Preparation and water-oxygen corrosion behavior of Si/Mullite+BSAS/Yb2Si2O7 environmental barrier coating by atmospheric plasma spraying

Abstract

The Si/Mullite+BSAS/Yb2Si2O7 tri-layer environmental barrier coating was prepared on the surface of the SiC substrate by atmospheric plasma spraying using solid-state sintering Yb2Si2O7 feedstock. Scanning electron microscope （SEM），energy dispersive spectrometer （EDS），X-ray diffraction analyzer （XRD） and nanoindentation testing machine etc were employed to study the microstructure，phase composition，and mechanical properties of the coating. The results indicate that the powder is composed of 83% Yb2Si2O7 phase and 17% Yb2Si2O7 phase，the porosity of the Yb2Si2O7 layer obtained by plasma spraying is （6.61±0.65）%，the bonding strength of the coating is （22.82±3.55）MPa and the fracture toughness of the coating is （1.98±0.12）MPa·m1/2. Furthermore，the water-oxygen corrosion test results of the coating at 1350 ℃ show that the monoclinic phase contents of the Yb2Si2O7 phase decrease first and then increase. The thermally grown oxide SiO2 formed by high-temperature oxidation of the silicon bonding layer is compatible with Mullite+BSAS，and interdiffusion between Mullite+BSAS and Yb2Si2O7 layers isn’t detected. Deterioration of the silicon layer is a major limiting factor in the lifetime of the coating.

Keywords

• environmental barrier coating
• atmospheric plasma spraying
• silicon carbide ceramic matrix composite
• yb2si2o7