Effect of Machining on the Oxide Film Formation of Austenite Stainless Steel in 300°C High Temperature Water

Abstract

The effect of machining on the oxide film of 304L and 316L austenite stainless steels (SS) were investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-Ray electron probe micro-analysis (EPMA), and transmission electron microscopy (TEM). The composition, microstructure, and corrosion resistance of the oxide film formed in 300°C high temperature water environment was analysed. The results shown that several kinds of metal oxides were formed on surface such as Fe₂O₃, Cr₂O₃, MoO₃, and Ni(OH)₂. The polished specimen of 316L SS can form integral oxide film after immersion for 20 days in 300°C high temperature water. However, the oxide film was loose and porous of milled specimen tested under same conditions. The corrosion resistance of the oxide film formed on polished specimens was better than those formed on milled specimens. The enrichments of Cr and Ni were detected at the interface of oxide film and matrix. The related diffused mechanism during the oxidation process was analysed.

Fig. 8 TEM morphologies of D120 specimen: (a) cross section morphology of oxide film, (b) and (c) were corresponding magnified figures.