Ion irradiation effect on the microstructure of Inconel 625 obtained by Selective Laser Melting and by the metallurgical process

Materials obtained by Selective Laser Melting (SLM) technique have been shown to possess a slightly different structure than those produced by the metallurgical process. Alloys from the Inconel superalloy group are used in reactors as tight fitting fuel channel annulus spacer. In this paper we undertook to compare the structural and mechanical changes of nickel superalloys induced by ion irradiation, in particular for Inconel 625 obtained by SLM technique and Inconel 625 obtained by the metallurgical process, which has never been examined prior to this study. Ion irradiation was used in order to simulate the influence of neutron irradiation on the mechanical and structural properties in the Inconel 625. The ion implantation took place at room temperature using Ni+ ions with an energy of 1.6 MeV, and fluences varying from 3E13 ions/cm(2) to 6E14 ions/cm(2), which corresponds to 0.1 dpa and 3.0 dpa, respectively. The SLM manufactured samples show a strong drop in nanohardness for 1.0 dpa and an increase in hardness for 3.0 dpa. The nanohardness at 3.0 dpa is the same as in the unirradiated case for the SLM manufactured Inconel 625. But for the Inconel 625 manufactured by the metallurgical process, nanohardness decreased gradually as the fluence increased. Microscopy and elemental analysis characterization of both samples show clear microstructural changes depend on manufactured process. The Inconel 625 manufactured by the metallurgical process consists of one phase characterized by regular micrograins. In turn, in the sample of Inconel 625 made by SLM technique, we observed a dendritic structure, with an interdendritic second phase and with globular precipitates of nanometric size, which also possesses notably higher dislocation density. The results show that Inconel 625 alloy manufactured by the metallurgical process exhibits higher irradiation resistant.