Real-time laser spot modulation in Laser Powder-Directed Energy Deposition via wobbling: A path to superior 316L stainless steel components

AAchieving high-quality Laser Powder-Directed Energy Deposition (LP-DED) components require the precise tuning of process parameters such as laser power, scanning speed, and laser spot size. Among these, laser spot size is a particularly critical factor. The use of a large spot size led to high building rate and process efficiency at the expense of surface finish and geometrical accuracy. This investigation aimed to understand how a variable laser spot affects the thermal history of LP-DED AISI 316L stainless steel components and consequently their microstructure and mechanical properties. The study first examined the effects of the laser spot and sample geometry on the microstructural features using optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). Secondly, the characterization of mechanical properties was conducted via tensile tests and the effects of the variable laser spot on ductility and on the various strengthening mechanisms were analysed. The results revealed that using a larger laser spot leads to heat accumulation, which becomes especially crucial when depositing geometries characterized by a small cross section. These findings lay the groundwork for enhancing the LP-DED process efficiency in a more viable manner taking advantage of the different solidification conditions.