• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제30회 추계학술대회
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• pp.257-262
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• 1999

The economic loss arisen from the abrasion wear have been increasing at every industrial field. To reduce the economic loss we developed a new process, which is named MAHa process(Metallic Adhesives for HArdening). MAHa process is a process to weld tungsten carbide(WC) to the surface of a plain carbon steel so that it may stay longer under the severe abrasive environment. The depth of the WC layer ranges from 0.5 mm to 5 m. Compared with the conventional technology, arc-augmented welding which bonds WC on the flat surface only, MAHa process has the merits that it can make a robust WC layer on the round or wave- shaped surface also. How to turn the WC powder into a flexible mat is the key technology of the MAHa process. We invented new polymer materials to accomplish such a goal and both the MAHa process and the invented materials were applied for patents. For the application, the inner wall of elbow of Concrete Pump Truck(CPT) was maharized(MAHa process-treated) and the new WC layer on the inner wall was made successfully. The elbow was equipped to a CPT.

• 한국광학회지
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• 제18권5호
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• pp.362-366
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• 2007

본 연구에서는 3 메가픽셀, 2.5배 줌 카메라폰 모듈용 비구면 유리렌즈 개발을 목적으로 실험계획법(DOE)을 적용하여 성형용 초경 코어의 연삭가공조건을 구하고, 이를 활용하여 비구면 Glass렌즈 성형용 초경합금(WC) 코어를 초정밀 연삭가공을 수행하였다. 또한 가공된 성형용 코어의 가공면 위에 이온증착법으로 다이아몬드상 탄소(Diamond-Like Carbon; DLC) 코팅을 수행하여 DLC 코팅이 성형용 코어의 형상정도(PV)와 표면조도(Ra)에 미치는 영향을 평가하였으며, 비구면 Glass렌즈를 동일한 조건에서 성형하여 성형렌즈의 광학적 특성을 비교하여 성형용 코어면의 DLC 코팅 효과에 대하여 검토하였다.

• Tribology and Lubricants
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• 제31권2호
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• pp.56-61
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• 2015

In this study, we investigated the effectiveness of an ultrasonic nanocrystal surface modification (UNSM) technique on the mechanical and wear properties of tungsten carbide (WC). The UNSM technique is a newly developed surface modification technique that increases the mechanical properties of materials by severe plastic deformation. The objective of this study was to improve the wear resistance of press die made of WC by applying the UNSM technique. We observed the microstructures of the untreated and UNSM-treated specimens using a scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDX) was used to investigate the chemical composition. The SEM observations showed the pore size and the number of pores decreased after the UNSM treatment. We assessed the wear behavior of both the untreated and UNSM-treated specimens using a scratch test. The test results showed that the wear resistance of the UNSM-treated specimens increased by about 46% compared with the untreated specimens. This may be attributed to increased hardness, reduced surface roughness, induced compressive residual stress, and refined grain size following the application of the UNSM technique. In addition, we found that the UNSM treatment increased the carbon concentration to 63% from 33%. We expect that implementing the findings of this study will lead to an increase in the life of press dies.

• 자원리싸이클링
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• 제19권4호
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• pp.41-50
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• 2010

초경공구의 제조공정에서 발생하는 WC-Co 초경합금 슬러지로부터 텅스텐의 순환활용을 위한 기초연구가 수행되었다. 왕수를 사용하여 슬러지로부터 코발트를 침출함과 동시에 탄화텅스텐을 텅스텐산으로 변환시켜 회수하였다. 왕수농도, 반응온도와 시간, 광액농도 등이 코발트의 침출과 텅스텐산의 생성에 미치는 영향을 조사하였으며 최적조건을 도출하였다. 왕수농도 100 vol.%, 반응온도 $100^{\circ}C$, 반응시간 60분에서슬러지의 광액농도가 400 g/L에 도달할 때 까지 슬러지로부터 코발트의 완전한 추출이 이루어졌으나, 슬러지에 존재하는 모든 탄화텅스텐이 텅스텐산으로 완전히 전환되는 것은 광액농도가 150 g/L 이하일 때 이었다. 생성된 텅스텐산을 암모니아 용액에 용해함으로서 금속 불순물들을 불용성 잔사로 제거하는 것이 가능하였다. 증발결정 공정을 통하여 정제된 암모늄 텅스테이트 용액으로부터 99.85%의 순도를 가지는 암모늄 파라텅스테이트($(NH_4)_{10}{\cdot}H_2W_{12}O_{42}{\cdot}4H_2O$)를 얻을 수 있었다.

• 한국정밀공학회지
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• 제27권7호
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• pp.117-122
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• 2010

Recently, aspheric glass lens molding core is fabricated with tungsten carbide(WC). If molding core is fabricated with silicon carbide(SiC), SiC coating process, which must be carried out before the Diamond-Like Carbon(DLC) coating can be eliminated and thus, manufacturing time and cost can be reduced. Diamond Like Carbon(DLC) is being researched in various fields because of its high hardness, high elasticity, high durability, and chemical stability and is used extensively in several industrial fields. Especially, the DLC coating of the molding core surface used in the fabrication of a glass lens is an important technical field, which affects the improvement of the demolding performance between the lens and molding core during the molding process and the molding core lifetime. Because SiC is a material of high hardness and high brittleness, it can crack or chip during grinding. It is, however, widely used in many fields because of its superior mechanical properties. In this paper, the grinding condition for silicon carbide(SiC) was developed under the grinding condition of tungsten carbide. A silicon carbide molding core was fabricated under this grinding condition. The measurement results of the SiC molding core were as follows: PV of 0.155 ${\mu}m$(apheric surface) and 0.094 ${\mu}m$(plane surface), Ra of 5.3 nm(aspheric surface) and 5.5 nm(plane surface).

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1699-1701
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• 1999

We prepared diamond thin films on WC-Co substrate in $H_2-CH_4-O_2$ gas mixture using 13.56MHz RF PACVD. Scanning electron microscopy, X-ray diffraction and Raman spectroscopy were used to analyze the nature of thin film. and Rockwell test to analyze the adhesion between thin film and substrate. The good diamond quality and adhesion was appeared with cemented tungsten carbide substrate treated with oxygen plasma.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 금형가공 심포지엄
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• pp.187-194
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• 2002

This paper describes the experimental results on direct selective laser sintering of WC-Co mixture for rapid tooling. The experiments were carried out within an air, argon and nitrogen atmosphere. Coupons of single layer were sintered at various laser powers, scanning speeds and scan spacings. As the energy density (energy per unit scanned area) is increased, the thickness of coupons is increased. The main problem took place during sintering within an air atmosphere was severe oxidation of WC-Co mixture. As the laser power is increased and/or scanning speed is decreased, more severe oxidation occurred. Within an argon and nitrogen atmosphere the oxidation is reduced significantly. Experiments on multi-layer sintering were also carried out.

• 한국재료학회지
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• 제15권10호
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• pp.621-625
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• 2005

Effects of rf power, pressure, sputtering gas composition, and substrate temperature on the deposition rate of the $WC_x$ coatings were investigated. The effects of rf power and sputtering gas composition on the hardness and corrosion resistance of the $WC_x$ coatings deposited by reactive sputtering were also investigated. X-ray diffraction (XRD) and Auger electron spectroscopy (AES) analyses were performed to determine the structures and compositions of the films, respectively. The hardnesses of the films were investigated using a nanoindenter, scanning electron microscopy, ana a salt-spray test, respectively. The deposition rate of the films was proportional to rf power and inversely proportional to the $CH_4$ content of $Ar/CH_4$ sputtering gas. The deposition rate linearly increased with increasing chamber pressure. The hardness of the $WC_x$ coatings Increased as rf power increased. The highest hardness was obtained at a $Ar/CH_4$ concentration of $10 vol.\%$ in the sputtering gas. The hardness of the $WC_x$ film deposited under optimal conditions was found to be much higher than that of the electroplated chromium film, although the corrosion resistance of the former was slightly lower than that of the latter.

• 한국정밀공학회지
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• 제11권5호
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• pp.42-55
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• 1994

Presently, abrasive processing is on eof several methods for cutting and grinding brittle materials, and high quality in dimensional accuracy and surface roughness are often required as a structural components, therefore most of them has to be ground. In manufacturing of tungsten-carbide components, grinding by diamond wheel is usually adopted in order to provide configurational and dimensional accuracy to the components. The present study proposes the experi- mental research of optimum condition to the high quality surface grinding of the WC-Co material using diamond abrasive wheel in order to minimize the damage on the ground surface and to pursue the precise dimension by conventional grinding machine. Brief investigation is carried out to decrease the dressing is constant, theoretical grinding effect such as machining precision is changed according to the speed of workpiece. Accordingly, normal and tangential grinding forces, which are Fn, Ft were analyzed for the machining processes of WC-Co material to obtain optimum grinding conditions, 3-point bending test is carried out to check machining damage on the ground surface layer, which is one of sintered brittle materials.

• 한국분말재료학회지
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• 제27권4호
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• pp.293-299
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• 2020

W₂C is synthesized through a reaction-sintering process from an ultrafine-W and WC powder mixture using spark plasma sintering (SPS). The effect of various parameters, such as W:WC molar ratio, sintering temperature, and sintering time, on the synthesis behavior of W₂C is investigated through X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) analysis of the microstructure, and final sintered density. Further, the etching properties of a W₂C specimen are analyzed. A W₂C sintered specimen with a particle size of 2.0 ㎛ and a relative density over 98% could be obtained from a W-WC powder mixture with 55 mol%, after SPS at 1700℃ for 20 min under a pressure of 50 MPa. The sample etching rate is similar to that of SiC. Based on X-ray photoelectron spectroscopy (XPS) analysis, it is confirmed that fluorocarbon-based layers such as C-F and C-F2 with lower etch rates are also formed.