A novel high-yttrium aluminosilicate glass-ceramic for fabricating dense SiC_f/SiC composite joints with enhanced hydrothermal corrosion resistance

A glass-ceramic derived from a high-yttrium aluminosilicate (HYAS) composition was developed for joining silicon carbide fiber-reinforced silicon carbide (SiC_f/SiC) composites. The as-prepared powder exhibited a high softening point (∼1396 °C), good wettability, and a thermal expansion coefficient (3.79 × 10⁻⁶/K) well matched to that of SiC_f/SiC. Dense joints were fabricated at 1420 °C for 60 min, achieving an average lap shear strength of ∼54 ± 2 MPa. The joining mechanism involved crystallization-assisted sintering, liquid-phase densification, and atomic-scale interdiffusion without interfacial reaction layer formation. Hydrothermal corrosion was evaluated in water containing ∼8 ppm dissolved oxygen, approximately three orders of magnitude higher than typical pressurized water reactor (PWR) conditions, to simulate long-term degradation. After 15 days, the joints retained a lap hear strength of ∼37 ± 2 MPa, with corrosion confined to the residual glass phase while interfacial integrity remained intact, demonstrating the promising durability of HYAS glass-ceramic as a durable sealant for SiC_f/SiC composites under accelerated hydrothermal conditions.