Microstructure and mechanical properties of Cf/SiC composite/GH99 joints brazed with BNi2-Ti composite filler

BNi2-Ti composite filler developed with which the brazing of Cf/SiC composite to GH99 superalloy was achieved in this study. The effects of Ti content (0-8 wt.%) and brazing temperature (1130-1190 °C) on the microstructure and mechanical properties of brazed joints were investigated. Cross-sectional scanning electron microscopy observations showed a defect-free bonding interface with the content of Ti ranging from 1 wt.% to 5 wt.%. Formation mechanism of the brazed joint shows that Cr in the brazing filler metal reacted with carbon fiber in the composite to produce Cr3C2 reaction layer while Ni infiltrated into composite reacted with SiC matrix to produce Ni3Si and C. The addition of Ti effectively suppressed the infiltration of Ni towards Cf/SiC composite, while reduced the quantity of large-sized Cr3C2 compounds, replaced by some uniformly dispersed TiC particles. As the brazing temperature increased, the volume fractions of Ni(s,s) in the brazing seam increased and Cr3C2 reaction layer gradually dissolved into the filler metal. When the Ti content was 3 wt.%, brazing temperature 1170 °C, the maximum shear strength of the brazed joint, 43.5 MPa, was achieved.