ZrO2 Environmental Barrier Coatings for Oxide/Oxide Ceramic Matrix Composites fabricated by Electron-Beam Physical Vapor Depostion

Kurzfassung

Oxide/oxide ceramic matrix composites were coated with Y-stabilized ZrO2 (YSZ) by electron-beam physical vapor deposition (EB-PVD). The typical columnar coating morphology is strongly influenced by CMC surface characteristics. The application of thin ceramic bondcoats provides a more homogeneous microstructure and less intercolumnar separation upon heat treatment. A serious hot-corrosion problem caused by airborne inorganic particles may arise for EBC-coated CMCs in service. The interaction of EBC-coated CMCs and CMAS-type inorganic deposits was studied in laboratory-scale experiments. It turns out that melting and subsequent penetration of CMAS-type deposits is highly critical for the CMC structural integrity, in particular near the coating/CMC interface. Moreover, the presence of iron oxide gives rise to severe YSZ recession via formation of an intermediate calcia-zirconia kimzeyite-type garnet.