Corrosion performance of heat-resisting steels and alloys in supercritical carbon dioxide at 650 °C and 15 MPa

Highlights: • Corrosion performance of T91, TP347HFG and 617 in supercritical carbon dioxide was investigated. • The corrosion kinetics of the investigated materials followed a sub-parabolic corrosion law. • Corrosion resistance of steels and alloys can be evaluated by the corrosion degradation zone. • Corrosion resistance of the investigated materials lay in the order: 617 > TP347HFG > T91. -- Abstract: The corrosion behavior of martensitic heat-resistant steel T91, austenitic heat-resistant steel TP347HFG and nickel-based alloy 617 in high-temperature supercritical carbon dioxide at 650 °C and 15 MPa was investigated. Raman spectrum, X-ray diffraction, and glow-discharge optical emission spectrometry were employed to characterize the corrosion products. Results show that weight gain of T91 in supercritical carbon dioxide at 650 °C was significantly higher than that of TP347HFG and 617. The corrosion kinetics of investigated materials follow a sub-parabolic corrosion law. The chromia-rich oxide scales formed on TP347HFG and 617 enhanced their corrosion resistance, which was mainly attributed to higher Cr content in TP347HFG and 617. The internal oxidation rate of 617 was much more serious than the rate of carburization. Oxidation products on T91 consisted of Fe₃O₄ and (Fe, Cr)₃O₄. Moreover, Cr-depletion and carburization zones were observed beneath the oxide scales. Based on the presence of Cr-depletion and carburization zones, it is proposed that corrosion resistance of heat-resistant steels and alloys in supercritical carbon dioxide can be evaluated by the corrosion degradation depth.