Fast-diffusion joining of SiC-coated three-dimensional C/SiC composites with a Mo-W-Mo interlayer by spark plasma sintering

In this study, Mo–W–Mo multi-interlayers were used to develop a diffusion bond with SiC-coated three-dimensional (3D) C/SiC composites by spark plasma sintering (SPS). The interfacial microstructure and the phase composition of the joints were investigated. Appropriate interfacial reaction resulted in higher interfacial bonding strengths (shear strength of the joints increased from 56 ± 5 MPa to 83 ± 6 MPa) for joining temperatures (lower than 1600 °C). However, higher joining temperatures (1800 °C) resulted in an excessive growth of interfacial species with high thermal expansion anisotropy (e.g., Mo₅Si₃ and Mo₅Si₃C). As a result, the thermal residual stress increase significantly and a large number of interfacial defects were generated, significantly decreasing the reliability of the joints.