Supercritical water oxidation (SCWO) process can rapidly degrade toxic or hazardous organics to harmless compounds such as H_2O and CO_2, and meanwhile recover the oxidizing reaction heat, which has been proven to be an efficient and clean technology to treat a variety of organic wastes. However, due to the inherent reaction characteristics of high temperature and pressure, and strong oxidizing, the corrosion behavior of potential construction materials becomes the focus. However, there is little literature available on the effects of oxidant contents on corrosion resistance of alloys in supercritical water atmospheres. In order to explore the influences of oxygen levels on corrosion behavior of austenitic steels in oxidizing supercritical water, corrosion behavior of stainless steel 316 and Alloy800 were investigated in supercritical water with oxygen levels from 0 mg/L to 5000 mg/L, by series of analytical methods such as SEM, XRD, Raman spectroscopy, XPS and so on. The formed scales were generally characterized by a duplex-layer structure: the outer layer was primary constituted by Cr-doped magnetite and (Fe, Cr)_2O_3, while the inner layer predominantly consisted of Cr-rich oxides. The chromium content of outer layer rose with exposure times and oxygen levels in experimental environments, maybe resulting from outward diffusion of Cr triggered by its higher oxygen affinity. Alloy800 owns higher Cr contents of the outer layer than S316L. In addition, the formation mechanism of scales and its stability variation with oxygen contents were also discussed in detailed.
展开▼
