Formation mechanism of delta-ferrite in fusion zone during fiber laser welding of SS-316L

Abstract

Abstract Fiber laser welding is conducted on 0.5 mm SS-316L steel plates. Microstructural evaluation in fusion zone (FZ) of welded specimens are investigated at three different welding speeds. Autogenous welding process favors epitaxial grain growth in the FZ. The morphology of delta ferrite changed from skeletal to lathy ferrite with the increase of welding speed and further at higher welding speed of 1000 mm/min cellular structure is developed in FZ. XRD patterns demonstrate the existence of δ-ferrite in FZ at all welding conditions. The tensile properties of weldments are increased with the increase of welding speed due to the change in morphology of austenitic structure in the FZ. Ductile mode of fracture is observed in both base material and the weldments.