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SIMS21, Poland 2017 - Yasser Al Aboura abstract

Yasser Al Aboura oral presentation (OA3-Tue1-3-3)

Detecting localised Deuterium in 303 Stainless Steel using NanoSIMS

Yasser Al Aboura1, Anthony Cook2, Laura Felisari3, Katie Moore2, Robert Akid2

1 The University of Manchester, Oxford Road, M13 9PL Manchester, United Kingdom
2 The University of Manchester, Oxford Road, M15 9PL Manchester, United Kingdom
3 BP formulated products technology, chiltern hills, RG8 7QR Pangbourne, United Kingdom

The exposure of high strength metallic alloys to an environment in which atomic hydrogen is produced at the metal/solution interface can lead to loss of toughness causing premature failure of components. This failure mechanism is known as hydrogen embrittlement. Its damaging effects can be reduced by controlling the microstructure of alloys so that hydrogen can be trapped locally within the microstructure thus preventing it from diffusing into the lattice, in particular to the sites of cracks, enhanced crack growth rates. Typical trap sites in alloys include second phase particles, phase interfaces and grain boundaries, each having different trapping capabilities [1]. However, analytically, it is difficult to distinguish between each type of trap site with regards to its capacity to attract and trap hydrogen; mainly due to the spatial resolution and sensitivity limitations imposed by conventional characterisation techniques for detecting hydrogen.

In this study, type 303 stainless steels were electrochemically charged to load samples with deuterium, therein eliminating the measurement of ‘artefact’ hydrogen arising from residual hydrogen in the vacuum chamber and/or hydrogen adsorbed on the sample surface. Although hydrogen and its isotope may differ slightly in their diffusibility and solubility in the metal, it is well established that, in principle, they behave the same way in steel microstructures [2]. After deuterium charging, samples were left to outgas at different durations in ambient conditions to allow lattice deuterium to effuse from the matrix leaving behind only trapped deuterium in the microstructure. Deuterium and hydrogen signals were collected in the NanoSIMS by selecting the ion detectors to detect 1H, 2H, 12C and 16O ions. Several challenges were encountered with detecting deuterium/hydrogen uptake using the NanoSIMS, for example, hydrogen contamination in the chamber and ion induced phase transformation of the analysed region. Other characterisation techniques such as Atomic Force Microscopy (AFM), Secondary electron (SE) imaging and Electron Backscatter Diffraction (EBSD) mapping were used to validate the observations made with the NanoSIMS analysis.

[1] H. K. D. H. Bhadeshia, “Prevention of Hydrogen Embrittlement in Steels,” ISIJ Int., vol. 56, no. 1, pp. 24–36, 2016.

[2] O. Sobol, F. Straub, T. Wirth, G. Holzlechner, T. Boellinghaus, and W. E. S. Unger, “Real Time Imaging of Deuterium in a Duplex Stainless Steel Microstructure by Time-of-Flight SIMS.,” Sci. Rep., vol. 6, no. February, p. 19929, 2016.