• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.213-214
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• 2002

WC cemented carbide are used as many die material to improve abration resistance. Mechanical properties of the cemented carbide were influenced by Co content and WC grain size. In this study, effects of Co content and WC grain size of WC cemented carbide on wear were examied. We prepared 13 cemented carbides with different Co content and WC grain size. Wear test was carried out against S45C under dry condition at 98N and 232mm/s. From the results, we found that wear increased with both Co content and WC grain size. Specific wear rate was range $10^{-7}mm^3/Nm$.

• 한국재료학회지
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• 제19권11호
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• pp.588-595
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• 2009

The knowledge of grain growth of carbide particles is very important for manufacturing micrograined cemented carbides. In the present study, continuous and discontinuous grain growth in WC-Co and WC-VC-Co cemented carbides is investigated using the Monte Carlo computer simulation technique. The Ostwald ripening process (solution/re-precipitation) and the grain boundary migration process are assumed in the simulation as the grain growth mechanism. The effects of liquid phase fraction, grain boundary energy and implanted coarse grain are examined. At higher liquid phase content, mass transfer via solid/liquid interfaces plays a major role in grain growth. Growth rate of the implanted grain was higher than that of the matrix grains through solution/re-precipitation and coalescence with neighboring grains. The results of these simulations qualitatively agree with experimental ones and suggest that distribution of liquid phase and carbide particle/carbide grain boundary energy as well as contamination by coarse grain are important factors controlling discontinuous grain growth in WC-Co and WC-VC-Co cemented carbides. The contamination by coarse grains must by avoided in the manufacturing process of fine grain cemented carbides, especially with low Co.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.355-356
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• 2006

WC-TiC-TaC binderless cemented carbide was oxidized under low partial pressure of oxygen (50ppm) at 873K for 1 to 20 h. Surface roughness was measured using atomic force microscope, and effect of TiC amount on oxidation behavior of the carbide was investigated. WC phase was oxidized more easily than WC-TiC-TaC solid solution phase. With an increase in TiC amount, WC-TiC-TaC phase increased and the oxidation resistance of the carbide increased.

• 한국분말재료학회지
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• 제18권4호
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• pp.332-339
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• 2011

Cemented tungsten carbide has been used in cutting tools and die materials, and is an important industrial material. When the particle size is reduced to ultrafine, the hardness and other mechanical properties are improved remarkably. Ultrafine cemented carbide with high toughness and hardness is now widely used. The objective of this study is synthesis of nanostructured WC-Co powders by liquid phase method of tungstate. The precursor powders were obtained by freezen-drying of aqueous solution of soluble salts, such as ammonium metatungstate, cobalt nitrate. the final compositions were WC-10Co. In the case of liquid phase method, it can be observed synthesis of WC-10Co. The properties of powder produced at various temperature, were estimated from the SEM, BET and C/S analyser.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 1999년도 춘계학술대회 및 발표대회 강연 및 발표논문 초록집
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• pp.18-18
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• 1999

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.211-212
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• 2002

Friction and wear of pressureless sintered Ti(C,N)-WC ceramics were studied using a ball-on-reciprocating flat apparatus in open air. The silicon nitride ball and the cemented carbide (WC-Co) ball were used against the Ti(C,N)-WC plate samples. The friction coefficients of the Ti(C,N)-WC samples against the silicon nitride ball and the cemented carbide ball were about 0.57 and 0.3, respectively. The wear coefficient of the sample without WC addition was 5 times as large as that of the sample with 10 mole % WC addition when tested against the silicon nitride ball under 98 N. The higher wear coefficient of Ti(C,N)-0WC was explained in part by larger grain size. Wear occurred mainly by grain dislodgment after intergranular cracking mainly caused by the accumulated stress within the grains.

• 한국재료학회지
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• 제10권9호
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• pp.612-618
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• 2000

WC-Co와 WC-Co 초경합금중 WC/WC 입계의 구조와 입계 편석상태를 알아볼 목적으로 HRTEM과 EDS를 이용하여 연구하였다. 일부의 입계들은 액상에 의하여 분리된 상태로 관찰되었으나, 상당수는 원자적 상태의 연소계면이었다. 또 연속계면 중 WC-Co 합금에서는 Co 상이 편석되어 있었으며, WC-VC-Co 합금에서는 Co와 V이 동시에 편석되어 있음을 알 수 있었다. 그 편석의 폭은 약6nm이었다. 연속 계면 중 V의 편석은 소결 또는 열처리 시에 일어나는 입계 이동을 억제하는 데 효과적인 역할을 할 것으로 여겨졌다. 동시에 이것은 WC-Co 초경합금에서 VC 첨가에 의한 입성상 억제기구를 설명할 수 있는 것으로 사료되었다.

• 대한기계학회논문집A
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• 제21권9호
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• pp.1520-1530
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• 1997

Machining pressed compacts of ceramic and WC-Co materials can be the most cost effective way of forming the bodies prior to sintering when the required number of pieces is small. In this study, in order to clarify the machinability for turning, the $Si_3N_4$ and the WC-Co green compacts unsintered were machined under different cutting conditions with various tools. Absorbing chips by vacuum hose decreases tool wear. The tool wear becomes larger in the order of the ceramic, CBN and cemented carbide tools in machining the $Si_3N_4$ green compacts. In machining the WC-Co green compacts, the tool wear becomes larger in the order of the ceramic, cemented carbide and CBN tools. The land of cutting edge does not affect tool wear. When machining with cemented carbide tool, the tool wear i equal cutting length is nearly identical in spite of the increase of cutting spee, and the roughness of machined surface was the best in the cutting speed of 90 m/min. The tool wear decreases with the increase of rake angle and relief angle and with the decrease of nose radius. The machined surfaces become worse with the increase of feed rate and depth of cut, and with the decrease of rake angle and relief angle. The tool wear is not affected by the feed and depth of cut.

• 소성∙가공
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• 제31권6호
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• pp.376-383
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• 2022

The potential damage region of a WC-Co cemented carbide die is investigated for cold forging process of a wheel-nut by numerical simulation with its chemical composition considered. Numerical simulation is utilized to calculate internal stress, especially for the WC-Co die, during the forging process. Finite element model is established, in which the elasto-plastic properties are applied to the work-piece of bulk steel, and elastic properties are considered for the lower die insert of the WC-Co alloy. This stress analysis enables to distinguish the potential damage regions of the WC-Co die. The regions from calculation are comparatively analyzed along with the crack area observed in the die after repetitive manufacturing. Effect of chemical composition of the WC-Co is also evaluated on characteristics of potential damage region of the die with variance of mechanical properties considered. Derived from Mohr-Coulomb fracture model, furthermore, a new stress index is presented and used for die stress analysis. This index inherently considers hydrostatic pressure and is then capable of deducing wide range of its distribution for representing stress state by modification of its parameter implying pressure sensitivity.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 1996년도 추계학술강연 및 발표대회 강연 및 발표논문 초록집
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• pp.18-18
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• 1996