Laser powder bed fusion for metal additive manufacturing: perspectives on recent developments

Abstract

While significant progress has been made in laser powder bed fusion (L-PBF) for metal additive manufacturing (AM), there is still limited large scale adoption of this advanced manufacturing technique by the industry. This paper covers the recent developments in L-PBF with discussions from the materials and process perspectives. High entropy alloys and high strength aluminum alloys have been identified as key materials development for L-PBF. Then, scanning strategies and multi-lasers applications for the process are also discussed. Other research trends and topics such as powder recycling, shape memory alloys and magnetic alloys are illustrated. The final part of this paper provides an outlook on the recent advancements while suggesting potential research topics for L-PBF.

Design and performance evaluation of additively manufactured composite lattice structures of commercially pure Ti (CP–Ti)

“…The CP-Ti with optimized composite lattice structures were manufactured by SLM 125HL machine (SLM Solutions GmbH, Lübeck, Germany) under an argon gas atmosphere with O 2 content ＜0.05 wt% to reduce oxidation. The process begins with the preparation of CAD files which are subsequently sliced into two-dimensional layers by Materialise Magics [ 40 , 41 ]. The detailed process parameters are as follows based on our previous study [ 34 ]: the layer thickness is 30 μm; the scanning speed is 900 mm/s; the laser power is 200 W; the hatching space is 0.14 mm; and the hatching type is a continuous laser mode, which is alternated 33° between each layer.…”

Improving Build Quality in Laser Powder Bed Fusion Using High Dynamic Range Imaging and Model-Based Reinforcement Learning

“…The roughness of LPBF surfaces mainly results from the layerwise build process using overlapping laser tracks, the applied process parameters, and incomplete melted material [8]. The following parameters have been investigated in literature for different materials and indicate a significant correlation to the surface roughness of LPBF parts: 1) Laser power -- [8,10] 2) Scan velocity + [10] 3) Build orientation ++ [10][11][12][13][14] 4) Layer thickness ++ [11,13] 5) Hatch distance + [15] 6) Scan strategy + [14,[16][17][18] From the physical point of view, as the laser power increases, the size of the melt pool also increases [19]. During the layer-wise build process, larger melt pools increase the intersection area between different tracks and therefore lead to a smoother surface.…”

Experimental and numerical investigation of the origin of surface roughness in laser powder bed fused overhang regions

“…This makes the effects of gravity and surface tension important in the determination of the resulting shape/size of the melt pool and, subsequently, the evolution of the microscale morphology of overhang regions. Moreover, due to the voids between powder particles, thermal conditions (such as energy absorption, energy loss, cooling rate, and thermal conductivity) of printing on a powder bed are inferior to printing on a solid substrate, worsening the surface quality, porosity, and metallurgical strength of the resulting part (Yu et al 2019;Karimi et al 2020;Sing and Yeong 2020). Surface roughness not only increases the (micro-) shape deviation but also deteriorates the mechanical strength by serving as initiation sites for micro-cracks during periodic loading (Günther et al 2018).…”