Study of the Effect of Thermal Aging on the Nanostructure of Oxide Dispersion-Strengthened Steels by Small-Angle X-Ray Scattering

A large number of oxide particles in dispersion-strengthened alloys and steels provides a significant increase in heat resistance to these materials. For detailed characterization of these nanostructed materials, multiple techniques are used such as transmission electron microscopy (TEM), atom probe tomography (APT), as well as small-angle X-ray and neutron scattering. Small-angle X-ray (SAXS) scattering is useful for analyzing comparatively large volumes of materials combined with an ability to detect phases from few to tens of nanometers in a single measurement. Thermal aging experiments can be used to determine the stability of oxides in dispersion-strengthened alloys and determine their usability in high heat applications. In this work, a stability of three different oxide dispersion-strengthened steels: Eurofer ODS, 10Cr ODS and KP-3 ODS (with different alloying systems) was studied using SAXS in the initial state and after thermal aging at 650°C up to 1000 h. To achieve most accurate results from SAXS analysis, a combination of TEM and APT was used to get proper parameters for correct data processing. The results of SAXS and TEM showed a good correlation in the oxides in the initial state of the steels. However, no cluster data was acquired from SAXS due to their relatively small contrast. According to SAXS results, there is no oxide dissolution present under thermal aging at 650°C up to 1000 h; meanwhile there is evidence of increase of number of oxides in KP-3 ODS due to the interaction between oxide and cluster subsystems.