Abstract
Charpy U-notch impact test was conducted on brazed joints of type 316 stainless steel. Two kinds of newly developed Ni-Cu based filler metals, two kinds of standard nickel filler metals, and a standard silver filler metal were tested. For each of the filler metals, brazing time was varied from 600 s to 7200 s under a constant brazing temperature. Each of the joints were made to have a constant joint clearance of 50 micrometers. The joints with the nickel filler metals showed brittle fracture and their absorbed impact energy were lower than 2 J for the brazing times up to 3600 s. Absorbed energy of the silver filler brazed joints were about 20 J although their fracture surface showed microscopic ductile fracture. The joint with Ni-Cu-Mn filler metal, one of the developed filler metals, showed 120 J of absorbed impact energy for the brazing at 1333 K for 3600 s. By micro-hardness measurement across the joint, the hardness of this joint was found to be practically identical with that of base metal. This implies that the excellent impact strength of this joint should be attributed to the uniformity in mechanical properties across the brazement to the base metal.
