Reaction-composite diffusion brazing of C_f/SiC composites and stainless steel with (Cu-15Ti)+SiC filler metal

Objective The aim is to obtain a C_f/SiC and stainless steel joint with low stress and high temperature resistance. Methods C_f/SiC composites and nickel plating stainless steel were brazed at 960 ℃ for 30 min with mixed powders of Cu-15Ti and SiC. After brazing, microstructure of the joints was studied and heat resistance and mechanical properties of the joints were tested by means of scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffractometer (XRD), comprehensive thermal analyzer (TG-DSC), and universal testing machine. The mechanism of joint formation and evolution was also analyzed. Results The results showed that active element Ti in the Cu-Ti alloy reacted with C_f/SiC composites to form a reaction layer composed of TiC and Ti₅Si₃. The added SiC powders rapidly consumed the element Ti in the matrix of joining layer and in-situ synthesized reinforcements of TiC, Ti₅Si₃ and Ti₃SiC₂, which are beneficial for relieving thermal stress. At the same time, consumption of Ti element also improved heat resistance of the joints. The nickel plating layer can not only completely prevent the generation of TiFe compounds, but also diffuse a small amount of Ni elements into the matrix of the joining layer, which is beneficial to further improve heat resistance of the connection layer. Conclusion The room-temperature shear strength of C_f/SiC composites and stainless steel joint brazed with (Cu-15Ti)+SiC filler metal reached 193.7 MPa ± 20.8 MPa. The initial melting temperature of the joints after brazing was approximately 1 020 ℃, achieving the “low temperature bonding/high temperature servicing” within a short brazing period.