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Mechnich, Peter

Naraparaju, Ravisankar

Schulz, Uwe

Yanel Guijosa Garcia, Cynthia

English

Engineering Conferences International

SYNTHESIS OF MULTI COMPONENT RARE-EARTH SILICATE SYSTEMS FOR T/EBC APPLICATION: STUDY OF THEIR HIGH TEMPERATURE INTERACTIONS WITH CMAS  Cynthia Yanel Guijosa García, Institute of Materials Research, German Aerospace Center (DLR), Germany cynthia.garcia@dlr.de Peter Mechnich, Institute of Materials Research, German Aerospace Center (DLR), Cologne, Germany Ravisankar Naraparaju, Institute of Materials Research, German Aerospace Center (DLR), Cologne, Germany Uwe Schulz, Institute of Materials Research, German Aerospace Center (DLR), Cologne, Germany   Key Words: Thermal-environmental barrier coatings, TEBCs, RE-silicates, CMAS, thermal conductivity, reaction products.  Ceramic matrix composites (CMCs), combined with environmental barrier coatings (EBCs), have been implemented in gas-turbine engines to achieve higher operation temperature (≈1500 °C) and more demanding efficiency standards. SiC-based CMCs are subjected to accelerated oxidation and rapid recession due to water vapor at high-temperature. To increase the operating temperature in detrimental environmental conditions such as high water vapor contents and CMAS-loading, an additional thermal-insulating overcoat capable of withstanding temperature >1500 °C with relative inertness to H2O and CMAS is needed to protect the EBC/CMCs systems (1,2). This configuration is identified as TBC/EBC/CMCs (Figure 1-a). However, the use of multiple layers with different thermomechanical properties and chemical compositions can result in detrimental performance at high temperatures. To reduce the possibility of their failure, the TEBC concept has been proposed. TEBCs aim to provide thermal and environmental protection, and high CMAS resistance to the underling CMC through a layer of a single material. This configuration is called TEBC/CMCs (1) (Figure 1-b). On the other hand, materials available to be used as TEBC are extremely limited. Some RE mono- and di-silicates (RE2SiO5/RE2Si2O7) where RE = Y, Yb, Er, and Ho have been identified as promising candidates due to their high-temperature phase stability (β-phase), low thermal conductivity, and coefficient of thermal expansion (CTE) near to the SiC´s (4.5x10-6 °C-1) (1,3). The main goal of this work is to synthesize multi-component di-silicates systems consisting of RE elements such as Y, Yb, Er, and Ho. The synthesis of silicates systems will be carried out by oxide mixtures in high energy milling and solid-state reaction. Additionally, thermal properties such as thermal conductivity and CTE by laser flash analysis (LFA) and dilatometry are evaluated. High temperature interactions with CMAS will be carried out at 1400 °C for various annealing times through powder-powder mixtures (RE silicate + CMAS). The synthesized phases and the reaction products will be characterized by XRD, SEM, and EDX. From this systematic study, synthesis of the β-phase multi-component RE di-silicates system will be explored and the corresponding thermal properties as well as CMAS resistance properties will be evaluated.    Figure 1 - Schematic examples of b) TBC/EBC architecture to protect ceramic structural (SiC/SiC), and c) the TEBC concept  (1). References 1.  Turcer LR, Padture NP. Scripta Materialia. 2018;154:111–7.  2.  Elizabeth. Opila, James L. Smialek, Raymond C.Robinson, Dennis S. Fox and NSJ. Journal of the American Ceramic Society. 1999;82(7):1817–25.  3.  Bakan E, Mack DE, Mauer G, Vaßen R, Lamon J, Padture NP. Advanced Ceramics for Energy Conversion and Storage. Elsevier Ltd.; 2020. 3–62.    

Synthesis of multi component rare-earth silicate systems for T/EBC application: Study of their high temperature interactions with CMAS

Guijosa-Garcia, Cynthia Y.

Institute of Transport Research:Publications

Synthesis of multi component rare-earth silicate systems for T/EBC application: study of their high temperature interactions with CMAS

https://dc.engconfintl.org/cgi/viewcontent.cgi?filename=0&article=1054&context=thermal_barrier_vi&type=additional

Synthesis of multi component rare-earth silicate systems for T/EBC application: Study of their high temperature interactions with CMAS

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Engineering Conferences International

Institute of Transport Research:Publications