• Title/Summary/Keyword: Direct Energy Deposition (DED)

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Study of High Speed Steel AISI M4 Powder Deposition using Direct Energy Deposition Process (DED 기술을 이용한 고속도 공구강 M4 분말 적층에 관한 연구)

  • Lee, E.M.;Shin, G.W.;Lee, K.Y.;Yoon, H.S.;Shim, D.S.
    • Transactions of Materials Processing
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    • v.25 no.6
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    • pp.353-358
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    • 2016
  • Direct energy deposition (DED) is an additive manufacturing technique that involves the melting of metal powder with a high-powered laser beam and is used to build a variety of components. In recent year, it can be widely used in order to produce hard, wear resistant and/or corrosion resistant surface layers of metallic mechanical parts, such as dies and molds. For the purpose of the hardfacing to achieve high wear resistance and hardness, application of high speed steel (HSS) can be expected to improve the tool life. During the DED process using the high-carbon steel, however, defects (delamination or cracking) can be induced by rapid solidification of the molten powder. Thus, substrate preheating is generally adopted to reduce the deposition defect. While the substrate preheating ensures defect-free deposition, it is important to select the optimal preheating temperature since it also affects the microstructure evolution and mechanical properties. In this study, AISI M4 powder was deposited on the AISI 1045 substrate preheated at different temperatures (room temperature to $500^{\circ}C$). In addition, the micro-hardness distribution, cooling rates, and microstructures of the deposited layers were investigated in order to observe the influence of the substrate preheating on the mechanical and metallurgical properties.

Effect of Groove Shapes on Mechanical Properties of STS316L Repaired by Direct Energy Deposition (직접 에너지 적층을 통한 STS316L 소재의 보수 공정에서 그루브 형상이 기계적 특성에 미치는 효과)

  • Oh, W.J.;Son, Y.;Son, J.Y.;Shin, G.W.;Shim, D.S.
    • Transactions of Materials Processing
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    • v.29 no.2
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    • pp.103-112
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    • 2020
  • This study explores the effects of different pre-machining conditions on the deposition characteristics and mechanical properties of austenitic stainless steel samples repaired using direct energy deposition (DED). In the DED repair process, defects such as pores and cracks can occur at the interface between the substrate and deposited material. In this study, we varied the shape of the pre-machined zone for repair in order to prevent cracks from occurring at the slope surface. After repairs by the DED process, macro-scale cracks were observed in samples that had been pre-machined with elliptic and trapezoidal grooves. In addition, it was not possible to completely prevent micro-crack generation on the sloped interfaces, even in the capsule-type grooved sample. From observation of the fracture surfaces, it was found that the cracks around the inclined interface were due to a lack of fusion between the substrate and the powder material, which led to low tensile properties. The specimen with the capsule-type groove provided the highest tensile strength and elongation (respective of 46% and 571% compared to the trapezoidal grooved specimen). However, the tensile properties were degraded compared to the non-repaired specimen (as-hot rolled material). The fracture characteristics of the repaired specimens were determined by the cracks at the sloped interfaces. These cracks grew and coalesced with each other to form macro-cracks, they then coalesced with other cracks and propagated to the substrate, causing final fracture.

Evaluation of Microstructures and Mechanical Properties in Functionally Graded Materials (STS 316L and Low Alloy Steel) Produced by DED Processes (DED 공정으로 제조된 경사조성재료 (STS 316L과 저합금강)의 미세조직 및 기계적특성 평가)

  • Shin, G.;Choo, W.;Yoon, J.H.;Yang, S.Y.;Kim, J.H.
    • Journal of Powder Materials
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    • v.29 no.4
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    • pp.309-313
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    • 2022
  • In this study, additive manufacturing of a functionally graded material (FGM) as an alternative to joining dissimilar metals is investigated using directed energy deposition (DED). FGM consists of five different layers, which are mixtures of austenitic stainless steel (type 316 L) and low-alloy steel (LAS, ferritic steel) at ratios of 100:0 (A layer), 75:25 (B layer), 50:50 (C layer), 25:75 (D layer), and 0:100 (E layer), respectively, in each deposition layer. The FGM samples are successfully fabricated without cracks or delamination using the DED method, and specimens are characterized using optical and scanning electron microscopy to monitor their microstructures. In layers C and D of the sample, the tensile strength is determined to be very high owing to the formation of ferrite and martensite structures. However, the elongation is high in layers A and B, which contain a large fraction of austenite.

Effect of Repair Width on Mechanical Properties of 630 Stainless Steel Repaired by Direct Energy Deposition Process (직접 에너지 적층 공정을 이용한 보수 공정에서 보수 폭에 따른 기계적 특성 관찰)

  • Oh, Wook-Jin;Shin, Gwang-Yong;Son, Yong;Shim, Do-Sik
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.19 no.3
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    • pp.42-50
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    • 2020
  • This study explores the effects of repair width on the deposition characteristics and mechanical properties of stainless steel samples repaired using direct energy deposition (DED). In the DED repair process, defects such as pores and cracks can occur at the interface between the substrate and deposited material. In this study, we changed the width of the pre-machined zone for repair in order to prevent cracks from occurring at the inclined surface. As a result of the experiment, cracks of 10-40 ㎛ in length were formed along the inclined slope regardless of the repair width. Yield and tensile strength decreased slightly as the repair width increased, but the total and uniform elongation increased. This is due to the orientation of the crack. For specimens with a repair width of 20 mm, yield and tensile strength were 883 MPa and 1135 MPa, respectively. Total and uniform elongations were 14.3% and 8.2%, respectively. During observation of the fracture specimens, we noted that the fracture of the specimen with an 8 mm repair width occurred along the slope, whereas specimens with 14 mm and 20 mm repair depths fractured at the middle of the repaired region. In conclusion, we found that tensile properties were dependent upon the repair width and the inclination of the crack occurred at the interface.

Development of a Metal 3D Printer Using Laser Powder Deposition and Process Optimization for Fabricating Titanium Alloy Parts (레이저 분말적층 방식을 이용한 금속 3D 프린터 개발 및 티타늄 합금 부품 제조공정 최적화)

  • Jeong, Wonjong;Kwon, Young-Sam;kim, Dongsik
    • Laser Solutions
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    • v.18 no.3
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    • pp.1-5
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    • 2015
  • A 3D printer based on laser powder deposition (LPD), also known as DED (direct energy deposition), has been developed for fabricating metal parts. The printer uses a ytterbium fiber laser (1070nm, 1kW) and is equipped with an Ar purge chamber, a three-dimensional translation stage and a powder feeding system composed of a powder chamber and delivery nozzles. To demonstrate the performance of the printer, a tapered cylinder of 320mm in height has been fabricated successfully using Ti-6Al-4V powders. The process parameters including the laser output power, the scan speed, and the powder feeding rate have been optimized. A 3D printed test specimen shows mechanical properties (yield strength, ultimate tensile strength, and elongation) exceeding the criteria to employed in a variety of Ti alloy applications.

Hardness and Microstructure evolution of SUS630 Stainless steel Fabricated by Directed Energy Deposition (Direct energy deposition 공정으로 제조된 SUS630 스테인리스강 적층조형체의 경도 및 미세조직 연구)

  • Back, Seong Eun;Noh, Kyung-Ho;Park, Jin Yong;Cho, Yong Ju;Kim, Jeoung Han
    • Journal of Powder Materials
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    • v.25 no.3
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    • pp.220-225
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    • 2018
  • The microstructure and mechanical characteristics of SUS630 specimens fabricated using the direct energy deposition (DED) process are investigated. In DED, several process parameters such as laser scan speed, chamber gas flow, powder carrier gas flow, and powder feed rate are kept fixed; the laser power is changed as 150 W, 180 W, and 210 W. As the laser power increases, the surface becomes smooth, the thickness uniformity improves, and the size and number of pores decreases. With the increase in laser power, the hardness deviation decreases and the average hardness increases. The microstructure of the material is columnar; pores are formed preferentially along the columnar interface. The lath-martensite phase governs the overall microstructure. The volumetric fraction of the retained austenite phase is measured to increase with the increase of laser input power.

A Study on Laser Welding for 3D Printed Metal Plate and Polymer (금속 3D 프린팅 소재와 폴리머 레이저접합에 관한 연구)

  • Ye, Kang-Hyun;Kim, Sung-Wook;Park, Geo-Dong;Choi, Hae-Woon
    • Journal of Welding and Joining
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    • v.34 no.4
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    • pp.23-27
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    • 2016
  • A 3D printed metal part and thermal plastic polymer part were joined by direct laser irradiation. The 3D metal part was fabricated by using DED(Direct Energy Deposition) with STS316 material. The experiment was carried out through no patterned metal surface, 3D metal printed surface and micro laser patterned surface. The most secure joining quality was obtained at the laser micro patterned surface specimen and the counterparts of polymers were PLA and PE based thermo plastics. The applied laser power was 350Watt and the distance of patterns was maintained at $150{\mu}m$. The laser line width was optimized at $450{\mu}m$ and the laser micro pattern depth was $180{\mu}m$ for the best joining quality. Based on the result analysis, the possibility of laser material joining for metal to polymer was proposed and multi-material joining will be possible in 3D laser direct material fabrication.

Measurement of minimum line width of an object fabricated by metal 3D printer using powder bed fusion type with stainless steal powder (스테인리스강을 사용한 분말 적층 용융 방식의 금속 3차원 프린터에서 제작된 물체의 최소 선폭 측정)

  • Son, BongKuk;Jeong, Youn Hong;Jo, Jae Heung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.10
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    • pp.346-351
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    • 2018
  • Metal three-dimensional (3D) printing technologies are mainly classified as powder bed fusion (PBF) and direct energy deposition (DED) methods according to the method of application of a laser beam to metallic powder. The DED method can be used to fabricate fine and hard 3D metallic structures by applying a strong laser beam to a thin layer of metallic powder. The PBF method involves slicing 3D graphics to be a certain height, laminating metal powders, and making a 3D structure using a laser. While the DED method has advantages such as laser cladding and metallic welding, it causes problems with low density when 3D shapes are created. The PBF method was introduced to address the structural density issues in the DED method and makes it easier to produce relatively dense 3D structures. In this paper, thin lines were produced by using PBF 3D printers with stainless-steel powder of roughly $30{\mu}m$ in diameter with a galvano scanner and fiber-transferred Nd:YAG laser beam. Experiments were carried out to find the optimal conditions for the width of a line depending on the processing times, laser power, spot size, and scan speed. The optimal conditions were two scanning processes in one line structure with a laser power of 30 W, spot size of $28.7{\mu}m$, and scan speed of 200 mm/s. With these conditions, a minimum width of about $85.3{\mu}m$ was obtained.

Preliminary Study on Improvement of Surface Characteristics of Stellite21 Deposited Layer by Powder Feeding Type of Direct Energy Deposition Process Using Plasma Electron Beam (플라즈마 전자빔을 이용한 분말공급형 직접식 에너지 적층 공정으로 제작된 Stellite21 적층층의 표면 특성 개선에 관한 기초 연구)

  • Kim, Dong-In;Lee, Ho-Jin;Ahn, Dong-Gyu;Kim, Jin-Seok;Kang, Eun Goo
    • Journal of the Korean Society for Precision Engineering
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    • v.33 no.11
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    • pp.951-959
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    • 2016
  • The aim of this paper is to investigate the improvement of surface characteristics of Stellite21 deposited layer by powder feeding type of direct energy deposition (DED) process using a plasma electron beam. Re-melting experiments of the deposited specimen is performed using a three-dimensional finishing system with a plasma electron beam. The acceleration voltage and the travel speed of the electron beam are chosen as process parameters. The effects of the process parameters on the surface roughness and the hardness of the re-melted region are examined. The formation of the re-melted region is observed using an optical microscope. Results of these experiments revealed that the re-melting process using a plasma electron beam can greatly improve the surface qualities of the Stellite21 deposited layer by the DED process.

Study on Effects of Direct Laser Melting Process Parameters on Deposition Characteristics of AlSi12 powders (AlSi12 분말의 직접 레이저 용융 적층 시 공정 조건에 따른 적층 특성에 관한 연구)

  • Seo, J.Y.;Yoon, H.S.;Lee, K.Y.;Shim, D.S.
    • Transactions of Materials Processing
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    • v.27 no.5
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    • pp.314-322
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    • 2018
  • AlSi12 is a heat-resistant aluminum alloy that is lightweight, corrosion-resistant, machinable and attracting attention as a functional material in aerospace and automotive industries. For that reason, AlSi12 powder has been used for high performance parts through 3D printing technology. The purpose of this study is to observe deposition characteristics of AlSi12 powder in a direct energy deposition (DED) process (one of the metal 3D printing technologies). In this study, deposition characteristics were investigated according to various process parameters such as laser power, powder feed rate, scan speed, and slicing layer thickness. In the single track deposition experiment, an irregular bead shape and balling or humping of molten metal were formed below a laser power of 1,000 W, and the good-shaped bead was obtained at 1.0 g/min powder feed rate. Similar results were observed in multi-layer deposition. Observation of deposited height after multi-layer deposition revealed that over-deposition occurred at all conditions. To prevent over-deposition, slicing layer thickness was experimentally determined at given conditions. From these results, this study presented practical conditions for good surface quality and accurate geometry of deposits.