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Selection of high temperature barrier coatings through phase diagram analysis.

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Title: Selection of high temperature barrier coatings through phase diagram analysis.
Authors: Kowalski, Ben1 (AUTHOR) benjamin.kowalski@nasa.gov, Stokes, Jamesa1 (AUTHOR)
Source: Ceramics International. Oct2025:Part C, Vol. 51 Issue 25, p46668-46677. 10p.
Subjects: Diopside, Thermal expansion measurement, Thermal barrier coatings, Water vapor, Internal combustion engines
Abstract: Environmental barrier coatings (EBC) are necessary to protect SiC components from water vapor corrosion in gas turbine engines. In this work, a method is proposed of determining viable EBC candidates by using known phase diagrams to presume the activity of the components a priori. Using this method, six candidate materials were chosen: Hf 6 Ta 2 O 17 , Ta 2 TiO 7 , MgTa 2 O 6 , CaAl 12 O 19 , CaAl 2 O 4 , and Y 3 Ga 5 O 12. The selected candidate materials are then subjected to high temperature exposures of water vapor, calcium magnesium aluminum silicates (CMAS), and a combination of water vapor and CMAS to determine how well they function as an EBC. The outcome of these experiments is combined with thermal expansion measurements and evaluated against the current state of the art EBC Yb 2 Si 2 O 7. The candidate compositions Hf 6 Ta 2 O 17 , CaAl 12 O 19 , CaAl 2 O 4 , and Y 3 Ga 5 O 12 performed comparably or better than Yb 2 Si 2 O 7 in the exposure of water vapor and CMAS. CaAl 2 O 4 performed the best for the properties studied with a CTE of 5.8 10−6/°C and 2 order of magnitude reduction in water vapor corrosion rate vs Yb 2 Si 2 O 7. Therefore, it is possible to use this method to find candidate materials outside of the state of the art silicates for EBC application. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:Environmental barrier coatings (EBC) are necessary to protect SiC components from water vapor corrosion in gas turbine engines. In this work, a method is proposed of determining viable EBC candidates by using known phase diagrams to presume the activity of the components a priori. Using this method, six candidate materials were chosen: Hf 6 Ta 2 O 17 , Ta 2 TiO 7 , MgTa 2 O 6 , CaAl 12 O 19 , CaAl 2 O 4 , and Y 3 Ga 5 O 12. The selected candidate materials are then subjected to high temperature exposures of water vapor, calcium magnesium aluminum silicates (CMAS), and a combination of water vapor and CMAS to determine how well they function as an EBC. The outcome of these experiments is combined with thermal expansion measurements and evaluated against the current state of the art EBC Yb 2 Si 2 O 7. The candidate compositions Hf 6 Ta 2 O 17 , CaAl 12 O 19 , CaAl 2 O 4 , and Y 3 Ga 5 O 12 performed comparably or better than Yb 2 Si 2 O 7 in the exposure of water vapor and CMAS. CaAl 2 O 4 performed the best for the properties studied with a CTE of 5.8 10−6/°C and 2 order of magnitude reduction in water vapor corrosion rate vs Yb 2 Si 2 O 7. Therefore, it is possible to use this method to find candidate materials outside of the state of the art silicates for EBC application. [ABSTRACT FROM AUTHOR]
ISSN:02728842
DOI:10.1016/j.ceramint.2025.07.372