Effect of temperature on intermetallic compound formation and mechanical properties of Mo/BNi2/304L vacuum brazed joints

• The interfacial microstructure of Mo/BNi2/304L joints evolves into a multilayer IMC system. • Mo 2 NiB 2 forms preferentially at the Mo interface and dominates joint strength. • Brazing temperature primarily affects joint strength by altering the thickness of Mo 2 NiB 2 . • The highest shear strength (253 MPa) is achieved at 1000 °C due to optimal IMC balance. This study systematically examines how brazing temperature influences interfacial intermetallic compounds (IMCs) formation and properties in Mo/BNi2/304L stainless steel joints for the EAST NBI electrode. Process parameters are optimized to enhance joint mechanical properties. Results reveal a layered interfacial microstructure: Mo/Mo 2 NiB 2 + Ni 3 Si/Ni 3 B + Ni-based solid solution + Cr-B/Cr 2 B + Fe-Ni solid solution/ 304L. IMC development progresses from the interface inward: Mo 2 NiB 2 , Ni 3 Si, Cr 2 B form immediately at the interfaces during brazing, while brittle phases (Ni 3 B, Cr-B) form in the brazing seam center during cooling. Notably, the Mo 2 NiB 2 layer is the weakest part of the interface. Brazing temperature primarily affects joint strength by altering the thickness of Zone I (Mo 2 NiB 2 , Ni 3 Si), with peak shear strength observed at 1000 °C.