Effect of Hatch Spacing on Melt Pool and As-built Quality During Selective Laser Melting of Stainless Steel: Modeling and Experimental Approaches

The sharp growth that additive manufacturing has been showing recently has broadened its application field and resulted in more varied demand of high-volume parts as well as a general increase in part series. The current focus on productivity enhancement of additive manufacturing has imposed the implementation of multiple-laser systems with larger scan fields. Its usage, combined with adequate layer thickness and laser power selection, makes high-volume parts less challenging to obtain. This paper focuses on understanding the influence of using multiple-scan fields for the fabrication of large components, especially on the parts region corresponding to scan field interface. The microstructure as well as mechanical behaviour of the multi-field manufactured samples are compared with parts fabricated using a single-field, for distinct processing parameters. Moreover, given the unreliability of additive manufacturing regarding dimensional and geometrical tolerances with increasing build rates, post-processing metal-cutting operations were studied towards additive manufacturing process hybridization. Despite the typical additive manufacturing process variability, a set of parameters, within testing conditions, could be identified as the most appropriate solution towards mechanical strength enhancement. Nonetheless, porosity levels can significantly impact the ductility of parts, which may be additionally compromised by its occurrence in the scan-field interface region.

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“…It is also observed that increase in hatch spacing gives rise to higher porosity, which is also detected by Dong et al. 29…”

Section: Resultssupporting

confidence: 75%

Influence of multiple scan fields on the processing of 316L stainless steel using laser powder bed fusion

Leça

Silva

Jesus

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part L:

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“…Higher laser power and lower hatching distance used in the manufacturing process of Sample 2 increased the heat accumulation [41] and, as a result, the amount of sintered powder at the border of the samples. Moreover, in the crosshatch scanning strategy, which is used for Sample 2, the laser passes two times in each layer, in two directions perpendicular to each other, which also increases the total heat input and leads to the formation of large fractions of sintered powders at the sample edges.…”

Section: Resultsmentioning

confidence: 99%

Mapping Spatial Distribution of Pores in an Additively Manufactured Gold Alloy Using Neutron Microtomography

et al. 2021

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A crucial criterion for the quality of the additively manufactured parts is the porosity content for achieving an acceptable final relative density. In addition, for jewelry applications, visible pores are unacceptable at or in the vicinity of the surface. In this study, non-destructive 3D neutron microtomography is applied to map the spatial distribution of pores in additively manufactured red-gold samples. The 3D imaging assessment underlines the high relative density of the printed red-gold sample and indicates residual pore sizes are predominantly below the limit of concern for jewelry applications. The 3D maps of pores within printed samples highlight the effect of the scanning strategy on the final quality and location of pores in the printed samples. These results confirm that neutron microtomography is a novel and precise tool to characterize residual porosity in additively manufactured gold alloys and other higher-Z materials where such investigation using other non-destructive methods (such as X-rays) is challenging due to the limited penetration depth.

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“…So far, no previous research has specifically determined what area of overlap is the most appropriate for building parts. This is a complex issue, because the overlap area is associated with many factors such as hatch spacing, laser energy density, fluidity of the melting pool, and the formation of oxide film during the printing process [ 25 , 26 ].…”

Section: Resultsmentioning

confidence: 99%

Densification, Microstructure, and Mechanical Properties of Additively Manufactured 2124 Al–Cu Alloy by Selective Laser Melting

et al. 2020

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Owing to its high specific strength and low density, Al–Cu alloys have been extensively used in aerospace for lightweight components. Additive manufacturing techniques such as selective laser melting, which offers geometric freedom, is suitable for topology-optimized designs. In this study, the effect of processing parameters on the densification, microstructure, and mechanical properties of additively manufactured Al–Cu alloy 2124 by selective laser melting was investigated. Parameters such as laser power, scanning speed, hatch spacing, and use of a support were studied. The results revealed that a grille support with a hollow structure played a resistant role in the transfer of heat to the base plate, thus reducing the temperature gradient and lessening cracks in the building part. Smaller hatch spacing was beneficial for the achievement of a higher relative density and strength due to track re-melting and liquid phase backflow, which could fill cracks and pores during the building process. An ultimate tensile strength as high as 300 MPa of the vertically built sample was obtained at optimized processing parameters, while the elongation was relatively limited. Moreover, columnar grains were found to be responsible for the anisotropy of the mechanical properties of the as-printed 2124 alloy.

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Effect of Hatch Spacing on Melt Pool and As-built Quality During Selective Laser Melting of Stainless Steel: Modeling and Experimental Approaches

Cited by 123 publications

References 41 publications

Influence of multiple scan fields on the processing of 316L stainless steel using laser powder bed fusion

Influence of multiple scan fields on the processing of 316L stainless steel using laser powder bed fusion

Mapping Spatial Distribution of Pores in an Additively Manufactured Gold Alloy Using Neutron Microtomography

Densification, Microstructure, and Mechanical Properties of Additively Manufactured 2124 Al–Cu Alloy by Selective Laser Melting

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