Applying Advanced Analytical In Situ TEM to Assess SCC 'Precursor' Reactions in Austenitic Stainless Steel in H_2O

摘要

In Situ transmission electron microscopy has become an increasingly important and dynamic research area in materials science with the advent of unique microscope platforms and a range of specialized in situ specimen holders. In metals research the ability to image and perform x-ray energy dispersive spectroscopy (XEDS) analyses of metals in liquids are particularly important for studying the localised interaction of the environment with specific microstructural features in the alloy of interest. In order to explore the reaction of MnS inclusions in H_2O, a technique to prepare electron-transparent specimens of austenitic stainless steel for use in a special liquid cell TEM specimen holder has been developed, and used to study the dissolution behaviour of MnS inclusions in austenitic stainless steel in an FEI Tecnai T20 Analytical Electron Microscope. The in situ TEM studies have been performed in parallel with bulk ex situ dissolution studies of MnS inclusions in Type 304 stainless steel during room temperature H_2O exposure. These results are interpreted in view of previous data concerning the effect of MnS on environmentally-assisted cracking behaviour of low alloy steels as well as recent results on the corrosion fatigue behaviour of austenitic stainless steels. The use of novel in situ liquid cell TEM approach can provide information on localised corrosion/oxidation reactions that can be helpful in identifying local microstructural features that can affect the "SCC Precursor" events ultimately leading to SCC initiation.