Erschienen in:Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Schriften des Forschungszentrums Jülich. Reihe Energie & Umwelt / Energy & Environment 528, VI, 150, 2 S. (2021). = Universität Bochum, Diss., 2020
Sprache:
Deutsch
ISBN:
978-3-95806-524-6
ISSN:
1866-1793
Entstehung:
Anmerkungen:
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Beschreibung:
The non-oxide ceramic matrix composites (CMCs), which exhibit good mechanical high-temperature properties and low density, represent a promising alternative to the temperature-limited metallic materials. However, a problem with these CMCs is their high susceptibility to corrosion in an atmosphere containing water vapor at temperatures above 1200°C. In order to protect the material from the influence of corrosive media, various protective coating systems (environmental barrier coatings, EBCs) are applied to the CMC. The aim of the work described here is to develop a coating system that protects the base material from corrosive atmospheres in cooperation with an industrial partner. The focus of the present work is on the manufacture and optimization of EBCs for the protection of silicon carbide-based CMCs. In a first step, different material candidates have been investigated for their thermal, thermomechanical, and mechanical properties to evaluate an optimal EBC candidate. In particular, the corrosion resistance against calcium-magnesium-aluminum-silicates (CMAS) has been considered. Subsequently, the best evaluated materials Yb$_{2}$Si$_{2}$O$_{7}$ and a mixture of Yb$_{2}$Si$_{2}$O$_{7}$ and Yb$_{2}$SiO$_{5}$ were applied to the CMC using different thermal spray processes. These two materials show a high corrosion protection against CMAS and coefficients of thermal expansion adapted to the CMC. Below the top layers of these two materials, the CMC is additionally coated with a silicon bond coat to create a complete EBC layer system. By varying the process parameters, it was possible to design the top layers in such a way that they were very dense, crackfree and crystalline at the same time. The layers developed with the different processes were subjected to evaluate the thermal shock resistance during thermal cycling and compared to each other. In addition to the material study and the optimization of layer deposition, the surface of the bond coat was structured with a laser to increase the adhesion of the top ...