Cycling water vapor corrosion behavior and degradation mechanism of air plasma sprayed ytterbium silicate environmental barrier coatings

Environmental barrier coatings （EBCs） are a key protective technology for the ceramic matrix composites （CMCs） hot end components of high-performance aircraft engines， which can significantly improve the service stability and reliability of the components. In this paper， Si/Yb2Si2O7/Yb2SiO5 tri-layer structural EBCs are prepared by air plasma spray， and their corrosion behavior and degradation mechanism under 1350 ℃ and cycling water vapor conditions are investigated. The results show that the as-annealed coating is mainly composed of monoclinic Yb2SiO5 phase and cubic Yb2O3 phase， with nano-sized Yb2O3 phase dispersed in Yb2SiO5. The surface of Yb2SiO5 coating exhibits a ridge-like structure accompanied by a certain number of pores after cyclic water vapor corrosion， and the content of corrosion products Yb2Si2O7 increases with the number of cycles. The formation of Yb2Si2O7 is related to the alternating wet to dry corrosive environment and the gaseous substance Si（OH）4. Penetrating cracks exist within the Yb2SiO5 coating but terminate at the Yb2SiO5/Yb2Si2O7 interface， and the SiO2 film generated from the oxidation of the Si bond coat is well bonded to the Yb2Si2O7 interlayer and the Si bond coat in general. The tri-layer EBCs system in this paper exhibits excellent resistance to cyclic water vapor corrosion at 1350 ℃.