High Temperature Corrosion of Super304H and Inconel625 in Carbon Dioxide Doping With Sulfur Dioxide Environment at 750℃
It is of great significance for supercritical carbon dioxide(S-CO2)power generation technology to study the corrosion behavior and mechanism of alloys in the environment of CO2 containing doping gas.High temperature corrosion experiment of Super304H and Inconel625 alloy in CO2,together with corrosion weighting method,scanning electron microscope and X-ray diffraction(XRD)are applied to study the corrosion behavior of the two heat resistant materials in CO2 doping with SO2 environment at 750℃.The results show that the oxidation kinetic of the materials follows the parabolic law under 750℃CO2 and 750℃CO2+SO2 environment.Inconel625 has a better corrosion resistant ability than Super304H,accompanied by less oxidation weight gain.The initial weight gain of Super304H in 750℃CO2 is higher than that in CO2+SO2,while the weight gain gets larger in CO2+SO2 after 120 h.The single Cr2O3 oxide scales and the double-layered oxide scales consist of nodular-typed Fe3O4 outer layer and FeCr2O4 inner layer formed on Super304H after exposure 500 h in two environments.Whereas a stable and dense Cr-rich oxide layer of about 1 µm in thickness grows on Inconel625.The Cr content plays a crucial role to improve the alloy corrosion resistance in high temperature CO2 environment.High temperature CO2 doping with SO2 has the effect of inhibiting carburization during the formation of Cr2O3,accelerating corrosion and carburization for iron oxide.
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