High Temperature Water Oxygen Corrosion Mechanism of Ytterbium Disilicate Environmental Barrier Coatings

Abstract

The composite components of ceramic matrix face serious water oxygen corrosion degradation in the aeroengine gas environment. The application of environmental barrier coatings on the surface of components for thermal protection is an effective measure to improve the high-temperature performance and extend the service life of ceramic matrix composite components. The high-temperature stability of the environmental barrier coatings plays a significant role on the structural integrity of the components. For elucidating the failure behavior and mechanism of environmental barrier coatings subjected to high-temperature water oxygen corrosion, this work conducted a static high temperature water oxygen corrosion experiment on an atmospheric plasma spraying Yb2Si2O7/mullite/silicon environmental barrier coating system at 1 350 ℃ and 90%(volume fraction) H2O-10%O2 water/oxygen vapor environment. Meanwhile, XRD, SEM, EDS and other material characterization analysis methods were employed to study the failure behavior of coatings in high-temperature static water oxygen corrosion environments, and obtain the evolution mechanisms of the microstructure and physical phases of EBCs coatings during the corrosion process. The failure mechanism of EBCs coatings was revealed. Results showed that Yb2Si2O7 on the surface reacted with oxidants(mainly water) in the environment to generate volatile substances Si(OH)4, leading to the continuous consumption of Yb2Si2O7. The silicon element in the mullite layer inter-diffused with the rare earth element in the Yb2Si2O7 layer, making the process and mechanism of high-temperature chemical reactions extremely complex. After 500 h of corrosion, the coating experienced bulging and detachment, resulting in the coating failure.

Keywords

• environmental barrier coating; high temperature; water oxygen corrosion