Abstract
Plasma spray-physical vapor deposition (PS-PVD) was used to prepare tri-layer environmental barrier coatings (EBCs) Si/mullite/Yb2SiO5 on SiCf/SiC substrate. Isothermal oxidation tests of EBCs were performed at 1300 ℃ for 1000 h. The thermochemical and thermomechanical interface interaction among EBCs were investigated. The results show that more dense EBCs can be obtained through PS-PVD process, which is attributed to the mixed deposition of liquid/gas states. After isothermal oxidation, many pores were observed in the Yb2SiO5 coating near the interface of Yb2SiO5/mullite coating, which results from the diffusion of Yb2O3 phase dissociated from Yb2SiO5 into mullite coating at high temperature. In the mullite coating, the Yb2O3 reacted with Al2O3 generating rod-like Yb3Al5O12 phase. Additionally, due to the thermal expansion mismatch and high temperature oxidation, cracks were formed at the interfaces of mullite/Si coating. Those interface cracks resulted in buckling in the mullite coating.
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