In situ photo-emission electron spectroscopy was used to identify the mechanism which limited thermally activated N diffusion in metallic alloys. The samples were prepared by bombarding stainless steel with a broad ion source in a high-vacuum chamber. The photo-emission spectra evolution upon increasing the controlled O partial pressure was correlated with the bulk material properties. The presence of O inhibited the formation of iron nitrides and the γN-phase (an austenitic face-centered-cubic lattice containing N), which proved to be fundamental for efficient N penetration into the alloy.

Identification of the Mechanism-Limiting Nitrogen Diffusion in Metallic Alloys by in situ Photo-Emission Electron Spectroscopy. C.A.Figueroa, A.S.Ferlauto, F.Alvarez: Journal of Applied Physics, 2003, 94[8], 5435-7