The Influence of Ar and N2 Process Gases on Melt Pool Stability in Laser Powder Bed Fusion of Alloys

Abstract Efficient and cost-effective fabrication of metallic components by laser powder bed fusion (PBF-LB) relies on using Ar or N 2 process atmospheres to deter oxidation. While previous studies have reported on how these gases impact the properties and performance of fabricated bulk forms, few have addressed their effect on generating stable melt pools. This work leverages knowledge from the laser welding community to experimentally evaluate which gas is more suitable for PBF-LB practitioners to use. It investigates how each gas influences melt pool stability under optimal and varying laser process parameters, an important consideration for fabricating complex geometries where heat input and dissipation are imbalanced. Melt pool stability was assessed by measuring dimensional variability and correlating it with changes in the vapor/plasma plume generated by the laser exposure. The influence of stability on defect generation was assessed via X-ray Computed Tomography and on mechanical behavior by tensile testing. The results indicated that Ar provided superior melt pool stability across a range of process parameters, which also translated to reduced defect generation and improved mechanical behavior. It was the clear choice of process gas for fabricating complex geometries with minimal defects by PBF-LB.