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Thermodynamic calculations in the Y-Si-C-O-H system for yttrium silicate based EBCs

Markel, Ingo Jürgen; Cupid, Damian Marlon; Steinbrück, Martin; Seifert, Hans Jürgen

Abstract (englisch): Si-based Ceramic Matrix Composites (CMCs) are promising structural materials for the hot sections of next generation gas turbines. Since the presence of water vapor in the combustion gas may lead to the formation of gaseous hydroxides which cause the volatilization of the protective SiO2 scale, environmental barrier coatings (EBC) are required. Combinations of yttrium silicates with Y2O3 or SiO2 are one of the most promising EBC materials, and it is necessary to understand their behavior at high-temperature and in O2/H2O containing combustion atmospheres. In this work, the CALPHAD method was used to develop a thermodynamic dataset of the multi-component Y-Si-C-O-H system to be able to simulate heterogeneous reactions between the EBC and various gas atmospheres. An existing thermodynamic description of the Y-Si-C-O system was therefore refined by updating the description of the Y2O3-SiO2 pseudo-binary system and including descriptions of the Gibbs free energies of the Si-O-H and Y-O-H gas species. The newly developed dataset was used to calculate the thermochemical reactions between the yttrium silicate coating and the SiC base material as well as with the O2/H2O containing combustion atmosphere. The stabilities of yttrium mono- and disilicate against erosion was also evaluated as a function of coating and gas composition, temperature and pressure.

Zugehörige Institution(en) am KIT Institut für Angewandte Materialien - Angewandte Werkstoffphysik (IAM-AWP)
Publikationstyp Vortrag
Jahr 2016
Sprache Englisch
Identifikator KITopen ID: 1000062754
HGF-Programm 34.13.01; LK 01
Erschienen in 9th International Conference on high Temperature ceramic matrix composites - HTCMC9, Toronto, Ontario Canada, June 26-July 1, 2016
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