Atom probe tomography of reactor pressure vessel steels: an analysis of data integrity

In this work, the importance of optimising experimental conditions for the analysis of reactor pressure vessel (RPV) steels using atom probe tomography is explored. The quality of the resultant atom probe data is assessed in terms of detection efficiency, noise levels and mass resolution. It is demonstrated that artefacts can exist even when experimental conditions have been optimised. In particular, it is shown that surface diffusion of some minority species, including P and Si, to major poles prior to field evaporation can be an issue. The effects were most noticeable during laser pulsing. The impact of surface migration on the characterisation of dislocations and grain boundaries is assessed. The importance of selecting appropriate regions of the reconstructed data for subsequent re-analysis is emphasised.