科研之友
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摘要
A bi-layer environmental barrier coating (EBC) consisting of silicon(Si) bond coat/mixed ytterbium disilicate (Yb 2 Si 2 O 7 ) and ytterbium monosilicate (Yb 2 SiO 5 ) topcoats has been successfully prepared to completely wrap up the SiC f /SiC composites and the protective effects of such EBC have been evaluated by soaking them in a mixed 50% O 2 and 50% H 2 O corrosive gases at 1300 °C for various times. In topcoats, Yb 2 Si 2 O 7 is the major phase, providing good thermal expansion coefficient (CTE) matching with composite substrate and thus excellent thermal shock resistance, whereas Yb 2 SiO 5 is the dispersing minor phase, providing improved water vapor corrosion resistance. The completely wrapping up of SiC f /SiC composites by above EBC system is employed to avoid direct exposure to the corrosive conditions, making it possible to evaluate the genuine protection effects of current EBCs. Under 1300 °C water vapor corrosion, the mass change, the phase composition and the evolution of microstructure are investigated, which suggest that the bi-layer EBC has excellent performance on protecting SiC f /SiC composites from water vapor corrosion at 1300 °C.
