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

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

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 96h. Three samples were investigated, one coating with a low porosity level (< 3%) and 1wt.% 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 1wt.% 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.

Citation

Tejero-Martin, D., Bai, M., Rincon Romero, A., Wellman, R. G., & Hussain, T. (2023). Steam Degradation of Ytterbium Disilicate Environmental Barrier Coatings: Effect of Composition, Microstructure and Temperature. Journal of Thermal Spray Technology, 32(1), 29-45. https://doi.org/10.1007/s11666-022-01473-2

• Journal Article Type: Article
• Acceptance Date: Sep 22, 2022
• Online Publication Date: Oct 20, 2022
• Publication Date: 2023-02
• Deposit Date: May 3, 2023
• Publicly Available Date: May 9, 2023
• Journal: Journal of Thermal Spray Technology
• Print ISSN: 1059-9630
• Electronic ISSN: 1544-1016
• Publisher: Springer Science and Business Media LLC
• Peer Reviewed: Peer Reviewed
• Volume: 32
• Issue: 1
• Pages: 29-45
• DOI: https://doi.org/10.1007/s11666-022-01473-2
• Keywords: Environmental barrier coating, steam, ytterbium disilicate, thermal spray
• Public URL: https://nottingham-repository.worktribe.com/output/18993073
• Publisher URL: https://link.springer.com/article/10.1007/s11666-022-01473-2#citeas
• Additional Information: 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/.