used the eddy current testing method to evaluate the life of TBCs and measure its thickness. Fahr [ 21 ] and Roge [ 22 ] used an eddy current combined with ultrasound methods to evaluate the performance of TBCs.…”

Section: Introductionmentioning

confidence: 99%

An Electromagnetic/Capacitive Composite Sensor for Testing of Thermal Barrier Coatings

Ren

Pan

Chen

2018

Sensors

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Thermal barrier coatings (TBCs) can significantly reduce the operating temperature of the aeroengine turbine blade substrate, and their testing technology is very urgently demanded. Due to their complex multi-layer structure, it is hard to evaluate TBCs with a single function sensor. In this paper, an electromagnetic/capacitive composite sensor is proposed for the testing of thermal barrier coatings. The dielectric material is tested with planar capacitor, and the metallic material is tested with electromagnetic coils. Then, the comprehensive test and evaluation of thermal barrier coating system can be realized. The sensor is optimized by means of theoretical and simulation analysis, and the interaction between the planar capacitor and the electromagnetic coil is studied. The experimental system is built based on an impedance analyser and multiplex unit to evaluate the performance of the composite sensor. The transimpedances and capacitances are measured under different coating parameters, such as thickness and permittivity of top coating as well as bond layer conductivity. The experimental results agree with the simulation analysis, and the feasibility of the sensor is proved.

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Detection of Thermally Grown Oxides in Thermal Barrier Coatings by Nondestructive Evaluation

Cited by 23 publications

References 9 publications

Modelling Thermal Conductivity Of Porous Thermal Barrier Coatings For High-Temperature Aero Engines Using Five Phase Model

Modelling Thermal Conductivity Of Porous Thermal Barrier Coatings For High-Temperature Aero Engines Using Five Phase Model

Nondestructive inspection of thermal barrier coating of gas turbine high temperature components

An Electromagnetic/Capacitive Composite Sensor for Testing of Thermal Barrier Coatings

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