• Applied Chemistry for Engineering
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• v.17 no.5
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• pp.498-503
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• 2006

i-(2',5'-Diketotetrahydrofuranyl)octadecenyl acid (OSA), an intermediate for the lubricating oil additive, was prepared by the ene-reaction of oleic acid with maleic anhydride. The reaction progress was monitored by gas chromatography by analyzing the amount of OSA. The series of succinimidyl compounds were synthesized by the reaction of alkyl amines and OSA. As a kind of lubricant additives, demulsibility, anti-wear, and anti-corrosion properties of these succinimidyl compounds were measured. The derivative of octadecylamine which has relatively long-chained alkyl group has showed good properties.

• Journal of the Korean institute of surface engineering
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• v.44 no.5
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• pp.190-195
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• 2011

Diamond-like carbon (DLC) has many outstanding properties such as low friction, high wear resistance and corrosion resistance. However, it is difficult to achieve enough adhesion on the metal substrates because of weak bonding between DLC film and the metal substrate. The purpose of this study is to enhance an adhesion of DLC film. For improving adhesion, the substrate was treated by active screen plasma nitriding before DLC film deposing. Nitrided substrates were investigated by Glow Discharge Spectrometer (GDS), Micro-Vickers Hardness. DLC films were deposited on several metals by linear ion source, and characteristics of the films were investigated using nano-indentation, Field Emission Scanning Electron Microscope (FESEM). The adhesion was measured by scratch tester. The adhesion of DLC films was increased when nitriding layer was formed before DLC deposition. Therefore, the adhesion of DLC film can be enhanced as increasing the hardness of materials.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.29-29
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• 2014

최근 화석에너지 고갈 및 에너지 수요의 폭발적 팽창을 해결하기 위하여 경량화와 내마모 측면에서 고효율 시스템을 적용한 자동차 및 각종 성형 기기들이 개발되고 있다. 특히 장치의 고성능화라는 요구조건을 충족시키기 위해서는 금속가공산업에서 표면개질의 중요성이 부각되고 있다. 이러한 표면개질에는 일반적으로 표면의 성질을 개선하여 마모(abrasion) 및 국부 압력(local stress) 또는 피로(fatigue), 마식(wear and corrosion)에 견디게 하여 부품의 수명증대와 제품의 소형화에 기여하고 있다. 이러한 표면개질법에는 경질의 물질을 표면에 코팅시켜 재료표면의 특성을 향상시키는 방법과 금속의 표면에 다른 원소를 침투 및 확산시키는 방법으로 나눌 수 있다. 확산방법으로 침탄, 질화, 보로나이징, 크마이징 처리 방법 등이 있다. 상업적으로 가장 많이 사용되는 표면 개질법은 침탄기술로서, 고온에서 짧은 시간내에 물성 향상이 가능하지만, 강의 변태점 이상의 온도에서 진행됨으로서, 변형에 따른 문제가 발생되어 후처리를 필요로 하는 문제점을 가지고 있다. 반면, 질화법은 변태점 이하의 저온에서 철강 표면에 N을 침투시켜 강을 경화시키는 특징을 가진다. 변형이 적고 질소원자가 강내에 침투함으로 인해 내마모성, 내피로성, 내식성 등의 물리적 성질을 향상시키는 점에서 유리하여 각종 정밀 부품 및 자동차 부품, 금형 등에 많이 사용된다. 또한, 경도 향상 및 결정구조의 영향으로 코팅처리시 모재와 코팅 층의 밀착력 향상을 가져오면 이러한 이유로 코팅 층의 하지 층으로써 각광 받고 있다. 본 발표에서는 플라즈마 질화의 이해를 높이기 위해 관련 기술에 대한 전반적인 소개와 향후 플라즈마 질화 기술의 적용이 기대되는 침탄대체 적용 가능 부품, 침류질화 기술, PECVD 공정과의 접목 등 산업적은 응용 측면에서 응용 분야에 대한 소개를 진행하고자 한다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.7-11
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• 2012

Plasma electrolytic oxidation of magnesium alloys is a well known technique to produce corrosion and wear resistant coatings. The addition of particles to the electrolyte provides a possibility to produce coatings with an increasing range of composition by in-situ incorporation of those particles into the coating. An extensive literature review has revealed that the mode of incorporation depends mainly on the melting point of the used particles and the energy provided by the discharges of the PEO process. The spectrum ranges from inert to partly reactive incorporation, but a complete reactive incorporation and a formation of a new single phase coating was not observed so far. Thus a new approach in PEO processing is introduced using specific particles as a kind of sintering additive, changing not only the composition but lowering the melting temperature and increase the liquid phase fraction during the discharges, resulting in a new amorphous coating.

• Nuclear Engineering and Technology
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• v.46 no.4
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• pp.521-528
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• 2014

The surface modification of engineering materials by laser beam scanning (LBS) allows the improvement of properties in terms of reduced wear, increased corrosion resistance, and better strength. In this study, the laser beam scan method was applied to produce an oxide dispersion strengthened (ODS) structure on a zirconium metal surface. A recrystallized Zircaloy-4 alloy sheet with a thickness of 2 mm, and $Y_2O_3$ particles of $10{\mu}m$ were selected for ODS treatment using LBS. Through the LBS method, the $Y_2O_3$ particles were dispersed in the Zircaloy-4 sheet surface at a thickness of 0.4 mm, which was about 20% when compared to the initial sheet thickness. The mean size of the dispersive particles was 20 nm, and the yield strength of the ODS treated plate at $500^{\circ}C$ was increased more than 65 % when compared to the initial state. This strength increase was caused by dispersive $Y_2O_3$ particles in the matrix and the martensite transformation of Zircaloy-4 matrix by the LBS.

• Korean Journal of Materials Research
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• v.23 no.1
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• pp.72-80
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• 2013

Recently, consumption of magnesium alloys has increased especially in the 3C (computer, communication, camera) and automobile industries. The structural application of magnesium alloys has many advantages due to their low densities, high specific strength, excellent damping and anti-eletromagnetic properties, and easy recycling. However, practical application of these alloys has been limited to narrow uses of mild condition, because they are inferior in corrosion resistance and wear resistance due to their high chemical reactivity and low hardness. Various wet and dry processes are being used or are under development to enhance alloy surface properties. Various conversion coating and anodizing methods have been developed in a view of eco-friendly concept. The conventional technologies, such as diffusion coating, sol-gel coating, hydrothermal treatment, and organic coating, are expected to be newly applicable to magnesium alloys. Surface treatments for metallic luster or coloring are suggested using the control of the micro roughness. This report reviews the recent R&D trends and achievements in surface treatment technologies for magnesium alloys.

• Journal of Welding and Joining
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• v.14 no.4
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• pp.43-52
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• 1996

The plasma sprayed Cr$_{2}$C$_{2}$-NiCr coatings are widely used as wear-resistant and corrosion-resistant materials. The mechanical properties of the plasma sprayed Cr$_{2}$C$_{2}$-NiCr coatings were examined in this study. The distribution of the residual stress with the coating thickness was also examined by X-ray diffraction method. The pore in the coatings could be classified into two types ; one is the intrinsic pore originated from the spraying powder, the other is the extrinsic pore formed during spraying. During the tensile adhesion test, the fracture occurred at the interface of top coat and substrate or top coat and bond coat depending on the existence of bond coat. It was found that the compressive residual stress near the interface decreased with the increase of the top coat thickness. The tensile adhesion strength of the coating without bond coat was higher than that with bond coat, because the coating with bond coat has higher horizontal crack density near the interface between bond coat and top coat.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.423-424
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• 2005

The performance of HANA claddings was evaluated in out-of-pile conditions. All the performance test results revealed that HANA claddings were superior to the reference claddings such as Zircaloy-4 and A-cladding. Corrosion resistance was improved by 60 to 70% compared to the commercial claddings. Creep, burst, tensile, LOCA, wear and microstructural properties were shown to be as good as the commercial claddings.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.2
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• pp.158-164
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• 2004

Steam generator tubes experience widespread degradations such as stress corrosion cracking, wear, tube rupture, denting, fatigue and so on. The resulting damages can cause tube bursting or leak of the primary water which contains radioactivity Therefore the allowable size of the damage is required to be determined on the maintenance purpose. The burst pressure of a tube with a T-type combination crack consisting of longitudinal and circumferential cracks is obtained experimentally and analytically. Fracture parameters such as stress intensity factor and crack opening angle are investigated. Also the burst pressure for a T-type combination crack is compared with that of a single longitudinal crack to develop a length-based criteria.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2928-2933
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• 2008

Trends of the automotive market require the application of new engine technologies, which allows for the use of different types of fuel. Since ethanol is a renewable source of energy and it contributes to lower $CO_2$ emissions, ethanol produced from biomass is expected to increase in use as an alternative fuel. It is recognized that for spark ignition (SI) engines ethanol has advantages of high octane number and high combustion speed. In spite of the advantages of ethanol, fuel supply system might be affected by fuel blends with ethanol like a wear and corrosion of electric fuel pumps. So the on-board hydrogen production out of ethanol reforming can be considered as an alternative plan. This paper investigates the influence of ethanol fuel on SI engine performance, thermal efficiency and emissions. The combustion characteristics with hydrogen-enriched gaseous fuel from ethanol reforming are also examined.