Characterization of Oxide Film Behaviors on 316 Stainless Steels in High-Temperature Water-Influence of Hydrogen and Oxygen Considerations for Initiation of SCC-

摘要

Oxide film analyses were carried out on 316 stainless steels to clarify the influence of dissolved hydrogen,dissolved oxygen and chromium concentration in alloy.The specimens were exposed to a high-temperature high-pressurized water environment.This paper presents results of the oxide film analyses,and the influence of corrosion phenomenon to the initiation process of SCC was discussed.The oxide films were composed of a double layer structure in both water chemistries.The outer layers formed in hydrogenated and oxygenated water were mainly consisted of magnetite and hematite,respectively.The inner layer of the oxide film was composed of porous oxide grains in oxygenated environment,while it consisted of fine grains of chromite in hydrogenated environment.In addition,it is considered that the original surface of the specimen might remain in the outer/inner interface in the hydrogenated environment.These differences of corrosion phenomena might affect the stress corrosion cracking susceptibility,especially in the initiation stage.