Investigating the effects of scanning strategy and re-melting on residual stresses in printed parts fabricated by selective laser melting

Purpose This study investigates the impact of in situ re-melting techniques on residual stress, surface quality and mechanical properties of selective laser melting (SLM) manufactured AISI 316 L stainless steel components. The research aims to address challenges related to residual stress, surface roughness and defects in SLM-produced parts, proposing innovative re-melting strategies to enhance part quality and performance. Design/methodology/approach The research uses a full factorial design of experiments to evaluate the effects of scanning strategies and re-melting techniques on residual stress. Three re-melting methods were tested: re-melting every layer with varying laser powers, re-melting every other layer and re-melting every layer with different scanning parameters. Residual stress was measured using the hole drilling method, while surface roughness, relative density, microstructure and corrosion resistance were analyzed through 3D profilometry, micro-CT, XRD, SEM and potentiodynamic polarization tests. Findings The study reveals that re-melting with 50% of the initial laser power significantly reduces residual stress by 52.9% and improves surface roughness by 193.6%. Re-melting every other layer also reduces residual stress while saving printing time. Microstructural analysis shows fewer defects and improved density in re-melted samples. In addition, re-melting enhances hardness and corrosion resistance, with the best performance observed in samples re-melted at lower laser power. Originality/value This research introduces innovative re-melting techniques that are compatible with SLM machines lacking built-in re-melting capabilities, addressing a critical gap in the field. By proposing a practical workaround using merged G-codes, this study democratizes access to re-melting benefits across a wider range of equipment. Furthermore, the novel inter-layer re-melting strategy achieves a remarkable 52.9% reduction in residual stress while saving 40% printing time, offering a scalable solution for industrial applications. The comprehensive analysis of re-melting’s effects on residual stress, surface quality and mechanical properties provides a foundational framework for future advancements in additive manufacturing.