Effects of Heat Treatment and Fast Neutron Irradiation on the Microstructure and Microhardness of Inconel 625 Fabricated via Laser-Powder Bed Fusion

The microstructure of Inconel 625 fabricated via Laser-Powder Bed Fusion (L-PBF) was investigated in as-printed and heat-treated conditions. The very high cooling rates inherent to the L-PBF process generally result in fine microstructures and complex residual stress fields which requires annealing to reduce stress and tailor the microstructure to obtain the desired mechanical properties. Inconel 625 alloy, a nickel-based superalloy, continues to be a common material employed with the L-PBF process. The unique microstructure produced by the L-PBF process and different phases introduced by different heat treatment processes require investigation to facilitate the material’s wide range of applications. This paper investigates the influence of heat treatments at 700°C, 900°C and 1050°C for one hour on the microstructure and microhardness of the L-PBF parts. The parts were irradiated using ‘fast’ neutrons in University of Missouri Research Reactor Center (MURR). The microhardness before and after radiation are also compared.