• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.10 no.1
• /
• pp.73-79
• /
• 2011

In this study, coring with diamond core drill on the sintered $Al_2O_3$ ceramic plate were carried out with different coring conditions such as various cutting speed and feed rate to evaluate their effectiveness on the wearing behavior of diamond tool and coring quality. The wearing rate of diamond core drill were getting better with increasing cutting speed and feed rate but the quality of cored hole were getting worse as increasing cutting speed and feed rate.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 1999.10a
• /
• pp.3-4
• /
• 1999

최근 산업이 고속도화, 고능률화 및 고정멸화의 추세로 발전함에 따라 우수한 내마모성, 인성, 고온 안정성 및 내구성을 갖는 공구 및 금형을 요구하게 되었다. 그러나 이와같은 성질들은 어떤 단일 재료에서는 얻을 수 없으며 적당한 기판공구나 금혈위에 내마모성 보호피막을 coating함으로 비교적 저렴하게 얻을 수 있다. 화학증착법으로 TiC, TiN등을 증착시킬때에는 $1000^{\circ}C$정도의 반응온도가 필요하며 이러한 증착온도는 모재가 초경합금일때는 문제가 안되나 강재일 경우 모재의 연화와 칫수변화의 문제를 야기시킨다. 최근에는 플라즈마를 사용하여 증착반응온도를 $550^{\circ}C$ 이하로 낮추는 플라즈마 화학 증착볍(PACVD)이 대두되고 있다. 그러나 이 방법어서 는 뚱착하려는 금속원소가 TiCl4의 형태로 공급되고 있으므로 생성된 층이 염소를 포함하고 있다. 이 층에 잔존하는 염소는 층의 기계적 성질을 저하시키고 층내의 stress를 유발시킨다. 또한 HCI개스의 생성으로 인하여 펌프 및 장비의 부식이 촉진 된다 이러한 결점을 극복하기 위하여 금속유기화합물 전구체(metallo-organic precursor)로 $TiCl_4$를 대체하고자 하는 연구가 활발하게 진행되고 있으며 본 연구실에서 이에 대하여 연구한 결과를 소개하고자 한다. diethylamino titanium을 전구체로 사용하여 $H_2,\;N_2,\;Ar$분위기하에서 pulsed d.c.를 사용하는 MO-PACVD에 의하여 $150~250^{\circ}C$의 저온에서 Al 2024 기판에 TiCN층 형 성을 하였다. 전구체 증발온도는 $74~78^{\circ}C$의 온도범위어야 하며 고경도의 코탱층은 54% duty, 14.2kHz, 450V의 조건에서 얻어졌으며 duty, 주파수, 전압이 증가함에 따라 경도는 저하되었다. 이때의 표면 morphology를 SEM으로 조사한바 dome structure가 크게 발달되었음을 알 수 있었다. 본 실험의 온도 범위내에서 얻은 TiCN 증착반응의 활성화에너지는 7.5Kcal/mol이었다. 증착된 TiCN층은 우수한 내마모섣을 나타내었으며 스크래치테스트 결과 17N의 엄계하중을 나타내었다. 본 연구에서 변화 시킨 duty, 주파수, 전압의 범위에서는 층의 밀착력은 크게 변화하지 않았다. titanium isopropoxide를 전구체로 사용하여 Hz, Nz 분위기하에서 d.c.를 사용하는 MO-PACVD에 의하여 Ti(NCO) 코팅층을 SKDll, SKD61, SKH9 공구강에 형성시키는 공정을 개발하였다. 최적의 Ti(NCO) 코탱층을 얻기 위해 유입전구체 부피%의 양은 향착압력의 5%를 넘지 않아야 되고 수소와 젤소 가스비가 1:1일 때 가장 높은 코팅층의 경도값을 나타내었다. 수소와 질소 가스비가 3:7일 때 TiFeCr(NCO)의 복화합물 코팅층이 형성됨을 알 수 있었고 500t의 증착온도에서 얻은 Ti(NCO) 코팅층이 높은 경도값과 좋은 내식성을 나타내었다. 또한 이와같은 Ti(NCO) 코팅공정과 본 실험실에서 개발한 확산층만 형성시키는 plsma nitriding 공정을 결합하여 복합코탱층을 형성하였는데 이 복합코팅층은 고경도와 우수한 내마모성, 내식성 뿐만 아니라 10)N 이상의 뛰어난 밀착력을 나타내었다. 현재 많이 사용되고 있는 PVD법은 step coverage가 좋지 않은 점과 cost intensive p process라는 단점이 있다. MO-PACVD법은 이러한 문제를 해결할 수 있는 방법으로서 앞으로 지속적인 도전이 요구되는 분야이다.

• Tribology and Lubricants
• /
• v.33 no.2
• /
• pp.52-58
• /
• 2017

An ultra-high precise ejection process is essential in a dispensing system for fabricating various precision parts such as a semiconductor, LED, and camera module. The size of such parts has been decreasing, which implies that a precise ejecting technique is required. A phosphor-containing liquid is ejected via a dispenser using dual piezoelectric actuators that are used for generating a high-speed dispensing mechanism. The rod and nozzle continuously contact in high speed to eject the liquid. However, the high-strength filler or phosphor in the liquid causes wear on the surfaces of the rod and nozzle during the dispensing process. As a result, the ejection reliability decreases as the wear on the surfaces increases. Therefore, it is necessary to estimate the wear characteristics of the rod and nozzle via an experiment and FE analysis. Reliability rests up to 1,000 cycles are conducted under relatively severe conditions. The flow rate and surfaces roughness of the rod and nozzle are measured in each ejection cycle. The surface images and wear volume are obtained before and after the tests and the ejection reliability is confirmed by measuring the flow rate of the liquid. The experimental results show that the ejection reliability is maintained up to 1,000k cycles; these results are validated by the simulation results.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.255-255
• /
• 2013

WC-Co 초경합금은 실온경도, 고온경도, 강도, 내마모, 내충격 등 기계적 특성이 우수하여 공구재료, 절삭공구 및 고압용 부품 등 다양한 응용분야를 가지고 있으며 WC-Co 분말 코팅같은 경우 항공분야, 일반 공업 분야에 내마모 특성 및 내열특성 향상을 위한 코팅용 소재로서 활용되어 지고 있다. 활용분야가 넓은 WC-Co 초경합금의 제조방법은 WC, Co 분말을 혼합하여 약 900도에서 1차 예비소결 후 원하는 형상 가공 후 약 1,300~1,600도에서 2차 소결을 진행한다. 지금 현재 초경분말의 조성, 크기와 같은 변수들에 따른 초경합금의 기계적 특성 변화에 대한 연구가 계속적으로 진행되고 있다. 본 연구에서는 WC-Co 분말의 소결 특성을 향상시키고자 Planetary ball mill 장비를 활용하여 볼 밀링 공정을 진행하였고 Spark plasma sintering 장비를 활용하여 빠른 소결을 진행하였다. WC-Co 분말의 미세구조, 입도, 조성 및 분산의 변화를 관찰하기 위해 볼 밀링 전, 후 분말을 분석하였고 제조된 분말의 소결 특성을 확인하기 위해 상용화 된 WC-Co 분말의 소결 특성과 비교 평가하였다. 분석 결과 볼 밀링 공정 후 분말은 약 15 ${\mu}m$에서 4.4 ${\mu}m$로 미세해지는 것을 확인하였고 밀링 후 분말로 초경합금을 제작하였을 때 기존 상용화 초경합금제작 온도보다 약 100~400도 낮아지면서 경도 값은 약 20% 향상된 것을 확인할 수 있었다.

• Journal of Energy Engineering
• /
• v.12 no.4
• /
• pp.302-308
• /
• 2003

The peformence tests of zinc-based desulfurization sorbents using the yellow earth as support for the hot gas clean up were carried out. The zinc-based sorbent with 25 wt％ yellow earth was prepared, and their properties such as the reaction rate, the sulfur capacity and the attrition resistance, were investigated. The reactivity tests for hot gas desulfurization was performed at middle temperatures (sulfidation/regeneration：480$^{\circ}C$/580$^{\circ}C$). During multi-cyclic desulfurization, the deactivation of zinc-based sorbent was decreased by the addition of yellow earth, and their efficiency was enhanced. The ZnO/yellow earth sorbent had high reactivity, good regenerability, long-term durability (about 19 gS/100 g sorbent for 10-cycles) and high attrition resistance (AI=19.1％). It was concluded that the peroperties of zinc-based sorbent were improved by metal oxides (Fe$_2$O$_3$, Na$_2$O, MnO$_2$, etc) in the yellow earth. From these results, it was confirmed that the desulfurization properties of zinc-based sorbents at middle temperatures could be improved by the yellow earth using as support.

• Journal of Climate Change Research
• /
• v.2 no.2
• /
• pp.107-113
• /
• 2011

In this research, we described the experimental results for the improvement of Potassium based sorbents. These sorbents have been actually used in the 0.5 MW $CO_2$ capture plant located in Hadong #3 Power Plant. Firstly, we had shaped two kinds of sorbents using a spray dryer. These sorbents applied magnetite & copper oxide as an additive. And the magnetite sorbent was evaluated more excellent relatively in the attrition index. Secondly, We had obtained TGA multicycle experimental results of the improved Potassium based sorbent which applied magnetite as an additive. Consequently, $CO_2$ sorption capacity had been sustained 5.5 wt% after 2nd cycle and attrition index was very excellent as 0.5%. Finally, we had investigated the characteristics of the sorbent following in properties of supporters. As a result, the sorption capacity of the KMO sorbent used base material as a supporter was appeared as 7.2 wt%.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.12
• /
• pp.5438-5442
• /
• 2011

In order to use as weight-reduced sintered parts for automobiles, mechanical properties of sintered compacts of 2712 Al-alloys containing 0, 10, 20, and 33% ceramics, respectively, were investigated in this study. (1)Regardless of ceramic contents, all sintered compacts possessed 4~7% pores. (2)After aging the compacts sintered for 12 minutes, tensile strength of the 2712 Al-alloys containing 0, 10, 20, and 33% ceramics was 165, 260, 256, and 166 N/$mm^2$, respectively, whereas those aged after sintering for 30 minutes exhibited the tensile strength of 186, 229, 219, and 202 N/$mm^2$, respectively. In addition, the 2712 sintered compact containing 10% ceramics showed the maximum elongation of about 3.6%, (3)After aging the 10% ceramic-containing sintered compacts reached a maximum apparent hardness ($H_RF$) of 97. (4)The minimum wear volume ($174{\times}10^{-3}mm^3$) was shown in the 10% ceramic-containing 2712 sintered compact after aging. From these results, the 2712 sintered compact containing 10% ceramics thought to be the most suitable one for the fabrication of aluminum engine part.

• Journal of the Korean Ceramic Society
• /
• v.32 no.9
• /
• pp.1027-1032
• /
• 1995

SiC had been widely applied for mechanical sealing as a sealing material. SiC sintering is commonly made of reaction sintering, presureless sintering, and hot isostatic pressing (HIP) sintering. In this investigation, however, clay bonded sintering was used to avoide any complications of the special sintering methods as mentioned above. In order to prevent harmful SiC oxidation in the clay bonded sintering, clay and frit were used to form the SiC oxidation protecting layer and graphite was added to provide high solid lubricity. As a result, the material with 6% clay (clay 5.4% and frit 0.6%) and 2~4% graphite (45 mesh) sintered at 140$0^{\circ}C$ for 3 hours, showed the following physical properties; porosity 6%, static friction coefficient 0.15, kinematic coefficient 0.1,. and specific wear rate 4.8$\times$10-8 $\textrm{mm}^2$kgf-1. On the other hand, the flexural strength was 900kgf/$\textrm{cm}^2$. This tribological characteristic properties were similar to those of the reaction sintered SiC except the flexural strength.

• Journal of the Korean Geotechnical Society
• /
• v.38 no.5
• /
• pp.47-59
• /
• 2022

A series of experiments were performed to investigate the design and application of a rubble-ground modification method with grout injection. A small-sized injection machine was designed, and the grouts with various mix proportions were injected into 25 mm aggregate using the designed small-sized injection machine. With the compressive strength of the grout ranging from 20 to 80 MPa, the uniaxial compressive strength of the grout-filling bodies with clean gravels was higher than 1/6th of the strength of grouts themselves. However, this fraction may reduce depending on the interface conditions. The erosion resistance of the hardened grout was evaluated, and it was determined that the grout with a strength greater than 15 MPa did not require erosion consideration. Moreover, a full-scale injection test was performed for 25 cm-sized rubbles in cages with a diameter greater than 1 m and a height of 1.2 m to evaluate the filling characteristics of the grout. Results from this test indicated that the grout flowability sensitively influenced the filling characteristics.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.6 no.6
• /
• pp.468-472
• /
• 2005

In order to prevent adhering of molten glass on a mold wall, the wall is swabbed with lubricant oil before forming. However, the swabbing process can be removed from the entire processes of the glass forming if the mold wall is made of a porous sintered material. The purpose of the present study is to manufacture a sintered material(having a sintered density of $85{\~}90\%$)which is the most appropriate into. plane material for a glass mold. For the research, SUS310L-based coarse powder (${\~}150{\mu}m$) and SUS420J2-based fine powder ($40{\~}50{\mu}m$) were used for the compact materials, and effects of compaction pressure and sintering condition(atmosphere, temperature) were investigated. The results obtained were as fellows. (1) By means of solid phase sintering, a desired sintering density could not be achieved in any case when using a 310L-based powder having a large particle size. (2) When sintering green compacts(compaction pressure of $2ton/cm^2$) in a commercial vacuum furnace(at $1300^{\circ}C$ for 2 hours), the sintered compacts had densities of $6.2g/cm^3(79\%)$ for 310L + 0.03$\%$B, $6.6g/cm^3 (86\%)$ for 420J2, $7.3g/cm^3(95\%)$ for 420J2+(0.03)$\%$B, and $7.6g/cm^3(99\%)$ for 420j2+(0.06)$\%$B, respectively. As a result, it is regarded that sintered compacts having a desired porosity may be achieved by vacuum sintering the 420J2-based powder (low pressure compaction) and the 310L+0.03$\%$B-based powder (high pressure compaction).