Influence of thermomechanical treatment on the liquid metal embrittlement of copperbrazed plate heat exchangers

摘要

Copper-brazed plate heat exchangers made of stainless steel can be damaged by corrosion in contact with potable water because of the difference between the electrochemical potential of brazing filler and base material. One reason for that is the so-called liquid metal embrittlement, which takes place during the brazing process. The brazing filler infiltrates the stainless steel along the grain boundaries and causes an embrittlement. This does not only lead to leakages, which decrease the reliability of the heat exchanger significantly. The dissolution of the corrosion products of brazing filler and base material also induces the migration of heavy metal ions, such as Cu~(2+) and Ni~(2+), into the potable water. This paper deals with the reduction of liquid metal embrittlement by a combined thermomechanical treatment targeting an adapted grain orientation of the base material. This should decrease the corrosion and therefor the migration of heavy metal ions into the potable water.