TY - THES

T1 - Characterisation of ion irradiated ferritic/martensitic materials for nuclear application

AU - Vieh, Christiane

N1 - embargoed until null

PY - 2010

Y1 - 2010

N2 - In order to increase the efficiency of a next generation reactor, designers require higher reactor operation temperatures and higher fuel burn-up which leads to a higher dose on the material. Ion beam accelerator experiments using low ion energy, have the advantage of allowing relatively fast and inexpensive irradiations of materials without activating the sample but do not irradiate a large sample volume. In order to mimic reactor and spallation source environment on materials typical ions used are helium and hydrogen. In this study, four different ferritic/martensitic steels (conventional materials e.g.: HT-9 with different micro structure) and Oxide Dispersion Strengthened (ODS) alloys (advanced materials: MA956 and MA957) were exposed to an ion beam and irradiated at different conditions. After ion irradiation these materials were characterized in detail using Atomic Force Microscopy, nanoindentation and Transmission Electron Microscopy. The implantation with Helium at RT, the irradiation with protons at RT, 300°C and 550°C showed a clear change in hardness due to the ion irradiation for the conventional materials but did not show any change in hardness for the advanced materials. An important result of the present study is that a clear difference can be seen in the HT-9 ferritic and tempered martensitic material. It appears that the fine tempered martensitic microstructure has a significant smaller effect in irradiation hardening. Therefore it should be a more radiation tolerant material. This can be explained by the fact that the martensitic microstructure has a high density of interfaces which act as recombination sites for radiation induced defects. The advanced materials did not show an increase in nanohardness compared to the conventional materials under any of those conditions. Therefore, a need to develop techniques to produce these ODS alloys with conventional steel processing technologies as the previous results indicate superior radiation resistance at elevated temperature, exists.

AB - In order to increase the efficiency of a next generation reactor, designers require higher reactor operation temperatures and higher fuel burn-up which leads to a higher dose on the material. Ion beam accelerator experiments using low ion energy, have the advantage of allowing relatively fast and inexpensive irradiations of materials without activating the sample but do not irradiate a large sample volume. In order to mimic reactor and spallation source environment on materials typical ions used are helium and hydrogen. In this study, four different ferritic/martensitic steels (conventional materials e.g.: HT-9 with different micro structure) and Oxide Dispersion Strengthened (ODS) alloys (advanced materials: MA956 and MA957) were exposed to an ion beam and irradiated at different conditions. After ion irradiation these materials were characterized in detail using Atomic Force Microscopy, nanoindentation and Transmission Electron Microscopy. The implantation with Helium at RT, the irradiation with protons at RT, 300°C and 550°C showed a clear change in hardness due to the ion irradiation for the conventional materials but did not show any change in hardness for the advanced materials. An important result of the present study is that a clear difference can be seen in the HT-9 ferritic and tempered martensitic material. It appears that the fine tempered martensitic microstructure has a significant smaller effect in irradiation hardening. Therefore it should be a more radiation tolerant material. This can be explained by the fact that the martensitic microstructure has a high density of interfaces which act as recombination sites for radiation induced defects. The advanced materials did not show an increase in nanohardness compared to the conventional materials under any of those conditions. Therefore, a need to develop techniques to produce these ODS alloys with conventional steel processing technologies as the previous results indicate superior radiation resistance at elevated temperature, exists.

KW - Charakterisierung Bestrahlung Strahlung Werkstoffschädigung ferritische Stähle martensitische Stähle ODS-Legierungen Rasterkraftmikroskopie Transmissionselektronenmikroskopie Nanohärte

KW - characterization irradiation ferritic steel martensitic steel Oxide Dispersion Strengthened Atomic Force Microscopy Transmission Electron Microscopy nanohardness

M3 - Diploma Thesis

ER -