Computation-guided design of an in-situ barrier via reactive carbon coating for ductile SiC_f/SiC-superalloy brazed joints

For next-generation aero-engines, reliable joining of SiC_f/SiC composites (CMC) to high-temperature alloys remains critical. The commonly used fillers readily decompose the SiC matrix into brittle compounds, degrading seam deformability. To address this, a reactive carbon coating was designed as a barrier precursor using a high-throughput CALPHAD model across 432 quaternary systems, preferentially consuming active elements to in-situ form a dense TiC barrier while directing the seam toward a ductile FCC structure. As a result, a gradient structure of dense TiC/dispersed TiC + Ni₂Si + Cr₇C₃/Ni₂Si + SiC formed on the CMC side, and a (Cu, Ni)ss matrix formed on the GH5188 side. Molecular dynamics simulations further revealed that disordered carbon caused outward dissolution of C atoms into the Ti melt, and even in the presence of microcracks, Ti–C bonds exceeded Ti–Si bonds by about two orders of magnitude. Excessive phenolic resin generated oversized cracks that prevented the completion of the in-situ process, while increasing brazing temperatures promoted the directional formation of the ductile (Cu, Ni)ss FCC seam. The optimized joint achieved a shear strength of 115 MPa, 167% higher than the uncoated joint, with acceptable retention of high-temperature strength. This work established a framework linking thermodynamic screening, reactive coating design, and atomic-scale verification for ceramic/metal joining.