scholarly journals Oxide Evolution During the Solidification of 316L Stainless Steel from Additive Manufacturing Powders with Different Oxygen Contents

2021 ◽  
Author(s):  
Xinliang Yang ◽  
Fengzai Tang ◽  
Xinjiang Hao ◽  
Zushu Li
Keyword(s):  
Stainless Steel ◽  
Additive Manufacturing ◽  
316L Stainless Steel ◽  
Surface Oxidation ◽  
Advanced Characterization ◽  
Phase Identification ◽  
Powder Materials ◽  
Lower Oxygen ◽  
Oxide Phases ◽  
Powder Fusion

AbstractThe oxide evolution during the solidification of 316L stainless steel from additive manufacturing powders with different oxygen contents is studied by in situ observation of the melting and solidification of the powder materials, advanced characterization of the solidified materials, and non-equilibrium thermodynamic analysis. An oxide evolution map is established for the 316L powders with different oxygen contents. It reveals the relationship between the surface oxidation in the reused powder and its expected oxide species and morphology in the as-solidified component. For the 316L powder with oxygen content higher than ~ 0.039 pct, the liquid oxide formed first from the steel melt and then crystallized to certain oxide phases during solidification, while for the powder with lower oxygen, oxide phases are suggested to directly form from the steel melt. The oxide species in the as-solidified sample was predicted by the Scheil–Gulliver cooling calculation and verified by the TEM-based phase identification. The oxides formed in the melt of low O 316L alloy (0.0355 pct O) are predicted to be (Mn, Cr)Cr2O4 spinel and SiO2 oxide. In the high O (0.4814 pct O) 316L melt solidification, the final oxides formed are (Mn, Cr)Cr2O4 spinel, SiO2 oxide, and Cr2O3 corundum. As an important characteristic of powder materials, the oxygen pick-up due to the powder surface oxidation significantly influences the inclusion evolution in the powder fusion process.

scholarly journals Effect of Surface Oxides on the Melting and Solidification of 316L Stainless Steel Powder for Additive Manufacturing

2021 ◽  
Author(s):  
Xinliang Yang ◽  
Feng Gao ◽  
Fengzai Tang ◽  
Xinjiang Hao ◽  
Zushu Li
Keyword(s):  
Stainless Steel ◽  
Additive Manufacturing ◽  
Service Life ◽  
Aspect Ratio ◽  
Oxidation Reaction ◽  
316L Stainless Steel ◽  
Surface Oxidation ◽  
High Oxygen ◽  
Solidification Behavior ◽  
Melting And Solidification

AbstractSurface oxidation of metallic powders may significantly affect their melting and solidification behavior and limit their service life in the additive manufacturing (AM) process. In the present work, three levels of surface oxide concentration were prepared on AM-grade 316L stainless steel powders, and their melting and solidification behavior was systematically studied through in-situ observation, advanced characterization, phase-field modeling, and theoretical analysis. Si, Mn, and Cr participated in the oxidation reaction in powder with low and medium oxygen contents, whereas Fe was involved in the oxidation reaction for the powder samples with high oxygen content. A higher full melting temperature is observed to lead to an integrated melt pool in the melting of the highly oxidized powder, which is due to the reduced permeability produced by the oxide cage effect. For the droplet samples prepared from high oxygen powders, the inclusion with increased volume fraction and coarsened size is attributed to the agglomeration of inclusion particles with the residual oxide in the melt. In the high oxygen powder fusion scenario, an undesired coarse columnar grain structure with a high aspect ratio is formed in the current nonequilibrium solidification process, and a consistent microstructure is predicted using solidification conditions with a high cooling rate and high thermal gradient similar to the conventional AM process. In contrast, fine equiaxed grains in the experiment and slim columnar grains with a small aspect ratio in the phase-field simulation are obtained for the low oxygen powder condition. This study illustrates the effect of powder oxide from a processing aspect and provides insight into the importance of improving the service life of powder feedstock by effectively reducing the surface oxidation process on the powder surface.

scholarly journals Advanced Characterization of Additively Manufactured 316L Stainless Steel for Nuclear Applications

2021 ◽  
Vol 27 (S1) ◽  
pp. 2160-2161
Author(s):  
Lingfeng He ◽  
Laura Hawkins ◽  
Jingfan Yang ◽  
Xiang Liu ◽  
Miao Song ◽  
...  
Keyword(s):  
Stainless Steel ◽  
316L Stainless Steel ◽  
Advanced Characterization ◽  
Nuclear Applications

Effects of Powder Characteristics on Selective Laser Melting of 316L Stainless Steel Powder

2011 ◽  
Vol 189-193 ◽  
pp. 3664-3667 ◽  
Author(s):  
Sheng Zhang ◽  
Qing Song Wei ◽  
Guang Ke Lin ◽  
Xiao Zhao ◽  
Yu Sheng Shi
Keyword(s):  
Stainless Steel ◽  
Selective Laser Melting ◽  
316L Stainless Steel ◽  
Fine Powder ◽  
Steel Powder ◽  
Laser Melting ◽  
Broad Size Distribution ◽  
Lower Oxygen ◽  
Powder Characteristics ◽  
Loose Powder

316L stainless steel parts were manufactured via selective laser melting . This work stu- dies the effects of powder characteristics such as particle size and particle shape composition on the density. It shows that the powder with a broad size distribution and using spherical fine powder can lead to an increase in the density of the loose powder and thus the densification of the laser melted powder. The aerosol powder forms parts of lower oxygen content well, and the density can reach to 90%.

Effect of contaminations on the acoustic emissions during wire and arc additive manufacturing of 316L stainless steel

2021 ◽  
pp. 102585
Author(s):  
André Ramalho ◽  
Telmo G. Santos ◽  
Ben Bevans ◽  
Ziyad Smoqi ◽  
Prahalad Rao ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Additive Manufacturing ◽  
316L Stainless Steel ◽  
Acoustic Emissions

scholarly journals A Comparative Study of the CMT+P Process on 316L Stainless Steel Additive Manufacturing

2020 ◽  
Vol 10 (9) ◽  
pp. 3284 ◽  
Author(s):  
Bin Xie ◽  
Jiaxiang Xue ◽  
Xianghui Ren ◽  
Wei Wu ◽  
Zhuangbin Lin
Keyword(s):  
Tensile Strength ◽  
Stainless Steel ◽  
Additive Manufacturing ◽  
Tensile Test ◽  
Heat Dissipation ◽  
316L Stainless Steel ◽  
Single Channel ◽  
Steel Wire ◽  
Energy Dispersive Spectrometer ◽  
Test Method

Adopting the cold metal transfer plus pulse (CMT + P) process, 316L stainless steel wire was treated with a single channel multi-layer deposition experiment under different linear energy. The microstructures of different regions on the deposited samples were observed by optical microscope and scanning electron microscope, and the element distribution in the structure was analyzed by energy dispersive spectrometer. The mechanical properties and microhardness were measured by tensile test method and microhardness tester, respectively, and the anisotropy of tensile strength in horizontal and vertical directions were calculated. Finally, the fracture morphology of the tensile samples were observed by SEM. Experiment results showed that when the difference between the actual and the optimal wire feeding speed matching the specific welding speed was too large, this led to an unstable deposition process as well as flow and collapse of weld bead metal, thus seriously deteriorating the appearance of the deposition samples. The results from metallographic micrograph showed that rapid heat dissipation of the substrate caused small grains to generate in the bottom region of deposition samples, then gradually grew up to coarse dendrites along the building direction in the middle and top region caused by the continuous heat accumulation during deposition. Tensile test results showed that with the increase of linear energy, the horizontal and vertical tensile strength of the as-deposited samples decreased. In addition, the higher linear energy would deteriorate the microstructure of as-deposited parts, including significantly increasing the tendency of oxidation and material stripping. The microhardness values of the bottom, middle and top regions of the samples fluctuated along the centerline of the cross-section, and the values showed a trend of decreasing first and then rising along the building direction. Meanwhile, the yield strength and tensile strength of each specimen showed obvious anisotropy due to unique grain growth morphology. On the whole, the results from this study prove that CMT+P process is a feasible MIG welding additive manufacturing method for 316L stainless steel.

scholarly journals On the Microstructures and Fatigue Behaviors of 316L Stainless Steel Metal Injection Molded with Gas- and Water-Atomized Powders

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 893 ◽  
Author(s):  
Yongyun Zhang ◽  
Ensheng Feng ◽  
Wei Mo ◽  
Yonghu Lv ◽  
Rui Ma ◽  
...  
Keyword(s):  
Stainless Steel ◽  
316L Stainless Steel ◽  
Fatigue Cracks ◽  
Selective Laser Sintering ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Metal Injection Molding ◽  
Strengthening Effect ◽  
Lower Oxygen ◽  
Order Of Magnitude

316L stainless steel samples are fabricated by metal injection molding using water-atomized and gas-atomized powder with different oxygen contents. The influences of oxygen on the microstructural evolution and fatigue properties of the samples are investigated. The oxygen tends to react with Mn and Si to form oxide particles during sintering. The oxides hamper the densification process and result in decreased sintered density. Moreover, their existence reduces the Mn and Si dissolving into the base metal and compromises the solution strengthening effect. The oxides lead to stress concentration in the tensile and fatigue tests and become the initiation sites of fatigue cracks. After sintering, the samples made from the gas-atomized powder have a much lower oxygen content compared to those made from the water-atomized powder, therefore, exhibiting much better mechanical properties. The tensile strength, yield strength and the elongation of the samples made from the gas-atomized powder are 560 MPa, 205 MPa, and 58%, respectively. Their fatigue lives are about one order of magnitude longer than the samples made from water-atomized powder, and also longer than those fabricated by powder metallurgy and selective laser sintering which were reported in other studies.

scholarly journals Effect of Powder Feedstock on Microstructure and Mechanical Properties of the 316L Stainless Steel Fabricated by Selective Laser Melting

Metals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 729 ◽  
Author(s):  
Wei Chen ◽  
Guangfu Yin ◽  
Zai Feng ◽  
Xiaoming Liao
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Additive Manufacturing ◽  
Selective Laser Melting ◽  
316L Stainless Steel ◽  
Hierarchical Structures ◽  
Fine Powder ◽  
Tensile Tests ◽  
Laser Melting ◽  
Powder Feedstock

Additive manufacturing by selective laser melting (SLM) was used to investigate the effect of powder feedstock on 316L stainless steel properties include microstructure, relative density, microhardness and mechanical properties. Gas atomized SS316L powders of three different particle size distribution were used in this study. Microstructural investigations were done by scanning electron microscopy (SEM). Tensile tests were performed at room temperatures. Microstructure characterization revealed the presence of hierarchical structures consisting of solidified melt pools, columnar grains and multiform shaped sub-grains. The results showed that the SLM sample from the fine powder obtained the highest mechanical properties with ultimate tensile strength (UTS) of 611.9 ± 9.4 MPa and yield strength (YS) of 519.1 ± 5.9 MPa, and an attendant elongation (EL) of 14.6 ± 1.9%, and a maximum of 97.92 ± 0.13% and a high microhardness 291 ± 6 HV0.1. It has been verified that the fine powder (~16 μm) could be used in additive manufacturing with proper printing parameters.

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