Mechanical Properties and Deformation Behavior of Additively Manufactured 316L Stainless Steel (FY2020)

Byun, Thak Sang; Gussev, Maxim N.; Mcalister, Michael; Simpson, J.; Garrison, Ben; Yamamoto, Yukinori; Joslin, Chase; Carver, Keith; List, F.A.; Dehoff, Ryan R.; Terrani, Kurt A.; Li, Meimei; Zhang, Xuan

doi:10.2172/1649091

Cited by 4 publications

(8 citation statements)

References 17 publications

(25 reference statements)

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“…There are often relatively smaller grains or grain groups between the clusters of larger crescent-shaped grains. Neither the postbuild annealing treatment at 650°C nor the postbuild annealing treatment at 1,050°C caused the apparent grain growth; the average intercept lengths of grain boundaries were measured at 13-15 µm for all three AM 316L conditions [10]. Figure 3 confirms that the grain structures of the AM steels are different from those of the WT 316L steel, which has much larger (~47 µm on average) and equiaxial grains with many straight grain or twin boundaries.…”

Section: Initial Microstructures Of Am and Wt 316l Stainless Steelsmentioning

confidence: 74%

“…Recent research efforts confirmed that austenitic SSs are highly suitable for additive manufacturing of complex shaped reactor components [8][9][10][11]. This is likely because the fast cooling that occurs during the AM process prevents the formation of the high-temperature ferrite (i.e., δ-ferrite) phase during cooling, which is metastable and undergoes degradation at high temperatures caused by phase decomposition and segregation.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, AM material properties can be tailored by changing processing parameters, such as scan speed, laser power, powder feedstock purity, and powder layer thickness [12][13][14]. In particular, the size and orientation of the fine-grained dislocation cell structure in metallic materials can be easily controlled by changing processing parameters [10,[15][16][17] or applying postbuild heat treatments [13]. However, because the LPBF process usually produces a very fine but metastable microstructure due to fast cooling in solidification, there are still many unknowns and adverse effects regarding the microstructural and chemical stability of AM materials in high-temperature, corrosion, and irradiation environments.…”

Section: Introductionmentioning

confidence: 99%

“…The as-printed materials were observed to have increased room temperature (RT) yield strength (YS) but less work hardening because of a characteristic microstructure of fine grains and dislocation cells formed during the localized rapid solidification [15,[18][19][20]. Recent test results indicate that these fine-grained structures with mobile dislocations can shorten the high-temperature creep life [8,10,21]. Furthermore, the fracture toughness of AM 316L SS could be negatively affected by the increased porosity from the build process, structural anisotropy relative to the build direction, and inclusions from impurities in the feedstock powder [12,22].…”

Section: Introductionmentioning

confidence: 99%

“…The extensive knowledge of conventionally manufactured 316L SS combined with the well-established AM processing route makes the 316L alloy an ideal core structural material for TCR. Therefore, the main metallic components that constitute the TCR core structures will be the 316L SS parts printed via the LPBF process [8,10].…”

Section: Introductionmentioning

confidence: 99%

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Mechanical Properties of Additively Manufactured 316L Stainless Steel Before and After Neutron Irradiation (FY21)

Collins¹,

Coq²,

Linton³

et al. 2021

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This report presents the materials property data of additively manufactured (AM) 316L stainless steel (SS) accumulated for the assessment of core materials in the Transformational Challenge Reactor (TCR) program. The TCR manufacturing approach includes using the laser powder bed fusion (LPBF) method for metallic (316L and Inconel 718) components. To assess the mechanical performance of printed components in reactor-relevant conditions and build a property database for the AM materials, mechanical tests and evaluations were performed before and after neutron irradiation. Miniature tensile specimens were irradiated in the High Flux Isotope Reactor to 0.2, 2, 8, and 10 dpa at target temperatures of 300 and 600°C. Postirradiation evaluation for the 0.2 and 2 dpa specimens was performed during FY20 and FY21, and the results are presented and discussed in this document.To obtain the baseline mechanical property data, uniaxial tension testing over a wide temperature range from room temperature (RT) to 600°C was performed for the same materials that were irradiated, including AM 316L SS in the as-built, stress-relieved, and solution-annealed conditions, as well as reference wrought (WT) 316L SS. Regardless of the postbuild heat treatment, the AM 316L SS showed higher strength than the WT 316L SS, but they had similar ductility. A statistical treatment of RT tensile data indicated that variations in the strength and ductility datasets of AM 316L steels were smaller than or similar to those of WT 316L SS. Additionally, 2D mapping of tensile properties for the stress-relieved AM plates also showed clear location dependence of the properties but with limited magnitudes.Postirradiation tensile testing was conducted at RT, 300, 500, and 600°C for selected irradiation conditions. Additional tests were performed near the measured irradiation temperatures of 260 and 390°C for checking the impact of the difference between the targeted and actual irradiation temperatures. Neutron irradiation induced significant changes in the mechanical behavior of the AM SSs, including hardening and softening. Although the as-built 316L SS tested at 300°C after irradiation to 2 dpa at 390°C showed unstable plastic deformation (i.e., necking) immediately after yielding, the overall property changes of the as-printed alloy became much less significant after higher temperature (610 and 690°C) irradiations or when tested at different temperatures. Irradiation-induced ductilization was also observed in the higher strength materials (i.e., in as-built and stress-relieved conditions) after higher temperature (>600°C) irradiations. The strength change after irradiation was generally smaller in the relatively stronger materials (i.e., the as-built and stress-relieved AM SSs) than in the solution-annealed AM and WT SSs. Overall, these relatively lower strength 316L SSs retained higher ductility in the irradiation conditions tested, but the stronger 316L SSs demonstrated a similar level of ductility after higher temperature irradiations. For the AM 316L mate...

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Section: Initial Microstructures Of Am and Wt 316l Stainless Steelsmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 99%