High temperature calcium-magnesium-alumina-silicate (CMAS) corrosion behavior of directionally solidified Al₂O₃/YAG eutectic ceramic

The corrosion resistance to CaO-MgO-Al₂O₃-SiO₂ (CMAS) is critically important for the high temperature structural parts applied in aero-engine. We herein studied the high-temperature CMAS corrosion behavior at 1300 °C of directionally solidified Al₂O₃/YAG (Y₃Al₅O₁₂) eutectic ceramic. The systematic correlations between the CMAS corrosion resistance and unique solidification microstructure were established. The rapid reaction between CMAS melt and Al₂O₃/YAG eutectic and CMAS attacking depth could be successfully decreased. This happened because of their low chemical activity, the dense structure of the eutectic substrate and the accelerated crystallization of anorthite (CaAl₂Si₂O₈) along the CMAS-eutectic interface. Additionally, the reaction layer thickness reached lower than 40.58 μm after the corrosion for 32 h, presenting excellent CMAS corrosion resistance for the solidified eutectic ceramic. The dissolution-reprecipitation mechanism of CMAS corrosion was clearly revealed by TEM and EDS analysis in the CMAS-YAG interaction region. The interfacial structure had a low misfit of −1.81% and well-matched crystallographic relationship based on the near-coincident site lattice (NCSL) model. The superior CMAS corrosion resistance and high flexural strength stability (up to 1873 K) of the directionally solidified Al₂O₃/YAG eutectic ceramic highlight it as a promising high-temperature structural candidate material in aerospace and aeronautics industries.