Investigation on interfacial reaction behavior of brazed joint of austenitic stainless steel/Cu filler metal

Focused on the cracking problem encountered in arc brazing of austenitic stainless steel, in this study the interfacial reaction behaviors between 316LN stainless steel and Cu-based brazing filler metal during arc brazing, furnace brazing and vacuum brazing processes were studied.The results revealed that during the arc brazing process, the wetting property of filler metals on the substrate was improved with increasing electric current,and the diffusion of filler metal along the grain boundaries of the substrate was not obvious. At higher electric current, a little bit of substrate melted and crack are more likely to form along the grain boundaries. During the furnace brazing process, the diffusion of filler metal along grain boundaries of substrate is obvious, but the boundaries were not likely to crack. During the vacuum brazing process, the diffusion of filler metal along grain boundary of the substrate was also obvious, forming an interfacial layer, but there was no cracking. A high thermal stress and grain-boundary weakness of the substrate induced by the diffusion of filler metal are necessary conditions for the interfacial cracking of the austenitic stainless steel substrate.