Structure design and fabrication of environmental barrier coatings for crack resistance

The elastic-modulus-graded environmental barrier coatings (EMG-EBCs) were designed and fabricated to resist crack propagation in this study. The cracks were introduced on the surface of EMG-EBCs by an indentator at room temperature to simulate the damages by foreign object impact. As a comparison, two single-layer coatings of Sc₂Si₂O₇ and barium strontium aluminosilicate (BSAS) were also fabricated and cracks were introduced on their surface with the same conditions of the EMG-EBCs. The results showed that the EMG-EBCs could resist the cracks from propagating through them due to the variation in elastic modulus along the depth beneath the surface, and thus could protect the composites from water-vapour corrosion, while the cracks could cross the single Sc₂Si₂O₇ or BSAS coating to provide channels for oxidative gas diffusing and attacking the composites inside. It is indicated that the EMG-EBCs could effectively resist the foreign object damage.