Effect of Helium on Grain Boundary Segregation of Austenitic Stainless Steel After Proton Irradiation

In ITER, austenitic stainless steels are under consideration as a blanket structural material for temperature below 200°C. Transmuted helium will be also produced in austenitic stainless steels by high-energy neutron irradiation, and it will affect microstructural development including grain boundary segregation. In this paper, the effects of helium on grain boundary segregation in austenitic stainless steels are studied using ion-irradiation experiment.

The result showed that the onset of radiation induced segregation (RIS) by proton irradiation occurs somewhere between 0.1 and 0.5 dpa. Helium pre-implantation significantly reduced RIS of the major alloying elements. Mechanisms are discussed. Comparison of this result with neutron irradiated induced segregation showed qualitative agreement in the data trends. However, a large amount of segregation was observed in the proton irradiated 304 austenitic stainless steels specimens.