Mechanistic understanding of the localized corrosion behavior of laser powder bed fused 316L stainless steel in pressurized water reactor primary water

• DOI: 10.1016/j.scriptamat.2023.115764
• Publication Date: 2023-09-16T21:40:23Z
• Authors: Yanling Ge; Litao Chang; Martin Bojinov; Timo Saario; Zaiqing Que
• Keywords: Austenitic stainless steel; 7. Clean energy; 6. Clean water; Localized corrosion; Laser powder bed fusion; 0103 physical sciences; and Infrastructure; Cellular structure; Innovation; ta216; 0210 nano-technology; SDG 9 - Industry; High-temperature water

The laser powder bed fused (LPBFed) stainless steels showed anomalous and localized corrosion behavior in the nuclear reactor high-temperature water compared to their wrought counterparts, which affects their performance during plant operation. In this study, advanced microstructural characterization was performed on LPBFed 316 L sample along with wrought 316 L sample after corrosion tests to understand the underlying mechanisms. The results showed that an inhomogeneous/discontinuous inner oxide layer formed on LPBFed 316 L, in contrast to the continuous inner oxide layer on the wrought 316 L specimen. This discontinuous inner oxide layer was identified to consist of Cr-enriched nano-sized spinel oxide and the barrier layer features a Ni-enriched hexagonal close-packed Laves phase. Localized/preferential oxidation was found to occur along the cellular walls which were tangled with high density dislocations and decorated with Mn and Si-enriched nano-sized precipitates, and the nano-precipitates were observed in the core of dispersed Cr-enriched inner oxide crystals.