Oxidation characteristics of two As-cast duplex stainless steels under simulated reheat conditions

摘要

This paper considers the high temperature oxidation of two duplex stainless steel grades with varying nickel and manganese contents. Samples with industrially hot ground and polished surface finishes have been oxidised under laboratory conditions at temperatures from 700 to 1300 deg C. The resulting oxides have been characterised using advanced techniques including scanning electron microscopy (SEM) and transmission electron microscopy (TEM) of thin sections produced using focused ion beam (FIB) milling of selected features. Results have shown that oxide features such as local nodule formation is critically dependant on the surface finish. The oxide on polished samples mirrors the underlying structure whereas that oxide on ground surfaces is more homogeneous, although both surface finishes lead to local nodule formation. The growth of oxide on the individual phases has been shown to be dependant on the formation of silica at the oxide/substrate interface as well as the nickel and manganese contents of the steels studied.