• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.872-876
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• 2017

Laser Based 3D Printing is an recently advance manufacturing technology for making complex shape comopnent such as automobile and aerospace. So in this article, stainless steel 316L was manufactured by Selective Laser Melting (SLM) and Laser Melting Deposition (LMD) method. SLM is an additive manufacturing process that allow for the manufacture of small and complex component by laser melting and solidification of powder in bed using a high intensity laser beam. The results showed that the laser scanning speed and laser power affects the defect, microstructure and the hardness of the components.

• Korean Journal of Metals and Materials
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• v.50 no.3
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• pp.191-200
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• 2012

The purpose of this paper is to review the state of laser processing technology using metal powders. In recent years, a series of research and development efforts have been undertaken worldwide to develop laser processing technologies to fabricate metal-based parts. Layered manufacturing by the laser melting process is gaining ground for use in manufacturing rapid prototypes (RP), tools (RT) and functional end products. Selective laser sintering / melting (SLS/SLM) is one of the most rapidly growing rapid prototyping techniques. This is mainly due to the processes's suitability for almost any materials, including polymers, metals, ceramics and many types of composites. The interaction between the laser beam and the powder material used in the laser melting process is one of the dominant phenomena defining feasibility and quality. In the case of SLS, the powder is not fully melted during laser scanning, therefore the SLS-processed parts are not fully dense and have relatively low strength. To overcome this disadvantage, SLM and laser cladding (LC) processes have been used to enable full melting of the powder. Further studies on the laser processing technology will be continued due to the many potential applications that the technology offers.

• Transactions of Materials Processing
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• v.22 no.6
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• pp.334-339
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• 2013

Direct Laser Melting is a prototyping process whereby a 3-D part is built layer wise by melting the metal powder with laser scanning. This process is strongly influenced by the shielding gas and the laser operating parameters such as laser power, scan rate, layering thickness, and rescanning. The shielding gas is especially important in affecting the microstructure and mechanical properties. In the current study, fabrication experiments were conducted in order to analyze the effect of shielding gas on the forming characteristics of direct laser melting. Cylindrical parts were produced from a Fe-Ni-Cr powder with a 200W fiber laser. Surface quality, porosity and hardness as a function of the layering thickness and shield gas were evaluated. By decreasing the layering thickness, the surface quality improved and porosity decreased. The selection of which shield gas, Ar or $N_2$, to obtain better surface quality, lower porosity, and higher hardness was examined. The formability and mechanical properties with a $N_2$ atmosphere are better than those parts formed under an Ar atmosphere.

• Journal of Dental Rehabilitation and Applied Science
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• v.37 no.1
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• pp.39-47
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• 2021

Compared to conventional method, if metal framework of removable partial denture is fabricated by selective laser melting, various laboratory works are omitted, saving time and simplifying the process. In addition, metal framework with homogeneous density can be obtained, expecting excellent mechanical properties, especially resistance to fatigue fracture. In these cases, impression were taken using conventional methods in partial edentulous patients, master casts were fabricated and scanned to obtain digital data. After designing the metal frameworks on the scanned data, removable partial dentures were fabricated using selective laser melting methods. Through these procedure, satisfactory outcomes were achieved both in functional and esthetic aspects.

• Transactions of Materials Processing
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• v.20 no.2
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• pp.118-123
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• 2011

Manufacturing of the bipolar plate of a direct methanol fuel cell (DMFC) by direct laser melting technology (DLM) was attempted. The DLM technology is highly influenced by process parameters such as laser power, scan rate and layering height. Therefore, an analysis of the DLM technology was performed under various conditions. The bipolar plates were fabricated using the DLM process with 316L stainless steel (STS 316L) plates and powder. Powder melting trials at various energy density were performed in order to select a feasible melting range for a given laser power. The melting line height increases and eventually saturates when the energy density increases, but decreases when the laser power increases at a given energy density. For the estimation of the potential performance of the bipolar plate, the surface roughness and contact resistance of the DLM layer were also analyzed. The changes of line height and thickness are useful information to report when manufacturing bipolar plate of fuel cell through the DLM process.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.139-144
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• 2003

Laser melting problems with deformed substrates are investigated by axisymmetric numerical simulations. Source-based method is used to solve the energy equation, and the momentum equations are solved in the liquid domain with SIMPLER algorithm. Using a laser beam with a top-hat heat flux distribution, this study is performed to examine the effect of surface deformation, beam power density and surface tension force on the melt pool during laser melting. Surface temperature decreases with increasing surface deformation, while surface velocity increases. It is found that surface deformation, beam power density and surface tension force have a very significant effect on heat transfer and fluid flow during laser melting.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.1 s.232
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• pp.1-8
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• 2005

Laser melting problems with deformed substrates are investigated by axisymmetric numerical simulations. Source-based method is used to solve the energy equation, and the momentum equations are solved in the liquid domain with SIMPLER algorithm. Using a laser beam with a top-hat heat flux distribution, this study is performed to examine the effect of surface deformation, beam power density and surface tension force on the molten pool during laser melting. Surface temperature decreases with increasing surface deformation, while surface velocity increases. It is found that surface deformation, beam power density and surface tension force have a very significant effect on heat transfer and fluid flow during laser melting.

• Transactions of Materials Processing
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• v.19 no.8
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• pp.517-522
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• 2010

Selective laser melting (SLM) is emerged as a new manufacturing technique to directly fabricate precise parts using metallic materials. The final characteristics of a component fabricated through the SLM process are strongly dependent upon various parameters such as laser power, scan rate and pulse duration, etc. This paper, therefore, focuses on the dimensional characteristics of melted $20{\mu}m$ Fe-Cr-Ni powder by fiber laser for the selective laser melting process. With energy density decrease, the height and depth were decreased. Although the conditions are of the same energy density, the shape is different by laser power and scan rate. The shapes at various laser parameters were divided into 3 groups based on depth over height. The smooth regular shape is obtained under the conditions of $50{\mu}m$ of powder height and $15-20{\mu}s$ of pulse duration. And the laser power influenced the variation of shape more significantly than the scan rate.

• Journal of Welding and Joining
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• v.34 no.1
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• pp.75-81
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• 2016

This study applied laser surface melting process using CW(Continuous wave) Yb:YAG laser and cold-work die steel SM45C and investigated microstructure and hardness. Laser beam speed, power and beam interval are fixed at 70 mm/sec, 2.8 kW and $800{\mu}m$ respectively. Depth of Hardening layer(Melting zone) was a minimum of 0.8 mm and a maximum of 1.0 mm that exceeds the limit of minimum depth 0.5 mm applying trimming die. In all weld zone, macrostructure was dendrite structure. At the dendrite boundary, Mn, Al, S and O was segregated and MnS and Al oxide existed. However, this inclusion didn't observe in the heat-affected zone (HAZ). As a result of interpreting phase transformation of binary diagram, MnS crystallizes from liquid. Also, it estimated that Al oxide forms by reacting with oxygen in the atmosphere. The hardness of the melting zone was from 650 Hv to 660 Hv regardless of the location that higher 60 Hv than the hardness of the HAZ that had maximum 600 Hv. In comparison with the size of microstructure using electron backscatter diffraction(EBSD), the size of microstructure in the melting zone was smaller than HAZ. Because it estimated that cooling rate of laser surface melting process is faster than water quenching.

• Transactions of Materials Processing
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• v.25 no.3
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• pp.195-202
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• 2016

Direct laser melting(DLM) is an additive manufacturing process that can produce parts by solidification of molten metallic powder layer by layer. The properties of the fabricated parts strongly depend on characteristics of the metallic powder. Atomized powders having spherical morphology have commonly been used for DLM. Mechanical ball-milling is a powder processing technique that can provide non-spherical solid powders without melting. The aim of the current study was to investigate the effect of powder morphologies on the deposition quality in DLM. To characterize the morphological effect, the performances of spherical and non-spherical powders were compared using both single- and multi-track DLM experiments. DLM experiments were performed with various laser process parameters such as laser power and scan rate, and the deposition quality was evaluated. The surface roughness, cross-section bead shape and process defects such as balling or non-filled area were compared and discussed in this study.