Observation of keyhole-mode laser melting in laser powder-bed fusion additive manufacturing

King, Wayne E.; Barth, Holly D.; Castillo, V.; Gallegos, G. F.; Gibbs, John W.; Hahn, D.; Kamath, Chandrika; Rubenchik, Alexander M.

doi:10.1016/j.jmatprotec.2014.06.005

Cited by 1,099 publications

(498 citation statements)

References 11 publications

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“…P-V) are varied through a series of experiments (single bead on plate, single layer pads, multi-layer pads, components and component features). Those experiments are combined with finite element thermal modeling of the melt pool geometry to define regimes of good quality deposits (e.g., avoiding lack of fusion, avoiding keyholing, 36 increasing build rate, increasing process precision) across wide ranges of process variables. Figure 5 shows a recently developed P-V map 35 for Ti-6Al-4V produced for electron beam (i.e.…”

Section: Process Control and Process Mappingmentioning

confidence: 99%

Overview of Materials Qualification Needs for Metal Additive Manufacturing

Seifi

Salem

Beuth

et al. 2016

JOM

470

183

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This overview highlights some of the key aspects regarding materials qualification needs across the additive manufacturing (AM) spectrum. AM technology has experienced considerable publicity and growth in the past few years with many successful insertions for non-mission-critical applications. However, to meet the full potential that AM has to offer, especially for flightcritical components (e.g., rotating parts, fracture-critical parts, etc.), qualification and certification efforts are necessary. While development of qualification standards will address some of these needs, this overview outlines some of the other key areas that will need to be considered in the qualification path, including various process-, microstructure-, and fracture-modeling activities in addition to integrating these with lifing activities targeting specific components. Ongoing work in the Advanced Manufacturing and Mechanical Reliability Center at Case Western Reserve University is focusing on fracture and fatigue testing to rapidly assess critical mechanical properties of some titanium alloys before and after post-processing, in addition to conducting nondestructive testing/evaluation using micro-computerized tomography at General Electric. Process mapping studies are being conducted at Carnegie Mellon University while large area microstructure characterization and informatics (EBSD and BSE) analyses are being conducted at Materials Resources LLC to enable future integration of these efforts via an Integrated Computational Materials Engineering approach to AM. Possible future pathways for materials qualification are provided.

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Section: Process Control and Process Mappingmentioning

confidence: 99%

Overview of Materials Qualification Needs for Metal Additive Manufacturing

Seifi

Salem

Beuth

et al. 2016

JOM

470

183

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“…5(a). On the contrary, when the laser energy density is excessive, the undesirable metallurgical pores are generated by entrapment of gases or improper closure of a keyhole 48) , as demonstrated in Fig. 5(d).…”

Section: Resultsmentioning

confidence: 99%

Densification Behavior of 316L Stainless Steel Parts Fabricated by Selective Laser Melting by Variation in Laser Energy Density

et al. 2016

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Selective laser melting (SLM) is an attractive manufacturing technique for the production of metal parts with complex geometries and high performance. This manufacturing process is characterized by highly localized laser energy inputs during short interaction times which signicantly affect the densi cation process. In this present work, experimental investigation of fabricating 316L stainless steel parts by SLM process was conducted to determine the effect of different laser energy densities on the densi cation behavior and resultant microstructural development. It was found that using a low laser energy density below 50 J/mm 3 produced an instable melt pool that resulted in the formation of unmelted particles, pores, cracks, and balling in the as-built parts with low densi cation. In contrast, the as-built parts at a high energy density above 200 J/mm 3 showed irregular scan tracks with a number of pores and metal balls that decreased part density. The optimal laser energy density range was accordingly determined to be 58-200 J/mm 3 by eliminating obvious SLM defects, which led to near full densi cation. The SLM samples fabricated using optimal parameters allowed observation of a microhardness of 280 Hv, ultimate strength of 570 MPa, and yield strength of 530 MPa that were higher than those of the as-cast and wrought 316L stainless steel.

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“…On the other hand, recent and highly valuable investigations carried out in Lawrence Livermore Laboratory have widely investigated the hydrodynamic instabilities in SLM. In a preliminary work by King et al (2014), the threshold for key-hole formation, assumed to be a major contributor to the formation of defects, was calculated by considering the depth variation versus a normalized enthalpy value. The experimental and numerical work detailed in Matthews et al (2016) focused on the denudation phenomena occurring near SLM beads and concluded that inward lateral gas flow induced by the melt-pool vaporization was the main dragging force for powder depletion.…”

Section: Introductionmentioning

confidence: 99%

Experimental analysis of spatter generation and melt-pool behavior during the powder bed laser beam melting process

Gunenthiram

Peyre

Schneider

et al. 2018

Journal of Materials Processing Technology

250

120

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. A B S T R A C TThe experimental analysis of spatter formation was carried out on an instrumented SLM set-up allowing the quantification of spatter ejections and possible correlation with melt-pool behavior. Considering nearly similar SLM conditions than those carried out on SLM machines, an increase of large spatters (> 80 μm) with volume energy density (VED) was clearly demonstrated on a 316L stainless steel, which was attributed to the recoil pressure applied on the melt-pool by the metal vaporization and the resulting high velocity vapor plume. In a second step, much lower spattering was shown on Al-12Si powder beds than on 316L ones. Fast camera analysis of powder beds indicated that droplet formation was mostly initiated in the powder-bed near the melt-pool interface. On Al-12 Si alloys, such droplets were directly incorporated in the MP without being ejected upwards as spatters like on 316L. Last, it was shown that a strong reduction of spattering was possible even on 316L, with the use of low VED combined with larger spots (≈0.5 mm), allowing to melt sufficiently deep layers in conduction regime and ensure adequate dilution between layers.

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Observation of keyhole-mode laser melting in laser powder-bed fusion additive manufacturing

Cited by 1,099 publications

References 11 publications

Overview of Materials Qualification Needs for Metal Additive Manufacturing

Overview of Materials Qualification Needs for Metal Additive Manufacturing

Densification Behavior of 316L Stainless Steel Parts Fabricated by Selective Laser Melting by Variation in Laser Energy Density

Experimental analysis of spatter generation and melt-pool behavior during the powder bed laser beam melting process

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