Abstract
A detailed study was conducted on the microstructure and the high temperature tensile properties of SUS304 stainless steel, Inconel X-750 nickel-base superalloy and 2⋅1/4Cr-1Mo heat resistant steel joint buttbrazed with a gold-nickel filler metal and an amorphous nickel-base filler metal. The high temperature strength of amorphous nickel-base alloy brazed joints was superior to that of gold-nickel alloy ones for all the base metals used, and in particular, the microstructure near brazed interface in nickel-base alloy joints, were indistinguishable from that of the base metal. On the other hand, the structure of SUS304 stainless steel and 2⋅1/4Cr-1Mo steel joints brazed with gold-nickel alloy, revealed inhomogeneity in nickel and gold distributions in filler metal layer, and particularly, a filler metal-base metal interface boundary enriched in nickel as a result of up-hill diffusion from base metal.
Although the tensile strength above 400°C of all the joints brazed with the gold-nickel filler metal was inferior to that of base metal, the obtained results suggested that these joints possessed excellent corrosion, erosion and oxidation resistance. Notch toughness test indicated that the joints brazed with the gold-nickel filler metal had higher toughness compared to the joints brazed with the amorphous nickelbase filler metal.
