Water vapor corrosion resistance and failure mechanism of SiCf/SiC composites completely coated with plasma sprayed tri-layer EBCs.

In this work, the corrosion behaviors of as-plasma sprayed Yb 2 SiO 5 and LaMgAl 11 O 19 coatings under an environment with a volumetric ratio of 90% H 2 O-10% O 2 were investigated at 1300 °C. The results showed that Yb 2 SiO 5 and LaMgAl 11 O 19 coatings had good water vapor corrosion resistance. Therefore, Si/Yb 2 SiO 5 /LaMgAl 11 O 19 tri-layer EBCs were designed and prepared to completely cover the surface of SiC f /SiC by using atmospheric plasma spraying (APS). The water vapor corrosion behaviors of SiC f /SiC with and without EBCs at 1300 °C were investigated. The results showed that tri-layer coating can provide better corrosion resistance for SiC f /SiC at a high-temperature steam environment at 1300 °C. By comparing the water vapor corrosion behaviors of single-layer coatings and the tri-layer EBCs under same corrosion environment, it was found that the thermal mismatch stress and the formation of TGO is the main causes of tri-layer coating failure. [ABSTRACT FROM AUTHOR]