Abstract：Insitu surface oxidation of 00Cr25Ni7Mo3.5N supper duplex stainless steel was studied by high temperature XRD. The samples were continually heated in the air and tested at several temperature. The growth of surface oxide was investigated and precipitation of secondphase was investigated. The results showed that the surface layer was only composed of α phase and γ phases below 600 ℃,α was oxidized to αFe2O3 at about 800 ℃, then to αFe2O3+Fe3O4 at about 900 ℃,and disappeared completely up to 1000 ℃. However, γ was not oxidized even at up to 1100 ℃. The microstructure of the samples quenched from various temperatures were of α and γ, and the fraction of α phase was gradually increased with the temperature. In addition, σ phase in surface layer and interior of quenched samples was almost precipitated and dissolved simultaneously during heating.
2008, Vol. 43 
