Type of presentation: Oral

IT-17-O-3072 An atom probe insight on corrosion of stainless steels

La Fontaine A. J.^{1, 2}, Cairney J.^{1, 2}

¹School of Aerospace, Mechanical, Mechatronic Engineering, The University of Sydney, NSW 2006, Australia, ²Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006, Australia

alex.lafontaine@sydney.edu.au

For high temperature applications, such as in new-generation energy technologies, high-performance stainless steels offer an attractive combination of economy and mechanical / corrosion properties. For example, concentrated solar power (CSP) requires cost-effective and corrosion resistant materials that can operate for extended periods at high temperatures and withstand thermal cycling between 900°C and room temperature.

Stainless steels develop a passive layer protecting the steel from detrimental corrosion. When used in extreme conditions at high temperature in ultra-corrosive atmosphere, with thermal cycling or high pressure, this passive layer can be destroyed and leave the steel exposed to corrosion resulting in material failure.

The analysis of the chemical composition and microstructure of oxide layers using traditional analytical spectroscopy techniques has some limitation due to either limited lateral resolution or mass resolution. Atom probe tomography (APT), however, is a unique 3D technique allowing for atomic scale chemical characterization.

In the last decade, local electrode atom probe (LEAP) was applied to study oxide layers. For example, surface oxide layers in stainless steels or nickel-based alloys [1-3] were characterized by using laser-pulsed LEAP. The current work demonstrates our efforts in studying by laser-pulsed LEAP the complexity of oxides layers in intergranular corrosion cracks formed in a commercial austenitic stainless steel during thermal cycling.

References

[1] Lozano-Perez S, Saxey DW, Yamada T, Terachi T. Scripta Materialia 2010;62:855.
[2] Kruska K, Lozano-Perez S, Saxey DW, Terachi T, Yamada T, Smith GDW. Corrosion Science 2012;63:225.
[3] Baik S-I, Yin X, Seidman DN. Scripta Materialia 2013;68:909.

This work was made possible by an ARENA PhD scholarship. The authors acknowledge scientific and technical input and support from the Australian Microscopy & Microanalysis Research Facility (AMMRF) at The University of Sydney as well as CSIRO Energy Centre.

Fig. 1: (a) Photo of the concentrated solar power (CSP) plant used to heat treat the samples (b) Z-contrast back-scattered electron image of cross section of the sample (c) EBSD pattern quality map of IGC area with b.c.c. phase highlited in red, EDS O-K map - EDS Cr-K maps, atom probe volume of grain boundaries in chromite (Cr,O and Fe)