Observing hydrogen in steel using cryogenic atom probe tomography: A simplified approach

This work demonstrates a new method to enable cryogenic atom probe tomography (cryoAPT) for the investigation of hydrogen in a high-strength steel, specifically to detect hydrogen localised to V-Mo-Nb carbides finely dispersed in the matrix. Prior cryogenic experiments required highly customised atom probe instrumentation to enable samples to be kept at cryogenic temperatures throughout the vacuum transfer process. Here we use an alternative approach without modification of the atom probe instrument itself, whilst still achieving hydrogen mapping. Additionally, we use this method to investigate the roles of solvent and solutes within the charging electrolyte, and we demonstrate that deuterated solute is not required when using heavy water as solvent, expanding the range of electrolytes that can be utilised in APT hydrogen charging experiments. This work reduces the experimental requirements for cryo-APT and makes the technique accessible to all APT equipped laboratories. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.