Inclusions in Stainless Steels − A Review

Park, Joo Hyun; Kang, Youngjo

doi:10.1002/srin.201700130

Cited by 133 publications

(61 citation statements)

References 120 publications

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“…Large oxides preferentially aligned to the rolling direction were found in the wrought material (2-4 μm diameters, Figure 3) which could be sites for pit initiation. [16][17][18][19] Oxides, enriched in Si and possibly Mn, were observed in the SLM 304L material ( Figure 5); however, these were of a much finer size scale (5-20 nm diameters). In the cellular regions, oxides precipitated preferentially at cell interfaces, as observed in Figure 5, whereas in the non-cellular regions, oxides precipitated throughout the material.…”

Section: Discussionmentioning

confidence: 99%

The Role of Microstructure and Surface Finish on the Corrosion of Selective Laser Melted 304L

Schaller

Mishra²,

Rodelas

et al. 2018

J. Electrochem. Soc.

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The corrosion behavior of selective laser melted (SLM) 304L was investigated and compared to conventional wrought 304L in aqueous chloride and acidic solutions. Through immersed electrochemical testing and exposure in acidic solutions, the SLM 304L exhibited superior pitting resistance in the polished state compared to wrought 304L. However, the surface condition of the SLM material had a great impact on its corrosion resistance, with the grit-blasted condition exhibiting severely diminished pitting resistance. Local scale, capillary micro-electrochemical and scanning electrochemical microscopy investigations, identified porosity as a contributing factor to decreased corrosion resistance. Preferential corrosion attack was not observed to be related to the characteristic underlying cellular microstructure produced through SLM processing. This study highlights the effects of SLM microstructural features on corrosion resistance, specifically the substantial influence of surface finish on SLM corrosion behavior and the need for development and optimization of processing techniques to improve surface finish. Powder bed selective laser melting (SLM) has become a desirable and widely used technique for the additive manufacturing (AM) of metal parts. While a significant amount of research has been carried out on the mechanical properties of SLM materials, little is known regarding their corrosion behavior. Of the few corrosion studies that do exist, the primary focus has been on evaluating general corrosion resistance.1,2 A few recent investigations have examined the role of processing and microstructure on the material corrosion behavior in more detail.3,4 However, there is still a need for further investigation in order to develop a full understanding of the microstructural and morphological characteristics inherent to AM materials due to the unique processing conditions and their relative contributions to the materials' corrosion behavior. Ideally, a ranking of the deleterious or advantageous properties formed in AM materials with respect to corrosion should be established. This is necessary for a variety of alloy systems in engineering relevant solutions and environments to help inform and guide future processing parameters, build designs, and materials selection.The powder bed process along with extremely high cooling rates and temperature gradients during SLM processing create microstructures and part surfaces that differ greatly from their conventional thermo-mechanically processed counterparts. Several characteristics are expected or have known effects on corrosion behavior including surface finish, porosity, inclusions (MnS, oxides, etc.), and microstructures formed through non-equilibrium cooling conditions. For example, a strong relationship between surface roughness and corrosion susceptibility has been observed in which pit initiation decreases with decreasing surface roughness in chloride solutions.5-7 Porosity, formed by entrapped gas or lack of fusion of powder particles in the SLM build, can also reduce...

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Section: Discussionmentioning

confidence: 99%

The Role of Microstructure and Surface Finish on the Corrosion of Selective Laser Melted 304L

Schaller

Mishra²,

Rodelas

et al. 2018

J. Electrochem. Soc.

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“…In some cases, inclusions were found to be detrimental to the mechanical properties [12][13][14]. The size and distribution of inclusions are of great importance to the workability of steel [15][16][17]. The fracture mechanisms caused by inclusions in stainless steels was revealed [15].…”

Section: Introductionmentioning

confidence: 99%

Microstructural effects on central crack formation in hot cross-wedge-rolled high-strength steel parts

et al. 2020

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Central cracking in cross-wedge-rolled workpieces results in high wastage and economic loss. Recent cross-wedge rolling tests on two batches of steel showed that one batch formed central cracks, while the other was crack-free. The batches were both nominally of the same chemical composition and thermomechanical treatment history. In addition, both batches had passed all the standard quality assessments set for conventional forging processes. It was suspected that the different cracking behaviours were due to differences in microstructure between the two as-received steel billets, and the material in cross-wedge rolling (CWR) was more sensitive to the initial microstructure compared with other forging processes due to its specific loading condition including ostensibly compression and large plastic strain. Nevertheless, no previous study of this important problem could be identified. The aim of this study is, therefore, to identify the key microstructural features determining the central crack formation behaviour in CWR. The hot workability of the as-received billets was studied under uniaxial tensile conditions using a Gleeble 3800 test machine. Scanning electron microscope with energy-dispersive X-ray spectroscopy and electron backscatter diffraction was applied to characterise, quantitatively analyse, and compare the chemical composition, phase, grain, and inclusions in these two billets, both at room temperature and also at the CWR temperature (1080°C). Non-metallic inclusions (oxides, sulphides, and silicates) in the billets were determined to be the main cause of the reported central cracking problem. The ductility of the steels at both room and elevated temperatures deteriorated markedly in the presence of the large volumes of inclusions. Grain boundary embrittlement occurred at the CWR temperature due to the aggregation of inclusions along the grain boundaries. It is suggested that a standard on specifying the inclusion quantity and size in CWR billets be established to produce crack-free products.

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“…Evolution of inclusions in 304 stainless steels at production steps have been widely studied . However, less attention has been paid to the variation of inclusions during the heat treatment of stainless steels.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic and Kinetic Analysis for Transformation of Oxide Inclusions in Solid 304 Stainless Steels

Wang

Ren

et al. 2019

steel research int.

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Inclusions in 304 stainless steels are transformed from manganese silicate to manganese chromite (spinel) upon heating in the range of 1000-1350 C, while this transformation is not observed when heating temperature is 1400 C. Thermodynamic analysis with software FactSage TM is applied in interpreting the transformation. Manganese chromite spinel, with light color under SEM, is deemed to be formed on the surface of MnO-SiO 2 inclusions by the reaction between Cr in steel matrix and MnO-SiO 2 in inclusions. Heating experiments with different time at 1235 C (rolling insulation temperature) are carried out to confirm the kinetics of the transformation reaction. Mass transfer coefficients of inclusions' composition, SiO 2 , MnO, and Cr 2 O 3 are ranging from 5 Â 10 À7 to 9 Â 10 À7 m s À1 , depending on diameters and components of inclusions.

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Inclusions in Stainless Steels − A Review

Cited by 133 publications

References 120 publications

The Role of Microstructure and Surface Finish on the Corrosion of Selective Laser Melted 304L

The Role of Microstructure and Surface Finish on the Corrosion of Selective Laser Melted 304L

Microstructural effects on central crack formation in hot cross-wedge-rolled high-strength steel parts

Thermodynamic and Kinetic Analysis for Transformation of Oxide Inclusions in Solid 304 Stainless Steels

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