Corrosion behavior of AlPO₄ as environmental barrier coating in water vapor enviroment

AlPO₄ was synthesized by a Sol-Gel method. Its coefficient of thermal expansion (CTE) was measured by dilatometer. Its corrosion behavior was tested in an environment of 50vol%H₂O/50vol%O₂ with a flow rate of 0.085 cm/s at 1350°C. The phases and composition of the samples were analyzed by X-ray diffraction and Energy Dispersive Spectroscope. The microstructures of AlPO₄ were characterized by Scanning Electron Microscope. The results indicate that the CTE of AlPO₄ matches with that of C/SiC composites and its corrosion resistance is much better than that of SiC. However, the decomposition of AlPO₄ at high temperatures is the main problem in the water vapor enviroment, which will be accelerated in combination with silica.