Enhanced hydrothermal corrosion resistance in SiC/SiC joints with CaO-modified Y-Al-Si-O interlayer under PWR condition

The study investigated the hydrothermal corrosion behavior of Y₂O₃-Al₂O₃-SiO₂ (YAS) and CaO-Y₂O₃-Al₂O₃-SiO₂ (CYAS) glass interlayers in SiC/SiC composite joints under simulated pressurized water reactor (PWR) conditions and evaluated their effects on mechanical performance. The corrosion rate of the YAS joint was ∼2.7 mg/(cm²·day), primarily due to the rapid dissolution of SiO₂, which triggered pitting corrosion and void formation. While the Y₂Si₂O₇ exhibited good stability, degradation of the glass network caused the hydrolysis of Al species, forming stable AlO(OH) corrosion products. These processes severely damaged the structural integrity, reducing shear strength to ∼6 ± 2 MPa after 15 days, making it unsuitable for application. In contrast, the CYAS joint showed superior corrosion resistance, with a corrosion rate of ∼0.16 mg/(cm²·day), only 2.2% of the YAS joint. The CYAS joint maintained structural integrity and interface bonding. During corrosion, Y₂Si₂O₇ crystals formed, while a layer of corrosion intermediates covered and eventually transformed into AlO(OH) particles. After 25 days, shear strength remained at 26 ± 2 MPa, still satisfying service requirements. The hydrothermal corrosion mechanism of YAS-based glasses basically involved the breakdown of the glass network and formation of stable products, including Y₂Si₂O₇ and AlO(OH).