Slurry based multilayer environmental barrier coatings for silicon carbide and silicon nitride ceramics — I. Processing

Ramakrishnan, Sivakumar; Tewari, Surendra N.; Lee, Kang N.; Bhatt, Ramesh S.; Fox, Dennis S.

doi:10.1016/j.surfcoat.2010.06.029

Cited by 29 publications

(6 citation statements)

References 11 publications

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“…Most of the current EBCs are variants of the second‐generation EBCs. Various aspects of current EBCs, including processing, volatility in water vapor, silica activity in Y 2 O 3 ‐SiO 2 and Yb 2 O 3 ‐SiO 2 systems, interactions with CMAS, stress analysis, fracture mechanism, impact damage, and oxidation, have been reported.…”

Section: Introductionmentioning

confidence: 99%

Yb₂Si₂O₇ Environmental barrier coatings with reduced bond coat oxidation rates via chemical modifications for long life

2018

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Spallation of environmental barrier coating (EBC) induced by thermally grown oxide (TGO) resulting from steam oxidation is a key EBC failure mode. A logical approach to improve EBC life, therefore, is to reduce TGO growth rates. A study was undertaken to investigate whether TGO growth rates can be reduced by adding modifier oxides. It was based on a hypothesis that modifier oxides dissolve in SiO2 TGO and modify the SiO2 structure, making the TGO less permeable to oxidants. Using a current state‐of‐the‐art EBC (Si/Yb2Si2O7) as the baseline, the Yb2Si2O7 layer was modified by adding Al2O3 or Al2O3‐containing oxide compounds, such as mullite and YAG (Y3Al5O12), and TiO2. EBCs were processed using air plasma spraying. Steam oxidation tests and post‐oxidation test oxidation kinetics, chemistry, microstructure, and phase analysis were used to test the hypothesis. The best modified EBC reduced the TGO thickness by ~87% compared with that of the baseline EBC in 90% H2O + 10% O2 at 1316°C under thermal cycling. Correlations between oxidation kinetics, chemistry, and microstructure of EBC and TGO were used to explain the effect of modifier oxides on reducing TGO growth rates.

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Section: Introductionmentioning

confidence: 99%

Yb₂Si₂O₇ Environmental barrier coatings with reduced bond coat oxidation rates via chemical modifications for long life

2018

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“…One is concerning the suitable deposition techniques and the optimization of deposition parameters. A lot of studies have tried various preparing techniques, such as sol-gel [25], slurry [26][27][28], chemical vapor deposition (CVD) [29], and thermal spray techniques including air plasma spray (APS) [6,[30][31][32], electron-beam physical vapor deposition (EB-PVD) [33], plasma spray physical vapor deposition (PS-PVD) [34][35][36][37], and so on. Among them, the thermal spray technique is primarily selected for its high deposition temperature, which can completely melt the powder materials and form a dense coating.…”

Section: Introductionmentioning

confidence: 99%

Pressure Infiltration of Molten Aluminum for Densification of Environmental Barrier Coatings

Dong

Liu

Zhang

et al. 2021

Preprint

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Environmental barrier coatings (EBCs) effectively protect ceramic matrix composites (CMCs) from harsh engine environment, especially steam and molten salts. However, open pores inevitably formed during deposition process provide transport channels for oxidants and corrosives and lead to premature failure of EBCs. This work proposed a pressure infiltration densification method that blocked these open pores in the coatings. Results showed that it was difficult for aluminum to infiltrate spontaneously, but with the increase of external gas pressure and internal vacuum simultaneously, the molten aluminum obviously moved forward, but finally stopped infiltrating at a depth of a specific geometry. Based on the wrinkled zigzag pore model, a mathematical relationship between the critical pressure and the infiltration depth and the pore intrinsic geometry was established. Infiltration results confirmed this relationship, indicating that for a given coating, a dense thick film can be obtained by adjusting the internal and external gas pressures to drive the melt infiltration.

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“…This process enables chemical bonding between coating and substrate after sintering. It has recently been demonstrated that this slurry coating process provides a reasonably uniform coating thickness after sintering 16,17,18 .…”

Section: Introductionmentioning

confidence: 99%

Enhanced oxidation resistance of SiC/SiC minicomposites via slurry infiltration of oxide layers

Zhou

Almansour

Morscher

2017

Journal of the European Ceramic Society

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SiC based composite materials commonly have protective silica surface in air. Under humid environments at high temperatures, like occur in jet engines, the silica surface layer reacts with water molecules to form volatile silicon hydroxide (Si(OH) 4) and the protection is reduced which cause jet engine degradation. An alternative approach to protect SiC based composites would be to infiltrate the SiC matrix via slurry with an oxide material that is resistant to the hightemperature and humid environment. As proof of concept, aqueous based mullite particle slurries were infiltrated by pressurized flow and by capillarity of the wetting slurry on the external surface of the porous SiC matrix of single-fiber-tow SiC/SiC minicomposites. Minicomposites were precracked at room temperature during tensile tests then tested in tensile creep in air at 1200 °C to study the degree of protection that the infiltrated mullite provided at high temperatures. Next, fracture surfaces were examined using SEM.

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Slurry based multilayer environmental barrier coatings for silicon carbide and silicon nitride ceramics — I. Processing

Cited by 29 publications

References 11 publications

Yb₂Si₂O₇ Environmental barrier coatings with reduced bond coat oxidation rates via chemical modifications for long life

Yb₂Si₂O₇ Environmental barrier coatings with reduced bond coat oxidation rates via chemical modifications for long life

Pressure Infiltration of Molten Aluminum for Densification of Environmental Barrier Coatings

Enhanced oxidation resistance of SiC/SiC minicomposites via slurry infiltration of oxide layers

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Slurry based multilayer environmental barrier coatings for silicon carbide and silicon nitride ceramics — I. Processing

Cited by 29 publications

References 11 publications

Yb2Si2O7 Environmental barrier coatings with reduced bond coat oxidation rates via chemical modifications for long life

Yb2Si2O7 Environmental barrier coatings with reduced bond coat oxidation rates via chemical modifications for long life

Pressure Infiltration of Molten Aluminum for Densification of Environmental Barrier Coatings

Enhanced oxidation resistance of SiC/SiC minicomposites via slurry infiltration of oxide layers

Contact Info

Product

Resources

About

Yb₂Si₂O₇ Environmental barrier coatings with reduced bond coat oxidation rates via chemical modifications for long life

Yb₂Si₂O₇ Environmental barrier coatings with reduced bond coat oxidation rates via chemical modifications for long life