Microstructure and properties of different carbon fiber reinforced ceramic composites brazed joint by Si–Ti alloy filler

Abstract

The brazing of C/C and Cf/SiC composites was achieved using Si–14Ti eutectic filler. The wetting behavior of the Si–Ti filler on the composites, as well as the microstructure and performance of the joints at different brazing temperatures, were characterized. The results showed that the contact angle of Si–Ti eutectic filler on precursor infiltration and pyrolysis (PIP)-Cf/SiC composite surface is only 60°, while it exhibits good spreading effect on liquid silicon infiltration (LSI)-Cf/SiC and C/C composite surfaces. Although Si–Ti filler and carbon fiber reinforced composites (C/C, PIP-Cf/SiC and LSI-Cf/SiC) react to form SiC, the joint shows different mechanical performance. The liquid filler infiltrates into the gaps between fiber bundles and reacts with C/C to form a SiC reaction layer at the interface. However, the presence of numerous defects at the brazed joint between Si–Ti filler and PIP-Cf/SiC results in the shear strength of only 28 MPa for the C/C-PIP-Cf/SiC joint. While for the C/C-LSI-Cf/SiC joint, due to the residual Si in the LSI-Cf/SiC composites, the liquid filler infiltrates intensely into LSI-Cf/SiC to form a unique Cf/SiC–Si–TiSi2 compound infiltration layer. The shear strength of C/C-LSI-Cf/SiC joints reaches 47 MPa, with fracture occurring in both substrates and brazed seam. The present study offers theoretical support for the investigation of Si-based fillers in brazing carbon fiber reinforced ceramic matrix composites.

Keywords

• Si–Ti filler alloy
• C/C composites
• Cf/SiC composites
• Interfacial reaction
• Brazed joint