Compatibility of Different Commercial Alloys in High Temperature Supercritical Carbon Dioxide

In this work, compatibility and long-term integrity of candidate structural materials, including austenitic stainless steel 316NG, Fe-Ni based alloy 800H and Ni-based alloy 625, were tested in high-temperature and high pressure SCO 2 . The exposure time was up to 3000 h. The results showed that the corrosion kinetics approximately followed a parabolic law for 316NG and 800H. After 3000 h exposure, all of oxide layers, mainly composed by Cr 2 O 3 , were continuous, compact and protective, and their thicknesses were about 21~45 nm, 64~88 nm and 34~43 nm respectively. In case of carburization, dark spots corresponding carbon deposition was observed on the surface and a little enriched in underneath the oxide for 800H. Moreover, enrichment of trace elements was found at oxide/substrate interface through GDOES and TEM analysis, i.e., enrichment of Mn, Si for 316NG, enrichment of Mn, Si, Al, Ti for 800H and enrichment of Ti, Al for alloy 625.