Process Intensification of Metal Laser-based Powder Bed Fusion using Nanoparticle Additives

The processability of fine metallic powders remains a major challenge in powder bed-based laser beam melting (PBF LB/M). The addition of nanoscale flow aids enables precise control of powder flow behavior and offers to extend the usable particle size range. This study investigates how dry nanoparticle coatings influence the flow characteristics of metallic powders and their effect on the laser melting process.
Applying dry nanoparticle coatings introduces artificial surface roughness, increases the separation distance between particles and thereby reduces adhesive forces such as van der Waals interactions. This phenomenon was systematically examined using various nanoparticle (SiO2, Al2O3, TiN) and metal powder (e.g. 316L, AlSi10Mg, CoCrFeNi) combinations. At sufficient surface area coverage, the dry nanoparticle coatings significantly improved the processability of cohesive powders, demonstrated for example by reductions in the dynamic angle of repose. The flow behavior was described using the dimensionless granular Bond number BoG, which represents the ratio of adhesive to gravitational forces acting on a particle. Correlating flow characteristics with BoG as a function of nanoparticle concentration and metal particle size provides a predictive model for macroscopic flow behavior.
Reducing adhesive forces resulted in enhanced powder layer densification during powder spreading. Characteristic porosity regimes and melt pool geometries linked the transition between conduction and keyhole dominated melting modes to the modified powder flow behavior. Furthermore, powder fractions containing a higher proportion of fine particles were successfully processed, expanding the applicable particle size range. The observed systematic shift in the process window corresponded directly to higher layer densities achieved through surface modification.
Nanoparticle dry-coating thus offers a scalable and cost efficient method for conditioning metallic powders for the PBF LB/M process. By tailoring inter particle interactions, the processability can be tailored and improved, increasing overall powder yield and ensuring stable, reliable powder spreading. This approach represents a promising step toward broader industrial adoption of fine metallic powders in additive manufacturing.