Microstructural investigation of Selective Laser Melting 316L stainless steel parts exposed to laser re-melting

TLDR

Selective Laser Melting offers many advantages but suffers from limited surface quality and residual porosity of 1–2 %, which can compromise strength and fatigue resistance. This study investigates how continuous‑wave laser re‑melting during SLM of AISI 316L stainless steel alters microstructure under different process parameters. Laser re‑melting is performed by re‑scanning the same slice after melting, either for every layer or selectively on the final layer or outer skin, to reduce roughness and enhance surface properties.

Abstract

Although Selective Laser Melting (SLM) provides many advantages compared to conventional machining, limited surface quality is one of the major drawbacks encountered in the process. Secondly, little residual porosity (1-2%) in SLM parts may be problematic for some applications where high strength and fatigue resistance are necessary. As a remedy, laser re-melting is employed during or after the SLM process. Laser re-melting means that after scanning a layer and melting the powder, the same slice is re-scanned before putting a new layer of powder. If done for each layer, it results in substantially longer production times. It can also be applied to only the last layer or the outer skin of the part if the aim is to reduce the roughness or to enhance the surface properties. In this study, laser re-melting is applied using a continuous wave laser during SLM of AISI 316L stainless steel parts mainly to study the microstructural changes by applying different process parameters.