Innovative inactive brazing strategy of C/C composites and Ni-based superalloy using CuPd filler and chromium carbide modification

Joining C/C composites to Ni-based superalloys can obtain integrated structures with superior comprehensive performance. This study presents a novel inactive brazing strategy that employed a CuPd high-temperature filler combined with a pre-fabricated chromium carbide (Cr-C) modification layer. The interfacial microstructure evolution, formation mechanisms, and mechanical properties of the inactive brazing joints were systematically investigated. A sound joint of C/C composites and Ni-based superalloys was obtained at the brazing temperature of 1180 °C for 10 min. The Cr-C modification layer enabled the wetting of the inactive CuPd filler on the C/C composites, avoiding detrimental reactions within the brazed seam using the active filler. For the first time, a lamellar Cu-Ni-Pd microstructure, primarily composed of ductile (Cu, Ni)Pd and (Cu, Ni)₃Pd phases, was observed in this work. The joint shear strength tested at room temperature and 800 °C can reach 35.1 MPa and 24.7 MPa, respectively. The joint failure occurred at the side of the C/C composites, which was the weak region of the joint. This work provides an effective high-temperature inactive brazing strategy for poorly wettable carbon materials.