Exceptional mechanical properties of dual-phase heterogenous structure in C_f/C and superalloy joints via cold spray additive manufacturing-assisted brazing

Heterogeneous alloy designs can significantly enhance the mechanical properties of metallic materials through synergistic effects. In this work, the cold spray additive manufacturing (CSAM)-assisted brazing is proposed to significantly improve the mechanical properties of C_f/C and superalloy joint. The CSAM process promotes the atomic diffusion and metallurgical reaction between the interlayer and superalloy substrate. The findings indicate that the diffusion of Fe, Cr, Ni and Ti within brazing seam promotes the formation of a novel dual-phase heterogeneous structure, comprising a Cr-rich σ phase and a Ni₃Ti phase. The σ and Ni₃Ti dual-phase heterogeneous structure significantly improves shear strength through a synergistic strengthening mechanism, achieving an effective combination of strength and toughness. The ductile Ni₃Ti phase enhances the deformation capacity, while the hard σ phase serves as a continuous barrier to dislocation movement, thereby significantly enhancing the mechanical properties of the brazed joint. The highest shear strength of the C_f/C and superalloy brazed joint reaches 20.9 MPa using a CSAM NiTi75 interlayer, compared to only 6.1 MPa for the joint brazed with conventional NiTi75 powder filler. This work demonstrates the significant potential of CSAM-assisted brazing to enhance the mechanical properties of brazed joints, offering a novel approach to directly prepare brazing interlayers from metal powders.