Transient liquid-phase bonding of T91 steel pipes using amorphous foil

T91 steel pipes were joined by the transient liquid-phase (TLP) bonding process using BNi2, Fe78Si9B13 and FeNiCrSiB amorphous filler in argon atmosphere. The microstructures and properties, as well as the element distribution of TLP joints of T91 martensitic steel with different filler metals have been examined. The testing results showed that the tensile strength and bend strength at room temperature of the joint with Fe–Ni–Cr–Si–B amorphous filler were equal to greater than that of the substrate. In contrast, however, boride is found in the joint region bonded with Fe78Si9B13 interlayer. TLP bonding using the nickel-base foil BNi2, resulted in a bond region stabilized by the high nickel concentration. It is considered that fracture of the joints is caused by these brittle intermetallics at the interface and the discontinuity of the bond line microstructure.