Laser welding of thin sheets by means of direct energy deposition technique

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The present paper is devoted to assessing the applicability of laser powder direct energy deposition in welding of thin stainless steel sheets. Considering the rapid development of laser cladding applications in modern industry and the availability of a relatively wide range of equipment, the idea was to transfer this application to the welding field, in order to set up a laser welding process where the filler material is constituted by the blown powder along the bead. In this direction a proper experimental campaign was carried out with the aim of evaluating the role of the main process parameters, such as laser power and powder feed rate on the characteristics of the weld bead. Several joint configurations were also considered with the purpose of assessing the best configuration both in terms of chamfer shape and of mutual position of the sheets. Butt and lap joints were considered in particular and, concerning the first ones, 30° and 45° V-groove configurations were tested and characterized. In order to assess the quality of the weldments, metallographic analyses were carried out with the purpose of measuring the main morphological parameters of the beads (width, penetration depth, reinforcement), the dilution between the filler and the base metal and the eventual presence of defects such as pores, cracks and lack of fusion. The tests demonstrated an overall good feasibility of the process and pointed out that lap joints and 30° V-grooved ones are the best configurations both in terms of weld bead quality and of fused zone morphology.