Synthesis of spherical mullite/Yb2SiO5 composite EBC powder by using mechanical alloying and spray dry processes

Abstract

Abstract Environmental barrier coatings (EBCs) have been widely used as protective layers to protect the surface of ceramic components from water vapor degradation and hot corrosion at operating temperature. In this study, ytterbium monosilicate (Yb2SiO5) and mullite (3Al2O3·2SiO2) powders were synthesized by mechanical alloying to be considered as a new environmental barrier coating. The composite powder was granulated by the spray dryer process and deposited on SiC reinforced by carbon fibers (SiC/Cf) substrate using the atmospheric plasma spray method. Phases in the synthesized composite powders and the deposited EBC were identified using X-ray diffraction. A field emission scanning electron microscope equipped with energy dispersive X-ray spectroscopy was utilized to study the powder morphology and coating microstructure. After the spray dry processing, the powders exhibited a spherical morphology and good-flowability with a mean particle size of 20–40 µm. The coating thickness was measured to be between 100 and 150 μm. In addition, the results of nanoindentation testing exhibited a hardness of about 8 GPa and an elastic modulus of about 111 GPa for the deposited coatings.