XPS study of oxide nucleation and growth mechanisms on a model FeCrNiMo stainless steel surface.

High resolution X-ray photoelectron spectroscopy analysis has been used to investigate, in-situ, the mechanisms for oxide nucleation and growth on a FeCrNiMo single crystal alloy. Ultra-high vacuum conditions provided the ideal environment in which an oxide-free surface could be oxidised in a controlled manner, using extremely low pressures and step-wise exposures of oxygen. In-situ snapshot measurements, which records an XPS spectrum every 10 s, provided insight into the mechanisms of chromium and nitrogen segregation during annealing of the sample. High resolution XPS spectra was used to follow the evolution of the key elements at step-wise intervals, allowing for detailed insights into the nucleation and growth mechanisms. Angular XPS analysis provided further information on the in-depth distribution and stratification of the oxide film. [Display omitted] • In-situ XPS indicates two different mechanisms for Cr segregation during annealing. • Surface rearrangement results in CrN behaving as nucleation site for Cr 2 O 3. • Oxidation of Mo is delayed until after formation of Fe and Cr oxide has begun. • Oxide growth became dominated by iron oxide owed to increased Fe cation mobility. • Fe2+ and Cr3+ became enriched at the oxide–metal alloy interface. [ABSTRACT FROM AUTHOR]