Corrosion behaviour of Ni-based alloy Inconel 740H in supercritical carbon dioxide at 650–700°C

ABSTRACT Corrosion tests of Ni-based alloy Inconel 740H were carried out in supercritical carbon dioxide (S-CO2) at 650–700°C under 25 MPa. The corrosion kinetics were measured by weight change as a function of time, and the surface oxide layers were characterised and identified by a series of characterisation methods. It is found that Inconel 740H experienced general oxidation, localised exfoliation and internal oxidation. A dense Cr2O3 oxide scale rapidly formed on the surface of Inconel 740H at 650–700°C, resulting in good general corrosion resistance. Nodular oxidation was triggered by Ti-rich and Nb-rich oxides. Internal oxidation selectively oxidised Al. The causes of oxide-induced exfoliation are discussed.