Parametric study of laser welding of copper to austenitic stainless steel

Welding of copper to stainless steel is challenging because of sharp difference in thermophysical properties of materials and the presence of miscibility gap in Fe-Cu system. The parametric study of continuous Yb:YAG laser welding between copper and austenitic stainless steel 316L has been performed. The influence of laser power, welding speed and beam offset from joint line on weld composition, microstructure and tensile properties was studied. The corrosion behaviour of the welds was evaluated in 0.1M NaCl with the potentiostatic pulse testing method, salt fog and immersion tests. In function of copper dilution in the melted zone, different types of microstructure were observed: homogenous solid solution (>= 2 at.% Cu), copper-rich net between austenite cells (2-5 at.% Cu) and formation of Cu-rich droplets (> 20 at.% Cu). Selective corrosion of Cu-rich microstructures took place in the melted zone. Tensile properties of the welds were determined by the formation of heat-affected zone in solid copper, where ductile fracture took place. (C) 2018 The Authors. Published by Elsevier Ltd.