Grain refinement in additively manufactured ferritic stainless steel by in situ inoculation using pre-alloyed powder

Durga, A.; Pettersson, Niklas; Malladi, Sri Bala Aditya; Chen, Zhuoer; Guo, Sheng; Nyborg, Lars; Lindwall, Greta

doi:10.1016/j.scriptamat.2020.113690

Cited by 50 publications

(26 citation statements)

References 29 publications

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“…The TiN/oxide complexes are expected to form during printing where TiN seems to nucleate on the fine oxides stable in the liquid phase. [22] In the current work, sizes and distribution of these oxide particles do not vary notably in the studied microstructures. Although the TiN particles should be present in all heat-treated microstructures, due to their low fraction they are only occasionally found.…”

Section: B Experimental Characterizations After Heat Treatmentmentioning

confidence: 52%

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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Section: B Experimental Characterizations After Heat Treatmentmentioning

confidence: 52%

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 machined samples were ground down to 4000 grits SiC paper followed by fine polishing using 3 and 1 μm suspended diamond solutions. All materials are fully austenitic and expected to contain oxide inclusions, 9 and the conventional 316L is expected to also contain manganese sulphide inclusions. 34 T A B L E 1 List of studied materials and their manufacturing route.…”

Section: Methodsmentioning

confidence: 99%

“…[1][2][3] Due to the inherent high thermal gradient and solidification rate, the resulting microstructure of the PBF-LB components typically consists of the epitaxially grown columnar grains and is unlike the microstructure of the components produced by traditional manufacturing techniques. [4][5][6][7][8][9][10] The ability to produce the parts on-demand, with near-fulldensification and near-net-shape components, makes PBF-LB a desirable technique for industrial applications. With the growing material portfolios of PBF-LB, there is also growing interest in the wide range of properties for the materials, and one such properties is the corrosion behaviour of the alloys.…”

Section: Introductionmentioning

confidence: 99%

Corrosion behaviour of additively manufactured 316L and CoCrNi

Malladi

Tam

Cao

et al. 2023

Surface & Interface Analysis

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Alloys such as 316L and the medium‐entropy alloy CoCrNi are known for their excellent strength and corrosion properties. In the present study, bulk samples of 316L and CoCrNi (without and with 0.11 wt.% N) alloys fabricated using powder bed fusion laser beam (PBF‐LB) were tested in the as‐printed state for their corrosion behaviour in 0.5 M H2SO4 without and with added 3 wt.% NaCl. The tests were done using potentiodynamic measurements and the results were compared with those of the conventionally manufactured 316L. By means of angle‐resolved X‐ray photoelectron spectroscopy (ARXPS), the passive film characteristics were studied in terms of composition and film thickness. The 316L fabricated using PBF‐LB showed favourable passivation and corrosion behaviour as compared with its conventionally manufactured counterpart. It was observed that all the alloys fabricated using the PBF‐LB showed similar corrosion behaviour, but with CoCrNi and CoCrNi‐N showing better passivation behaviour than 316L alloys in the presence of NaCl. The ARXPS showed the presence of both hydroxide and oxides in all the alloys, with outer hydroxide layer and inner oxide layer. The ARXPS of both 316L alloys showed the expected presence of Cr–Fe oxide on the surface of as‐passivated samples, whereas the presence of sulphide was also depicted for the conventionally manufactured 316L, supposed to be detrimental to its corrosion behaviour. The CoCrNi‐based alloys showed the presence of only Cr2O3 layer in their passivated state, with Co and Ni acting as noble elements in the formation of the passive film. Upon micro‐alloying with the strong solid solution strengthener N, CoCrNi did not show any negative effect on either the corrosion behaviour or the passivation behaviour of the alloy.

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“…In order to alleviate grain coarsening in ferritic stainless welds, a number of studies detail the use of heterogeneous nucleating agents, such as titanium nitride, e.g. in gas tungsten arc welding (GTAW) [34] or laser-based powder-bed-fusion (PBF-LB) [35]. Other studies report on the superimposition of ultrasound by ultrasonically excited filler material, which results in grain refinement within the WM [36].…”

Section: Introduction and State-of-the-artmentioning

confidence: 99%

Grain growth and precipitation behaviour of AISI 430 ferritic stainless steel subjected to pulsed laser beam welding using free-form pulse shaping

et al. 2022

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Ferritic stainless steels are prone to grain coarsening and precipitation of chromium-rich grain boundary phases during fusion welding, which increase intergranular corrosion susceptibility. State-of-the-art techniques to overcome these challenges mainly feature heterogeneous nucleating agents with regard to grain coarsening or alternating alloy concepts as well as post-weld heat treatments as for restoration of intergranular corrosion resistance. The present investigation seeks to depart from these traditional approaches through the use of a tailored heat input during pulsed laser beam welding by means of free-form pulse shaping. Grain size analysis using electron backscatter diffraction shows a substantial reduction of grain size as compared to continuous-wave lasers due to a distinctive columnar to equiaxed transition. Moreover, phase analyses reveal the overcoming of chromium carbide precipitation within the heat-affected zone. As corrosion tests demonstrate, intergranular attack is therefore concentrated on the weld metal. In comparison to continuous-wave laser beam welding, intergranular corrosion susceptibility is substantially reduced for very short pulse durations. From these results, it can be derived that pulsed laser beam welding using free-form pulse shaping enables direct control of heat input and, thus, tailored grain growth and precipitation formation properties.

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Grain refinement in additively manufactured ferritic stainless steel by in situ inoculation using pre-alloyed powder

Cited by 50 publications

References 29 publications

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

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

Corrosion behaviour of additively manufactured 316L and CoCrNi

Grain growth and precipitation behaviour of AISI 430 ferritic stainless steel subjected to pulsed laser beam welding using free-form pulse shaping

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