IMPROVING RADIATION AND STRESS CORROSION CRACKING RESISTANCE OF AUSTENITIC STAINLESS STEELS BY LASER SHOCK PEENING

Structural alloys for Generation-IV nuclear reactors need to endure a high neutron dose, high temperature, and corrosive coolant. Austenitic stainless steels, particularly the oxide-dispersion-strengthened (ODS) austenitic steels, are promising candidate materials, but they suffer several limits such as irradiation damage and stress corrosion cracking (SCC). This research applies a laser shock peening (LSP) process to improve the radiation and SCC resistance of austenitic stainless steels in simulated nuclear reactor environments. A high density dislocation networks, stacking faults and twin boundaries were generated in the surface region of 304 steels by the shock wave-material interactions in the LSP process. In-situ TEM irradiation experiments suggest that laser-peened 304 steels suffer less radiation damage than the untreated samples because the generated dislocation networks and twin boundaries serve as sinks for the annihilation of irradiation defects. Stress corrosion cracking tests show that transgranular cracks propagate in the untreated 304 steels, while no apparent cracks were observed in laser peened 304 steel samples on the same conditions. Advisor: Bai Cu