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An In-situ Non-Destructive Evaluation Method for the Failure Detection of Thermal Barrier Coatings (TBC)

IP.com Disclosure Number: IPCOM000199034D
Published in the IP.com Journal: Volume 10 Issue 9A (2010-09-09)
Included in the Prior Art Database: 2010-Sep-09
Document File: 3 page(s) / 151K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

Thermal barrier coatings (TBCs) offer great potential to substantially increase the operating temperature and then improve thermal efficiency of gas turbines for power generation. State-of-the-art TBCs are typically composed of an yttria-stabilised zirconia (YSZ) top coat and a metallic bond coat deposited onto a superalloy substrate (see Figure 1). The premature failure of the currently used TBCs is now a primary concern and it will cause severe degradation for the TBCs-coated turbine blades/vanes or combustion liners and then limits the full realization of their potential benefit offered by TBCs. Therefore, different types of inspection methods were proposed and developed to detect these failures before it leads to unconceivable catastrophic consequences, in which non-destructive evaluation (NDE) methods are extensively investigated and demonstrate their promising applicability due to their quick, precise detection of the failures. The simplest and basic NDE method is a visual inspection of the TBCs for cracks, spallation, erosion or other damages. These visual inspections require the gas turbine to be taken out of service and to be partially disassembled to provide access to the TBCs by borescope. However, in most cases only the regions with very large spelled area can be seen visually, as is the basis for borescope inspection today. Therefore, several general non-destructive evaluation (NDE) methods that can detect the presence of small defects in TBC have been developed up to now. There are the acoustic emission (AE) method, the infrared thermography (IR), the impedance spectroscopy (E-IS), and photo-stimulated luminescence spectroscopy (PSLS).

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An In-situ Non-Destructive Evaluation Method for the Failure Detection of Thermal Barrier Coatings (TBC)

Idea: Guofeng Chen, PhD, CN-Beijing; Lei Cao, PhD, CN-Beijing; Lirong Ren, PhD, CN-Beijing

Thermal barrier coatings (TBCs) offer great potential to substantially increase the operating temperature and then improve thermal efficiency of gas turbines for power generation. State-of-the-art TBCs are typically composed of an yttria-stabilised zirconia (YSZ) top coat and a metallic bond coat deposited onto a superalloy substrate (see Figure 1). The premature failure of the currently used TBCs is now a primary concern and it will cause severe degradation for the TBCs-coated turbine blades/vanes or combustion liners and then limits the full realization of their potential benefit offered by TBCs. Therefore, different types of inspection methods were proposed and developed to detect these failures before it leads to unconceivable catastrophic consequences, in which non-destructive evaluation (NDE) methods are extensively investigated and demonstrate their promising applicability due to their quick, precise detection of the failures.

The simplest and basic NDE method is a visual inspection of the TBCs for cracks, spallation, erosion or other damages. These visual inspections require the gas turbine to be taken out of service and to be partially disassembled to provide access to the TBCs by borescope. However, in most cases only the regions with very large spelled area can be seen visually, as is the basis for borescope inspection today. Therefore, several general non-destructive evaluation (NDE) methods that can detect the presence of small defects in TBC have been developed up to now. There are the acoustic emission (AE) method, the infrared thermography (IR), the impedance spectroscopy (E-IS), and photo- stimulated luminescence spectroscopy (PSLS).

However, neither of the above-mentioned NDE methods can be used for in situ examination of the failure of TBCs during engine/gas turbine operation. Substantial savings in engine maintenance can be obtained if the TBCs failure can be detected during engine/gas turbine operation.

Therefore, a novel method without the above mentioned disadvantages and altering route in TB...