The impact of outgassing on the nano-oxides kinetics of ferritic oxide dispersion strengthened steel

• Published in: Materials today communications Vol. 33; p. 104929
• Main Authors: Spartacus, Gabriel, Malaplate, Joël, De Geuser, Frédéric, Sornin, Denis, Mouton, Isabelle, Guillou, Raphaëlle, Deschamps, Alexis
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2022; Elsevier
• Subjects: Atom Probe Tomography (APT); Condensed Matter; In-situ; Materials Science; Outgassing; Oxide Disperssion Strenghened (ODS) steel; Physics; Precipitation; Small Angle XRay Scattering (SAXS); Atom Probe Tomography (APT); Outgassing; Small Angle XRay Scattering (SAXS); Precipitation; Oxide Disperssion Strenghened (ODS) steel; In-situ
• ISSN: 2352-4928; 2352-4928
• DOI: 10.1016/j.mtcomm.2022.104929

Oxide Dispersion Strengthened (ODS) steels are studied for their application in fission and fusion nuclear power plants. These steels are processed by powder metallurgy involving a high energy milling of Fe-Cr with oxides powders, followed by outgassing and hot consolidation. The temperature increase during these last two stages triggers the precipitation of a fine dispersion of nano-oxides. The outgassing stage is generally conducted at temperature between 300 and 800 °C for several hours, which can already trigger the formation of nano-oxides, and thus may have an influence on the final nano-oxide characteristics. In this work we assess the nano-oxides size by Small Angle X-Ray Scattering (SAXS) and get insight on the nano-oxides chemical and structural properties by comparison between SAXS and Atom Probe Tomography (APT) during a thermal treatment at 700 °C for 5 h, simulating the outgassing stage. We show that despite that the nano-oxides slightly grow during the 700 °C heating, the final properties of the nano-oxides in term of size and number density are extremely close to those where no 700 °C isothermal was applied. Moreover, the growth rate of the nano-oxides is surprisingly higher at 700 °C than 1100 °C. APT and SAXS comparison shows that the nano-oxides do not stabilize in terms of stoichiometry and structure in the studied conditions, and that a small quantity of Al remain in the precipitates during this 700 °C isothermal treatment. Both of these factors could influence the nano-oxides kinetics at low temperature. [Display omitted] •The outgassing shows no influence on the final nano-oxides size and number density.•No stabilization of the nano-oxides is observed at 700 °C after 5 h isothermal.•The nano-oxides growth rate is surprisingly higher at 700 °C than at 1100 °C.•Nano-oxides contain Al on the 700 °C isothermal, which is removed after heating at 1100 °C.•TiC or Ti(C,N) is likely to form after the outgassing, between 700 and 1100 °C.