Corrosion of the ferritic, ferritic-mantensitic and austenitic steels including SA213-T24, SA213-P92, SA213-SUPER304H, SA213-TP347HFG, SA213-HR3C were investigated in supercritical water at the temperature of 550 and 600 °C under the pressure of 25 MPa. To probe the influence of dissolved oxygen content on corrosion, the dissolved oxygen contents were controlled at 0, 100, 300 and 2000 ppb, respectively. The exposing time was 200, 400, 600, 800 and 1000 h. The surface morphologies and composition were observed using SEM, EDS and XRD. The cross-sectional structure and element distribution of the oxide scale were analyzed. The results indicated dissolved oxygen has an obvious effect on weight gain and exfoliation of oxide scale. The influence of Cr concentration was also discussed. Based on the different effects of dissolved oxygen on corrosion of tubes in different operating conditions, a new treatment method of feed water which was appropriate for ultra supercritical power plant was proposed. The method can avoid flow-accelerated corrosion in high and low pressure heaters and decrease corrosion of boiler tubes effectively at the same time.

Subject
X-ray diffraction, Steel structures, Supercritical water, Water, Oxides, Oxide layers, Weight gain, Surface morphology, Oxide scales, Steel, Dissolved oxygen, Alloys, Oxidation
Keywords:
corrosion, supercritical water, dissolved oxygen, treatment method of feed water
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2013
Association for Materials Protection and Performance (AMPP)
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