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Volcanic Ash-Induced Decomposition of EB-PVD Gd2Zr2O7 Thermal Barrier Coatings to Gd-Oxyapatite, Zircon, and Gd, Fe-Zirconolite

Mechnich, Peter and Braue, Wolfgang (2013) Volcanic Ash-Induced Decomposition of EB-PVD Gd2Zr2O7 Thermal Barrier Coatings to Gd-Oxyapatite, Zircon, and Gd, Fe-Zirconolite. Journal of the American Ceramic Society, 96 (6), pp. 1958-1965. Wiley. DOI: 10.1111/jace.12251 ISSN 0002-7820

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Abstract

The resistance of EB-PVD Gd2Zr2O7 thermal barrier coatings against high-temperature infiltration and subsequent degradation by molten volcanic ash is investigated by microstructural analysis. At 1200°C, EB-PVD Gd2Zr2O7 coatings with silica rich, artificial volcanic ash (AVA) overlay show a highly dynamic and complex recession scenario. Gd2O3 is leached out from Gd2Zr2O7 by AVA and rapidly crystallizes as an oxyapatite-type solid-solution (Ca,Gd)2(Gd,Zr)8(Si,Al)6O26. The second product of Gd2Zr2O7 decomposition is Gd2O3 fully stabilized ZrO2 (Gd-FSZ). Both reaction products are forming an interpenetrating network filling open coating porosity. However, first-generation Gd-oxyapatite and Gd-FSZ are exhibiting chemical evolution in the long term. The chemical composition of Gd-oxyapatite does evolve from Ca,Zr enriched to Gd-rich. AVA continuously leaches out Gd2O3 from Gd-FSZ followed by destabilization to the monoclinic ZrO2 polymorph. Finally, zircon (ZrSiO4) is formed. In addition to the prevalent formation of Gd-oxyapatite, a Gd-, Zr-, Fe-, and Ti-rich oxide is observed. From chemical analysis and electron diffraction it is concluded that this phase belongs to the zirconolite-type family (zirconolite CaZrTi2O7), exhibiting an almost full substitution Ca2+ + Ti4+ <> Gd3+ + Fe3+. As all Gd2Zr2O7 decomposition products with the exception of ZrSiO4 exhibit considerable solid solubility ranges, it is difficult to conclusively assess the resistance of EB-PVD Gd2Zr2O7 coatings versus volcanic ash attack.

Item URL in elib:https://elib.dlr.de/85789/
Document Type:Article
Title:Volcanic Ash-Induced Decomposition of EB-PVD Gd2Zr2O7 Thermal Barrier Coatings to Gd-Oxyapatite, Zircon, and Gd, Fe-Zirconolite
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Mechnich, PeterWF-KSWUNSPECIFIED
Braue, WolfgangWF-KSWUNSPECIFIED
Date:2013
Journal or Publication Title:Journal of the American Ceramic Society
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:96
DOI :10.1111/jace.12251
Page Range:pp. 1958-1965
Publisher:Wiley
ISSN:0002-7820
Status:Published
Keywords:Artificial Volcanic Ash, Thermal Barrier Coatings, Corrosion
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Propulsion Systems (old)
DLR - Research area:Aeronautics
DLR - Program:L ER - Engine Research
DLR - Research theme (Project):L - Combustion Chamber Technologies (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Research > Keramische Strukturwerkstoffe
Deposited By: Mechnich, Dr.rer.nat. Peter
Deposited On:27 Nov 2013 13:57
Last Modified:08 Mar 2018 18:45

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