Setting of L-PBF parameters for obtaining high density and mechanical performance of AISI 316L and 16MnCr5 alloys with fine laser spot size

Laser powder bed fusion is one of the most common metal additive applications for manufacturing industry and high-level research. It is common to have in a company, mechanical workshop or laboratory, machines of different manufacturers and powders of different suppliers. Therefore, there is the need for users of this technology to transfer optimized process parameters easily and quickly from one machine to another. Despite several multiphysics models being available, they are not always easy to use, especially by technical staff. Furthermore, particularly attention must be given to machines equipped with small laser spot size (i.e., < 50 µm) that are able to produce complex geometry with a fine resolution and smooth finish. Generally, these machines produce a deeper melt pool and are employed with fine powder (e.g., 5–35 µm) and consequently small layer (e.g., 20–40 µm). In this paper, simple and analytical rules to adjust the main process parameters (i.e., layer thickness, hatch distance, etc.) and to scale the volumetric energy density on a machine with a fine laser spot size have been proposed. Relative density, microstructure, and mechanical performance have been evaluated for AISI 316L stainless steel and 16MnCr5 case hardening steel. The results show that after a careful tuning of process parameters, it is possible to obtain relative densities close to 100% for both alloys. Mechanical tests coupled with microstructural investigations also highlighted that the alloy mechanical behavior depends on heat input and cooling rates which, in turn, are affected by process parameters.