Meaning
Metallic powder particles characterized by specific size distributions and spherical geometries used as the build material in layer-by-layer laser consolidation processes. Laser powder bed fusion feedstock directly influences the flowability of the powder bed and the density of the final printed part. This metal powder is typically produced by gas atomization to ensure optimal packing and melting behavior.
Material Specification
Particle size distribution is controlled to remain within a range of fifteen to forty-five micrometers to ensure even spreading across the build plate. While larger particles can lead to incomplete melting and high surface roughness, very fine particles are prone to agglomeration and erratic flow. Spherical morphology is preferred because it maximizes flow rate and packing density.
Fluidity is assessed using standardized test methods such as the Hall flow meter.
Powder Quality
Residual internal porosity within individual particles can be transferred directly to the finished product as microstructural defects. During gas atomization, pockets of atomizing gas can become trapped inside the droplets as they solidify. When the laser melts this powder, the trapped gas is released into the melt pool, where it can form spherical pores if it cannot escape before solidification occurs.
High-purity feedstock minimizes these gas-induced voids and ensures excellent mechanical properties.
Storage Behavior
Moisture absorption on the surface of the metal powder increases the risk of hydrogen porosity during the print cycle. To mitigate this hazard, the powder is kept in sealed containers under dry nitrogen or argon. Reused powder must be sieved to remove oversized weld spatter and partially melted agglomerates before it can be mixed with transit material.
Exposure to air is restricted to prevent oxidation and maintain chemical purity.
