Effect of the Process Gas and Scan Speed on the Properties and Productivity of Thin 316L Structures Produced by Laser-Powder Bed Fusion

Pauzon, Camille Nicole Géraldine; Leicht, Alexander; Klement, Uta; Forêt, Pierre; Hryha, Eduard

doi:10.1007/s11661-020-05923-w

Cited by 23 publications

(14 citation statements)

References 44 publications

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“…The Vickers microhardness results for samples fabricated with both PSDs and protective atmospheres are shown in Figure 7 c. The Vickers microhardness of the samples fabricated from the bimodal powder feedstock is observed to be 10% higher than those from the unimodal one, regardless of the protective atmosphere, which is also mentioned in [ 38 ]. Moreover, for bimodal powder, the average Vickers microhardness of the printed samples processed in the nitrogen was slightly higher than that for samples processed in the argon, which is in agreement with the results obtained in [ 15 ].…”

Section: Resultssupporting

confidence: 91%

“…Based on the average cell size estimated from the SEM images, the samples fabricated from the bimodal powder have a smaller cell spacing ( Figure 9 ). This finding can be attributed to higher cooling rates [ 40 ] and the presence of nitrogen in the powder feedstock [ 15 ]. Thus, according to the Hall–Petch relation, the Vickers microhardness of 3D-printed samples from the bimodal powder is observed to be higher ( Figure 7 c).…”

Section: Resultsmentioning

confidence: 99%

“…For instance, McGeary et al [13] revealed that a 1:7 particle size ratio leads to the optimal packing density. The protective atmosphere (or shielding gas) and its pressure during printing also have a critical influence on the material [14,15]. It is well-known that inert atmospheres, such as argon, nitrogen, and helium, are applicable for L-PBF.…”

Section: Introductionmentioning

confidence: 99%

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Hardening of Additive Manufactured 316L Stainless Steel by Using Bimodal Powder Containing Nanoscale Fraction

et al. 2020

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The particle size distribution significantly affects the material properties of the additively manufactured parts. In this work, the influence of bimodal powder containing nano- and micro-scale particles on microstructure and materials properties is studied. Moreover, to study the effect of the protective atmosphere, the test samples were additively manufactured from 316L stainless steel powder in argon and nitrogen. The samples fabricated from the bimodal powder demonstrate a finer subgrain structure, regardless of protective atmospheres and an increase in the Vickers microhardness, which is in accordance with the Hall-Petch relation. The porosity analysis revealed the deterioration in the quality of as-built parts due to the poor powder flowability. The surface roughness of fabricated samples was the same regardless of the powder feedstock materials used and protective atmospheres. The results suggest that the improvement of mechanical properties is achieved by adding a nano-dispersed fraction, which dramatically increases the total surface area, thereby contributing to the nitrogen absorption by the material.

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Section: Resultssupporting

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hardening of Additive Manufactured 316L Stainless Steel by Using Bimodal Powder Containing Nanoscale Fraction

et al. 2020

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“…The as-built material appears to have the same nitrogen content as the virgin powder. And a slight oxygen decrease of about 30 ppm (10%) is noted from the powder to the cylinder, which is consistent with previously reported trend for 316L stainless steel [20,21]. This oxygen loss was attributed to the partial removal of surface bound oxygen during melting and oxygen removal by the process gas and spatter particles.…”

Section: Resultssupporting

confidence: 90%

Oxygen Balance During Laser Powder Bed Fusion of Alloy 718

et al. 2021

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The generation of spatters during laser powder bed fusion (L-PBF) of Alloy 718 is known to be detrimental for the re-use of the feedstock powder and the quality of the final product. In this study, dedicated powder sampling from different positions within the build chamber and powder bed was performed. The results clearly indicate the importance of the surface-to-volume ratio of the built components on powder degradation, as demonstrated by the analysis of the powder using capsules filled with dense lattice structures. Extensive formation of Al-and Cr-rich oxides on the entrained powder deposited on the gas inlet and outlet was detected. Significant oxygen pick-up by spatter particles compared to the virgin powder was measured (>300 ppm O 2 ); while the as-built material experienced a slight loss (~30 ppm O 2 ). The change in the microstructure of spatter particles in comparison to the virgin powder, namely the primary dendrite arm spacing, indicates significantly higher cooling rate during spatter solidification, estimated to be of about 10 8 K/s, compared to around 10 6 K/s for the virgin powder and 10 7 K/s for the L-PBF component. These findings allows to evaluate the extent of powder degradation during L-PBF and establish the oxygen balance of the process.

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“…These investigations highlight the sensitivity of Alloy 718 powder to the AM process conditions and particularly to the residual oxygen. It has already been established that the properties of alloys such as Ti-6Al-4V, which is characterised by higher sensitivity to oxygen and known to be prone to oxygen dissolution, are very strongly impaired when produced by L-PBF if the residual oxygen is not monitored properly [14,15], while other alloys such as 316L stainless steel are more robust in this respect [16,17]. This underlines the importance of the analysis of the sensitivity of specific alloys to oxygen and nitrogen pick-up and hence powder degradation, and its effect on defect characteristics and the final mechanical properties of as-built material.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Process Atmosphere Composition on Alloy 718 Produced by Laser Powder Bed Fusion

Pauzon

Markström²,

Goff

et al. 2021

Metals

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The detrimental effect of nitrogen and oxygen when it comes to the precipitation of the strengthening γ’’ and γ’ phases in Alloy 718 is well-known from traditional manufacturing. Hence, the influence of the two processing atmospheres, namely argon and nitrogen, during the laser powder bed fusion (L-PBF) of Alloy 718 parts was studied. Regardless of the gas type, considerable losses of both oxygen of about 150 ppm O2 (≈30%) and nitrogen on the level of around 400 ppm N2 (≈25%) were measured in comparison to the feedstock powder. The utilization of nitrogen as processing atmosphere led to a slightly higher nitrogen content in the as-built material—about 50 ppm—compared to the argon atmosphere. The presence of the stable nitrides and Al-rich oxides observed in the as-built material was related to the transfer of these inclusions from the nitrogen atomized powder feedstock to the components. This was confirmed by dedicated analysis of the powder feedstock and supported by thermodynamic and kinetic calculations. Rapid cooling rates were held responsible for the limited nitrogen pick-up. Oxide dissociation during laser–powder interaction, metal vaporization followed by oxidation and spatter generation, and their removal by processing atmosphere are the factors describing an important oxygen loss during L-PBF. In addition, the reduction of the oxygen level in the process atmosphere from 500 to 50 ppm resulted in the reduction in the oxygen level in as-built component by about 5%.

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Effect of the Process Gas and Scan Speed on the Properties and Productivity of Thin 316L Structures Produced by Laser-Powder Bed Fusion

Cited by 23 publications

References 44 publications

Hardening of Additive Manufactured 316L Stainless Steel by Using Bimodal Powder Containing Nanoscale Fraction

Hardening of Additive Manufactured 316L Stainless Steel by Using Bimodal Powder Containing Nanoscale Fraction

Oxygen Balance During Laser Powder Bed Fusion of Alloy 718

Effect of the Process Atmosphere Composition on Alloy 718 Produced by Laser Powder Bed Fusion

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