Forming and densification of lunar regolith simulant based on millimeter-scale energy beam melting

The cost of building a lunar outpost can be greatly reduced by adopting melting of lunar regolith using concentrated solar energy beam based on in-situ additive manufacturing, there are still considerable obstacles to boosting the compactness and mechanical strength of the fabricated samples. The exploration of optimizing process parameters to address the above challenges are severely limited by solar time and space on Earth. Herein, a system for millimeter-scale energy beam melting of the lunar regolith simulant was set up to investigate the effects of process parameters, including laser power, scanning speed, hatching space (track overlapping ratio), and powder layer thickness (layer overlapping ratio) on the processes of single-track, multi-track, and multi-layer forming. The best range of single-track forming quality is the regular type with linear energy density of 27.5–100 J/mm. The surface is smooth and devoid of apparent fissures when the track overlapping rate is between 20% and 45% during the multi-track scanning procedure. For multi-layer sample forming, Samples with high density and few defects appear in the range of 45%–73% layer overlapping rate. The process parameters window for sample forming is determined by the combination of linear energy density, track overlapping rate, and layer overlapping rate. The relative density of single-track, multi-track, and multi-layer increases sequentially under the action of remelting, reaching 62.9%, 70%, and 86%, respectively. The average compressive strength of the test specimen is 5.6 MPa satisfies the specifications for the load-bearing structures on the moon. These results would provide essential data for the development of in-situ additive manufacturing.