EDDY CURRENT INVERSION AND ESTIMATION METRICS FOR EVALUATING THERMAL BARRIER COATINGS

2010 ◽  
Author(s):  
Harold A. Sabbagh ◽  
Jeremy S. Knopp ◽  
John C. Aldrin ◽  
R. Kim Murphy ◽  
Elias H. Sabbagh ◽  
...  
Keyword(s):  
Thermal Barrier Coatings ◽  
Eddy Current ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Eddy Current Inversion ◽  
Current Inversion

Porosity Determination of Thermal Barrier Coatings

1988 ◽  
Author(s):  
Mark Van Roode ◽  
Brad Beardsley
Keyword(s):  
Thermal Conductivity ◽  
Optical Microscopy ◽  
Thermal Barrier Coatings ◽  
Eddy Current ◽  
Water Immersion ◽  
Critical Factor ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Thickness Measurements

Coating porosity is believed to be a critical factor for the thermal conductivity of thermal barrier coatings (TBC’s). A number of different techniques have been used to determine the porosities of thermal barrier coatings for diesel applications as part of a NASA/DOE sponsored study. A comparison is made between methods based on water immersion, optical microscopy, eddy current thickness measurements, and Archimedes principle for TBC porosity determination.

Evaluation of Plasma Sprayed Thermal Barrier Coatings Using NDE and SEM

2007 ◽  
Author(s):  
Abbas Fahr ◽  
Catalin Mandache ◽  
Marc Genest ◽  
Weijie Chen ◽  
Xijia Wu ◽  
...  
Keyword(s):  
Thermal Barrier Coatings ◽  
Eddy Current ◽  
Thermal Imaging ◽  
Bond Coat ◽  
Elevated Temperatures ◽  
Internal Stresses ◽  
Thermal Barrier ◽  
Infrared Thermal Imaging ◽  
Barrier Coatings ◽  
Metallic Bond

Thermal barrier coatings (TBC) are used to protect the hot section components of gas turbine engines from high temperatures. A TBC system consists of a ceramic topcoat and a metallic bond coat sprayed or deposited onto the metal substrate. TBC failure is often associated with oxidation of the metallic bond coat at elevated temperatures via formation of thermally grown oxides (TGO) that cause internal stresses leading to the final spallation of the TBC. The present study explores the application of eddy current and infrared thermal imaging techniques for the detection of TGO in thermally-exposed TBC with a view of finding the damage criteria and a suitable solution for nondestructive evaluation (NDE) of TBC. The eddy current technique is based on the induction of an electromagnetic field and is sensitive to minute changes in electrical or magnetic properties of the test piece while infrared thermal imaging is based on thermal diffusion process and measures small differences in surface temperature. The NDE results are validated through destructive testing and microscopic examination of the TBC samples in as-sprayed condition and after exposure to elevated temperatures.

Characterization of thermal barrier coatings formed by electon-beam physical vapor deposition (EB-PVD)

1989 ◽  
Vol 47 ◽  
pp. 426-427
Author(s):  
Ozer Unal
Keyword(s):  
Thermal Barrier Coatings ◽  
Physical Vapor Deposition ◽  
Ceramic Coating ◽  
High Vacuum ◽  
Ceramic Coatings ◽  
High Energy ◽  
Thermal Barrier ◽  
Protective Oxide ◽  
Barrier Coatings ◽  
Energy Beam

Interest in ceramics as thermal barrier coatings for hot components of turbine engines has increased rapidly over the last decade. The primary reason for this is the significant reduction in heat load and increased chemical inertness against corrosive species with the ceramic coating materials. Among other candidates, partially-stabilized zirconia is the focus of attention mainly because ot its low thermal conductivity and high thermal expansion coefficient.The coatings were made by Garrett Turbine Engine Company. Ni-base super-alloy was used as the substrate and later a bond-coating with high Al activity was formed over it. The ceramic coatings, with a thickness of about 50 μm, were formed by EB-PVD in a high-vacuum chamber by heating the target material (ZrO2-20 w/0 Y2O3) above its evaporation temperaturef >3500 °C) with a high-energy beam and condensing the resulting vapor onto a rotating heated substrate. A heat treatment in an oxidizing environment was performed later on to form a protective oxide layer to improve the adhesion between the ceramic coating and substrate. Bulk samples were studied by utilizing a Scintag diffractometer and a JEOL JXA-840 SEM; examinations of cross-sectional thin-films of the interface region were performed in a Philips CM 30 TEM operating at 300 kV and for chemical analysis a KEVEX X-ray spectrometer (EDS) was used.

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