Investigations on Inconel 718 irradiated with 800 MeV protons

In spallation sources, the neutrons (utilized as probes for condensed matter research or for inducing nuclear transmutations) are generated by protons of around 1 GeV energy which cause spallation of the nuclei in a heavy metal target. The beam powers of the proposed future facilities are in the range of 1 to several 10 MW and the corresponding high particle fluxes make radiation damage the crucial effect for the lifetime of target structural materials in or close to the proton beam. In order to establish a database on spallation-relevant radiation effects, post-irradiation investigations of components of spent targets from operating medium power sources are being performed. Here we report first results on Inconel 718 irradiated in LAMPF up to a fluence of 3 × 10²⁵ p/m². Microhardness and bending tests together with SEM and TEM investigations show a considerable degradation of the mechanical properties of the material requiring additional highly controlled tests, now underway, to determine fracture toughness and tensile properties as a function of dose.