Evaluation of Neutron-Irradiated Additively Manufactured Zircaloy-2

Additive manufacturing (AM) is an enabling technology for novel designs and complex shapes that cannot be produced using traditional manufacturing methods. Although AM technologies can produce unique geometries that may offer substantial performance benefits, there are significant technical challenges that require resolution prior to application of AM zirconium alloy components. The objective of this exploratory study was to characterize the mechanical properties of both as-fabricated and neutron-irradiated Zircaloy-2 materials produced using laser powder bed fusion AM. Westinghouse developed additively manufactured Zircaloy-2 material that was subsequently machined into miniature tensile samples by electrical discharge machining. Tensile specimens were inserted into the Massachusetts Institute of Technology test reactor for irradiation using prototypical pressurized water reactor conditions for a planned maximum exposure of 3 dpa. Post-irradiation examinations were performed on tensile specimens with 0.9 dpa and 1.6 dpa exposures. The effects of AM processing on material properties such as hardness, tensile strength, and ductility were investigated. Comparisons between conventional Zircaloy-2 material and as-fabricated AM miniature tensile specimens were performed. Additional characterization of AM material was also completed, including microstructure, microhardness, texture, and corrosion. The limiting property for implementation of as-fabricated AM zirconium in light water reactors is corrosion. A high-temperature alpha anneal of AM Zircaloy-2 material resulted in recrystallization of the as-fabricated AM martensitic microstructure. In addition, the corrosion performance of the recrystallized AM was comparable to the corrosion of conventionally processed Zircaloy-2 plate as assessed by short-term corrosion testing. While further development is required, the potential now exists for utilizing AM zirconium components in light water reactors.