Corrosion Products and Formation Mechanism of Hastelloy C-276 Alloy in Supercritical Water at 600℃

The corrosion products of nickel-base alloy Hastelloy C-276 was investigated in supercritical water（SCW） at 600℃/25MPa through grazing incidence X-ray diffractometry,X-ray photoelectron spectroscopy and scanning electron microscopy,respectively.The results show that the uniform and complete oxide film was observed in SCW,which was identified to mainly consist of NiO,NiCr₂O₄,Cr₂O₃ and MoO₂;The oxide films that had duplex structure were in poor in Ni and Mo,but the inner layer was rich in Cr.The loose outer layer lacked of protective,while the compact inner layer was favor of antioxidation.The formation mechanism of corrosion products on alloy C-276 in supercritical water seemed to be similar to that in high temperature water.The Ni（OH）₂,NiO outer layer grew by dissolution and precipitation mechanism,while the Cr₂O₃ inner layer oxide was formed by oxygen diffusing inward and reacting with the retained Cr.