scholarly journals Comparison and Selection of Data Processing Methods for the Application of Cr3+ Photoluminescence Piezospectroscopy to Thermal Barrier Coatings

Coatings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 181
Author(s):  
Ning Lu ◽  
Yanheng Zhang ◽  
Wei Qiu
Keyword(s):  
Data Processing ◽  
Thermal Oxidation ◽  
Spectral Data ◽  
Thermal Barrier Coatings ◽  
Thermal Barrier ◽  
Processing Methods ◽  
Oxidation Stress ◽  
Barrier Coatings ◽  
Quantitative Stress ◽  
Selection Of

Thermal barrier coatings (TBCs) are an indispensable part of the blades used in aeroengines. Under a high-temperature service environment, the thermal oxidation stress at the interface is the main cause of thermal barrier failure. Cr3+ photoluminescence piezospectroscopy has been successfully used to analyze the thermal oxidation stress of TBCs, but systematic and quantitative analysis results for use in data processing are still lacking, especially with respect to the identification of peak positions. The processing methods used to fit spectral data were studied in this work to accurately characterize TBC thermal oxidation stress using Cr3+ photoluminescence spectroscopy. Both physical and numerical experiments were carried out, where Cr3+ photoluminescence spectra were detected from alumina ceramic samples under step-by-step uniaxial loading, and the simulated spectra were numerically deduced from the measured spectral data. Then, the peak shifts were obtained by fitting all spectral data by using Lorentzian, Gaussian and Psd-Voigt functions. By comparing the fitting results and then discussing the generation mechanism, the Lorentzian function—not the Psd-Voigt function that is most widely utilized—was regarded as the most applicable method for the application of Cr3+ photoluminescence piezospectroscopy to TBCs because of its sufficient sensitivity, stability and confidence for quantitative stress analysis.

scholarly journals Optimal Data Processing Method for the Application of Eu3+ Photoluminescence Piezospectroscopy in Thermal Barrier Coatings

Coatings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 678
Author(s):  
Yanheng Zhang ◽  
Ning Lu ◽  
Wei Qiu
Keyword(s):  
Data Processing ◽  
Internal Stress ◽  
Thermal Barrier Coatings ◽  
Turbine Blades ◽  
Gaussian Function ◽  
Luminescence Spectra ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Data Processing Method ◽  
Evaluation Of Data

Thermal barrier coatings (TBCs) are widely used to protect gas turbine blades but internal stress near the interface in TBCs is one of the main causes of thermal barrier failure under thermal cycling. A non-destructive inspection technique based on Eu3+ photoluminescence piezospectroscopy has been successfully used to analyze the residual stress in TBCs, but systematic and quantitative evaluation of data processing is still needed, especially with respect to the identification of peak positions. In this work, processing methods for Eu3+ photoluminescence spectroscopy data were studied to characterize TBC internal stress. Both physical and numerical experiments were carried out where Eu3+ luminescence spectra were obtained from a sample of europium-doped yttria-stabilized zirconia (YSZ:Eu3+) under step-by-step uniaxial loading, and the simulated spectra were numerically deduced from the measured spectra. The peak shifts were then obtained by processing the spectral data in different ways (Gaussian, Lorentzian, pseudo-Voigt fitting, and the barycenter method), and comparing the results. We found that the Gaussian function, rather than the commonly used Lorentzian function, is the most appropriate method for the application of Eu3+ photoluminescence piezospectroscopy in TBCs because it provides sufficient sensitivity, stability and confidence for quantitative stress analysis.

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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