Influence of keyhole and conduction mode melting for top-hat shaped beam profiles in laser powder bed fusion

Tenbrock, Christian; Fischer, Felix Gabriel; Wissenbach, Konrad; Schleifenbaum, Johannes Henrich; Wagenblast, Philipp; Meiners, Wilhelm; Wagner, J.

doi:10.1016/j.jmatprotec.2019.116514

Cited by 77 publications

(44 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The connection between the shape of the laser beam profile and the melt pool was extensively studied in the literature [51,91,92]. Furthermore, the top-hat shape employed in laser welding [93] was shown to produce keyholes having a shorter depth and, for this reason, Tenbrock et al [94] recently applied this profile in laser powder bed fusion of 316 L stainless steel, showing that an efficient LPBF processes can also be realized by applying diode lasers as long as a proper defined intensity threshold is exceeded (I ≈ 8-10 × 10 5 W/cm 2 [94]).…”

Section: Heat Sourcementioning

confidence: 99%

Material Reuse in Laser Powder Bed Fusion: Side Effects of the Laser—Metal Powder Interaction

Santecchia

Spigarelli

Cabibbo

2020

Metals

View full text Add to dashboard Cite

Metal additive manufacturing is changing the way in which engineers and designers model the production of three-dimensional (3D) objects, with rapid growth seen in recent years. Laser powder bed fusion (LPBF) is the most used metal additive manufacturing technique, and it is based on the efficient interaction between a high-energy laser and a metal powder feedstock. To make LPBF more cost-efficient and environmentally friendly, it is of paramount importance to recycle (reuse) the unfused powder from a build job. However, since the laser-powder interaction involves complex physics phenomena and generates by-products which might affect the integrity of the feedstock and the final build part, a better understanding of the overall process should be attained. The present review paper is focused on the clarification of the interaction between laser and metal powder, with a strong focus on its side effects. Figure 1. Schematics of the laser powder bed fusion (LPBF) equipment. Adapted from Reference [9] with permission from Elsevier.While the market and the applications of laser powder bed fusion continuously and impressively grew in recent years, there is a common view across users and researchers concerning the repeatability of the process in terms of chemical composition and mechanical properties of the final parts, which are of paramount importance when challenging environmental or testing conditions are considered [10][11][12][13][14][15][16].The most typical approach to study the microstructural and mechanical properties of parts built by LPBF is to compare them with castings of the same alloy or, rather, the corresponding alloy since the starting material is metal powder rather than a fuse. However, in some existing alloys designed for cast and wrought parts, laser additive manufacturing processing results in cracking or other microstructure deficiencies [11,12,16,17]. It is worth noting that LPBF has more similarities with laser welding rather than casting, since the two laser-based techniques have some common features (i.e., melt-pool formation, moving heat source) [18]. However, process parameters are, in general, quite different in terms of laser power and scan speed, and the laser-matter interaction is much more complicated in LPBF processes, since the powder feedstock is inherently unstable and the solidified material undergoes multiple thermal cycles corresponding to the fusion of subsequent layers during the additive process [19][20][21][22]. Furthermore, owing to the similarities with welding and to the complicated interaction between laser and metal particles, when comparing laser powder bed fusion with other metal forming processes, it is evident that the range of processable alloys is very limited and the number of high-productivity commercially available alloys is even smaller [23]. One of the reasons behind this is that the level of metal powder sensitivity to the laser action during LPBF is not yet fully understood, despite the efforts of the scientific community to uncover it [24][25][26][27], and ...

show abstract

Section: Heat Sourcementioning

confidence: 99%

Material Reuse in Laser Powder Bed Fusion: Side Effects of the Laser—Metal Powder Interaction

Santecchia

Spigarelli

Cabibbo

2020

Metals

View full text Add to dashboard Cite

show abstract

“…Recently, laser beam shaping strategies have been used in the context of engineering light-matter interactions to tackle the drawbacks of using focused Gaussian beams in metal AM (12,(24)(25)(26)(27)(28)(29)(30). In particular, inverse Gaussian (annular) beams were shown to mitigate spatter generation (24) and reduce defects over a broader range of scan parameters compared to Gaussian beams (28).…”

Section: Introductionmentioning

confidence: 99%

Nondiffractive beam shaping for enhanced optothermal control in metal additive manufacturing

et al. 2021

View full text Add to dashboard Cite

High thermal gradients and complex melt pool instabilities involved in powder bed fusion-based metal additive manufacturing using focused Gaussian-shaped beams often lead to high porosity, poor morphological quality, and degraded mechanical performance. We show here that Bessel beams offer unprecedented control over the spatiotemporal evolution of the melt pool in stainless steel (SS 316L) in comparison to Gaussian beams. Notably, the nondiffractive nature of Bessel beams enables greater tolerance for focal plane positioning during 3D printing. We also demonstrate that Bessel beams significantly reduce the propensity for keyhole formation across a broad scan parameter space. High-speed imaging of the melt pool evolution and solidification dynamics reveals a unique mechanism where Bessel beams stabilize the melt pool turbulence and increase the time for melt pool solidification, owing to reduced thermal gradients. Consequently, we observe a distinctively improved combination of high density, reduced surface roughness, and robust tensile properties in 3D-printed test structures.

show abstract

“…When transitioning to keyhole‐mode welding the depth of the melt pool increases disproportionally causing the aspect ratio to increase above 0.5. Different threshold values are used in the literature, ranging from 0.5 to 2, sometimes adding a third transition welding mode in between conduction and keyhole‐mode welding [6, 13, 15, 16]. The present welding mode is influenced by the material properties and the process parameters and can be set via laser power, scanning speed and focus diameter [13].…”

Section: Introductionmentioning

confidence: 99%

Influence of contour scans on surface roughness and pore formation using Scalmalloy® manufactured by laser powder bed fusion (PBF‐LB)

Reiber

Rüdesheim

Weigold

et al. 2021

Materialwissenschaft Werkst

View full text Add to dashboard Cite

The scandium modified aluminium alloy Scalmalloy® is specifically developed for the use in laser‐based powder bed fusion (PBF‐LB). It is supposed to show potential in the production of lightweight structures due to its high specific strength compared to other aluminium alloys. A limiting factor is the high surface roughness of additively manufactured parts, which has a negative influence on its mechanical properties, especially under cyclic loads. In order to reduce the surface roughness, methods of design of experiments (DoE) are applied to develop contour parameters. Additionally, the formation of pores in keyhole‐mode welding and strategies to reduce the porosity in the contour area are investigated. The surface roughness of vertical walls can be reduced down to Ra < 7 μm using contour scans with a line energy EL >0.9 J mm−1 but keyhole pores start to form applying EL >0.6– 0.75 J mm−1. Two contour parameter sets in different EL‐ranges are developed that can be used to reduce the surface roughness compared to parameter sets without contour scans, without increasing the porosity in the contour area. Their impact on the mechanical properties has to be further investigated.

show abstract

Influence of keyhole and conduction mode melting for top-hat shaped beam profiles in laser powder bed fusion

Cited by 77 publications

References 14 publications

Material Reuse in Laser Powder Bed Fusion: Side Effects of the Laser—Metal Powder Interaction

Material Reuse in Laser Powder Bed Fusion: Side Effects of the Laser—Metal Powder Interaction

Nondiffractive beam shaping for enhanced optothermal control in metal additive manufacturing

Influence of contour scans on surface roughness and pore formation using Scalmalloy® manufactured by laser powder bed fusion (PBF‐LB)

Contact Info

Product

Resources

About