Effect of proton irradiation dose rate and implanted hydrogen ions on spinodal decomposition in thermally aged EQ308L stainless steel weld metal

Abstract

Abstract Stainless steel welds with a ferritic phase are extensively utilized in nuclear power plants. Spinodal decomposition stands as the primary factor contributing to the degradation of their service performance. Ion irradiation has been widely employed to investigate the damage behavior of materials. However, varying irradiation parameters, such as dose rate and implanted ions, are believed to result in significant differences in the extent of spinodal decomposition. In this paper, proton irradiation experiments were conducted at different dose rates on thermally aged EQ308L stainless steel welds. Spinodal decomposition within the ferrite at various radiation depths was compared and analyzed by using atom probe tomography to unveil the effects of dose rate and implanted hydrogen ions. The results reveal that, under conditions of high dose rate irradiation, spinodal decomposition can be partially alleviated when compared to the initial thermally aged state. Conversely, under low dose rate irradiation conditions, spinodal decomposition exhibits an enhancement trend. This difference may be attributed to the interplay between irradiation-enhanced diffusion and atomic mixing. Therefore, the dose rate significantly influences the progression of spinodal decomposition. Furthermore, implanted hydrogen ions may also inhibit spinodal decomposition within the ferrite, potentially by promoting the recombination of irradiation defects.