Enhanced mechanical properties of TZM joint brazed at high temperature using Mo-Ni filler metal with Boron addition

Controlling the growth of brittle intermetallic compounds (IMCs) and interfacial structure is crucial to obtaining desirable mechanical properties of the high-temperature brazing joints of titanium-zirconium-molybdenum (TZM) alloy. The effect of B addition on the mechanical properties of the joints and the microstructures in the brazing seam was investigated. The results show that the addition of 1%B enhances significantly the wettability of Mo-45Ni filler metal. The strength of the brazed joint with Mo-45Ni-1B filler metal is 30% higher than that of the joint with Mo-45Ni filler metal. The microstructure of the brazed joint with Mo-45Ni filler metal consisted of TZM/NiMo/eutectic (Mo + NiMo) + NiMo /NiMo/TZM. B addition led to the formation of Mo₂B intermetallic compounds at the interface between NiMo layer and TZM alloy during heating and the precipitation of faceted Mo₂B IMCs in the brazing seam during solidification, promoting the brittle-to-ductile fracture transition. This study provides a deep insight into the HT brazing of TZM alloy.