In-situ fabrication of amorphous/eutectic Al2O3-YAG ceramic composite coating via atmospheric plasma spraying

The microstructure and property of plasma-sprayed Al2O3-Y3Al5O12 (YAG) composite coatings were investigated. The sprayable feedstock was composed of Al2O3/Y2O3 granules obtained from the spray drying. As-sprayed Al2O3-YAG composite coating showed obvious amorphous characteristics. Post-heat treatment facilitated the complete crystallization of the Al2O3-YAG composite coating. The heat-treated Al2O3-YAG ceramic coating possessed the deposition microstructure comprising three-dimensional interpenetrating network of α-Al2O3/YAG eutectic phases, which is very similar to the directional solidification microstructure of Al2O3/YAG eutectic bulk ceramics. This eutectic coating microstructure does not correspond to a traditional eutectic microstructure. Al2O3-YAG ceramic coating with eutectic composition is obtained from the crystallization of an amorphous solid ceramic instead of the solidification of the liquid. Furthermore, the plasma-sprayed Al2O3-YAG eutectic ceramic coating with the heat treatment exhibits excellent microstructure and performance stabilities under high temperature.