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EB-PVD alumina (Al2O3) as a top coat on 7YSZ TBCs against CMAS/VA infiltration: Deposition and reaction mechanisms.

Naraparaju, Ravisankar and Pubbysetty, Raghu Praveen and Mechnich, Peter and Schulz, U. (2018) EB-PVD alumina (Al2O3) as a top coat on 7YSZ TBCs against CMAS/VA infiltration: Deposition and reaction mechanisms. Journal of the European Ceramic Society, 38 (9), pp. 3333-3346. Elsevier. ISSN 0955-2219

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Abstract

Al2O3 was deposited as a top coat on a standard 7YSZ layer (or layers) by means of EB-PVD technique and the corresponding morphology of the Al2O3/7YSZ coatings was studied in detail. This multi-layer TBC system was tested against calcium-magnesium-aluminium-silicate (CMAS) recession by performing infiltration experiments for different time intervals from 5 min to 50 hours at 1250 ºC using two types of synthetic CMAS compositions and Eyjafjallajökull volcanic ash (VA) from Iceland. The results show that the studied EB-PVD Al2O3/7YSZ coatings react quickly with CMAS or VA melt and form crystalline spinel (MgAl2-xFexO4) and anorthite (CaAl2Si2O4) phases. The presence of Fe-oxide in the CMAS has been found to be key element in influencing the spinel formation which was proved to be more efficient against CMAS sealing in comparison to the Fe-free CMAS compositions. Even though a rapid crystallization was assured, shrinkage cracks in the EB-PVD alumina layer produced during the crystallization heat treatment have proven to be detrimental for the CMAS/VA infiltration resistance. To overcome these microstructural drawbacks, an additional alumina deposition method, namely reaction-bonded alumina oxide (RBAO), was applied on top of EB-PVD Al2O3. RBAO acts as a sacrificial layer forming stable reaction products inhibiting further infiltration.

Item URL in elib:https://elib.dlr.de/119740/
Document Type:Article
Title:EB-PVD alumina (Al2O3) as a top coat on 7YSZ TBCs against CMAS/VA infiltration: Deposition and reaction mechanisms.
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Naraparaju, Ravisankarravisankar.naraparaju (at) dlr.deUNSPECIFIED
Pubbysetty, Raghu PraveenUNSPECIFIEDUNSPECIFIED
Mechnich, PeterUNSPECIFIEDUNSPECIFIED
Schulz, U.UNSPECIFIEDUNSPECIFIED
Date:April 2018
Journal or Publication Title:Journal of the European Ceramic Society
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:38
Page Range:pp. 3333-3346
Publisher:Elsevier
Series Name:Elsevier
ISSN:0955-2219
Status:Published
Keywords:EB-PVD alumina, 7YSZ, CMAS, Volcanic ASh, Anorthite
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:propulsion systems
DLR - Research area:Aeronautics
DLR - Program:L ER - Engine Research
DLR - Research theme (Project):L - Turbine Technologies
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Research > High Temperature and Functional Coatings
Institute of Materials Research > Structural and Functional ceramics
Deposited By: Naraparaju, Dr Ravisankar
Deposited On:09 Nov 2018 11:33
Last Modified:31 Jul 2019 20:17

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