Multilayer interface design for reliable brazing of C/C-SiC to stainless steel: Cr-driven interfacial control and stress redistribution

Reliable brazing of C/C-SiC composites to stainless steel is hindered by severe residual stresses and uncontrolled interfacial reactions. Here, we introduce a CuMnCr/Mo/Cu multilayer interface that aims to simultaneously regulates stress distribution and interfacial chemistry. Cr from the CuMnCr layer preferentially reacts with C/C-SiC, forming a Cr7C3 + Cr3Si reaction layer, while Fe and Cr from stainless steel diffuse into Cu to produce a (Cu, Fe, Cr) solid solution. The Mo interlayer mainly acts as both a diffusion barrier and a compliant stress absorber, isolating reaction zones and concentrating part of the residual stress within itself. Finite-element simulations confirm that this design reduces peak Mises stress from 684 MPa to 444 MPa. At an optimized brazing temperature of 980 °C, the joint achieves a shear strength of 32.2 MPa, corresponding to 57.5% of the intrinsic strength of C/C-SiC. Thermodynamic, kinetic, and first-principles analyses suggest that Cr plays a dominant role in interfacial bonding, whereas Mo contributes to the redistribution of residual stress and mitigation of brittle fracture. Overall, this multilayer strategy provides mechanistic insight into how Cr-driven interfacial control can be combined with Mo-assisted stress management to design reliable C/C-SiC-metal joints, while the long-term service behavior and extension to other composite/steel combinations remain to be clarified in future work.