Effect of heat treatment on the microstructure and corrosion resistance of laser powder bed fusion ODS-316L

As a candidate cladding material for fourth-generation nuclear energy systems, the microstructure and properties of oxide dispersion strengthened 316L (ODS-316L) steel are significantly affected by heat treatment (HT) processes. This paper highlights the influence mechanism of HT temperature on the microstructural evolution and corrosion resistance of ODS-316L alloys prepared by laser powder bed fusion (LPBF) technology. The results show that HT can significantly regulate the microstructure of ODS-316L alloys. After heat treatment, the ODS-316L alloy consists of a single austenitic phase, indicating no phase transformation occurs before and after heat treatment. With the increase of HT temperature, the fish-scale molten pool morphology characteristic of the as-fabricated ODS-316L alloy disappears, and recrystallized grains coarsen. When the HT temperature reaches 1150 °C, the grain size reaches a maximum of 43.1 μm, the proportion of low-angle grain boundaries (LAGBs) is the highest at 76.7 %, and the Kernel Average Misorientation (KAM) value drops to a minimum of 0.28°. At the HT temperature of 1150 °C, the alloy exhibits excellent corrosion resistance: the self-corrosion potential (Ecorr) reaches a maximum of −0.255 V, the self-corrosion current density (Icorr) decreases to a minimum of 7.797 × 10−7 A/cm2, the pitting potential (Ep) reaches a maximum of 0.632 V, and the passivation interval reaches a maximum of 0.659 V. Moreover, two types of nano-oxide particles, Y–Si–O and Si–O, are uniformly distributed in the 316L matrix heat-treated at 1150 °C, which helps to reduce the self-corrosion current density, thereby improving its corrosion resistance. Furthermore, the correlation between nano-oxides and corrosion resistance is elaborate. This study provides a theoretical basis and reference value for further optimizing the microstructure and corrosion resistance of nuclear-grade ODS-316L alloy components.