Chemical States of Stainless Steel in nm to Several Tens of nm Region from Surface Observed by the Depth-Resolved X-ray Absorption Spectroscopy.

ABSTRACT

Chemical states of Fe, Cr, Ni, Mn, and O in stainless steel, SS304, are nondestructively observed over a wide range of depth from nanometer (nm) to several tens of nm by means of the depth-resolved X-ray absorption spectroscopy in the soft X-ray region. It is revealed that Cr is more oxidized in the surface region than the inner region, while Fe is also oxidized at the surface though the oxidation is less prominent compared to Cr. The chemical states of Cr are described by a mixture of Cr-O and Cr-OH coordinations, with more OH components at the surface. Mn and Ni spectra show MnO and metallic Ni features, respectively, throughout the depth of at least up to several tens of nm.