• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.6
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• pp.107-112
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• 2011

FFV(Flexible Fuel Vehicle) is the vehicle that can be used liberally from gasoline to E100(Ethanol 100%) for fuel. Recently, interest in the bio-fuel is increased by the environmental factors like exhaustion of the fossil fuel and ruduction of greenhouse gases. For the reason, adopting of FFV is activated in the world including North and South America. In general, bio-ethanol has highly corrosive substance in compare with gasoline. In the part of fuel system, corrosion can make a safety problem in case of fuel leakage and engine starting problem. So the fuel system of FFV have to be made of high corrosion-resistant materials. This study examined the effect of bio-ethanol on the durability properties according to component materials in FFV fuel pump motor and regulator using the High Temperature Fuel Circulation Test.

• Korean Journal of Metals and Materials
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• v.48 no.9
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• pp.813-818
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• 2010

In current automobile and electronic industries, the use of magnesium alloys where both energy and weight saving are attainable is increasing. Despite their light weight, there has been an inherent drawback arising from the surface vulnerable to be oxidized with ease, specifically under corrosive environments. To protect magnesium alloy from corrosion, the present work deals with the electrochemical response of the oxide layer on magnesium alloy specimen prepared by plasma electrolytic oxidation (PEO) method in an electrolyte with zirconia powder. Surface observation using scanning electron microscopy evidences that a number of zirconia particles are effectively incorporated into oxide layer. From the results of potentio-dynamic tests in 3.5 wt% NaCl solution, the PEO-treated sample containing zirconia particles shows better corrosion properties than that without zirconia, which is the result of zirconia incorporation into the coating layer. Corrosion resistance is also measured by utilizing salt spray tests for 120 hrs.

• Journal of Korea Foundry Society
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• v.43 no.2
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• pp.55-63
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• 2023

Due to the importance of the surface on the final slab quality, it is essential to maintain a smooth segment roll surface that is in touch with the thin solid shell during solidification. In this paper, the surface of the used continuous casting guide roll was analyzed to realize the mechanism of its surface deterioration. Surface analysis has revealed severe corrosion at two distinct areas leading to deep roughness occurring on the guide roll. Firstly, the severe corrosion follows prior austenite grain boundary due to exposure with acidic environment. Also, in heat affected zone (HAZ) where two cladding beads overlap, more severe corrosion takes place. The overheat input results in local ferritization without full melting which increases retained δ-ferrite content almost 10 times higher than surrounding area. Corrosion was observed to happen at the δ-γ interface where Cr depletion takes place.

• Restorative Dentistry and Endodontics
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• v.46 no.2
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• pp.18.1-18.13
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• 2021

Composite resins are the most commonly used dental restorative materials after minimally invasive dental procedures, and they offer an aesthetically pleasing appearance. An ideal composite restorative material should have wear properties similar to those of tooth tissues. Wear refers to the damaging, gradual loss or deformation of a material at solid surfaces. Depending on the mechanism of action, wear can be categorized as abrasive, adhesive, fatigue, or corrosive. Currently used composite resins cover a wide range of materials with diverse properties, offering dental clinicians multiple choices for anterior and posterior teeth. In order to improve the mechanical properties and the resistance to wear of composite materials, many types of monomers, silane coupling agents, and reinforcing fillers have been developed. Since resistance to wear is an important factor in determining the clinical success of composite resins, the purpose of this literature review was to define what constitutes wear. The discussion focuses on factors that contribute to the extent of wear as well as to the prevention of wear. Finally, the behavior of various types of existing composite materials such as nanohybrid, flowable, and computer-assisted design/computer-assisted manufacturing materials, was investigated, along with the factors that may cause or contribute to their wear.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.5
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• pp.470-483
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• 2002

The purpose of this study was to investigate further the mechanics of failure of magnets used for denture retention. Dyna magnets were retrived from denture that had failed after 34 months of clinical use. The magnets were observed and sectioned in order to analyse with high resolution scanning electron microscope. From this study, corrosion behaviors of used magnetic attachment were analysed. The results were as follows ; 1. In Nd-Fe-B based magnetic materials, the erosion-corrosion was started at ununiformed part of stainless steel cover. 2. Corrosion was initiated at weared stainless steel surface and then magnetic materials were spalled by corrosive solution. 3. Spatting was occurred in Nd-Fe-B magnet materials due to corrosion products and then corrosion rate was increased drastically. 4. Corrosion started from ununiformed stainless steel surface as well as welded zone. In conclusion, the failure of magnets may occur by either breakdown of the welding or breakdown of the encapsulating material. So, it is considered that the corrosion problem of dental magnetic materials could be solved to some extent with surface treatment of dental magnetic materials.

• Journal of the Korean Society of Marine Environment & Safety
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• v.5 no.2
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• pp.15-26
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• 1999

The marine structures with sea water cooling system always expose to the oceanic atmosphere. Therefore, the protection of the equipments is very important. To investigate the effectiveness of advanced composite materials for the application in offshore environments, the tensile test, hardness test, undercutting property test, permeance test and the friction and wear test were carried out by using various applicable coating materials. The main results obtained can be summarized as follows; 1. The micro-hardness of the Archcoat 502B showed the highest value. 2. The coefficient of friction of the Rigspray coating at the speed of 2.21m/sec showed the lowest value, and that of the Archcoat 502B coating at 1.08m/sec and 0.18m/sec indicated the lowest values. 3. The wear mass at the speed of 0.18m/sec and 1.08m/sec in dry condition showed the smallest values. 4. The Archcoat 502B coating is fitted to the dynamic instruments in the range of low speed and middle speed. Rigspray coating is fitted to the dynamic instruments in the range of high speed. 5. The wear mass of five kinds of coating materials at the range of low speed was very small, and those of the Archcoat S02B, Archcoat 402B and Rigspray coating at high speed range were quitely smaller than those of the Modified Epoxy and Tar Epoxy.

• Corrosion Science and Technology
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• v.14 no.4
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• pp.172-176
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• 2015

Austenitic stainless steel was investigated under cyclic loading in electrolytes with different chloride contents and pH and at different temperatures. The testing solutions were 13.2 % NaCl (80,000 ppm $Cl^-$) at $80^{\circ}C$and 43 % $CaCl_2$ (275,000 ppm $Cl^-$) at $120^{\circ}C$. In addition to S-N curves in inert and corrosive media, the fracture surfaces were investigated with a scanning electron microscope (SEM) to analyse the type of attack. The experimental results showed that a sharp decrease in corrosion fatigue properties can be correlated with the occurrence of stress corrosion cracking. The correlation of occurring types of damage in different corrosion systems is described.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.10a
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• pp.166-173
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• 1996

There are kinds of materials for protective heat shield, i.e.Zn-coated steel, AI-coated steel and aluminum alloy sheets. This study compare formability, corrosion resistance, heat protectability, weight, and cost of these materials for heat protective shield. Generally aluminum alloy sheets are less formable than steel sheets, but A1100 alloy sheet shows almost same press quality of steel parts, using the press dies which producing steel parts. The heat shields using aluminum alloy sheet and steel sheet show almost same heat protectibility. It is the conclusion that Zn-coated merit, and AI-coated steel sheet and aluminum alloy sheet can be used to protect functional corrosion in severely corrosive market area. The material cost of AI-coated steel sheet and aluminum alloy sheet for a mid-size car is almost same, so aluminum alloy sheet is more recommendable in the point of weight reduction of vehicle.

• Corrosion Science and Technology
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• v.5 no.1
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• pp.15-22
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• 2006

The introduction of two-grid inside a conventional process system produces a reactive coating deposition and increases metal ion ratio in the plasma, resulting in denser and smoother films. The corrosion behaviors of TiN coatings were investigated by electrochemical methods, such as potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) in deaerated 3.5% NaCl solution. Electrochemical tests were used to evaluate the effect of microstructure on the corrosion behavior of TiN coatings exposed to a corrosive environment. The crystal structure of the coatings was examined by X-ray diffractometry (XRD) and the microstructure of the coatings was investigated by scanning electron microscopy (SEM) and transmission electron spectroscopy (TEM). In the potentiodynamic polarization test and EIS measurement, the corrosion current density of TiN deposited by two grid-attached magnetron sputtering was lower than TiN deposited by conventional magnetron type and also presented higher Rct values during 240 h immersion time. It is attributed to the formation of a dense microstructure, which promotes the compactness of coatings and yields lower porosity.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.942-943
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• 2006

To meet the demands for use in extremely abrasive and corrosive environments, a new material was developed. The VeKo25Cr distinguishes itself through specifically selected amounts of carbon and carbide forming elements such as Cr, Mo, V, W and Nb. The alloy is based on a Fe matrix. The strength after heat treatment and the wear and corrosion properties are compared to those of other materials. VeKo25Cr can be combined with easy-to-process materials such that the difficult handling is minimized to those places on the piece most subjected to operational wear.