30.06.2016 Brazing

New nickel based brazing alloy suitable for very corrosive environments

A new application for plate heat exchangers used in cooling units are subjected to a very aggressive coolant. This means both base material and brazing alloy needs to have very high corrosion resistance to the coolant. As base material high alloyed austenitic stainless steels were identified as available with necessary corrosion resistance. The only braze material on the market with good enough corrosion resistance in these environments was BrazeLet® Ni613. However, when testing this alloy it was early recognized that the melting range of this alloy was not compatible with these base materials. High alloyed austenitic stainless steels may form excessive amounts of inter metallic phases if heat treated incorrectly. Therefore a rapid cooling from above the critical temperature range for the specific base material is necessary. A new alloy with corrosion resistance similar to BrazeLet® Ni613 but with higher melting range was developed and is presented in this paper.