Electrophoretic deposition of CNTs on a Cu foam interlayer for enhancing Cf/SiC–Nb brazed joint performance

Abstract

The high residual stress and low toughness of ceramic matrix composite/metallic brazed joints poses severe challenges for the stable operation of high-speed aircraft under harsh conditions. This article innovatively tackles this issue with electrophoretic deposition (EPD), creating a CNT covered Cu foam composite interlayer for brazing Cf/SiC and Nb with an Ag–Cu–Ti alloy filler. A layer of mass ratio-controllable and percolated CNTs was physically adsorbed on the surface of the Cu foam substrate. EPD time was systematically investigated for its impact on the microstructure and mechanical properties of the joints. Results indicate that during brazing, the CNTs reacted with the active Ti element, transforming into ultrafine TiC grains with particle sizes ranging from 6 to 16 nm. These were dispersed evenly in the Ag solid solution. The elastic recovery rate of the cluster regions showed an increase of 123 % compared to the Ag solid solution, showing improved toughness of the seam. When the EPD time was 80 min, the shear strength of the joint produced with the composite interlayer reached 128.6 MPa, a 69 % increase over the directly brazed joint. Moreover, the fracture location of the joint shifted from the brazed seam towards the interior of the bulk Cf/SiC. Additionally, finite element analysis was utilized to confirm a significant decrease in residual stresses within the joint, and verified the findings.