Process-Based Control of Heat Input to Mitigate Anisotropy in CMT-Based Wire Arc Additive Manufacturing of AISI 316LSi Stainless Steel

Additive manufacturing (AM) technologies are prone to microstructural and mechanical anisotropy, driven primarily by directional solidification and the non-uniform thermal history associated with their layer-by-layer fabrication. This problem is more pronounced in Wire Arc Additive Manufacturing (WAAM), where elevated heat input and large molten pools increase thermal gradients and favor columnar grain development accompanied by δ-ferrite segregation in stainless steels. To address these issues, post-processing strategies such as inter-pass rolling, hammer peening, and heat treatment are frequently implemented. Nevertheless, regardless of being partially effective, these methods will add more processing steps that will result in an increase of time and costs. In this context, the present study seeks solutions to commonly reported limitations in the WAAM fabrication of AISI 316LSi stainless steel, which is widely used in industrial applications, by varying the wire feed speed (WFS) to regulate heat input with the aim of improving microstructural characteristics and mechanical performance. Accordingly 3 different heat input was attained by changing WFS in the system of CMT based WAAM method. Based on this approach, subsequent microstructural analysis revealed changes in δ-ferrite morphology from skeletal δ-ferrite to more refined lathy and globular forms across the investigated conditions. Within the examined processing parameters, samples corresponding to higher heat input levels, associated with increased wire feed speed (WFS), showed reduced anisotropy in grain orientation. Furthermore, samples produced under these conditions exhibited yield strength values of approximately 390 MPa, ultimate tensile strength values of approximately 620 MPa, and enhanced impact toughness, accompanied by a reduction in anisotropy. Overall, the findings indicate that adjustment of heat input during WAAM provides a viable process-engineering route for microstructural refinement and anisotropy reduction in AISI 316LSi stainless steel. © ASM International 2026.