POSTIRRADIATION TENSILE BEHAVIOR OF NICKEL-DOPED FERRITIC STEELS

Tensile specimens of normalized and tempered 9Cr-1MoVNb, 9Cr-1MoVNb-2Ni, 12Cr-1MoVW, 12Cr-1MoVW-1Ni, and 12Cr-1MoVW-2Ni steels were irradiated in the High-Flux Isotope Reactor (HFIR) at 300, 400, and 500 degree C to displacement damage levels of up to 11 dpa. The nickel was added to the ferritic steels to produce helium by a two-step (n, alpha ) reaction during irradiation. Up to 103 appm He was produced in the steels with 2% Ni. Irradiation at 300 and 400 degree C caused an increase in strength of all steels relative to the strength in both the normalized and tempered condition and after aging the steel for a time period similar to that in the reactor. The strength increases were accompanied by a loss of ductility. At 500 degree C, there was little change in strength properties. The results at 300 and 400 degree C indicate an effect of helium.