High-Temperature thermochemical interactions of molten silicates with Yb2Si2O7 and Y2Si2O7 environmental barrier coating materials

Stokes, Jamesa L.; Harder, Bryan J.; Wiesner, Valerie L.; Wolfe, Douglas E.

doi:10.1016/j.jeurceramsoc.2019.06.051

Cited by 93 publications

(70 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…CaCO 3 (>99.0%, Alfa Aesar), MgO (99.95%, Cerac Inc.), Al 2 O 3 (>99.0%, Almatis, Inc.), and SiO 2 (99.5%, Alfa Aesar) were used as starting powders for glass synthesis, using the same procedure utilized in a previous study. 22 Three of the CMAS compositions match that of this previous study, CMAS-1, CMAS-2, and CMAS-3. A fourth CMAS composition, CMAS-2.5, was synthesized as an intermediate composition between CMAS-2 and CMAS-3 regarding CaO content.…”

Section: Methodssupporting

confidence: 82%

“…More recent literature has begun to focus on the effects that deposit chemistry (varying based on geographical location) can also have on apatite crystallization and stability with Yb 2 Si 2 O 7 and Y 2 Si 2 O 7 . [20][21][22] These investigations further demonstrated a decrease in apatite formation with ytterbium and yttrium disilicate as CaO content is decreased across CMAS melts. Similar results on RE silicate crystal structures confirm metastability of apatite crystal structures with smaller RE cations as shown in studies on cation substitution in RE 9.33 (SiO 4 ) 6 O 2 , absent of CaO.…”

Section: Introductionmentioning

confidence: 75%

“…Thus, some interaction of the EBC with the molten deposit is preferred. More recent literature has begun to focus on the effects that deposit chemistry (varying based on geographical location) can also have on apatite crystallization and stability with Yb 2 Si 2 O 7 and Y 2 Si 2 O 7 . These investigations further demonstrated a decrease in apatite formation with ytterbium and yttrium disilicate as CaO content is decreased across CMAS melts.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effects of crystal structure and cation size on molten silicate reactivity with environmental barrier coating materials

et al. 2019

Self Cite

View full text Add to dashboard Cite

Rare earth (RE) disilicates are utilized in environmental barrier coatings to protect Si‐based engine components from destructive reactions with water vapor and other combustion species. These coating materials, however, degrade when exposed to molten silicate deposits in the engine. Four RE‐disilicates (RE2Si2O7, RE = Er, Dy, Gd, Nd) are analyzed herein in thermochemical interactions with glassy calcium‐magnesium‐aluminosilicate (CMAS) compositions at 1400°C. Crystalline reaction products included RE2Si2O7, SiO2, and a Ca2+yRE8+x(SiO4)6O2+3x/2+y apatite‐type silicate. RE2Si2O7 formation was favored in interactions with CMAS having low CaO:SiO2 ratios. Increased reactivity was observed for higher CaO:SiO2 ratios in CMAS combined with larger RE3+ cation size, resulting in apatite formation of varying stoichiometry and changes in lattice parameters. The crystallization of SiO2 was dependent on both thermodynamic equilibrium at low CaO:SiO2 ratios and sequestration of silicate modifiers at higher CaO:SiO2 ratios, although residual amorphous content after CMAS exposure in both cases was still substantial.

show abstract

Section: Methodssupporting

confidence: 82%

Section: Introductionmentioning

confidence: 75%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effects of crystal structure and cation size on molten silicate reactivity with environmental barrier coating materials

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…Reactions of molten silicate deposits with RE monosilicates and disilicates exhibit significant similarities and differences. Disilicates frequently react with the deposits to form apatite, nominally of composition Ca 2 RE 8 (SiO 4 ) 6 O 2 .…”

Section: Introductionmentioning

confidence: 99%

Reactions of molten silicate deposits with yttrium monosilicate

et al. 2020

View full text Add to dashboard Cite

The article addresses effects of silicate deposit composition on reactions with yttrium monosilicate (YMS), a candidate environmental barrier coating for aero-engine components. Computed phase equilibria are used to predict the nature and relative proportions of reaction products and the extent of YMS consumption upon reaction with twelve deposits of varying composition at 1300°C. These predictions are compared with results of a corresponding experimental study on three exemplary deposits.Although the nature and sequence of reaction products formed (typically apatite and yttrium disilicate) depend on the Ca:Si ratio of the deposit, the degree of consumption of YMS at equilibrium is relatively insensitive to deposit composition and is predicted to proceed to a greater extent than that in yttrium disilicate. However, sluggish reaction kinetics associated with the formation of a thin apatite layer above the YMS prevents reactions from reaching their terminal equilibrium states within the experimental times investigated (250 hours). For deposit loadings of 18 mg/cm 2 (corresponding to a thickness of about 100 µm), the degree of consumption following 250 hours exposures is only about 10%-40% of the predicted terminal values, depending on deposit composition. K E Y W O R D Schemical reactions, CMAS, Environmental barrier coating, yttrium silicate 2920 | SUMMERS Et al.

show abstract

“…The formation of other phases has been reported depending on composition and CMAS exposure temperature elsewhere. Cyclosilicate has been reported as a reaction product of Yb 2 Si 2 O 7 and CMAS with a CaO-SiO 2 ratio of 0.635 at 1200°C for 1 h, though was not detected after CMAS exposures >1300°C in nominally dense substrates [19]. For other RE disilicate systems, including Y 2 Si 2 O 7 and Gd 2 Si 2 O 7 , both cyclosilicate and silicocarnotite have been observed between 1200 and 1300°C, despite the presence of apatite [20,21].…”

Section: Introductionmentioning

confidence: 99%

Molten calcium–magnesium–aluminosilicate interactions with ytterbium disilicate environmental barrier coating

et al. 2020

Self Cite

View full text Add to dashboard Cite

Thermochemical interactions between calcium–magnesium–aluminosilicate (CMAS) glass and an environmental barrier coating of ytterbium disilicate (Yb2Si2O7) and ytterbium monosilicate (Yb2SiO5) were investigated. Top coats were deposited by plasma spray-physical vapor deposition onto silicon carbide substrates. CMAS powder was prepared as a glass and cast into a tape to yield a CMAS loading of ~29 mg/cm2. Samples were heat treated with CMAS at 1300 °C for 1–10 h or at 1400 °C for 1 h in air. Polished specimen cross-sections were characterized using scanning electron microscopy, X-ray diffraction, X-ray energy-dispersive spectroscopy, and transmission electron microscopy to evaluate resulting microstructures, phases, and compositions at CMAS/Yb2Si2O7 interfaces. Coatings exposed at 1300 °C—10 h and 1400 °C—1 h were fully infiltrated and compromised by CMAS. Dissolution of ytterbium silicate into molten CMAS followed by precipitation of cyclosilicate, silicocarnotite, and Yb2Si2O7 at 1300 °C and Yb2Si2O7 at 1400 °C enabled CMAS to effectively infiltrate top coats, rendering the predominantly Yb2Si2O7 coating ineffective at arresting molten CMAS degradation.

show abstract

High-Temperature thermochemical interactions of molten silicates with Yb2Si2O7 and Y2Si2O7 environmental barrier coating materials

Cited by 93 publications

References 36 publications

Effects of crystal structure and cation size on molten silicate reactivity with environmental barrier coating materials

Effects of crystal structure and cation size on molten silicate reactivity with environmental barrier coating materials

Reactions of molten silicate deposits with yttrium monosilicate

Molten calcium–magnesium–aluminosilicate interactions with ytterbium disilicate environmental barrier coating

Contact Info

Product

Resources

About