Additive manufacturing of the ferritic stainless steel SS441

Karlsson, Dennis; Chou, Chia-Ying; Pettersson, Niklas; Helander, Thomas; Harlin, Peter; Sahlberg, Martin; Lindwall, Greta; Odqvist, Joakim; Jansson, Ulf

doi:10.1016/j.addma.2020.101580

Cited by 19 publications

(33 citation statements)

References 26 publications

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“…Using the Scheil-Gulliver model, the phases formed under non-equilibrium solidification can be estimated, providing a first indication of the phases expected to be formed during the PBF-LB process [40]. The Scheil-Gulliver model has previously been applied in studies of solidification during welding [42] and PBF-LB processing of other metals [43,44].…”

Section: Introductionmentioning

confidence: 99%

An Enhanced Understanding of the Powder Bed Fusion–Laser Beam Processing of Mg-Y3.9wt%-Nd3wt%-Zr0.5wt% (WE43) Alloy through Thermodynamic Modeling and Experimental Characterization

Åhman

Thorsson²,

Mellin

et al. 2022

Materials

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Powder Bed Fusion–Laser Beam (PBF–LB) processing of magnesium (Mg) alloys is gaining increasing attention due to the possibility of producing complex biodegradable implants for improved healing of large bone defects. However, the understanding of the correlation between the PBF–LB process parameters and the microstructure formed in Mg alloys remains limited. Thus, the purpose of this study was to enhance the understanding of the effect of the PBF–LB process parameters on the microstructure of Mg alloys by investigating the applicability of computational thermodynamic modelling and verifying the results experimentally. Thus, PBF–LB process parameters were optimized for a Mg WE43 alloy (Mg-Y3.9 wt%-Nd3 wt%-Zr0.5 wt%) on a commercially available machine. Two sets of process parameters successfully produced sample densities > 99.4%. Thermodynamic computations based on the Calphad method were employed to predict the phases present in the processed material. Phases experimentally established for both processing parameters included α-Mg, Y2O3, Mg3Nd, Mg24Y5 and hcp-Zr. Phases α-Mg, Mg24Y5 and hcp-Zr were also predicted by the calculations. In conclusion, the extent of the applicability of thermodynamic modeling was shown, and the understanding of the correlation between the PBF–LB process parameters and the formed microstructure was enhanced, thus increasing the viability of the PBF–LB process for Mg alloys.

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Section: Introductionmentioning

confidence: 99%

An Enhanced Understanding of the Powder Bed Fusion–Laser Beam Processing of Mg-Y3.9wt%-Nd3wt%-Zr0.5wt% (WE43) Alloy through Thermodynamic Modeling and Experimental Characterization

Åhman

Thorsson²,

Mellin

et al. 2022

Materials

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“…The used powder particle size distribution was 10 to 45 lm. The studied samples were built using an EOS M100, equipped with a 200 W laser with a spot size of approximately 40 lm, in a flowing argon gas atmosphere, see previous work by Karlsson et al [12] The cylindrical samples were vertically built (0 deg) with a laser power of 130 W, a scanning speed of 1000 mm/s, a hatch distance of 0.07 mm and layer thickness of 0.02 mm, resulting in a laser energy density of 92.6 J/mm 3 . The scanning strategy of each layer was based on bidirectional scan vectors with 5 mm wide stripes overlapping 0.1 mm, and between each layer there was a 67 deg rotation.…”

Section: A Experimental Methodsmentioning

confidence: 99%

“…[8,9] Previous work has shown that AM of AISI 441 by laser-powder bed fusion (L-PBF) lead to excellent mechanical properties compared to the conventional material produced by casting and hot rolling, attributed to the finer structure with small grain size in the printed material. [12] Conventionally manufactured AISI 441 is usually used in the hot or cold rolled and heat-treated state. The extremely high cooling rates and thermal gradients of L-PBF process conditions are significantly different from the conventional manufacturing conditions resulting in different as-manufactured microstructures, and the response to post-heat treatments may differ.…”

Section: Introductionmentioning

confidence: 99%

“…Hence, conventional post-heat treatment procedures may not be transferable to the L-PBF-processed material without modification. [11,12] In this work, the microstructure response of L-PBF-processed AISI 441 during post-heat treatments is studied in detail for the temperature range 850 °C to 1150 °C. Focus is on the precipitation kinetics as well as the grain structure evolution.…”

Section: Introductionmentioning

confidence: 99%

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Precipitation Kinetics During Post-heat Treatment of an Additively Manufactured Ferritic Stainless Steel

Chou

Karlsson

Pettersson

et al. 2022

Metall Mater Trans A

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The microstructure response of laser-powder bed fusion (L-PBF)-processed ferritic stainless steel (AISI 441) during post-heat treatments is studied in detail. Focus is on the precipitation kinetics of the Nb-rich phases: Laves (Fe2Nb) and the cubic carbo-nitride (NbC), as well as the grain structure evolution. The evolution of the precipitates is characterized using scanning and transmission electron microscopy (SEM and TEM) and the experimental results are used to calibrate precipitation kinetics simulations using the precipitation module (TC-PRISMA) within the Thermo-Calc Software package. The calculations reproduce the main trend for both the mean radii for the Laves phase and the NbC, and the amount of Laves phase, as a function of temperature. The calibrated model can be used to optimize the post-heat treatment of additively manufactured ferritic stainless steel components and offer a creator tool for process and structure linkages in an integrated computational materials engineering (ICME) framework for alloy and process development of additively manufactured ferritic steels.

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“…In literature, there are only a few published studies on the subject of processing ferritic materials using L-PBF [ 19 , 20 , 21 , 22 , 23 , 24 ]. To date, there are no empirical values or published parameter windows for the processability of 22NiMoCr3-7 using the L-PBF method.…”

Section: Introductionmentioning

confidence: 99%

Feasibility Study on Additive Manufacturing of Ferritic Steels to Meet Mechanical Properties of Safety Relevant Forged Parts

2022

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Additive manufacturing processes such as selective laser melting are rapidly gaining a foothold in safety-relevant areas of application such as powerplants or nuclear facilities. Special requirements apply to these applications. A certain material behavior must be guaranteed and the material must be approved for these applications. One of the biggest challenges here is the transfer of these already approved materials from conventional manufacturing processes to additive manufacturing. Ferritic steels that have been processed conventionally by forging, welding, casting, and bending are widely used in safety-relevant applications such as reactor pressure vessels, steam generators, valves, and piping. However, the use of ferritic steels for AM has been relatively little explored. In search of new materials for the SLM process, it is assumed that materials with good weldability are also additively processible. Therefore, the processability with SLM, the process behavior, and the achievable material properties of the weldable ferritic material 22NiMoCr3-7, which is currently used in nuclear facilities, are investigated. The material properties achieved in the SLM are compared with the conventionally forged material as it is used in state-of-the-art pressure water reactors. This study shows that the ferritic-bainitic steel 22NiMoCr3-7 is suitable for processing with SLM. Suitable process parameters were found with which density values > 99% were achieved. For the comparison of the two materials in this study, the microstructure, hardness values, and tensile strength were compared. By means of a specially adapted heat treatment method, the material properties of the printed material could be approximated to those of the original block material. In particular, the cooling medium/cooling method was adapted and the cooling rate reduced. The targeted ferritic-bainitic microstructure was achieved by this heat treatment. The main difference found between the two materials relates to the grain sizes present. For the forged material, the grain size distribution varies between very fine and slightly coarse grains. The grain size distribution in the printed material is more uniform and the grains are smaller overall. In general, it was difficult and only minimal possible to induce grain growth. As a result, the hardness values of the printed material are also slightly higher. The tensile strength could be approximated to that of the reference material up to 60 MPa. The approximation of the mechanical-technological properties is therefore deemed to be adequate.

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Additive manufacturing of the ferritic stainless steel SS441

Cited by 19 publications

References 26 publications

An Enhanced Understanding of the Powder Bed Fusion–Laser Beam Processing of Mg-Y3.9wt%-Nd3wt%-Zr0.5wt% (WE43) Alloy through Thermodynamic Modeling and Experimental Characterization

An Enhanced Understanding of the Powder Bed Fusion–Laser Beam Processing of Mg-Y3.9wt%-Nd3wt%-Zr0.5wt% (WE43) Alloy through Thermodynamic Modeling and Experimental Characterization

Precipitation Kinetics During Post-heat Treatment of an Additively Manufactured Ferritic Stainless Steel

Feasibility Study on Additive Manufacturing of Ferritic Steels to Meet Mechanical Properties of Safety Relevant Forged Parts

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