• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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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.

• Korean Journal of Materials Research
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• v.19 no.11
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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.

• Journal of Powder Materials
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• v.18 no.4
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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.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.889-890
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• 2006

In recent years, PCB drills with smaller diameters less than 0.1 mm are used and thus there are growing needs for ultra-fine grained cemented carbides. However, ultra-fine WC powder usually causes extraordinary grain growth during sintering which weakens mechanical strength of ultra-fine grained cemented carbides. So we examined several kinds of WC powders to make new ultra-fine grained cemented carbides having superior performance. We found that direct carburized WC powder is very good as a WC raw material. The PCB drills made of the developed ultra-fine grained cemented carbides have higher hardness, toughness and stiffness than conventional ones.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.887-888
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• 2006

The present study describes the wear and mechanical behaviour of carbide composites in cyclic loading applications (blanking of sheet metal). Adhesive wear as well as fatigue endurance were tested, complemented by XRD studies. It was found that the blanking performance of a carbide composite is controlled by its resistance to adhesion wear and fatigue sensitivity. XRD studies revealed that fatigue damage is preceded by plastic strain in both phases of the composites

• 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.

• Resources Recycling
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• v.29 no.6
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• pp.35-40
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• 2020

In this study were carried out basic experiments mainly to investigate important reaction mechanism, the reaction temperature, time and the addition amount of Zn in recycling of waste cemented carbide by the zinc bath process. As a result, it was required that the Zn bath reaction was heated more than at 800℃ to accelerate reaction of melted Zn and Co inside of wasted cemented carbide. Furthermore, thickness of the waste cemented carbide was reduced linearly according to increase of reaction time at 700℃ for 0.5~2h in the zinc bath reaction. Also the zinc bath reaction was examined that heating in lower than at 800℃ for 3h and then heated more than at 900℃ for 1h(above 3.0×10 torr-2 vaccum) was suitable to reduce vapour loss amount of Zn in the zinc bath process.

• Journal of the Korean institute of surface engineering
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• v.15 no.3
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• pp.138-145
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• 1982

The effects of the simultaneous variations of the ratio of feed gases(H2/N2 Flow ratio), feed gas flow rate (H2/N2, total-flow rate) and partial pressures of TiCl4 (PTiCl41) as well as deposition time and cobalt content of the substrate on the deposition rate of the TiN Coated Cemented Tungsten Carbide Tools were investigated. Deposition was carried out in the temperature range of 930$^{\circ}C$-1080$^{\circ}C$ and an activation energy of 46.5 Kcal/mole can be calculated. Transverse rupture strength was noticeably reduced by the TiN coating on the virgin surfa-ce of Cemented Tungsten Carbide, the extent of which was decreased according to the coa-ting thickness. Microhardness value observed on the work was in the range of 1700∼2000kg/mm, which were in well agreement with the value of bult TiN. The wear resistance of TiN layers was performed by turning test and it was observed that crater and flank resistance remarkably enhanced by TiN coating.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.37-42
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• 2007

We present a powder injection molding technique of fabricating cemented tungsten carbide(WC) balls for milling and dispersing nano-powder in this paper. The conventional powder metallurgy approach is investigated to reveal its drawbacks of density non-homogeneity. New procedures of powder injection molding for the homogeneous high-precision WC balls, involving the binding process, powder injection molding process and sintering process, are presented in detail. Each process is investigated empirically and numerically to obtain its engineering information, which can used for process optimization.

• Tribology and Lubricants
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• v.11 no.5
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• pp.66-70
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• 1995

In this investigation, a controlled-environment tribological test device has been used to study the friction coefficients of several grades of commercially-available coated and uncoated cemented carbide cutting tools in a dry air environment at different environmental chamber pressures. Tests were run in the block-on-ring configuration. The results suggest that the friction coefficient is sensitive to the level of air present, with a noticeable rise in friction coefficient with decreasing pressure or increasing vacuum level. The uncoated cemented carbide sufaces resulted in the highest friction values, whereas the coated grades yielded somewhat lower values even after the coating was removed. The results suggest the importance of friction control in the design of coatings for metal removal processes.