Investigation of microstructure and liquid lead corrosion behavior of a Fe-18Ni-16Cr-4Al base alumina-forming austenitic stainless steel

The microstructure of an alumina-forming austenitic stainless steel with a composition design of Fe-18Ni-16Cr-4Al-2Mo-0.4 Nb (in wt%) is characterized. The steel contains about 75 vol% austenitic phase and 25 vol% ferritic phase. B2-NiAl precipitates with round shape can be found only in the ferritic phase in the as-rolled sample. The corrosion behavior in static liquid lead with different oxygen content of 10−9 and 10−6% by mass at 700 °C for 1000 h is investigated. After exposure for 1000 h in liquid lead with oxygen content of 10−9%, obvious lead penetration combined with nickel dissolution is found. In the case of liquid lead with 10−6% oxygen content, a thin oxide layer can be formed on the surface, thus protecting the steel from liquid lead attack. After the corrosion test, significant precipitations are found in both austenitic and ferritic phases in the matrix of the steel.