Role of Nb elements in SiC_f/SiC/(CoFeNiCrMn)_100-xNb_x/GH536 brazed joints: Joint residual stress transfer and pinning of dislocations

Brazing is a critical method to address the challenge of connecting composite materials to metals. This study joined SiC_f/SiC composites and GH536 superalloy using (CoFeNiCrMn)_100-xNb_x high-entropy alloy filler with varying Nb element contents successfully. The microstructural evolution and mechanical property changes of brazed joints were systematically investigated. Notably, when the Nb element content in the filler reached 12 %, a diffuse distribution of Nb(s, s) emerged in the joint, playing a vital role in effectively transferring residual stress on the SiC_f/SiC side. This effect is attributed to the disparity in thermal expansion coefficients between the Nb(s, s) and face-centered cubic (FCC) phases. The resulting joint exhibited remarkable room temperature and high temperature shear strengths of 89.7 MPa and 49.7 MPa, respectively. Furthermore, the presence of Nb(s, s) in the brazing seam proved to impede the movement of dislocations during joint fracture. This work introduces a new technical paradigm for aero-engine manufacturing.