Metal 3D printing on Mars: shielding gas from the atmosphere instead of argon

For longer missions on Mars, metal 3D printing will become important as a tool for repair and infrastructure. A preprint study (arXiv) tested three shielding-gas environments when selectively laser melting 316L stainless steel: argon, CO₂, and air. Result: CO₂ is weaker than argon, but sufficient for many non-critical parts—and could replace expensive argon transport by using the Martian atmosphere.

The authors produced 316L stainless-steel samples under argon, CO₂, and ambient air, varying laser parameters to assess effects on morphology, cohesion, and oxidation behavior. As a practical indicator, they used, among other things, how well printed solid areas hold their target geometry: under argon, area stability was about 98%, under CO₂ around 85%. In air, the value dropped to below 50%, reflecting the expected strong oxidation.

From a technical standpoint, CO₂ is not an obvious shielding gas because at the high temperatures in the laser melt pool it can partially dissociate. According to the study, the decisive factor is that the effective oxygen exposure in a CO₂ environment is significantly lower than in air, meaning less oxide is introduced into the melt. Accordingly, the oxygen contents detected in the material fell between those of the argon and air samples.

For Mars, this would mean: not every part has to be manufactured in argon-pure conditions to be functional—for example, non-safety-critical infrastructure. On Earth, CO₂ could become an interesting lower-cost alternative for certain applications, provided surface quality and corrosion behavior meet the relevant specification.