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김수식,김한삼 대한금속재료학회(대한금속학회) 1992 대한금속·재료학회지 Vol.30 No.9
To obtain fundamental informations for fine tungsten carbide powders, the preparation of fine tungsten carbide by vapor phase reaction of WCl_6-CCl₄-H₂ system has been carried out in the temperature range of 800-1300℃. The effects of reaction conditions on particle size and morphology of tungsten carbide powders have been investigated by utilizing X-ray diffraction, SEM and TEM techniques. The content of WC increased remarkably with increasing the reaction temperature and the maximum content was about 97% at 1100℃ in the condition of the flow rate of Ar gas 200㎖/min, H₂ gas 100㎖/min and CCl₄ gas 40㎖/min. The particle size of the reation products obtained at 1100℃ was about 0.05㎛ and the shape of WC was spherical. The particle size decreased linearly with increasing reation temperature. Also the crystallite size increased gradually with increasing reaction temperature.
김수식,김한삼 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.6
Ta obtain fundamental informations for fine tungsten carbide powders, the preparation of fine tungsten carbide by vapor phase reaction of WCI_6-CH₄,-H₂ system has been carried out in the temperature range of 1000-1400℃. The effects of reaction conditions on particle size and morphology of tungsten carbide powders have been investigated by utilizing X-ray diffraction, SEM and TEM technique . The synthesis temperature of only WC powders is above 1350℃ in the condition of the flow rate of argon and Hz gas is 220㎖/min respectively and CH₄, gas 40㎖/min. 'The particle size of the reaction products obtained at 1400℃ is about 0.02㎛ and the shape of WC is spherical. Temperature dependence of the particle size is weak and the lattice parameters a and c decrease gradually with increasing reaction temperature. Also the crystallite size increases gradually with increasing reaction temperature.
김수식,김한삼 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.7
To obtain fundamental informations for fine tungsten carbide powders, the preparation of fine tungsten carbide by vapor phase reaction of WCl_6-C₂H₄-H₂ system has been carried out in the temperature range of 800-1300℃ The effects of reaction conditions on particle size and morphology of tungsten carbide powders have been investigated by utilizing X-ray diffraction, SEM and TEM techniques. The content of WC increased remarkably with increasing the reaction temperature and the maximum content was about 95% at 1100℃ in the condition of the flow rate of argon and H₂ gas 200㎖/min respectively and C₂H₄, gas 15㎖/min. The particle size of the reaction products obtained at 1100℃ is about 0.007㎛ and the shape of WC is spherical. The particle size decrease linearly with increasing reaction temperature. On the other hand, the agglomerate particle size increase linearly with increasing temperature. The lattice parameters a and c increase gradually with increasing reaction temperature.
김수식,김한삼,윤영식 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.4
In order to improve the mechanical properties and the corrosion resistance, paste boronizing was carried out in the temperature range of 700℃∼1050℃. Mechanical properties were measured by the microhardness and abrasion tests, and corrosion resistance was examined by potentio dynamic polarization test. The microhardness and wear resistance were increased with the increase of the boronizing temperature. The microhardness of boronized samples was about 1600Hv, which is approximately ten times higher than those of the low carbon steel. The increase of microhardness can be attributed to the formation of borides such as FeB and Fe₂B within the samples. The wear resistance of the boronized samples also were 5 times higher than that of the low carbon steel. Annealing of the samples enhanced the wear resistance and the corrosion resistance significantly, but did not enhance the microhardness. The activation energy for boronizing on the low carbon steel measured as 227 kJ/㏖ below 874℃ and 117kJ/㏖ above 874℃
플라즈마용사에 의한 ZrO2-MgO 피복층의 열처리효과에 관한 연구
김수식,김한삼,정병근 대한금속재료학회(대한금속학회) 1993 대한금속·재료학회지 Vol.31 No.6
The plasma spray process was used to deposit. coatings of ZrO₂- MgO powders onto SM45C substrate, and the characteristics of as-deposited and heat. treated coatings have been investigated. Particulary, the variations of microstructure, porosity, wear resistance, thermal shock resistance and thermal barrier in ZrO₂- MgO coatings after heat treatment under lower pressure have been investigated. It was found that coatings of ZrO₂- MgO is consist of layered structure with thickness 2-3㎛, and with grain size of 0.O6㎛. The amount of prosity was increased with increased spray distance, and the lowest amount of porosity was obtained at the arc current of 450A, and at the spray distance of 50mm. After heat treatment, the amount of porosity was found to be decreased, and wear resistance, microhardness and thermal shock resistance were improved. However, the thermal barrier were decreased.
플라즈마 용사 Wc-12%Co 피복층의 탄화처리에 관한 연구
김수식,김한삼,이홍주 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.5
Tungsten Carbide(WC) coatings were formed on mild steel substrates using the plasma spray process. As a mean to enhance the mechanical properties such as microhardness and wear resistance, as-sprayed coatings were annealed and then subsequently were subjected to the carburization under methane and hydrogen atmospheres. When the heat treatment was carried out under the hydrogen atmosphere, the amounts of WC phase were decreased and the amounts of α-W₂C and W phase were increased with the increase of temperature, which leaded to a slight reduction of the microhardness. In case of the carburization under methane atmosphere, the microhardness of the coatings was increased with the increase of temperature and show the highest value of 1540Hv at 1100℃. The wear resistance also was increased with the increase of the carburization temperature. The wear resistance of the coatings heat treated at 1100℃ were 17 times higher than the as-sprayed coatings. The increase of methane concentration at constant temperature at 900℃ showed the improvement of the microhardness and the wear resistance of coatings. The highest microhardness and wear resistance obtained at the methane concentration of 11%.