Thermodynamic assessment of evaporation during molten steel testing onboard the International Space Station

Abstract A series of 54 experiment cycles were performed on an FeCr21Ni19 (at. %) sample in vacuum, He and Ar gas atmospheres using the Electromagnetic Levitation facility onboard the International Space Station (ISS-EML). Evaporation control is a critical facility resource that limits processing time and must be tracked to ensure astronaut safety. Species specific evaporation during this test has been estimated using a mathematical model based on thermodynamic assessment and Langmuir’s equation to track the dynamic mass loss during each thermal cycle. The findings from this study were validated using post-mission SEM-EDX evaluations. The predicted mass loss and elemental distribution from the evaporation model was consistent with experimental observations. Based on facility geometry, deposit layer thicknesses at various locations have also been calculated and results showed excellent agreement with near-real-time predictions using software developed by the German Space Agency (DLR) Microgravity User Support Center (MUSC).