Ion-induced swelling of ODS ferritic alloy MA957 tubing to 500 dpa

Abstract

In order to study the potential swelling behavior of the ODS ferritic alloy MA957 at very high dpa levels, specimens were prepared from pressurized tubes that were unirradiated archives of tubes previously irradiated in FFTF to doses as high at 110 dpa. These unirradiated specimens were irradiated with 1.8 MeV Cr+ ions to doses ranging from 100 to 500 dpa and examined by transmission electron microscopy. No coinjection of helium or hydrogen was employed. It was shown that compared to several ferritic/martensitic steels irradiated in the same facility, these tubes were rather resistant to void swelling, reaching a maximum value of only 4.5% at 500 dpa and 450°C. In this fine-grained material, the distribution of swelling was strongly influenced by the presence of void denuded zones along the grain boundaries.

Impact of friction stir welding on the microstructure of ODS steel

“…6 shows a relatively good correlation between the measured average grain size and the values derived using Eq. (6). This implies that the oxide dispersion strongly influences the grain size in the matrix, by acting as pinning particles for grain boundaries.…”

“…Their attractiveness as structural materials for future nuclear energy systems lies in their enhanced high-temperature strength and creep resistance, which allows to extend the high-temperature safe limit of reactor operation beyond the value of ∼600°C characteristic of ferritic/martensitic steels [4], coupled to their high resistance to the expected neutron doses potentially beyond 100 dpa [5,6]. ODS steels are Fe-Cr based materials that contain a high density of yttrium-based oxide particles, of only a few nm in size, embedded in the ferritic matrix [7,8].…”

Oxide Dispersion Strengthened Steels for Advanced Blanket Systems

“…The HT-9 tempered martensitic steel shows good resistance to swelling up to 400 dpa, then shows a rapid increase in swelling at the similar rate with EP-450. The swelling of MA957, however, is still small even after the irradiation up to 500 dpa, which is considered to be due to large trapping capacity of defects in the microstructures of the ODS steel, such as fine oxide particles, grain boundaries and dislocations [50].…”

“…Void swelling behavior up to several hundreds dpa was investigated by Toroczko et al with use of a van de Graf electrostatic accelerator of heavy ions with an external injector of 1.8 MeV Cr 3+ ions [50]. Three different steels were irradiated: HT-9 and MA957 at 450 • C, and 480 • C for EP-450 (Fig.…”

Applications of Transient Grating Spectroscopy to Radiation Materials Science

“…Data on swelling of ferrite and sorbite grains, showing bilinear and exponential fitting curves drawn to explain the data 53. In situ TG analysis could fill in gaps in this data, helping to explain which, if any, proposed models and mechanisms are most valid.…”