Abstract: |
Ceramic matrix composites (CMC) could represent the next step in aerospace engines, replacing Ni-super alloys as the standard material in the hot path. To prevent degradation due to the steam present in the environment, environmental barrier coatings (EBC) are being developed. To fulfil this role, the deposited coating must have a coefficient of thermal expansion close to the CMC, low steam volatility and low water permeability at high temperatures. In this work, thermal spraying was used with powder and suspension feedstock to produce a multi-layered EBC. The microstructure was controlled through the spraying parameters, producing a crack-free coating with a level of porosity that ensured a low level of thermal stresses during thermal cycling. X-ray diffraction measurements were performed to quantify the phases present, which played a critical role in the steam cycling performance. Finally, as mentioned, the deposited coatings were exposed to a flowing steam atmosphere with thermal cycles, analysing the mechanisms behind the degradation of the coating and the phase transformations induced.
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