• Archives of Metallurgy and Materials
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• 제65권4호
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• pp.1365-1369
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• 2020

Direct energy deposition (DED) is a three-dimensional (3D) deposition technique that uses metallic powder; it is a multi-bead, multi-layered deposition technique. This study investigates the dependence of the defects of the 3D deposition and the process parameters of the DED technique as well as deposition characteristics and the hardness properties of the deposited material. In this study, high-thermal-conductivity steel (HTCS-150) was deposited onto a JIS SKD61 substrate. In single bead deposition experiments, the height and width of the single bead became bigger with increasing the laser power. The powder feeding rate affected only the height, which increased as the powder feeding rate rose. The scanning speed inversely affected the height, unlike the powder feeding rate. The multi-layered deposition was characterized by pores, a lack of fusion, pores formed by evaporated gas, and pores formed by non-molten metal inside the deposited material. The porosity was quantitatively measured in cross-sections of the depositions, revealing that the lack of fusion tended to increase as the laser power decreased; however, the powder feeding rate and overlap width increased. The pores formed by evaporated gas and non-molten metal tended to increase with rising the laser power and powder feeding rate; however, the overlap width decreased. Finally, measurement of the hardness of the deposited material at 25℃, 300℃, and 600℃ revealed that it had a higher hardness than the conventional annealed SKD61.

• 소성∙가공
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• 제25권6호
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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.

• 한국분말재료학회지
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• 제31권4호
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• pp.302-307
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• 2024

This study explored the process-structure-property (PSP) relationships in Ti-6Al-4V alloys fabricated through direct energy deposition (DED) additive manufacturing. A systematic investigation was conducted to clarify how process variables-specifically, manipulating the cooling rate and energy input by adjusting the laser power and scan speed during the DED process-influenced the phase fractions, pore structures, and the resultant mechanical properties of the samples under various processing conditions. Significant links were found between the controlled process parameters and the structural and mechanical characteristics of the produced alloys. The findings of this research provide foundational knowledge that will drive the development of more effective and precise control strategies in additive manufacturing, thereby improving the performance and reliability of produced materials. This, in turn, promises to make significant contributions to both the advancement of additive manufacturing technologies and their applications in critical sectors.

• 소성∙가공
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• 제27권5호
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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.

• 한국분말재료학회지
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• 제29권1호
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• pp.8-13
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• 2022

In this study, we have prepared a Ti-6Al-4V/V/17-4 PH composite structure via a direct energy deposition process, and analyzed the interfaces using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The joint interfaces comprise two zones, one being a mixed zone in which V and 17-4PH are partially mixed and another being a fusion zone in the 17-4PH region which consists of Fe+FeV. It is observed that the power of the laser used in the deposition process affects the thickness of the mixed zone. When a 210 W laser is used, the thickness of the mixed zone is wider than that obtained using a 150 W laser, and the interface resembles a serrated shape. Moreover, irrespective of the laser power used, the expected σ phase is found to be absent in the V/17-4 PH stainless steel joint; however, many VN precipitates are observed.

• 한국기계가공학회지
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• 제19권3호
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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.

• The Korean Journal of Ceramics
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• 제3권3호
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• pp.173-176
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• 1997

Direct metal ion beam deposition is considered to be a whole new thin film deposition technique. Unlike other conventional thin film deposition processes, the individual deposition particles carry its own ion beam energies which are directly coupled for the formation of this films. Due to the nature of ion beams, the energies can be controlled precisely and eventually can be tuned for optimizing the process. SKION's negative C- ion beam source is used to investigate the initial nucleation mechanism and growth. Strong C- ion beam energy dependence has been observed. Complete phase control of sp3 and sp3, control of the C/SiC/Si interface layer, control of crystalline and amorphous mode growth, and optimization of the physical properties for corresponding applications can be achieved.

• 한국정밀공학회지
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• 제33권11호
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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.

• 한국레이저가공학회지
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• 제18권3호
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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.

• 한국분말재료학회지
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• 제25권3호
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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.