Experimental study of structural materials for prolonged venus surface exploration missions

Abstract

Materials used in the fabrication of landers for Venus exploration need to be carefully selected to assure functional durability throughout anticipated prolonged future mission durations in the harsh conditions that include 460°C and 9.2 MPa pressure with supercritical CO2 and trace corrosive gases. Previous work has shown the adverse effects that trace quantities of the atmospheric sulfide and halogen Venus gas constituents have on some materials used in sensor and electronic component fabrication. In this study, a limited, systematic evaluation of several pure elemental metals as well as Ti-6Al-4 V is conducted to determine on an elemental level the constituents of structural materials that could survive prolonged Venus exploration. The metals are characterized before and after exposure to a simulated Venus surface atmosphere using X-ray photoelectron spectroscopy, Auger electron spectroscopy, energy-dispersive spectroscopy, and field-emission-scanning electron microscopy. Ti-6Al-4 V, titanium, and molybdenum all demonstrate stability when exposed to the simulated Venus surface environment. In contrast, cobalt, palladium, and to some extent chromium have adverse reactions to the sulfur constituents. The 96% supercritical CO2 leads to the complete oxidation of niobium and zirconium, as well as spalling oxide layers on tantalum and formation of a thick oxide layer on tungsten.