Effects of scan speed on vapor plume behavior and spatter generation in laser powder bed fusion additive manufacturing

Zheng, Hang; Li, Huaixue; Lang, Lihui; Gong, Shuili; Ge, Yulong

doi:10.1016/j.jmapro.2018.09.011

Cited by 83 publications

(53 citation statements)

References 24 publications

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“…Ly et al [35] reported recently that, while the dominant mechanism of denudation is vapor recoil pressure, the formation of ejections is mostly influenced by vapor-driven entrainment of micro-particles. Since laser powder bed fusion is a very fast process involving high temperatures and very rapid cooling rates, it is of paramount importance to be successful in monitoring the process in terms of laser vapor plume, in order to control its interaction with the metal powder particles, as well as to study the redeposition of the ejections generated during the process itself [116][117][118].…”

Section: Heat-affected Powdermentioning

confidence: 99%

See 1 more Smart Citation

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

Santecchia

Spigarelli

Cabibbo

2020

Metals

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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 ...

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Section: Heat-affected Powdermentioning

confidence: 99%

“…Images of plume and spatter formation under different scan speeds (500 W, 304L stainless steel). Reproduced from Reference[116] with permission from Elsevier.…”

mentioning

confidence: 99%

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

Santecchia

Spigarelli

Cabibbo

2020

Metals

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“…Also, the explanation of the occurrence of extremely fast spatters (i.e., >40 m=s in the case of Ti-6Al-4V) is still vague and unclear. While high-speed visible-light and thermal imaging techniques allow the observation of the surface feature evolutions [17][18][19][20], the subsurface information (i.e., keyhole fluctuations and melt pool dynamics) are largely unknown and often subject to speculation. Laboratory x-ray sources have been used for detecting the subsurface structural changes [21,22]; however, the limited x-ray flux yields low imaging resolutions in both space and time domains.…”

Section: Introductionmentioning

confidence: 99%

Bulk-Explosion-Induced Metal Spattering During Laser Processing

Zhao

Guo

et al. 2019

Phys. Rev. X

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Spattering has been a problem in metal processing involving high-power lasers, like laser welding, machining, and recently, additive manufacturing. Limited by the capabilities of in situ diagnostic techniques, typically imaging with visible light or laboratory x-ray sources, a comprehensive understanding of the laser-spattering phenomenon, particularly the extremely fast spatters, has not been achieved yet. Here, using MHz single-pulse synchrotron-x-ray imaging, we probe the spattering behavior of Ti-6Al-4V with micrometer spatial resolution and subnanosecond temporal resolution. Combining direct experimental observations, quantitative image analysis, as well as numerical simulations, our study unravels a novel mechanism of laser spattering: The bulk explosion of a tonguelike protrusion forming on the front keyhole wall leads to the ligamentation of molten metal at the keyhole rims and the subsequent spattering. Our study confirms the critical role of melt and vapor flow in the laser-spattering process and opens a door to manufacturing spatter-and defect-free metal parts via precise control of keyhole dynamics.

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“…Despite attractive monitoring abilities presented in these studies, some inherent drawbacks constrain their abilities and the applicability in defect diagnosis. Temperature and image measured from the molten pool [12][13][14], spatter [15,16], or powder bed [17] can only provide the surface information. Although X-ray technology can capture the defects inside the components [18], the considerably high cost for data acquisition and complex sensing systems obstruct their practical industry applications.…”

Section: Introductionmentioning

confidence: 99%

In-Situ Monitoring of Laser Additive Manufacturing for Al7075 Alloy Using Emission Spectroscopy and Plume Imaging

Ren

Zhang

et al. 2021

IEEE Access

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Most aluminum alloys, especially the 7xxx series, are incompatible with laser additive manufacturing due to many factors. In-situ process monitoring technology offers an excellent opportunity for process understanding and control, which improves the component quality and repeatability of AM. In this study, emission spectroscopy and plume imaging were utilized to monitor and understand the laser-directed energy deposition of Al7075 alloy. Characteristics of plasma were analyzed using spectra and plume image signals. Emission lines of Al I, Mg I, and Cr I observed in spectra signals demonstrated that primary elements in Al7075 were evaporated and excited during the AM process forming a plasma plume. The plasma plume intensity increased significantly as the laser power increasing. The periodic fluctuation of plasma was revealed using plume images, indicating that laser powers inputted into the target surface were unstable due to the laser and plasma interaction. The elemental evaporation and inconsistent laser input are the main challenges for Al7075 AM and are potentially monitored by plasma signals. Methods of signal process and feature extraction for spectra and plume images were developed. Experimental results showed that the aluminum emission spectral energy, the average baseline spectral intensity, and the plume area are practical for rough surface monitoring. Correlations between spectral features and key printing parameters were developed, demonstrating an excellent response of spectra features to the laser power and laser scanning speed. This investigation revealed the potentials and challenges of emission spectroscopy in the in-situ monitoring of laser AM, making progress towards intelligent additive manufacturing.INDEX TERMS Additive Manufacturing, directed energy deposition, emission spectroscopy, process monitoring, signal processing.

show abstract

Effects of scan speed on vapor plume behavior and spatter generation in laser powder bed fusion additive manufacturing

Cited by 83 publications

References 24 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

Bulk-Explosion-Induced Metal Spattering During Laser Processing

In-Situ Monitoring of Laser Additive Manufacturing for Al7075 Alloy Using Emission Spectroscopy and Plume Imaging

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