Microstructure and Fracture of 50Mo-50Re Vacuum Brazed with Fe-Si-B Filler Metal

Abstract

Microstructural evolution, interfacial reaction and fracture during vacuum brazing of 50Mo-50Re alloys using amorphous alloy Fe-5.6Si-2.6B(wt%) were investigated. A binary intermetallic compound, σ(Mo 2 Re 3) formed as parallel contiguous layers in the diffusion zone. In addition, Fe from the braze alloy, in combination with dissolved Mo from the substrate, formed two layers of binary compounds μ-Mo 6 Fe 7 and λ-MoFe 2 , adjacent to diffusion zone. The unreacted Fe-based filler metal solidified as α-Fe solid solution. Fracture analysis showed that the mode of failure was mainly transgranular cleavage with partly intergranular and the fracture located on the interface of 50Mo-50Re alloy and the central area of brazing seam.