Corrosion behavior of alloy 316L stainless steel after exposure to supercritical water at 500 °C for 20,000 h

- Oxidation of alloy 316L stainless steel in supercritical water (500 °C/25 MPa).
- The layer thickness and weight gain vs. exposure time followed parabolic law.
- Fe3O4 (outer layer), (Fe,Ni)Cr2O4/(Mn,Cr)2O3 (inner layer) on the substrate.
- Ni and Mo elements are segregated by the selective oxidation of Cr.
- Oxidation mechanism was discussed based on the obtained results.

Oxidation behavior of alloy 316L stainless steel static capsules were investigated by long-term exposure to the supercritical water at 500 °C and 25 MPa for various exposure times. It was found that the thickness and weight gain vs. exposure time followed parabolic law. Elemental and phase analyses indicated that long-term exposure to the SCW resulted in formation of scales identified as Fe3O4 (outer layer), Mn-Fe-Ni-Cr spinel (inner layer) on the substrate, and Ni-enrichment (chrome depleted region) in the alloy 316L. Oxidation phenomena and scales grown on the Alloy 316L as the result of long term exposure to the supercritical water was discussed.

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