Effect of dissolved oxygen content on the oxide structure of Alloy 625 in supercritical water environments at 700 °C

The corrosive behavior of Alloy 625 in supercritical water at 700 degrees C and 24.8 MPa with dissolved oxygen contents of 150 ppb, 1 ppm, and 8.3 ppm was studied. The oxides grown on all test samples exhibited a duplex-layer structure. The outer layer was composed of a spinet oxide Ni(Cr, Fe)(2)O-4 and the inner layer was mainly continuous Cr2O3. Ni-containing oxides, such as spinel Ni(Cr, Fe)(2)O-4, did not form on samples exposed to the supercritical water environment containing 150 ppb dissolved oxygen. Oxygen content might considerably affect the composition and structure of oxides grown in supercritical water for Alloy 625. (C) 2013 Elsevier Ltd. All rights reserved.