Parametric study of Martian regolith steel using ionic liquids iron and Bosch byproduct carbon for laser powder bed fusion

With the anticipated manned missions and future long-term habitation of the Martian surface, in-situ resource utilization (ISRU) methods remain critical to provide raw materials and subsequent manufacturing of tools, replacement components, electronics, and more. Due to the overwhelming costs and flight time associated with launching supplies to extraterrestrial bodies, the sustainability of these astronaut colonies will rely on readily available feedstocks and energy-efficient production methods on the surface. The Martian environment contains numerous elements, mostly in the form of compounds within the regolith and local atmosphere, that could be used for producing metallic components. Ionic liquids (ILs) have been demonstrated as a low-temperature regolith and meteorite metal harvesting system by NASA’s Marshall Space Flight Center (MSFC). Additionally, the Bosch process has shown success as an oxygen (O₂) generation system possessing theoretical 100 % hydrogen (H₂) recovery, producing a solid carbon (C) byproduct. Studies on the use of IL-metals and Bosch C in ferrous castings have been conducted in recent years with immense success. This study further investigates an alloy composition based on IL harvested iron (IL-Fe) and Bosch C to produce a novel IL-steel alloy for additive manufacturing (AM) by combining the products of IL’s and Bosch C into a printable steel composition. The IL-steel powder was produced using commercially available elements and the addition of Bosch C from the rotary kiln C-formation reactor (C-FR) at MSFC’s Environmental Controls and Life Support Systems (ECLSS) branch. Raw materials were alloyed into steel ingots and atomized to a targeted powder size distribution of 15-45 μm. A series of progressively refined build parameters (laser power and exposure time) were used to produce cubic samples that were investigated to determine baseline laser powder bed fusion (PBF-LB) settings for printing with IL-steel. Bulk density was used as the initial filtering mechanisms, with Vickers microhardness and microstructural investigations being conducted on the final matrix of samples. Moving forward, IL and Bosch C production will need further refinement to limit elements that could negatively affect printed products, and production volumes will need to be increased beyond laboratory scales. Future investigations with IL-Steel will require characterization of the powder’s flowability, laser interaction, and printability in reduced gravity and extraterrestrial atmospheric conditions. Additionally, further mechanical characterization, i.e. tension, fatigue, etc., will be required to determine the potential use cases of IL-Steel on Mars and solidify its applicability. The results indicated that the alloying of IL-Fe and Bosch C to create an IL-steel could serve as a viable means of producing a multitude of components and tools, such as rebar for concrete reinforcement, replacement gears, hand tools, and more in-situ for long-term manned missions to Mars.