• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.851-853
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• 1999

DLC thin films have been fabricated by pulsed laser deposition with various deposition parameters. The characterization of fabricated thin films was performed depending on the deposition parameters. As the kinetic energies provided by deposition temperature and the laser energy density were increased, the film showed graphite properties. Structural properties of the films were investigated by Raman spectroscopy. The growth energy should be optimized to fabricate high quality DLC thin films. DLC films showed high hardness and their friction coefficient was measured to be about 0.2 regardless of the load of the ball pin.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.350-355
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• 2001

Minimum clearance between the piston seal groove of a piston and cylinder bore to ensure against extrusion of the piston seal and leakage of working fluids is an important design parameter for a seal designer in hydraulic cylinder application. Contact force, critical pressure at which extrusion occurs, leakage rate, fluid film thickness and friction force have been analyzed for some design parameter such as clearance between cylinder wall piston, depth of rectangular groove and pressure of sealed hydraulic fluid. In this paper, we analyze displacement and stress of ACGT seal by finite element analysis to understand Contact Behaviour Characters

• Journal of the Korean institute of surface engineering
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• v.37 no.4
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• pp.208-214
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• 2004

The influence of the boron content on the various properties of Ni-B alloy films produced by electrodeposition was investigated. The considerable reduction in grain size was observed with increasing boron content. The internal stress was tensile and increased linearly with increasing boron content. Hardness increased up to $750H_{v}$ at 2 at% boron and then kept the value to 11 at% boron for as-plated Ni-B coatings. The hardness of Ni-B films increased up to $1,250H_{v}$ due to the intermetallic$ Ni_3$B precipitation by the heat treatment, and maximum hardness of each coating increases with boron content. Wear resistance decreased with increasing the boron content because of high friction coefficient and brittle fracture of film which has higher content of boron.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.6
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• pp.861-870
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• 1999

An experimental study was carried out to investigate the effects of using various shapes of turbulence promoter on the heat-transfer enhancement of 2-D and 3-D arrays of rectangular modules in a rectangular channel for design of noiseless and low-powered cooling fan in the electronic systems. Measurements of heat/mass transfer coefficients were made using a naphthalene sublimation technique, and the friction factors were measured for Reynolds numbers in the range$3.3{\time}10^3$~$1.6{\time}10^4$. Flow visualization was peformed by oil-film method. It was found that heat transfer and pressure drop increased remarkably due to the existence of the promoter. The results of the performance evaluation based on equal pumping power were showed that substantial heat-transfer enhancement was obtained at low Reynolds number range by use of a turbulence promoter.

• Tribology and Lubricants
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• v.13 no.3
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• pp.20-27
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• 1997

The tribological behavior for $MoS_2$ bonded films is evaluated according to the international standard testing methods, such as ASTM D 2625 (Falex tester) and ASTM D 2714 (LFW1 tester). It has been well known that the tribological behavior for $MoS_2$ bonded films is affected by several factors. However, in this work, the wear life for $MoS_2$ bonded films is mainly experimentally measured with different contact geometry, and evaluated in terms of the frictional heating according to the contact geometry of tribotester. The test results show that the wear life of $MoS_2$ bonded films is significantly affected not only by the frictional heating, but also by the contact pressure, test running-in conditions, and the contact conformity.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.616-621
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• 2005

Most machine element, such as gears and bearings, are operated in the mixed lubrication region. Contact between two asperities has an effect on machine life by increasing local pressure. To estimate fatigue lift exactly, asperity contact should be considered as a factor of fatigue liff because this happening produce friction, abrasion and make flash temperature. In this paper, asperity contact is considered as a result of film breakdown when lubricant pressure is not enough to separate two asperities. Contact pressure is calculated to asperity overlap region and added to lubricant pressure. For this model, numerical procedure is introduced and the result on surface roughness and velocity for wheel bearing is presented. Results of EHL analysis for wheel bearing show that asperity contact is occurred at the edge of EHL conjunction where has a insufficient lubricant pressure to separate two surface.

• Journal of the Korean institute of surface engineering
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• v.21 no.1
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• pp.28-33
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• 1988

$MoS_2$의 상용 고체 윤할제 코팅의 마찰 계수를 하중 100-1000g, Sliding 속도 분당 91-608m 의 범위에서 측정하여 고체윤활체(Sandsttrom 9A)의 하중과 Sliding 속도에 따른 마찰특성을 조사한 결, 하중이 증가함에 따라 또한 Sliding 속도가 증가함에 따른 마찰 계수가 감소함을 나타났다. 또한 고체윤할제 코팅의 전처리인 인삼염 피막처리의 열적특성을 망간계와 아연계 인삼염 피막에 대하여 TGA 와 DTA 방법으로 비교 분석하여 망간계 피막이 아연계 피막에 비하여 열적으로 안정하여 적합함을 밝혔다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.338-339
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• 2012

This study examined the friction and wear behavior of diamond-like carbon (DLC) films deposited from a radio frequency glow discharge using a hydrogen diluted benzene gas mixture. The DLC films were deposited on Si (100) and polished stainless steel substrates by r.f.-PACVD at hydrogen to benzene ratios, or the hydrogen dilution ratio, ranging from 0 to 2.0. The wear test was carried out in both ambient and aqueous environments using a home-made ball-on-disk type wear rig. The stability of the DLC coating in an aqueous environment was improved by diluting the benzene precursor gas with hydrogen, suggesting that hydrogen dilution during the deposition of DLC films suppress the initiation of defects in the film and improved the adhesion of the coating to the interface.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.1
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• pp.81-89
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• 2022

It is necessary to increase the surface hardness and improve the wear resistance and peeling resistance through the surface treatment and performance evaluation of the mold steel. As a result of vacuum heat treatment analysis, residual austenite measurement and surface treatment wear test, retained austenite should be removed by sub-zero treatment, and retained austenite was completely removed by treatment at -196℃. The TiMon film coated on the sub-zero treated STD11 specimen showed the lowest coefficient of friction.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2000.11a
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• pp.3-4
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• 2000

Many researchers are interested in the synthesis and characterization of carbon nitride and diamond-like carbon (DLq because they show excellent mechanical properties such as low friction and high wear resistance and excellent electrical properties such as controllable electical resistivity and good field electron emission. We have deposited amorphous carbon nitride (a-C:N) thin films and DLC thin films by shielded arc ion plating (SAIP) and evaluated the structural and tribological properties. The application of appropriate negative bias on substrates is effective to increase the film hardness and wear resistance. This paper reports on the deposition and tribological OLC films in relation to the substrate bias voltage (Vs). films are compared with those of the OLC films. A high purity sintered graphite target was mounted on a cathode as a carbon source. Nitrogen or argon was introduced into a deposition chamber through each mass flow controller. After the initiation of an arc plasma at 60 A and 1 Pa, the target surface was heated and evaporated by the plasma. Carbon atoms and clusters evaporated from the target were ionized partially and reacted with activated nitrogen species, and a carbon nitride film was deposited onto a Si (100) substrate when we used nitrogen as a reactant gas. The surface of the growing film also reacted with activated nitrogen species. Carbon macropartic1es (0.1 -100 maicro-m) evaporated from the target at the same time were not ionized and did not react fully with nitrogen species. These macroparticles interfered with the formation of the carbon nitride film. Therefore we set a shielding plate made of stainless steel between the target and the substrate to trap the macropartic1es. This shielding method is very effective to prepare smooth a-CN films. We, therefore, call this method "shielded arc ion plating (SAIP)". For the deposition of DLC films we used argon instead of nitrogen. Films of about 150 nm in thickness were deposited onto Si substrates. Their structures, chemical compositions and chemical bonding states were analyzed by using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and infrared spectroscopy. Hardness of the films was measured with a nanointender interfaced with an atomic force microscope (AFM). A Berkovich-type diamond tip whose radius was less than 100 nm was used for the measurement. A force-displacement curve of each film was measured at a peak load force of 250 maicro-N. Load, hold and unload times for each indentation were 2.5, 0 and 2.5 s, respectively. Hardness of each film was determined from five force-displacement curves. Wear resistance of the films was analyzed as follows. First, each film surface was scanned with the diamond tip at a constant load force of 20 maicro-N. The tip scanning was repeated 30 times in a 1 urn-square region with 512 lines at a scanning rate of 2 um/ s. After this tip-scanning, the film surface was observed in the AFM mode at a constant force of 5 maicro-N with the same Berkovich-type tip. The hardness of a-CN films was less dependent on Vs. The hardness of the film deposited at Vs=O V in a nitrogen plasma was about 10 GPa and almost similar to that of Si. It slightly increased to 12 - 15 GPa when a bias voltage of -100 - -500 V was applied to the substrate with showing its maximum at Vs=-300 V. The film deposited at Vs=O V was least wear resistant which was consistent with its lowest hardness. The biased films became more wear resistant. Particularly the film deposited at Vs=-300 V showed remarkable wear resistance. Its wear depth was too shallow to be measured with AFM. On the other hand, the DLC film, deposited at Vs=-l00 V in an argon plasma, whose hardness was 35 GPa was obviously worn under the same wear test conditions. The a-C:N films show higher wear resistance than DLC films and are useful for wear resistant coatings on various mechanical and electronic parts.nic parts.