Corrosion behavior of pre-oxidized HR-224 superalloy in supercritical water environment at 700 °C

• Published in: Journal of nuclear materials 2018-07, Vol.505, p.7-14
• Main Authors: Liu, Yu-Chen, Chen, Shih-Ming, Ouyang, Fan-Yi, Kai, Ji-Jung
• Format: Article
• Language: English
• Subjects: Alumina-forming alloys; Aluminum alloys; Aluminum oxide; Chromium; Cladding; Corrosion; Corrosion resistance; Corrosion resistant alloys; Electron microscopes; Electron microscopy; Environment; High temperature corrosion; High temperature physics; Marine environment; Metal ions; Migration; Nickel; Nickel base alloys; Nuclear accidents & safety; Nuclear energy; Nuclear engineering; Nuclear power plants; Nuclear safety; Oxidation; Oxygen content; Plant reliability; Superalloys; Supercritical water
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2018.03.053

Corrosion of cladding materials in supercritical water (SCW) environment is a key reliability issue for the safety of nuclear power plant. In this study, we propose to use the pre-oxidized treatment to provide better corrosion resistance of cladding materials in the SCW environment. The nickel-based superalloy HR-224 was first pre-oxidized in flowing air at 982 °C for 100 h to establish a continuous and dense scales and then exposed in the SCW environment with high oxygen content (8.3 ppm) at 700 °C and 24.8 MPa for cyclic oxidation testing up to 1300 h. The pre-oxidized samples exhibit better corrosion resistance than as-received samples in the SCW environment. After pre-oxidizing process, triple scales, Ni(Cr, Fe)2O4 spinel/Cr2O3/α-Al2O3 were observed, and the growth of inner α-Al2O3 layer is predominant in the SCW environment. The α-Al2O3 layer in pre-oxidized samples was found to effectively decrease outward migration of metal ions in Alloy HR-224 and thus provides better corrosion resistance than as-received samples in SCW environment. •Pre-oxidized HR-224 provides better corrosion resistance than as-received one.•Ni(Cr, Fe)2O4 spinel/Cr2O3/α-Al2O3 were observed after pre-oxidized treatment.•Continuous Al2O3 layer can effectively decrease outward migration of metal ions.