Qualification of L-DED 316L for nuclear reactor core applications – Material characteristics before and after neutron irradiation

The mechanical and microstructural properties of heat treated laser direct energy deposition (L-DED) fabricated austenitic stainless steel 316L were investigated before and after neutron irradiation in the LVR-15 research reactor dry capsule. Tensile tests were carried out at room temperature and elevated temperature followed by light optical microscopy (LOM) and scanning electron microscopy (SEM) analyses of the microstructure. The results showed that the L-DED material exhibited superior ultimate tensile strength (R_m) and yield strength (Rp_0.2) mainly due to its smaller grain size (approximately 4x smaller), compared to conventionally manufactured steel. Despite promising mechanical properties, microstructure misorientation analyses revealed incomplete recrystallization after heat treatment, which may affect long-term performance under nuclear reactor conditions. However, no notable differences were observed in the material microstructure between conventionally fabricated and L- DED fabricated materials due to neutron radiation. These findings support the potential of not only laser-deposition but also AM in general as a viable technique for producing in-reactor components.