Additive manufacturing by laser powder bed fusion and thermal post-treatment of the lunar-regolith-based glass-ceramics for in-situ resource utilization

Abstract

Powder bed fusion is one of the most promising additive manufacturing approaches for in-situ resource utilization (ISRU) in the following lunar exploitation missions. However, the harsh conditions for energy supply and equipment operation on the lunar surface and the amorphization of materials due to rapid heat-cooling cycles could hinder the efforts to produce high-quality lunar regolith-based products. Laser powder bed fusion (LPBF) with large laser spot sizes and low scan speeds were used to print the glassy lunar regolith simulant (LRS) precursors. Then the thermal post-treatment was carried on to transform the LRS precursors into glass–ceramic products. The precursors and glass–ceramic samples' microstructure, mechanical properties, and thermophysical properties were investigated. The results indicated that the acceptable range of volumetric energy density (VED) for the LPBF process of lunar regolith was from 3.5 to 4.3 J/mm3. The porous structure resulting from the large molten pools leads to low thermal conductivities and an acceptable strength compromise. The glassy precursors formed augite phase-dominated LRS glass-ceramics at 823 °C during thermal post-treatment and augite-plagioclase polycrystalline LRS glass-ceramics with better mechanical properties at 1100 °C. The increase of the augite phases precipitation contributed to the strength enhancement, and the grain coarsening caused by the prolonged crystallization process at 1100 °C would reduce the strength. The average compressive strength, fracture toughness, and Vickers hardness of the LRS glass-ceramics could reach 50.71 MPa, 1.49 MPa·m1/2, and 897.91 HV1/15, respectively. This multi-process method of laser powder bed fusion of glass-ceramics can maximize the application potential of the ubiquitous lunar regolith in future in-situ additive manufacturing to produce lunar regolith-based building materials for different stages of future lunar exploitation missions.