Advanced Environmental Barrier Coatings for SiC/SiC Composites

Bhatia, Tania; Eaton, Harry E.; Sun, Ellen Y.; Lawton, Thomas; Vedula, Venkata

doi:10.1115/gt2005-68241

Cited by 5 publications

(4 citation statements)

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“…8. The eutectic temperature for the BAS–silica system is ∼1300°C, and the SAS–silica eutectic is ∼1350°C 37,38 . The higher eutectic temperature of the SAS–silica resulted in reduced interdiffusion between the two phases in the interlayer than between the mullite and the BSAS.…”

Section: Resultsmentioning

confidence: 98%

“…The discrepancy between the predicted and the experimental values is attributed to through‐thickness cracks found in both layers before transformation. The cracks in the BSAS topcoat close and sinter during the heat treatment, but do not in the mullite due to its higher sintering temperature 37 . The model predicted that the stress in the silicon layer of the model would drop by ∼40% after the topcoat was replaced with the low CTE celsian.…”

Section: Resultsmentioning

confidence: 99%

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Residual Stress Analysis of Multilayer Environmental Barrier Coatings

Harder

Almer

Weyant

et al. 2009

Journal of the American Ceramic Society

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Silicon‐based ceramics (SiC, Si3N4) are promising materials systems for high‐temperature structural applications in gas turbine engines. However, the silica layer that forms on these materials is susceptible to attack from water vapor present in combustion environments. To protect against this degradation, environmental barrier coatings (EBCs) have been developed to shield the underlying substrate and prevent degradation. Here we report on elastic and thermal properties, as well as internal stresses of candidate multilayer coatings, as measured in situ using microfocused high‐energy X‐rays in a transmission diffraction geometry. Doped aluminosilicate coatings were investigated for their stability on a SiC/SiC melt‐infiltrated substrate. The coatings consisted of a Ba1−xSrxAl2Si2O8 topcoat with a mullite or mullite+SrAl2Si2O8 interlayer, and a silicon bond coat. A numerical model was used to compare the stress results with an ideal coating system. Experiments were carried out on as‐sprayed and heat‐treated samples in order to analyze the strain and phase evolution as a function of multilayer depth and temperature. The phase transformation of the topcoat promoted healing of cracks in the EBC and reduced stresses in the underlying layers and the addition of SAS to the interlayer reduced stresses in thermally cycled coatings, but did not stop cracks from forming.

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Residual Stress Analysis of Multilayer Environmental Barrier Coatings

Harder

Almer

Weyant

et al. 2009

Journal of the American Ceramic Society

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“…In the past two decades, CMCs have attracted a lot of research in gas turbine components such as combustor liners, shrouds, and nozzles. 22–27 Research on CMC blades for high-pressure turbine blades is still in its preliminary design and development stages. CMCs have been identified as a good candidate for vanes and blades because of their high-temperature endurance capability (over 1200°C).…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics of CMC bladed marine gas turbine-LM 2500: Effect of cycle operating parameters

Rathore

Kar

Sanjay

2022

International Journal of Engine Research

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Recent developments in ceramic-matrix composites and their successful use in combustor liners and shrouds have generated interest among researchers to adopt these materials in rotating gas turbine blades, especially in the first stages of high-pressure turbines where gas temperatures are highest. CMC blades have the potential of being retrofitted to replace superalloy turbine blades in operating gas turbines. In this paper, a comparative study on the thermodynamic performance of a marine gas turbine engine, LM 2500, featuring directionally solidified nickel superalloy blades versus novel CMC blades in the high-pressure turbine sections has been reported. Mathematical modeling of the gas turbine cycle components has been developed and then coded in C++ language. The effects of turbine inlet temperature on thermodynamic efficiencies, coolant mass flow rates, and work ratios on the two systems have been analyzed. Finally, the exergy analysis of the systems’ components has been done to identify the benefits of adopting CMC blades in the LM 2500 system. It has been observed that when compared to the directionally solidified bladed turbine system, the projected first law efficiency of CMC bladed LM 2500 gas turbines can be enhanced over 7% (from 34.17% to 41.21%). The projected work ratio can be improved by over 16% (from 0.49 to 0.57) at the turbine inlet temperature of 1725 K.

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“…The particle size distribution for each powder was evaluated using a laser scattering particle size analyzer (LS 13320, Beckman Coulter, Miami, FL, USA). Their respective d 10 Using an air plasma spray (APS) torch (Axial III, Northwest Mettech, North Vancouver, BC, Canada), the powders were sprayed onto 5 cm 9 5 cm sintered a-SiC substrates (Hexaloy SA, Saint-Gobain, Niagara Falls, MA, USA). The Axial III Plasma Spray Torch is a three anodethree cathode plasma torch with axial injection feed of the powder.…”

Section: Sample Preparationmentioning

confidence: 99%

Elastic Modulus Evolution and Behavior of Si/Mullite/BSAS-Based Environmental Barrier Coatings Exposed to High Temperature in Water Vapor Environment

et al. 2010

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Elastic modulus evolution and behaviour of Si/Mullite/BSAS-based environmental barrier coatings exposed to high temperature in water vapour environment Cojocaru, C. V.; Kruger, S. E.; Moreau, C.; Lima, R. S. Submitted May 14, 2010; in revised form October 22, 2010) Si-based ceramics (e.g., SiC and Si 3 N 4 ) are known as promising high-temperature structural materials in various components where metals/alloys reached their ultimate performances (e.g., advanced gas turbine engines and structural components of future hypersonic vehicles). To alleviate the surface recession that Si-based ceramics undergo in a high-temperature environmental attack (e.g., H 2 O vapor), appropriate refractory oxides are engineered to serve as environmental barrier coatings (EBCs). The current stateof-the-art EBCs multilayer system comprises a silicon (Si) bond coat, mullite (3Al 2 O 3 AE2SiO 2 ) interlayer and (1 2 x)BaOAExSrOAEAl 2 O 3 AE2SiO 2 ,0 £ x £ 1 (BSAS) top coat. In this article, the role of hightemperature exposure (1300°C) performed in H 2 O vapor environment (for time intervals up to 500 h) on the elastic moduli of air plasma sprayed Si/mullite/BSAS layers deposited on SiC substrates was investigated via depth-sensing indentation. Laser-ultrasonics was employed to evaluate the E values of as-sprayed BSAS coatings as an attempt to validate the indentation results. Fully crystalline, crack-free, and near-crack-free as-sprayed EBCs were engineered under controlled deposition conditions. The absence of phase transformation and stability of the low elastic modulus values (e.g.,~60-70 GPa) retained by the BSAS top layers after harsh environmental exposure provides a plausible explanation for the almost crack-free coatings observed. The relationships between the measured elastic moduli of the EBCs and their microstructural behavior during the high-temperature exposure are discussed.

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Advanced Environmental Barrier Coatings for SiC/SiC Composites

Cited by 5 publications

References 0 publications

Residual Stress Analysis of Multilayer Environmental Barrier Coatings

Residual Stress Analysis of Multilayer Environmental Barrier Coatings

Thermodynamics of CMC bladed marine gas turbine-LM 2500: Effect of cycle operating parameters

Elastic Modulus Evolution and Behavior of Si/Mullite/BSAS-Based Environmental Barrier Coatings Exposed to High Temperature in Water Vapor Environment

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