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Title:: Corrosion behavior of Si/Yb2Si2O7 environmental barrier coating in mixed CMAS and Na2SO4 molten salts

Author(s):: LI Qian; Cao Xinxin; HAN Guifang; 1.School of Materials Science and Engineering，Shandong University，Jinan 250061，China 2.School of Materials Science and Engineering，Shanghai University，Shanghai 200072，China

Keywords:: Environmental barrier coatings; Yb2Si2O7; CMAS; Na2SO4; Mixed molten salt corrosion

Abstract:: SiC-based ceramic matrix composites protected by environmental barrier coatings (EBCs) are applied as hot-section components in aero-engines.However, the aggressive gas environment contains calcium?magnesium?aluminosilicate (CMAS) and sodium salts that easily attack the hot-section components. In this study, the microstructural evolution of the Si/Yb2Si2O7 EBC coating was compared after being exposed at 1350℃ for 10 h to pure CMAS1, pure Na2SO4, and mixed molten salts of CMAS1+Na2SO4 and CMAS2+Na2SO4, respectively. The results show that in the mixed molten salt systems, the reduced viscosity promotes the in?situ formation of a rod?like apatite reaction layer on the Yb2Si2O7 surface, which consumes Ca2+ and part of the SiO2 in the melt, thereby decreasing the fluidity of the molten salt.Meanwhile, Na+ is dissolved into the glass phase, resulting in a reduction in overall melt penetrability. Consequently, the corrosion intensity of the mixed molten salts was significantly lower than that of the pure Na2SO4 molten salt environment, demonstrating a “1+1?< 2” synergistic corrosion mitigation effect. This study reveals that in multi-salt coexisting environments, the material corrosion process is governed by the dynamic competition between the infiltration capability of the molten salt and the selfforming ability of the interfacial reaction layer. The findings provide experimental evidence and theoretical support for the design of highperformance EBCs