Diffusion Bonding of Stainless Steel Pipes by using Fe-base and Ni-base Interlayer Alloys

Abstract

Austenitic stainless steel pipes, type 316 and 304, were joined by liquid phase diffusion bonding process. Six specially designed interlayer alloys, three Fe-base and three Ni-base, which were produced by rapid quenching from the liquid state, were used in this experiment.
Austenitic stainless steel pipes bonded by Fe-base interlayer alloys have proper mechanical properties same as the base metal although intergranular corrosion was observed after Strauss tests because of the diffusion of boron near bonding interface.
Welded joints by Ni-base interlayer alloys have good resistance to intergranular corrosion even after Strauss test.
Intergranular cracks were observed in the straight seam weld metal of type 304 pipe heated up to the sensitization temperature after Strauss test, but were prevented by solution treatment before joining. Lowering the carbon content in austenitic stainless steel was also effective to prevent the intergranular cracks.