Kinetics of the radiation-induced hardening of EP-823 steel after Ni++ ion irradiation, annealing, and re-irradiation

The ferritic-martensitic steel 12Cr-MoWSiVNbB (EP-823) was irradiated with Ni⁺⁺ ions with the energy 7 MeV, and fluences of 2.7 × 10²⁰ and 3.9 × 10²⁰ ion/m² at 380 C. The irradiated samples were annealed at 600°C and then re-irradiated under the same conditions. After re-irradiation, the microhardness increased to the maximum value and achieved about 70% of the value corresponding to that after primary irradiation. After primary and secondary irradiation with increasing doses, the hardening reaches its saturation level at approximately similar damaging doses and behaves similar to that obtained in the case of the neutron irradiation of ferritic chromium steels.