Impact of neutron irradiation on the thermophysical properties of additively manufactured stainless steel and inconel

This paper presents the initial results of a multi-year irradiation project to evaluate the impact of manufacturing method and neutron irradiation (at doses up to 1.63 displacements per atom) on the heat capacity and thermal diffusivity of Additively Manufactured (AM) stainless steel 316 L, Inconel 718, and Inconel 625 samples at temperatures between 50 °C and 400 °C. When complete, the project will have tested 48 irradiated Laser Flash Analysis (LFA) and 48 irradiated Differential Scanning Calorimetry (DSC) specimens. At the current time, the project has tested 10 irradiated DSC and 11 irradiated LFA specimens. The unirradiated AM specimens have heat capacity values similar to, or lower than, the reference values, regardless of manufacturing method or material. The irradiated AM specimens have average heat capacities greater than the unirradiated specimens and reference values in every case. The thermal diffusivities of the unirradiated AM specimens are either larger or statistically similar to the reference values obtained from materials manufactured in conventional methods. The irradiated AM specimens exhibit lower thermal diffusivities compared to the reference unirradiated thermal diffusivity values. One of the stainless steel 316 L laser powder bed fusion samples exhibited thermal diffusivity values with statistically significant anisotropy prior to and after irradiation.