Initial stages of oxide growth on AM stainless steel exposed to a supercritical CO2 environment

Wrought and additively manufactured (AM) 316 L stainless steel samples were exposed to a simulated Brayton cycle supercritical CO2 (sCO2) environment, at temperature of 450 °C and pressure of 76 bar in 99.999% CO2 for 2 weeks. The ground surfaces of wrought and AM 316 L specimens had average oxide thickness of 95 and 51 µm, respectively, composed primarily of Fe and Cr oxides. An as-printed AM 316 L sample was also exposed to the sCO2 environment and exhibited negligible oxidation during the 2-week exposure because of a thick Cr rich Mn silicate native oxide covering most of surface. •As-printed surface of AM316L material is covered in a 20–1000 nm thick Si/Mn/Cr oxide.•Polished surfaces of AM oxidized at half the rate of a wrought 316 L counterpart in sCO2.•The as-printed surface experienced minimal oxidation in sCO2.