An Integrated Approach With Innovative NDTS for Thermal Barrier Coating Assessment: Optical and Frequency Scanning Eddy Current Testing (F-SECT) Combination With Pulsed Thermography

2006 ◽  
Author(s):  
Claudia Rinaldi ◽  
Letizia de Maria ◽  
Federico Cernuschi ◽  
Giampiero Antonelli
Keyword(s):  
Eddy Current ◽  
Gas Turbines ◽  
Current System ◽  
Field Measurements ◽  
Integrated Approach ◽  
Ceramic Coatings ◽  
Thermal Barrier ◽  
Pulsed Thermography ◽  
Damage Level ◽  
The Right

The components of the hot gas path in gas turbines can survive to very high temperatures because they are protected by ceramic Thermal Barrier Coatings (TBC); the failure of such coatings can dramatically reduce the component life. A reliable assessment of the Coating integrity and/or an Incipient TBC Damage Detection can help both in optimising the inspection intervals and in finding the appropriate remedial actions. In this paper the potential of three different NDT techniques applicable to the metallo/ceramic coatings of hot parts are discussed in the light of both results obtained on laboratory aged specimens and in field measurements on operated components. An investigation of the NDTs capability to detect damage evolution was performed on thermal-cycled specimens coated with TBC (both EB-PVD and pseudocolumnar APS) by means of an F-SECT eddy current system, by an innovative portable Piezospectroscopic system and by pulsed thermography. The observation of metallographic sections of the thermal cycled specimens allowed to give the right interpretation to the results of each NDT methodology and enlightened its specific characteristics and potentiality. Moreover in field applicability is discussed for each technique. Finally it is shown how an integrated approach of suitable coating evolution models and complimentary NDT techniques can provide an interesting assessment of the damage level of the metallo/ceramic coatings of operated rotating blades.

Bending Fatigue of Thermal Barrier Coatings

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Robert Eriksson ◽  
Zhe Chen ◽  
Krishna Praveen Jonnalagadda
Keyword(s):  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Base Alloy ◽  
Ceramic Coatings ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Bending Fatigue ◽  
Crack Configuration ◽  
Lower Load ◽  
Delamination Damage

Thermal barrier coatings (TBCs) are ceramic coatings used in gas turbines to lower the base metal temperature. During operation, the TBC may fail through, for example, fatigue. In this study, a TBC system deposited on a Ni-base alloy was tested in tensile bending fatigue. The TBC system was tested as-sprayed and oxidized, and two load levels were used. After interrupting the tests, at 10,000–50,000 cycles, the TBC tested at the lower load had extensive delamination damage, whereas the TBC tested at the higher load was relatively undamaged. At the higher load, the TBC formed vertical cracks which relieved the stresses in the TBC and retarded delamination damage. A finite element (FE) analysis was used to establish a likely vertical crack configuration (spacing and depth), and it could be confirmed that the corresponding stress drop in the TBC should prohibit delamination damage at the higher load.

STUDY FOR BLADE CERAMIC COATING DELAMINATION DETECTION FOR GAS TURBINE

2008 ◽  
Vol 22 (31n32) ◽  
pp. 5699-5704 ◽  
Author(s):  
CHOUL-JUN CHOI ◽  
SEUNG HYUN CHOI ◽  
JAE-YEOL KIM
Keyword(s):  
Thermal Barrier Coating ◽  
Gas Turbines ◽  
Life Assessment ◽  
Thermal Barrier ◽  
Large Area ◽  
Pulsed Thermography ◽  
Barrier Coating ◽  
Reliable Assessment ◽  
Coating Delamination ◽  
Remedial Actions

The component of the hot gas path in gas turbines can survive to very high temperatures because they are protected by ceramic Thermal Barrier Coating (TBC); the failure of such coating can dramatically reduce the component life. A reliable assessment of the Coating integrity and/or an Incipient TBC Damage Detection can help both in optimizing the inspection intervals and in finding the appropriate remedial actions. This study gives the TBC integrity; so other methods are required, like thermography to obtain indications of TBC delamination. Pulsed Thermography detects coating detachments and interface defects, with a large area of view but a spatial resolution of few mm. The mentioned techniques as a whole constitute a powerful tool for the life assessment of thermal barrier coating.

Bending Fatigue of Thermal Barrier Coatings

2017 ◽  
Author(s):  
Robert Eriksson ◽  
Zhe Chen ◽  
Krishna Praveen Jonnalagadda
Keyword(s):  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Base Alloy ◽  
Ceramic Coatings ◽  
Thermal Barrier ◽  
Element Analysis ◽  
Barrier Coatings ◽  
Bending Fatigue ◽  
Lower Load ◽  
Delamination Damage

Thermal barrier coatings (TBCs) are ceramic coatings used in gas turbines to lower the base metal temperature. During operation, the TBC may fail through, for example, fatigue. In the present study, a TBC system deposited on a Ni-base alloy was tested in tensile bending fatigue. The TBC system was tested as-sprayed and oxidized and two load levels were used. After interrupting the tests, at 10000–50000 cycles, the TBC tested at the lower load had extensive delamination damage whereas the TBC tested at the higher load was relatively undamaged. At the higher load, the TBC formed vertical cracks which relieved the stresses in the TBC and retarded delamination damage. A finite element analysis was used to establish a likely vertical crack configuration (spacing and depth) and it could be confirmed that the corresponding stress drop in the TBC should prohibit delamination damage at the higher load.

Frequency-Scanning Eddy Current NDE for Duplex Metallic Coatings

2003 ◽  
Author(s):  
Kenji Krzywosz ◽  
Vis Viswanathan
Keyword(s):  
Eddy Current ◽  
Gas Turbines ◽  
Current System ◽  
Life Assessment ◽  
Metallic Coatings ◽  
Multiple Frequency ◽  
Β Phase ◽  
Frequency Scanning ◽  
Current Coil ◽  
Eddy Current Nde

EPRI is involved in a multi-year program to test, evaluate, and develop a field-deployable eddy current NDE system for life assessment of blade coatings for advanced gas turbines. An eddy current system was assembled and tested on service-aged 7FA first stage blade buckets, which were coated with GT 33+ duplex metallic coatings. Testing of transverse cutout sections showed presence of normal coating, coating degradation due to β-phase depletion, and cracked coatings with some cracks penetrating into the GTD-111 substrate. By plotting normalized multiple-frequency eddy current coil impedance values, the eddy current technique was able to assess and provide the following coating and airfoil conditions: 1) normal coating; 2) degraded coating; 3) cracked coating; and 4) possible corrosion of GTD-111 substrate. Using a built-in three-layer inversion program, conductivity values of topcoat, bond coat, and GTD-111 substrate were also estimated using aged blade buckets.

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.

scholarly journals Progress in Novel Electrodeposited Bond Coats for Thermal Barrier Coating Systems

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4214
Author(s):  
Kranthi Kumar Maniam ◽  
Shiladitya Paul
Keyword(s):  
Gas Turbine ◽  
Thermal Barrier Coating ◽  
Gas Turbines ◽  
High Performance ◽  
Turbine Engines ◽  
Thermal Barrier ◽  
Gas Turbine Engines ◽  
Potential Cost ◽  
Bond Coats ◽  
Barrier Coating

The increased demand for high performance gas turbine engines has resulted in a continuous search for new base materials and coatings. With the significant developments in nickel-based superalloys, the quest for developments related to thermal barrier coating (TBC) systems is increasing rapidly and is considered a key area of research. Of key importance are the processing routes that can provide the required coating properties when applied on engine components with complex shapes, such as turbine vanes, blades, etc. Despite significant research and development in the coating systems, the scope of electrodeposition as a potential alternative to the conventional methods of producing bond coats has only been realised to a limited extent. Additionally, their effectiveness in prolonging the alloys’ lifetime is not well understood. This review summarises the work on electrodeposition as a coating development method for application in high temperature alloys for gas turbine engines and discusses the progress in the coatings that combine electrodeposition and other processes to achieve desired bond coats. The overall aim of this review is to emphasise the role of electrodeposition as a potential cost-effective alternative to produce bond coats. Besides, the developments in the electrodeposition of aluminium from ionic liquids for potential applications in gas turbines and the nuclear sector, as well as cost considerations and future challenges, are reviewed with the crucial raw materials’ current and future savings scenarios in mind.

Detection of internal defects in CFRP strengthened steel structures using eddy current pulsed thermography

2021 ◽  
Vol 282 ◽  
pp. 122642 ◽  
Author(s):  
Jing Xie ◽  
Changwei Wu ◽  
Lemei Gao ◽  
Changhang Xu ◽  
Yinsheng Xu ◽  
...  
Keyword(s):  
Eddy Current ◽  
Steel Structures ◽  
Internal Defects ◽  
Pulsed Thermography
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