Influence of nitrogen in the brazing atmosphere on the creep resistance of corrosive loaded CrNi-steel joints brazed with nickel based filler metals

The widespread use of nitrogen as a process or cooling gas sometimes leads to massive problems in the brazing of CrNi steels with nickel-base braze metals. A reduction of the corrosion resistance of the brazed joints are observed then, which is apparently related to the nitriding of the materials in the area of the joining zone. Within the scope of the research project, it is therefore intended to clarify to what extent and under which brazing process conditions nitrogen enrichment takes place in the brazed seam area and how this influences the corrosion behavior and also the lifetime of the brazed joints. Specifically, it is investigated which correlation exists between the degree of nitrogen enrichment and the selected process conditions during brazing, how the different nitriding degrees affect the electrochemical corrosion behavior of the brazed joints and what consequences the degree of nitriding and the resulting corrosion damage have on the durability of the brazed joints. The results are used to derive process conditions for furnace brazing, in which the consequences of nitrogenification can be avoided without having to forego nitrogen, which is very cost-effective and easy to handle in terms of safety compared to alternative process gases (argon, hydrogen).