Abstract
Environmental barrier coatings, typically rare earth silicates, have been successfully employed on ceramic matrix composites in the hot zone of gas turbine engines, allowing for high fuel burn temperatures and increased flight efficiency. Yet, environmental barrier coatings face challenges as turbine temperatures continue to increase, such as increased oxidation of the underlying substrate, environmental degradation, and coating spallation. Here, we show how multi-component rare earth silicates offer a unique solution for simultaneously co-optimizing phase stability, thermo-chemical, and thermo-mechanical properties through variation of the rare earth elements implemented in the coating material. Each rare earth element added in solution was chosen to enhance specific material properties. We found that chemical stability with the turbine gaseous environment or with molten deposits could be retained, and in some cases enhanced, without detrimental effects on the phase stability or thermo-mechanical behavior. Our results demonstrate how rare earth cation mixing can lead to a 50% reduction in thermal conductivity for the given rare earth silicate mixtures. Such decreases in thermal conductivity show promise for reducing the substrate operating temperature during use, thus making multi-component rare earth silicates a novel class of dual-purpose thermal/environmental barrier coating materials.
Original language | English |
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Article number | 101557 |
Journal | Materialia |
Volume | 26 |
DOIs | |
State | Published - Dec 2022 |
Externally published | Yes |
Funding
This work was funded through the National Science Foundation DMREF: Collaborative Research: GOALI: Accelerating Discovery of High Entropy Silicates for Extreme Environments, Award #1921973. We also appreciate support from the Office of Naval Research, Grant No. N00014-21-1-2477. The authors would like to acknowledge the Nanoscale Materials Characterization Facility at the University of Virginia for supporting this research through characterization equipment.
Keywords
- CMAS
- Environmental barrier coating
- Phase stability
- Thermal conductivity