Interface Structure and Formation Mechanism of Directly-Bonded Joints of Silicated Graphite to Fe-based Alloys

Commercially available 000Cr30Mo2 ferritic stainless steel and 4J33 ferromagnetic expansion alloy were directly bonded to silicated graphite at 1180-1200℃ and 1100-1150℃, respectively. Interracial microstructures were examined by scanning electron microscopy, electron probe microanalysis, and X-ray diffraction. The results showed that transient liquid-phase present during bonding promoted the interfacial reactions during bonding. Plenty of brittle chromium carbides, such as (Cr, Fe)7C3 and (Cr2.5Fe4.3Mo0.1)C3, were observed in 000Cr30Mo2/silicated graphite joints. Besides, transverse cracks were also found. In case of 4J33/silicated graphite system, well bonded joints free of defects were obtained.