Effect of stress and Si on liquid metal embrittlement of 316L(N)-copper

Abstract

Vacuum brazing of austenitic stainless steel (SS) under stress with copper-based filler was carried out to assess the susceptibility of liquid metal embrittlement (LME) on stress. Dipping of the SS pipe into molten copper and CuSi3 was performed for comparison. The mechanisms of stress on Cu-SS LME and the effect of Si during cracking were discussed. Test results indicated that microcracks caused by stress concentration increase the possibility of LME. Furthermore, LME was suppressed by the Fe₃Si layer between copper and SS. However, the melting range of the filler extended by the addition of Si increases the probability of LME for longer contacting. Accordingly, the addition of Si into copper-based filler should be avoided for most joining methods of SS with high stress concentration.