Microstructure and Mechanical Properties of Solid-State Sintered SiC Brazed with a Novel Si-Ti-Al/Mo Composite Filler

In this study, to advance the research on near-homogeneous welding technology for silicon carbide ceramics required for service in nuclear environments and to meet the high-performance welding and reliable service requirements of silicon carbide ceramic fuel elements, a novel Si-Ti-Al/Mo composite filler was employed to achieve the joining of solid-state sintered silicon carbide (SiC) via vacuum brazing, thereby providing an innovative technical solution for the integration of high-performance SiC components. The research systematically elucidated the interfacial metallurgical mechanism governed by this novel alloy, and comprehensively investigated the effects of brazing temperature on joint microstructure, room-temperature and high-temperature mechanical properties, as well as fracture morphology. In the filler metal design, the pre-added Mo served as a heterogeneous nucleating agent, preferentially reacting with Si, which effectively suppressed the extensive formation of the TiSi2 phase. Concurrently, the introduction of Mo significantly refined the grain structure within the joint region. Brazing at 1360 °C yielded a peak room-temperature shear strength of 144 MPa. Moreover, the joints exhibited excellent high-temperature service reliability, retaining a shear strength of 64 MPa at a test temperature of 1000 °C. This novel joining technology is expected to promote the widespread engineering application of high-performance SiC components in extremely harsh environments.