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혼합조건에 따른 철분말 소결체의 특성 변화에 관한 연구
김한삼 ( Han-sam Kim ),최태규 ( Tae-kyu Choi ),박종성 ( Chong-sung Park ) 한국고등직업교육학회 2002 한국고등직업교육학회논문집 Vol.3 No.4
The microstructure and mechanical characteristics of sintered materials composed oi Fe-xwt.%P with mixing times had been studied. The Fe+xwt.%P(x = 0.25, 0.5, 0.75,1) powders were sintered for 2 hours at 940°C. Before sintering of the powders, each of powder composition was worked into ball-mill machine for 12, 24, and 48 hours. The shrinkage of preform increased with phosphorus amount and mixing time during sintering. Pores and Fe<sub>3</sub>P facet type phase in the grain boundary and grain of sintered materials were observed by means of scanning electron microscope. Amounts of pores and the size of Fe<sub>3</sub>P phase decreased with increase of the mixing time. The hardness of sintered materials depended upon the content of phosphorus and the mixing time of powder. The hardness increased with the increase of phosphorus content and mixing times.
최태규 ( Tae-kyu Choi ),김한삼 ( Han-sam Kim ) 한국고등직업교육학회 2003 한국고등직업교육학회논문집 Vol.4 No.1
Effect of ultrasonic agitation has been studied for metallization of ceramic boards by Cu electroless plating method. 96% Al203 ceramic boards were used as substrate. In electroless plating, plating rates were obtained as 0.44~1.0/an/hr. And plating rate was increased with increasing temperature and addition of Rochelle Salts. Weight of absorbed Pd was increased 3.5 times by appling ultrasonic agitation. And, adhesion strength was increased by 35% as using ultrasonic agitation during 5min at 30°C.
Na2B4O7-KCl-LiCl 용융염에서 탄소강과 스테인리스강의 전해붕산처리
김정기,김수식,김한삼 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.5
The electrolytic boronizing on low carbon steel was conducted at 700-900℃ for 2 hours under the current density of 0.5A/㎠ using various contents of KCl-LiCl in the fused salt of Na₂B₄,O_γKCl-LiCl. The KCl·LiCl compound has the eutectic composition (54wt.%KCl and 46wt%LiCl). The effect of the additives such as Al or B₄C into the 4Na₂B₄O_7·KCl·LiCl(weight ratio) on the formation of boronized layer was investigated. The boronized layers were composed of two sublayers, i. e., FeB and Fe₂B, which have tooth structure. The electrolytic boronizing on medium carbon steel SM45C and stainless steel STS304 was also conducted at 800-950℃ for 1-6 hours under the current density of 0.5A/㎠ in the electrolyte of 4(Na₂B₄O_7·Al)·KCl LiCl. In this electrolyte, the average boronized layer thicknesses of the low carbon steel, SM45C and STS304 at 800℃ for 2 hours were 70, 47 and 15 ㎛, respectively. The thickness of the two sublayers was significantly increased with increasing boronizing temperature. To obtain a single Fe₂B layer without FeB sublayer, the boronized low carbon steels were homogenized at 900℃ for 2 hours and the boronized SM45C and STS304 were homogenized at 950℃ for 4 hours. It was found that the single layer with the microhardness of Hv=1300 was formed.
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%.
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.
플라즈마 용사법에 의한 내식 · 내마모 피복층의 형성에 관한 연구
김수식,김한삼,신진택 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.5
The plasma sprayed NiCoCrAlY coatings on Inconel 713C substrates were boronizeci or boronized and aluminized. The mechanical properties and hot corrosion resistance of the NiCoCrAlY coatings were studied. Mechanical properties were measured by the microhardness and abrasion tests, and hot corrosion resistance was examined by the cyclic hot corrosion test. The microhardness at the 30㎛ from the surface of the boronized samples was about 1200Hv, which is approximately five times, relative to the as-sprayed NiCoCrAlY coatings probably because of the formation of borides such as Ni₂B and Co₂B within the samples. When the samples were aluminized after boronizing, the samples showed the cross sectional hardness of more than 1200Hv because of the homogeneous distribution of the borides and good hot corrosion resistance, relative to the boronized samples. The heat treated samples after the boronizing and aluminizing contained NiAl phase at the surface. The heat treated samples showed increased cyclic hot corrosion resistance, compared with aluminized after boronizing. Also the heat treatment enhanced abrasion resistance significantly, but did not affect the hot corrosion resistance. It can be, therefore, concluded that the heat treatment after boronizing and subsequent aluminizing for the NiCoCrAlY coatings is necessary to improve the mechanical properties and hot corrosion resistance.