Effect of Brazing Atmosphere on the Corrosion Resistance of Ferritic Stainless Steels Brazed with Ni- and Fe-base Filler Metals
Ferritic stainless steels are gaining interest due to the combination of low cost, low thermal expansion and good high temperature scaling resistance compared to the commonly used austenitic stainless steels. These materials are of special interest for exhaust gas system components in gasoline cars, where the service temperatures are higher than for diesel cars. Previous research on the corrosion resistance of brazed ferritic stainless steel components have focused largely on vacuum brazed components, while the focus on belt furnace brazing has been limited. The presence of nitrogen in the brazing atmosphere has been found to affect the corrosion resistance of the base materials and filler materials in studies with austenitic stainless steels, but the effect on ferritic stainless steels has not yet been studied. In this investigation, AISI 430 and AISI 441 test samples were brazed with the common Ni-base brazing filler metals BNi-2, BNi-7, BrazeLet® Ni613 and Höganäs Fe-base brazing filler metal BrazeLet F300.