Erosion-corrosion behavior of Nickel based alloys in supercritical water oxidation environment

In this study, the erosion-corrosion experiment of Ni based alloys in high-temperature and high-pressure supercritical water environment was performed. SiO₂ and Al₂O₃ particles with the average diameter of 30 µm and 50 µm were used as erodent. The special designed specimens were fixed on a blade impeller, and the erosion tests were performed in a high pressure autoclave with a magnetic stirrer system. Results show that the basic corrosion mechanism is not changed by the erosion process. A Cr-rich inner oxide layer and a Fe/Ni rich outer oxide layer were formed on the alloy surface. However, the oxidation rates of the alloys were affected by the erosion process. Parts of the outer Fe and Ni oxides were removed by the erodent particles during the tests. The inner Cr oxide layer still exists owing to the self-healing ability of the Cr₂O₃ layer, acting as a barrier to resist further corrosion of the alloys. The factors that affect the degree of erosion and the erosion-corrosion mechanism in SCW environment is analyzed.