With the increasing industrial implementation of additively manufactured metal parts, the welding of such components gains importance. Due to size limitations of laser powder-bed fusion (PBF-LB) machines and design constraints, subsequent joining processes are required. However, the weld seam quality of PBF-LB manufactured parts, particularly aluminum parts, is still limited by pore formation in the weld seam. These pores are believed to be primarily caused by the agglomeration of hydrogen. Therefore, this study investigates the pore formation during laser beam welding of PBF-LB manufactured AlSi10Mg parts by means of in-situ high-speed synchrotron X-ray imaging. In addition, an in-situ laser powder drying process is investigated to reduce the hydrogen content of PBF-LB manufactured aluminum parts in order to prevent the formation of hydrogen porosity during the subsequent welding process. Results show that pores predominantly form in the interdendritic region at the solidification front due to the locally increased hydrogen concentration. By applying laser powder drying, the hydrogen content can be reduced by up to 25%, thereby effectively preventing the formation of hydrogen pores.
Kramer et al. (Thu,) studied this question.