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

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