Ab initio molecular dynamics simulation on interfacial reaction behavior of Fe-Cr-Ni stainless steel in high temperature water

Abstract

The interfacial reaction behavior of Fe-Cr-Ni stainless steel in 320 °C high temperature water is investigated using an ab initio Born-Oppenheimer molecular dynamics simulation. After the Fe-Cr-Ni stainless steel is immersed in water, the water molecule is dissociated into OH and H ions. The dissociated OH makes bond with the Cr and Fe atoms to form (Cr,Fe)-OH hydroxide, and the dissociated H adsorbs on the Fe atoms with a certain negative charge. The surface layers of Fe-Cr-Ni stainless steel are negatively charged before immersion, whereas after immersion there is a net positive charge in the surface layers. Most of the valence electrons lost from the surface layers transfer to the water solution through the interface, only a small amount of electrons comes into the inner layer atoms of Fe-Cr-Ni stainless steel. The dissociation characteristics of dissolved oxygen molecule and dissolved hydrogen molecule in high temperature water are also analyzed, and both of them can enhance the interfacial charge transfer.