Joining of Si-Ti-C-O fiber reinforced ceramic composite and Fe-Cr-Ni stainless steel

Joining of Si-Ti-C-O fiber reinforced ceramic composite and Fe-Cr-Ni stainless steel with Ag-Cu-Ti brazing alloy was carried out. The joining interfaces were perpendicular to the direction of fibers. For relaxation of thermal stress caused by thermal expansion mismatch between the composite and the stainless steel during cooling, a pure copper thin plate was set between the specimens to be joined. Joining strength was evaluated by bending test at room temperature. The highest strength of composite/metal joint attained in this study was 230 MPa. The scattering of the strength data was narrow. The composite-side fracture surfaces of the high strength joints were divided into many regions by fiber/matrix interfacial clacks. It was inferred that those interfacial cracks, which were perpendicular to the main crack along the joining interface, decreased the stress intensity factor of the main crack and increased the strength of the joints. On the other hand, no fiber/matrix interfacial crack was observed on the fracture surfaces of a weak composite/composite joint. Formation of many holes oil the composite surfaces to be joined by etching caused damage to the fibers during joining, and had an adverse effect on the joining strength.