Microstructure understanding of high Cr-Ni austenitic steel corrosion in high-temperature steam

Journal article

The microstructure and microchemistry of the oxide scales formed on Fe-21Cr-32Ni and Fe-17Cr-9Ni steels after exposure to deaerated high-temperature high-pressure steam at 600 °C for 1500 h have been analysed and compared by several advanced characterization techniques. By comparing the oxide scales formed at different-stages of exposure, it is shown that Fe-21Cr-32Ni steel was internally oxidized at the early-stage, and then an external oxide scale was developed together with an inner chromia band under the internal oxidation zone. In comparison, Fe-17Cr-9Ni steel was internally oxidized together with an external Fe-rich oxide scale during the entire experimental period. The thicknesses of the internal oxidation zone of Fe-21Cr-32Ni and Fe-17Cr-9Ni steels were ∼7 and ∼70 µm, respectively. Further characterisation revealed that the internal oxidation zone contained (Cr, Fe, (Ni))₃O₄ and nanoscale nickel networks, together with numerous nano-pores. The effects of these structures on mass transfer and reaction product formation were discussed, in connection with the alloy composition and the formation of the chromia layer.

Authors: Shen, Z; Zhang, J; Wu, S; Luo, X; Jenkins, BM

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Elsevier
• Journal: Acta Materialia
• Volume: 226
• Article number: 117634
• Publication date: 2022-01-09
• Acceptance date: 2022-01-07
• DOI: 10.1016/j.actamat.2022.117634
• EISSN: 1873-2453
• ISSN: 1359-6454
• Language: English
• Keywords: multilayers; high Cr-Ni austenitic steel; transmission electron microscopy; internal oxidation; FFR; transmission Kikuchi diffraction