Powder spreading in laser-powder bed fusion process

Laser-Powder Bed Fusion (LPBF) has been extensively utilized by a broad range of manufacturing industries in recent years. Fabricating parts with high mechanical properties and smooth surfaces has motivated such industries and academic communities to study different aspects and steps of the LPBF process, including powder spreading, laser scanning, and solidification. Creation of highly dense powder layers with lower surface roughness before laser scanning step is a must for producing non-porose part layers after laser scanning step of LPBF process. Thus, the initial powder spreading step of the LPBF process has been investigated to correlate the powder spreadability to powder layer quality and consequent part properties. The current review paper summarizes the previous work performed to define some spreadability metrics and determine the impact of LPBF process parameters and powder characteristics on powder spreadability. The spread powder layer's quality, which is called powder spreadability, is discussed in terms of empty areas on the substrate, powder bed density, powder surface roughness, powder dynamic repose angle, and powder mass flow rate. Also, the influence of LPBF process parameters, including recoating velocity, layer thickness, and recoater type, and powder characteristics, like particle size distribution, on the defined spreadability metrics are reviewed.