• Tribology and Lubricants
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• v.29 no.6
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• pp.366-371
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• 2013

Various heat treatment and surface coating methods have been applied to machine parts. Nowadays, diamond-like carbon (DLC) coatings are widely used because of their excellent tribological characteristics. Despite the numerous studies on DLC-coated engineering surfaces, the exact wear mechanisms related to the coating thickness and elastic modulus have not been fully examined. In this study, a sliding contact problem between a small spherical hard particle and a DLC-coated steel surface is analyzed using a nonlinear finite element code, MARC. The maximum principal stress distributions and deformed surfaces are compared for different coating thicknesses and Young's modulus values. Plastically deformed surface shapes such as a groove and torus indicate that the most dominant wear mechanism for a DLC-coated surface is abrasive wear. Fatigue wear can also play a role in a case where the coating thickness is relatively large and the elastic modulus is high.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.1
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• pp.67-74
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• 2008

In this paper, the surface characteristics of the AIP-TiN coated of the SKH51 and SKD11 steels under various deposition times are presented with emphasis on the comparison of the two materials. The micro-particle, the surface roughness, the micro-hardness, the coated layer thickness, the atomic distribution of Ti, N and Fe elements and the adhesion are measured for various deposition times. It has been shown that the micro-particle, the surface roughness, the coated layer thickness and the atomic distribution of Ti, N and Fe elements are similar for the two cases regardless of the test deposition time from 10 to 180 minutes. However, it has been shown that the micro-hardness and the adhesion of the SKH51 steel are higher than the SKD11 steel, indicating that they are much affected by the hardness of the material to be coated.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.603-609
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• 2008

The recycled aggregates which were produced from the waste concretes have the disadvantages of inferior properties for natural aggregate. Therefore, in order to reuse the recycled aggregate it must be solved to improve the quality of recycled aggregate. In this study, the quality of recycled aggregate was improved by the surface treatment method using the colloidal silica solution. And, in order to examine the possibility of reusing the surface coated recycled aggregate in constructing concrete structures, we studied the mechanical properties and durability of the concrete using the surface coated recycled aggregates and the other concrete.

• Journal of the Korean institute of surface engineering
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• v.30 no.2
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• pp.93-103
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• 1997

High temperature materials used in the elevated temperature and corrosive atmosphere must have the good oxidation resistance and preserve their own mechanical properties simultaneously. For the oxidation resistance, it is very important to form a protective oxide scale such as $Al_2O_3$ or $Cr_2O_3$ on the substrate. However, the additions of protective oxide forming elements such as Cr and Al in the alloy to enhance its oxidation resistance are limited due to the deleterious effects on their mechanical properties. PECVD(P1asma Enhanced Chemical Vapor Deposition) coating processes were employed to improve the oxidation resistance at high temperature. Cr and/or A1 were coated on the substrates of Ni and Inconel 600 at various temperatures of 400, 500, $600^{\circ}C$ and at different conditions of specimen surfaces. Then, coated specimens were exposed to isothermal and cyclic oxidation conditions in air at 1000 and $1100^{\circ}C$. In order to enhance the adhesion between the substrate and coated layer, heat treatments of the coated specimens were conducted in a vacuum. At isothermal oxidation experiments, Al-coated Ni specimen showed better oxidation resistance than pure Ni. At cyclic oxidation experiments at $1000^{\circ}C$. Cr and Al-coated specimen showed better oxidation resistance. Cr-coated Inconel 600 had also showed better oxidation resistance due to Cr in the substrate. By PECVD coating process, oxidation resistance could be improved, but it was not improved as expected due to the weakness of the adhesion between the substrate and the coated layer.

• Journal of the Korean institute of surface engineering
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• v.51 no.5
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• pp.263-270
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• 2018

Ag-coated Cu dendrites were prepared as a filler for an electromagnetic interference shielding application. Ag layers on the Cu dendrites was coated by two approaches. One is a direct autocatalytic plating with a reducing agent. The other approach was achieved by two-step plating, a galvanic displacement reaction to form Ag seed layers on Cu following by an autocatalytic plating with a reducing agent. The procedure-dependent average particle size and tap density of Ag-coated Cu dendrites were characterized. The electrical resistance and electromagnetic interference shielding effect (EMI SE) were analyzed with the Ag-coated Cu dendrites prepared in the two approaches. Additionally, the content of the Ag coated on Cu dendrites was controlled from 2% to 20%. The electrical resistance and EMI SE were critically determined by Ag contents coated on Cu.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.1
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• pp.85-91
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• 2003

The experimental study for turning circular free fanned surface with TiN coated insert tool was conducted for different cutting conditions such as cutting speed, feed rate and depth-of-cut. For the fluctuation of 1.0mm depth-of-cut, the characteristics for machined surface and tool wear were less influenced by the feed rate and cutting speed than those of higher depth of cut. The higher surface roughness and surface precision were obtained in lower cutting speed. For the fluctuation of 1.5mm depth-of-cut, the higher surface roughness was obtained for the case of the lower feed rate of 0.05-10mm/rev and the higher cutting speed of 80m/min. For the fluctuation of 2.0mm depth-of-cut, the surface roughness and surface precision were too worse to machine the specimen And the flank wear on the tool was increased rapidly rather than the crater wear.

• Journal of the Korean institute of surface engineering
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• v.31 no.6
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• pp.400-406
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• 1998

Tool life characteristics were investigated for the TiN coated (PVD) tungsten carbide cutting tools to improve the tool life Experimental variables for Tin coating were coating time and cathode bias voltage and cuting variables were cutting speed and feel rate. As a experiment result, TiN coated tool was extended about from 2.14 to 2.7 times than that of not coated tungsten carbide tools. Also, coating thinkness is much affected to tool life.

• Journal of the Korean institute of surface engineering
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• v.24 no.2
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• pp.80-87
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• 1991

Investigations have been made in order to improve the toughness of TiC coated Cemented Carbide tools by CVD. The effects of coating parameters on TiC layer and eta phase and the effects of the thickness of TiC Coated layer and eta phase on TRS were studied.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.645-649
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• 2009

Liquid desiccant cooling technology can supply cooling by using waste heat and solar heat which are hard to use effectively. For compact and efficient design of a dehumidifier, it is important to sustain sufficient heat and mass transfer surface area for water vapor diffusion from air to liquid desiccant on heat exchanger. In this study, the plate type heat exchanger is adopted which has extended surface, and hydrophilic coating and porous layer coating are adopted to enhance surface wettedness. PP(polypropylene) plate is coated by porous layer and PET(polyethylene terephthalate) non-woven fabric is coated by hydrophilic polymer. These coated surfaces have porous structure, so that falling liquid film spreads widely on the coated surface foaming thin liquid film by capillary force. The temperature of liquid desiccant increases during dehumidification process by latent heat absorption, which leads to loss of dehumidification capacity. Liquid desiccant is cooled by cooling water flowing in plate heat exchanger. On the plate side, the liquid desiccant can be cooled by internal cooling. However the liquid desiccant on extended surface should be moved and cooled at heat exchanger surface. Optimal mixing and distribution of liquid desiccant between extended surface and plate heat exchanger surface is essential design parameter. The experiment has been conducted to verify effective surface treatment and distribution characteristics by measuring wall side flow rate and visualization test. It is observed that hydrophilic and porous layer coating have excellent wettedness, and the distribution can be regulated by adopting holes on extended surface.

• The Korean Journal of Ceramics
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• v.2 no.4
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• pp.203-211
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• 1996

CVD diamond tools are becoming more widely used in industry as an economic alternative to polycrystalline diamond (PCD) for machining non-ferrous and non-metallic materials. Although CVD diamond-sheet tools have been on the market for several years, diamond-coated carbide inserts have become available only recently, with the successful resolution of long-standing adhesion problems. Diamond coating morphology on the rake surface of the tool affects chip formation favorably, whereas a microscopically rough, faceted morphology on the flank surface of the tool produces a rough workpiece finish. Workpiece finish can be improved by using a coated tool with a larger nose radius. The tool life provided by diamond-coated tools(~30 $\mu\textrm{m}$ thick) can meet or exceed that of PCD tools, depending on the characteristics of the workpiece material. When using diamond-coated carbide tools in milling, a sharp-edged PCD tool should be used in the wiper position of the cutter to minimize workpiece roughness and burr formation.