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Analysis of pore morphology and thermal conductivity of alternative EB-PVD deposited TBC-compositions

Saruhan-Brings, Bilge and Ryukhtin, Vasyl and Kelm, Klemens (2010) Analysis of pore morphology and thermal conductivity of alternative EB-PVD deposited TBC-compositions. MSE 2010, 24.-26.08.2010, Darmstadt, Deutschland.

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Abstract

Thermal barrier coatings (TBCs) consist of a ceramic top coat deposited onto a bond-coated superalloy substrate and are used to increase lifetime and efficiency of highly loaded turbine blades and vanes by reducing the average metal temperature and mitigating the detrimental effects of hot spots. Electron-beam physical vapor deposition (EB-PVD) of the standard top coat, partially yttria-stabilized zirconia (PYSZ), produces various anisotropic pores which contribute in the reduction of thermal conductivity. However, increases in combustion temperature for improved turbine efficiency causing greater thermal loading alters the pore morphology resulting in an increase of thermal conductivity. Long-term dignity of the ceramic top coat of TBCs can be provided through the development of new materials with ultra-low thermal conductivity, excellent phase stability and improved sintering-resistance. Fully yttria (14 wt.% Y2O3) stabilised zirconia (FYSZ) yields intrinsically lower thermal conductivity. Further optimization of the TBC properties is possible by tailoring its microstructure, since an important relationship exists between thermal conductivity and process-induced pore structure of EB-PVD-TBCs. Pore morphology and microstructure of EB-PVD pyrochlore differ significantly from those of PYSZ and FYSZ. The influence of the pore morphology on reduction of thermal conductivity and resistance to thermal loading are not well-investigated in the new TBC compositions. This work describes the anisotropic nano-sized pore morphology in FYSZ and Pyrochlore (La2Zr2O7) TBCs obtained by small angle neutron scattering (SANS) analysis method. In order to differentiate between the 3D closed and open pores in 400 µm thick coatings, a contrast matching liquid SANS technique was employed. Samples in several arrangements such as free-standing EB-PVD-layers and TBCs deposited on metallic substrates were analysed by the Laser-Flash technique for their thermal diffusivity in the as-coated condition and after ageing at 1100°C in air. The pore migration and pore morphology changes were investigated by advanced TEM/SEM-analysis on FIB sections. Thermal derived changes in crystal structure as well as pore size and morphology observed by TEM and SANS have been correlated with the thermal conductivity changes.

Item URL in elib:https://elib.dlr.de/66690/
Document Type:Conference or Workshop Item (Speech)
Title:Analysis of pore morphology and thermal conductivity of alternative EB-PVD deposited TBC-compositions
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Saruhan-Brings, BilgeWFUNSPECIFIED
Ryukhtin, VasylHZ-berlinUNSPECIFIED
Kelm, KlemensWFUNSPECIFIED
Date:25 August 2010
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:WDS, Thermal conductivity, Neutron scattering analysis, TEM-Analysis
Event Title:MSE 2010
Event Location:Darmstadt, Deutschland
Event Type:international Conference
Event Dates:24.-26.08.2010
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Aeronautics
HGF - Program Themes:Propulsion Systems (old)
DLR - Research area:Aeronautics
DLR - Program:L ER - Engine Research
DLR - Research theme (Project):L - Turbine Technologies (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Research > High Temperature and Functional Coatings
Deposited By: Saruhan-Brings, Dr. Bilge
Deposited On:30 Nov 2010 15:34
Last Modified:30 Nov 2010 15:34

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