In-situ ToF-SIMS analyses of deuterium re-distribution in austenitic steel AISI 304L under mechanical load

Andreas Röhsler,Hannu Hänninen,Thomas Böllinghaus,Oded Sobol

doi:10.1038/s41598-020-60370-2

Abstract

Hydrocarbons fuel our economy. Furthermore, intermediate goods and consumer products are often hydrocarbon-based. Beside all the progress they made possible, hydrogen-containing substances can have severe detrimental effects on materials exposed to them. Hydrogen-assisted failure of iron alloys has been recognised more than a century ago. The present study aims to providing further insight into the degradation of the austenitic stainless steel AISI 304L (EN 1.4307) exposed to hydrogen. To this end, samples were electrochemically charged with the hydrogen isotope deuterium (2H, D) and analysed by scanning electron microscopy (SEM), electron back-scatter diffraction (EBSD) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). It was found that deuterium caused a phase transformation from the original γ austenite into ε- and α’-martensite. Despite their low solubility for hydrogen, viz. deuterium, the newly formed phases showed high deuterium concentration which was attributed to the increased density of traps. Information about the behaviour of deuterium in the material subjected to external mechanical load was gathered. A four-point-bending device was developed for this purpose. This allowed to analyse in-situ pre-charged samples in the ToF-SIMS during the application of external mechanical load. The results indicate a movement of deuterium towards the regions of highest stress.

Highlights

Researchers already warned against climate change in the 1970s, but only the “special report on the impacts of global warming of 1.5 ° C above pre-industrial levels”, published by the Intergovernmental Panel on Climate Change (IPCC) together with massive civic engagement, brought this topic back to the agendas of policymakers[1,2]
Another effect that is still under debate is the hydrogen-induced transformation of the face-centred cubic (FCC) structure via the close-packed hexagonal (HCP) into the body-centred cubic (BCC) structure[17,18,19,20]
The results of the electron back-scatter diffraction (EBSD) analyses before and after electrochemical charging for five days are shown in Figs. 1 and 2

Summary

Introduction

Www.nature.com/scientificreports formed BCC martensite is more brittle and has a lower solubility and higher diffusivity for hydrogen as compared to its parent lattice[21,22]. Samples made from austenitic stainless steel AISI 304L were electrochemically charged with deuterium and analysed by electron back-scatter diffraction (EBSD) and scanning electron microscopy (SEM). The distribution of hydrogen and its behaviour within the specimen before and during the application of mechanical load were examined by time-of-flight-secondary ion mass spectrometry (ToF-SIMS).

Results

Conclusion