About this Abstract |
| Meeting |
MS&T23: Materials Science & Technology
|
| Symposium
|
Thermodynamics of Materials in Extreme Environments
|
| Presentation Title |
Thermodynamic and Kinetic Considerations of CMAS Reactions with Rare-earth Monosilicates |
| Author(s) |
Cameron Miller, Elizabeth J. Opila |
| On-Site Speaker (Planned) |
Elizabeth J. Opila |
| Abstract Scope |
Rare-earth monosilicates (REMS) are proposed for top coats on state-of-the-art environmental barrier coatings (EBCs) for SiC-based composites used in hot-section aeroturbine applications. REMS are relatively resistant to reaction with molten siliceous debris (CMAS – CaO-MgO-Al2O3-SiO2) ingested into the engine compared to their disilicate counterparts. In this study, REMS-CMAS reactions were studied where the RE-cation was varied to identify CMAS-resistant compositions. REMS were exposed to CMAS at 1300C for 1 to 24h. Rare-earth- or calcium-stabilized silicate apatite phases were observed to form from the REMS-CMAS reaction. Periodic trends were observed. REMS containing large lanthanides formed thin dense apatite bi-layers, small lanthanides also formed reasonably dense apatite layers, whereas mid-lanthanide REMS formed thick porous reaction product layers. In contrast, the early and late lanthanide REMS showed higher dissolution rates in CMAS than the mid-lanthanide REMS compositions. Thermodynamic and kinetic aspects of these REMS-CMAS degradation mechanisms will be discussed. |