Microstructural damage and hardening behavior of multi-laser powder bed fusion 316L SS irradiated with Xe ions

Xe ion irradiation was carried out to investigate the differences in microstructural damage and hardening behavior in ML-PBF 316L stainless steel (SS) between single laser forming zone and overlap zone at room-temperature (RT) and 700 °C. The results showed that both zones exhibited irradiation hardening saturation at RT and 700 °C while the overlap zone exhibited lower irradiation hardening degree. Notable irradiation swelling was observed in both zones at RT, with the overlap zone displaying a moderately lower swelling rate. No phase transformations were confirmed via GIXRD, although slight shifts in the diffraction peaks were found. Furthermore, TEM observations demonstrated that after RT irradiation, the average diameters of dislocation loops in the single laser forming zone and overlap zone were 10.2 nm and 12.5 nm, with corresponding average densities of 6.2 × 10 22 m -3 and 5.7 × 10 22 m -3 , respectively. The average sizes of the Xe bubbles in the single laser forming zone and overlap zone after 700 °C irradiation were 6.5 nm and 7.2 nm, respectively, with corresponding average densities of 5.2 × 10 22 m -3 and 3.7 × 10 22 m -3 . According to calculations using the dispersed barrier hardening (DBH) model, the dislocation loops induced by RT irradiation and Xe bubbles generated at 700 °C irradiation were identified as the dominant factors governing the irradiation hardening response. These findings provided critical insights into the irradiation damage mechanisms of ML-PBF 316L SS, thereby offering guidance for ML-PBF process in the fabrication of large-scale nuclear components.