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

Abstract In this work, the corrosion behaviors of as-plasma sprayed Yb2SiO5 and LaMgAl11O19 coatings under an environment with a volumetric ratio of 90% H2O-10% O2 were investigated at 1300 °C. The results showed that Yb2SiO5 and LaMgAl11O19 coatings had good water vapor corrosion resistance. Therefore, Si/Yb2SiO5/LaMgAl11O19 tri-layer EBCs were designed and prepared to completely cover the surface of SiCf/SiC by using atmospheric plasma spraying (APS). The water vapor corrosion behaviors of SiCf/SiC with and without EBCs at 1300 °C were investigated. The results showed that tri-layer coating can provide better corrosion resistance for SiCf/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.