Stainless steel components, such as heat exchangers for energy and air-conditioning technologies are commonly manufactured using nickel-based brazing fillers, which provide the highest corrosion and oxidation resistance of the resulting joints. However, the use of nitrogen during the brazing process in shielding gas furnaces or as cooling gas in vacuum furnace processes, may have a significant influence on the corrosion resistance of the brazed joints, as a possible nitriding of the materials during brazing may change their chemical compositions. When operating such brazed assemblies in corrosive environments like exhaust gas condensates, corrosion could affect the brazed joint in such way, that its creep resistance is reduced. To investigate the influence of nitrogen on brazed specimens made of AISI 304 and Ni60CrPSi brazing filler, brazing processes were carried out at temperature of 1,125°C in a vacuum furnace and in a conveyor belt furnace applying nitrogen containing process gases. The amount of nitrogen in the braze metal as well as in the base material were determined using a carrier gas hot extraction technique. A corrosive load was applied by aging brazed specimens in the exhaust gas condensate K1.2 according to VDA 230-214. Fatigue tests on corrosion affected specimens as well as unaffected reference specimens were carried out at ambient temperature on a RUMUL resonance pulsator under load controlled conditions with a load ratio of R = 0.1. The microstructure of the brazed joints and the fracture surfaces of the tested samples were investigated by SEM. Results of the fatigue behavior of the joints before and after corrosive attack are presented and discussed with respect to the influence of nitrogen in the brazing atmosphere.
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