Microstructure and mechanical properties of thermal simulated MHC/GH4099 diffusion brazing joints

The molybdenum alloy (MHC) and the nickel alloy (GH4099) were successfully joined with NiCrSiB as the interlayer by the Gleeble-3800 thermal simulated machine. Microstructure of MHC/GH4099 welded joints were characterized by scanning electron microscope (SEM), energy dispersive scanning (EDS) and X-ray diffraction (XRD). The effects of bonding temperature on microstructure and shear strength were also investigated. Results indicated that a reliable welded joint can be obtained at peak temperatures of 950 ℃, 1 000 ℃ and 1 050 ℃ and holding time of 600 s. The MHC/GH4099 joints were mainly composed of γ-Ni solid solution, CrMo solid solution, MoNi and CrB, Ni3Si phase. The shear strength of the joint at 1 050 ℃ can reach 116 MPa. The larger stress concentration in the heat affected zone of MHC side was the main reason of brittle fracture for MHC/GH4099 joints.