Development and processability of AISI S2 tool steel by Laser Powder Bed Fusion

Nowadays, the advantages of Laser Powder Bed Fusion (LPBF) technology attract both industry and researchers. Indeed, it is possible to build up complex geometrical parts with higher mechanical properties than those obtained by conventional methods. However, LPBF involves complex phenomena due to the high heating and cooling rates that lead to out-of-equilibrium conditions. For this reason, few metal alloys are easily processable up to now. Nevertheless, research on new steels by LPBF has been growing in recent years, in particular, regarding the development of tool steels. This work thus focuses on the development of the tool steel AISI S2 by LPBF. The process map has been investigated by varying the laser power from 100 to 250 W and the scan speed from 400 to 2000 mm/s. By combining surface analysis by means of profilometer observations, density measurements by pycnometry, defects characterization and quantification and investigations on the melt pool morphology, the best process window is selected to have fully dense, defect-free parts. Furthermore, this study allows to have comprehensive insights on the effect of the parameters on the type of defects generated during the manufacturing.