Effects of Solution Depletion and Segregation Oxidation on Morphology of Modified 310 Austenitic Stainless Steel

摘要

The oxidation morphologies of modified 310 steel exposed in 900 and 1 100 ℃ air were investigated.A double layer morphology consisting of a (Cr,Mn)-rich outer layer and a fine Cr-rich inner layer was formed at 900 ℃.It was related to the breakaway oxidation induced by the Cr-depletion and the Mn-segregation in inner layer.Some Cr-rich oxides with amorphous state were formed along grain boundaries.And some new finer oxide grains,voids and Cr-rich precipitates were observed in spallation areas at 1 100 ℃.Correspondingly,the oxidation kinetic curve dropped with the spallation of scale and increased with the formation of some new oxide grains.It was caused by segregation of Cr and the transformation of oxides from Cr2 O 3 to the volatile oxides at elevated temperature.XRD analysis showed that the precipitates were mainly composed of CrO 3 .Segregation and depletion for solutions were also dis-cussed by oxidation diffusion mechanisms.