Parametric study and experimental characterization of 316LSi stainless steel produced by wire-arc directed energy deposition using cold metal transfer

Abstract

This study presents a combined parametric and experimental investigation of 316LSi austenitic stainless steel fabricated by Directed Energy Deposition-Arc (DED-Arc) with wire feed using the Cold Metal Transfer (CMT) process. This alloy was selected for its high ductility and good impact toughness, making it suitable for additive manufacturing applications. Tensile and Charpy V-notch impact specimens were extracted from deposited walls and tested in both the as-built condition and after solution heat treatment to evaluate the effect of this treatment on mechanical behavior and ferrite content. In addition to heat treatment, the influence of key deposition parameters, including torch travel speed and interpass cooling time, was analyzed with particular attention to ferrite formation and mechanical performance. The results show that post-deposition heat treatment significantly decreases yield strength and ultimate tensile strength while increasing elongation at break by about 13–15% and Charpy impact energy by approximately 20–25 J. Mechanical anisotropy was also observed depending on the orientation of the specimens relative to the deposition layers: vertically oriented specimens exhibit higher strength and stiffness, whereas horizontally oriented specimens display improved ductility and impact toughness. Increasing the interpass cooling time leads to moderate improvements in both strength and impact toughness without significantly affecting ductility, while the influence of torch travel speed remains limited within the investigated range. Overall, this study provides a systematic and quantitative evaluation of the influence of torch travel speed and interpass cooling time, while highlighting the dominant role of heat treatment and specimen orientation relative to the deposition layers on the mechanical properties and ferrite content of 316LSi stainless steel produced by DED-Arc (wire, CMT), contributing to a better understanding of process–property relationships and providing practical guidance for process optimization under industrially relevant conditions.