Microstructure and properties of 20 steel pipe joints by transient liquid phase bonding and high temperature brazing

20 steel pipes were joined with a convention nickel base brazing filler metal BNi2 and a novel iron-nickel base foil,and the mechanical properties and microstructure of them were investigated using scanning electron microscope,energy dispersive X-ray analysis and electron probe microanalysis.The results showed that BNi2 brazing produced Ni solid solution joints with silicide precipitates and heterogeneity composition.In contrast,however,transient liquid phase bonding using iron-nickel base foil,resulted in homogenous joints with microstructure and composition similar to the parent metal and free of silicide precipitates.Mechanical tests showed that bonding properties of joints made using iron-nickel base foil were superior to those obtained using BNi2.When the iron-nickel base foil was used,bonding toughness was near parent toughness.