Rare earth silicate environmental barrier coatings for SiC/SiC composites and Si3N4 ceramics

Lee, Kang N.; Fox, Dennis S.; Bansal, Narottam P.

doi:10.1016/j.jeurceramsoc.2004.12.013

Cited by 673 publications

(451 citation statements)

References 14 publications

(34 reference statements)

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“…10 Initial work through the 1990s focused on mullite, which had a good CTE match but suffered from silica volatilization at high temperatures. This issue was partially mitigated through the addition of a yttrium-stabilized zirconia (YSZ) top coat, but the multilayer coating was limited in cyclic durability because of the relatively high CTE of the zirconia.…”

Section: Materials Selection For Environmental Barrier Coatings Ebc Rementioning

confidence: 99%

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Addressing Rare-Earth Element Criticality: An Example from the Aviation Industry

Dosch

Grossman³

et al. 2014

JOM

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Rare-earth (RE) elements are enablers for a wide range of technologies, including high-strength permanent magnets, energy-efficient lighting, hightemperature thermal barrier coatings, and catalysts. While direct material substitution is difficult in many of these applications because of the specific electronic, optical, or electrochemical properties imparted by the individual rare-earth elements, we describe an example from the aviation industry where supply chain optimization may be an option. Ceramic matrix composite engine components require environmental barrier coatings (EBCs) to protect them from extreme temperatures and adverse reactions with water vapor in the hot gas path. EBC systems based on rare-earth silicates offer a unique combination of environmental resistance, thermal expansion matching, thermal conductivity, and thermal stability across the service temperature window. Several pure rare-earth silicates and solid solutions have been demonstrated in EBC applications. However, all rely on heavy rare-earth elements (HREEs) for phase stability. This article considers the possibility of using separation tailings containing a mixture of HREEs as a source material in lieu of using the high-purity HREE oxides. This option arises because the desired properties of RE-silicate EBCs derive from the average cation size rather than the electronic properties of the individual rare-earth cations. Because separation tailings have not incurred the costs associated with the final stages of separation, they offer an economical alternative to high-purity oxides for this emerging application.

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Section: Materials Selection For Environmental Barrier Coatings Ebc Rementioning

confidence: 99%

“…Since then, EBCs based on the rare-earth silicates have been identified as top candidates for high-temperature, high-cycle applications. 10 Fig . 1.…”

Section: Materials Selection For Environmental Barrier Coatings Ebc Rementioning

confidence: 99%

Addressing Rare-Earth Element Criticality: An Example from the Aviation Industry

Dosch

Grossman³

et al. 2014

JOM

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“…Coatings for components formed of Si-based materials must fulfill an important coincident role namely to provide an environmental protection against water vapors and corrosive molten aluminosilicates. Thus these coatings have been named environmental barrier coatings (EBCs) (Ref [1][2][3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

“…In gas turbines, a low permeability for water vapors is a critical characteristic for an EBC system so as to inhibit the formation of silicon hydroxide (Si(OH) 4 ) gas by the reaction of the water vapor originating from the jet fuel combustion with the SiO 2 scale formed on the Si-based substrate (Ref [1][2][3][4][5][6]. Future hypersonic vehicles flying in low Earth orbit will also employ Si-based materials on their external structure.…”

Section: Introductionmentioning

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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“…In the quest to replace metallic components, for instance in specific hot-sections of gas turbine engines, multilayered environmental barrier coatings (EBCs) are envisioned and tested to protect Si-based ceramics (e.g., SiC and Si 3 N 4 ) (Ref [1][2][3]. Mullite (3Al 2 O 3 AE2SiO 2 ) is a low cost refractory oxide that currently constitutes the building block of an efficient EBC architecture.…”

Section: Introductionmentioning

confidence: 99%

Mechanical Behavior of Air Plasma-Sprayed YSZ Functionally Graded Mullite Coatings Investigated via Instrumented Indentation

et al. 2010

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Yttria-stabilized zirconia (YSZ)-mullite multilayer architectures with compositional grading between the bond coat and YSZ top coat are envisioned as solutions to ease their coefficient of thermal expansion mismatch induced stress. In this work, two different types of mullite powder (spray-dried and freezegranulated) and a mullite-YSZ 75/25 vol.% mixture spray-dried powder were employed. Using instrumented indentation with loads between 10 and 500 mN, the role of the powder characteristics on the mechanical behavior of air plasma-sprayed mullite bond coats deposited on SiC substrates was investigated. Hardness (H) and elastic modulus (E) were measured for the as-sprayed coatings and for coatings heat-treated at 1300°C, in water vapor environment, for periods up to 500 h. Both H and E values of the coatings are found to be highly dependent on the size distribution of the starting powders. It is aimed the fabrication of an efficient and cost-effective EBC prototype based on YSZ compositionally graded mullite.

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Rare earth silicate environmental barrier coatings for SiC/SiC composites and Si3N4 ceramics

Cited by 673 publications

References 14 publications

Addressing Rare-Earth Element Criticality: An Example from the Aviation Industry

Addressing Rare-Earth Element Criticality: An Example from the Aviation Industry

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

Mechanical Behavior of Air Plasma-Sprayed YSZ Functionally Graded Mullite Coatings Investigated via Instrumented Indentation

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