Steam Degradation of Ytterbium Disilicate Environmental Barrier Coatings: Effect of Composition, Microstructure and Temperature

Daniel Tejero-Martin; Mingwen Bai; Acacio Rincon Romero; Richard G Wellman; Tanvir Hussain

doi:10.1007/s11666-022-01473-2

Steam Degradation of Ytterbium Disilicate Environmental Barrier Coatings: Effect of Composition, Microstructure and Temperature

Daniel Tejero-Martin, Mingwen Bai, Acacio Rincon Romero, Richard G Wellman, Tanvir Hussain

Centre for Manufacturing and Materials

Research output: Contribution to journal › Article › peer-review

13 Citations (Scopus)

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Abstract

Recession of environmental barrier coatings (EBC) in environments containing steam is a pressing concern that requires further research before their implementation in gas turbine engines can be realized. In this work, free-standing plasma-sprayed Yb2Si2O7 coatings were exposed to flowing steam at 1350 and 1400 °C for 96 h. Three samples were investigated, one coating with a low porosity level ( < 3%) and 1 wt.% Al2O3 representing traditional EBCs porosity levels; and two coatings with higher porosity levels (~ 20%) representing abradable EBCs. Phase composition and microstructural evolution were studied in order to reveal the underlying mechanism for the interaction between high temperature steam and ytterbium disilicate. The results show depletion of Yb2SiO5 near the surface and formation of ytterbium garnet (Yb3Al5O12) on top of all three coatings due to the reaction with gaseous Al-containing impurities coming from the alumina furnace tubes. The 1 wt.% Al2O3 added to the EBC sample exacerbated the formation of garnet at 1400 °C compared to the abradable samples, which presented lower quantities of garnet. Additionally, inter-splat boundaries were visible after exposure, indicating preferential ingress of gaseous Al-containing impurities through the splat boundaries.

Original language	English
Pages (from-to)	29-45
Number of pages	17
Journal	Journal of Thermal Spray Technology
Volume	32
Issue number	1
Early online date	20 Oct 2022
DOIs	https://doi.org/10.1007/s11666-022-01473-2
Publication status	Published - Feb 2023

Bibliographical note

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Funder

This work was supported by the Engineering and Physical Sciences Research Council (EPSRC) (grant number EP/L016206/1).

Keywords

environmental barrier coating
steam
ytterbium disilicate
thermal spray

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10.1007/s11666-022-01473-2Licence: CC BY

PublishedFinal published version, 10.8 MBLicence: CC BY

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title = "Steam Degradation of Ytterbium Disilicate Environmental Barrier Coatings: Effect of Composition, Microstructure and Temperature",

abstract = "Recession of environmental barrier coatings (EBC) in environments containing steam is a pressing concern that requires further research before their implementation in gas turbine engines can be realized. In this work, free-standing plasma-sprayed Yb2Si2O7 coatings were exposed to flowing steam at 1350 and 1400 °C for 96 h. Three samples were investigated, one coating with a low porosity level ( < 3%) and 1 wt.% Al2O3 representing traditional EBCs porosity levels; and two coatings with higher porosity levels (~ 20%) representing abradable EBCs. Phase composition and microstructural evolution were studied in order to reveal the underlying mechanism for the interaction between high temperature steam and ytterbium disilicate. The results show depletion of Yb2SiO5 near the surface and formation of ytterbium garnet (Yb3Al5O12) on top of all three coatings due to the reaction with gaseous Al-containing impurities coming from the alumina furnace tubes. The 1 wt.% Al2O3 added to the EBC sample exacerbated the formation of garnet at 1400 °C compared to the abradable samples, which presented lower quantities of garnet. Additionally, inter-splat boundaries were visible after exposure, indicating preferential ingress of gaseous Al-containing impurities through the splat boundaries.",

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AU - Wellman, Richard G

AU - Hussain, Tanvir

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AB - Recession of environmental barrier coatings (EBC) in environments containing steam is a pressing concern that requires further research before their implementation in gas turbine engines can be realized. In this work, free-standing plasma-sprayed Yb2Si2O7 coatings were exposed to flowing steam at 1350 and 1400 °C for 96 h. Three samples were investigated, one coating with a low porosity level ( < 3%) and 1 wt.% Al2O3 representing traditional EBCs porosity levels; and two coatings with higher porosity levels (~ 20%) representing abradable EBCs. Phase composition and microstructural evolution were studied in order to reveal the underlying mechanism for the interaction between high temperature steam and ytterbium disilicate. The results show depletion of Yb2SiO5 near the surface and formation of ytterbium garnet (Yb3Al5O12) on top of all three coatings due to the reaction with gaseous Al-containing impurities coming from the alumina furnace tubes. The 1 wt.% Al2O3 added to the EBC sample exacerbated the formation of garnet at 1400 °C compared to the abradable samples, which presented lower quantities of garnet. Additionally, inter-splat boundaries were visible after exposure, indicating preferential ingress of gaseous Al-containing impurities through the splat boundaries.

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Steam Degradation of Ytterbium Disilicate Environmental Barrier Coatings: Effect of Composition, Microstructure and Temperature

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