A Fundamental Study of an Fe-Cr (111) Binary Alloy-Metal Oxide (110)—Water Interfaces

Stress corrosion cracking (SCC) initiation in light water reactor (LWR) environments is localized and accelerates the oxidation at interfaces depending on the microstructure, surface condition, and local environment. The formation of an oxide film on the metal surface is an inevitable process when the metal is exposed to the environment. Accordingly, an alloy-metal oxide-solution configuration develops at the metal surface, with different reaction dynamics at the oxide-solution and oxide-metal interfaces. All of the interfaces are important in understanding the material degradation processes or the protective capability of a passive film. In the present study, tight-binding quantum chemical molecular dynamics (QCMD) applied to study the Fe-Cr/Cr₂O₃/H₂O interfaces at boiling water reactor (BWR) environment. Cr₂O₃ (110) surface placed on the Fe-Cr (111) binary alloy surface where single layer four water molecules embedded on top of metal oxide surface. The metal-metal oxide interface interaction causes diffusion of oxygen ions into the metal surface and segregation of metallic atoms, and the metal oxide-water interface interaction causes the dissociation of water molecules. As a result, dissociated hydrogen atom diffuses into the oxide film and trapped in the interstitial sites. Atomic charge analysis might clear the bonding mechanism during the reaction process. However, the oxide film degradation at the metal-metal oxide film and metal oxide-water interfaces will be analyzed in details from the atomic scale.