Directed energy deposition (DED) additive manufacturing: Physical characteristics, defects, challenges and applications

Svetlizky, David; Das, Mitun; Zheng, Baolong; Vyatskikh, Alexandra L.; Bose, Susmita; Bandyopadhyay, Amit; Schoenung, Julie M.; Lavernia, Enrique J.; Eliaz, Noam

doi:10.1016/j.mattod.2021.03.020

Cited by 621 publications

(202 citation statements)

References 155 publications

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“…The relatively high surface roughness of the WLAM samples may have been due to an excessive wire-feeding rate or insufficient heating during the printing process [29]. In addition, the absence of inherent fusion defects in the WLAM samples located at the melt pool boundaries was probably also the result of insufficient heating conditions [38].…”

Section: Roughness Analysismentioning

confidence: 99%

The Effect of a Slow Strain Rate on the Stress Corrosion Resistance of Austenitic Stainless Steel Produced by the Wire Laser Additive Manufacturing Process

Bassis

Kotliar²,

Koltiar³

et al. 2021

Metals

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The wire laser additive manufacturing (WLAM) process is considered a direct-energy deposition method that aims at addressing the need to produce large components having relatively simple geometrics at an affordable cost. This additive manufacturing (AM) process uses wires as raw materials instead of powders and is capable of reaching a deposition rate of up to 3 kg/h, compared with only 0.1 kg/h with common powder bed fusion (PBF) processes. Despite the attractiveness of the WLAM process, there has been only limited research on this technique. In particular, the stress corrosion properties of components produced by this technology have not been the subject of much study. The current study aims at evaluating the effect of a slow strain rate on the stress corrosion resistance of 316L stainless steel produced by the WLAM process in comparison with its counterpart: AISI 316L alloy. Microstructure examination was carried out using optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction analysis, while the mechanical properties were evaluated using tensile strength and hardness measurements. The general corrosion resistance was examined by potentiodynamic polarization and impedance spectroscopy analysis, while the stress corrosion performance was assessed by slow strain rate testing (SSRT) in a 3.5% NaCl solution at ambient temperature. The attained results highlight the inferior mechanical properties, corrosion resistance and stress corrosion performance, especially at a slow strain rate, of the WLAM samples compared with the regular AISI 316L alloy. The differences between the WLAM alloy and AISI 316L alloy were mainly attributed to their dissimilarities in terms of phase compositions, structural morphology and inherent defects.

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Section: Roughness Analysismentioning

confidence: 99%

The Effect of a Slow Strain Rate on the Stress Corrosion Resistance of Austenitic Stainless Steel Produced by the Wire Laser Additive Manufacturing Process

Bassis

Kotliar²,

Koltiar³

et al. 2021

Metals

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“…Due to the significant advantages of additive manufacturing (AM) over traditional Ti6Al4V manufacturing processes, for example, the ability to form near-net-shape parts and complex geometries, a relatively short lead time, design flexibility, and minimal material waste, the interest in AM of Ti6Al4V has rapidly increased [1,[4][5][6][7][8]. Despite the abovementioned advantages of metal AM in general, and AM of Ti6Al4V specifically, the ability to fabricate fully dense, defect-free parts with homogeneous microstructure, good surface finish, and good mechanical properties are still considered to be a challenge [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

“…There is a direct relationship between the processing parameters, microstructure, and properties of AM materials. Among others, the energy source scan rate and power, deposition atmosphere, feedstock quality, and powder mass flow rate (PMFR, for DED) control the evolved thermal history during part fabrication, and thus may affect the resulting microstructure evolution, defects, and anisotropy of the microstructure and mechanical properties [4,9].…”

Section: Introductionmentioning

confidence: 99%

Measurement of the Anisotropic Dynamic Elastic Constants of Additive Manufactured and Wrought Ti6Al4V Alloys

et al. 2022

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Additively manufactured (AM) materials and hot rolled materials are typically orthotropic, and exhibit anisotropic elastic properties. This paper elucidates the anisotropic elastic properties (Young’s modulus, shear modulus, and Poisson’s ratio) of Ti6Al4V alloy in four different conditions: three AM (by selective laser melting, SLM, electron beam melting, EBM, and directed energy deposition, DED, processes) and one wrought alloy (for comparison). A specially designed polygon sample allowed measurement of 12 sound wave velocities (SWVs), employing the dynamic pulse-echo ultrasonic technique. In conjunction with the measured density values, these SWVs enabled deriving of the tensor of elastic constants (Cij) and the three-dimensional (3D) Young’s moduli maps. Electron backscatter diffraction (EBSD) and micro-computed tomography (μCT) were employed to characterize the grain size and orientation as well as porosity and other defects which could explain the difference in the measured elastic constants of the four materials. All three types of AM materials showed only minor anisotropy. The wrought (hot rolled) alloy exhibited the highest density, virtually pore-free μCT images, and the highest ultrasonic anisotropy and polarity behavior. EBSD analysis revealed that a thin β-phase layer that formed along the elongated grain boundaries caused the ultrasonic polarity behavior. The finding that the elastic properties depend on the manufacturing process and on the angle relative to either the rolling direction or the AM build direction should be taken into account in the design of products. The data reported herein is valuable for materials selection and finite element analyses in mechanical design. The pulse-echo measurement procedure employed in this study may be further adapted and used for quality control of AM materials and parts.

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“…The formation of a product layer-by-layer means that the deposited material undergoes quasi-periodic heating and cooling processes, including partial remelting of already formed layers. The resulting non-stationary thermal conditions significantly affect the local microstructure, residual stresses, and deformations, as well as the distribution of defects [ 8 ]. Gushchina et al [ 9 ] investigated the effect of the interpass temperature on the Ti-6Al-4V structure in the direct laser deposition (DLD) process.…”

Section: Introductionmentioning

confidence: 99%

“…In the AM process, defects are also encountered, such as non-fusion, the main cause of which is insufficient heat source energy while simultaneously feeding an excess amount of filler material into the melt pool [ 16 ]. The incorrect choice of the mode can also lead to the formation of cracking and delamination [ 8 ]. At the same time, the above effects can be combated by optimizing the process, which includes strict control of operating parameters, the presence or absence of preheating, control of the cooling rate, and the choice of a scanning strategy.…”

Section: Introductionmentioning

confidence: 99%

An Extended Analytical Solution of the Non-Stationary Heat Conduction Problem in Multi-Track Thick-Walled Products during the Additive Manufacturing Process

et al. 2021

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An analytical model has been developed for calculating three-dimensional transient temperature fields arising in the direct deposition process to study the thermal behavior of multi-track walls with various configurations. The model allows the calculation of all characteristics of the temperature fields (thermal cycles, cooling rates, temperature gradients) in the wall during the direct deposition process at any time. The solution of the non-stationary heat conduction equation for a moving heat source is used to determine the temperature field in the deposited wall, taking into account heat transfer to the environment. The method considers the size of the wall and the substrate, the change in power from layer to layer, the change in the cladding speed, the interpass dwell time (pause time), and the heat source trajectory. Experiments on the deposition of multi-track block samples are carried out, as a result of which the values of the temperatures are obtained at fixed points. The proposed model makes it possible to reproduce temperature fields at various values of the technological process parameters. It is confirmed by comparisons with experimental thermocouple data. The relative difference in the interlayer temperature does not exceed 15%.

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Directed energy deposition (DED) additive manufacturing: Physical characteristics, defects, challenges and applications

Cited by 621 publications

References 155 publications

The Effect of a Slow Strain Rate on the Stress Corrosion Resistance of Austenitic Stainless Steel Produced by the Wire Laser Additive Manufacturing Process

The Effect of a Slow Strain Rate on the Stress Corrosion Resistance of Austenitic Stainless Steel Produced by the Wire Laser Additive Manufacturing Process

Measurement of the Anisotropic Dynamic Elastic Constants of Additive Manufactured and Wrought Ti6Al4V Alloys

An Extended Analytical Solution of the Non-Stationary Heat Conduction Problem in Multi-Track Thick-Walled Products during the Additive Manufacturing Process

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