• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.22-29
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• 2001

Plasma-sprayed coatings were prepared using by spray-dried Cr$_2$O$_3$ powder with and without MoO$_3$ addition. A reciprocal type tribe-tester was employed to examine friction and wear behavior of the specimens at room temperature. The worn surfaces of plasma spray coated specimens were observed by SEM. The results showed that friction coefficient of the MoO$_3$-added coatings were lower than those without MoO3 addition. However pure Cr$_2$O$_3$ coating showed the lowest wear loss at the self-mated test. The larger protecting layers were observed at the worn surface of plasma spray coated specimens with MoO$_3$ addition.

• Tribology and Lubricants
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• 제34권6호
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• pp.254-261
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• 2018

In order to reduce resistance torque and energy loss, minimizing friction between race surface and rolling elements of a bearing is necessary. Recently, to reduce friction in bearing element, solid lubricant coating for the bearing raceway surface has been receiving much attention. Considering the operating conditions of real bearings, verifying the effect of solid lubricant coatings under extreme conditions of high load that is more than 1 GPa is necessary. In this study, we evaluated the friction and wear characteristics of SUJ2 bearing steels deposited by carbon-based coatings (Si-DLC, ta-C), $MoS_2$ and graphite. In case of $MoS_2$ and graphite coatings, different surface treatments were applied to the coatings to verify the effect of surface treatment. A pin-on-disc type tribotester was used to evaluate the tribological characteristics of the coatings. It was possible to quantitatively estimate the friction and wear characteristics of solid lubricant under dry and lubrication conditions. The carbon-based coatings improved the friction and wear properties of SUJ2 bearing steels under the high load condition, but $MoS_2$ and graphite coatings were not suitable for high load conditions due to its low hardness. Different friction and wear behaviors were found for different substrate surface treatment method. Also, it was confirmed that solid lubricant coatings had a more positive effect than just applying the lubricant for improving the tribological characteristics.

• 한국정밀공학회지
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• 제12권3호
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• pp.62-72
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• 1995

The present study was undertaken to investigate the dry wear mechanism of the alumina ceramics in the purity variation for the wear of STB2. The wear test was carried out under different experimental condition various sliding speed, contact pressure and sliding distance. According as the alumina purity increased, wear volume of the STB2 decreased and minimum value of wear volume was over to high speed side. According as the sliding speed and sliding distance increased, friction coefficient decreased owing to drop of the shear strength, it decresed largely owing to decreased of elastic modulus and thermal conductivity with decrease in alumina purity. Indicative of minimum, value of wear volume, low speed side was abrasive wear, high speed side was wear of heat softening. The friction surface of ceramics protacted by oxide was transfer from STB2.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.16-19
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• 2005

There are about 13,000 freight cars in Korea. The holding amount of the freight cars are many more than the other types of cars. But the bogie structure has many friction parts, so three are many hold-ups for the maintenance problem on the spot. As seen in Fig. 1 friction parts are organized of 30 parts in case of welding structure bogie. Especially left-right positions of the axle box have severe problems for the wear, they occurs the reduction of maintenance period, a lowering of the running safety. Generally the thickness of wear plate is 4.5mm and attached to bogie by way of welding method. At the running situation the friction occurs in wear plate each other. Namely the role of the wear plate reduce the load from the carbody. So we need the wear plate fur low-wearing, adequate friction power.

• Tribology and Lubricants
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• 제37권5호
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• pp.179-188
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• 2021

Reputed for their low friction coefficient and wear protection effect, diamond-like carbon (DLC) materials are considered amongst the most important lubricant coatings for tribological applications. In this framework, this investigation aims to elucidate the effect of a few operating parameters, such as applied stress and sliding amplitude on the friction lifetime of DLC coatings. Fretting wear tests are conducted using a 12.7 mm radius counterpart of 52100 steel balls slid against a substrate of the same material coated with a 2 ㎛ thickness DLC. Approximately, 5 to 57 N force is applied, generating a maximum Hertzian contact pressure of 430 to 662 MPa, corresponding to the applied force. The coefficient of friction (CoF) generates three regimes, first a running-in period regime, followed by a steady-state evolution regime, and finally a progressive increase of the CoF reaching the steel CoF value, as an indicator of reaching the substrate. To track the wear scenario, interrupted tests are performed with analysis combining scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), 3D profilometer and micro-Raman spectroscopy. The results show two endurance values: one characterizing the coating failure (Nc₁), and the other (Nc₂) indicating the friction failure which is situated where the CoF reaches a threshold value of μ_th = 0.3 in the third regime. The Archard energy density factor is used to determine the two endurance values (Nc₁, Nc₂). Based on this approach, a master curve is established delimitating both the coating and the friction endurances.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.231-234
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• 2004

Chemical mechanical polishing(CMP) process was studied in terms of tribology in this paper. CMP performed by the down force and the relative motion of pad and wafer with the slurry is typically tribological system composed of friction, wear and lubrication. The piezoelectric quartz sensor for friction force measurement was installed and the friction force was detected during CMP process. Various coefficient of friction was attained and analyzed with the kind of pad, abrasive and the abrasive concentration. The lubrication regime is also classified with ${\eta}v/p(\eta,\;v\;and\;p;$ the viscosity, relative velocity and pressure). Especially, the co-relation not only between the friction force and the removal per unit distance but also between the coefficient of friction and within-wafer-nonuniformity was estimated.

• Tribology and Lubricants
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• 제33권6호
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• pp.275-281
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• 2017

In this work, we have fabricated anodic aluminum oxide (AAO) with ordered nanoscale porosity through an anodization process. We deposited gold and nano-organic thin films on the porous AAO surface to protect its structure and reduce friction. We investigated the tribological characteristics of the porous AAO with respect to the protective surface coatings using tribometers. While investigating the frictional characteristics of the samples by applying normal forces of the order of micro-Newton, we observed that AAO without a protective coating exhibits the highest friction coefficient. In the presence of protective surface coatings, the friction coefficient decreases significantly. We applied normal forces of the order of milli-Newton during the tribotests to investigate the wear characteristics of AAO, and observed that AAO without protective surface coatings experiences severe damage due to the brittle nature of the oxide layer. We observed the presence of several pieces of fractured particles in the wear track; these fractured particles lead to an increase in the friction. However, by using surface coatings such as gold thin films and nano-organic thin films, we confirmed that the thin films with nanoscale thickness protect the AAO surface without exhibiting significant wear tracks and maintain a stable friction coefficient for the duration of the tribotests.

• Journal of Mechanical Science and Technology
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• 제20권6호
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• pp.738-747
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• 2006

The friction behaviour of Si-wafer, diamond-like carbon (DLC) and two self-assembled monolayers (SAMs) namely dimethyldichlorosilane (DMDC) and diphenyl-dichlorosilane (DPDC) coated on Si-wafer was studied under loading conditions in milli-newton (mN) range. Experiments were performed using a ball-on-flat type reciprocating micro-tribo tester. Glass balls with various radii 0.25 mm, 0.5 mm and 1 mm were used. The applied normal load was in the range of 1.5 mN to 4.8 mN. Results showed that the friction increased with the applied normal load in the case of all the test materials. It was also observed that friction was affected by the ball size. Friction increased with the increase in the ball size in the case of Si-wafer. The SAMs also showed a similar trend, but had lower values of friction than those of Si-wafer In-terestingly, for DLC it was observed that friction decreased with the increase in the ball size. This distinct difference in the behavior of friction in DLC was attributed to the difference in the operating mechanism. It was observed that Si-wafer and DLC exhibited wear, whereas wear was absent in the SAMs. Observations showed that solid-solid adhesion was dominant in Si-wafer, while plowing in DLC. The wear in these two materials significantly Influenced their friction. In the case of SAMs their friction behaviour was largely influenced by the nature of their molecular chains.

• 한국기계가공학회지
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• 제8권4호
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• pp.122-128
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• 2009

The purpose of this study is to show the friction and wear characteristics on the vapor deposited coating layers on the SCM415 steel. In this research, frictional wear characteristic of coating materials such as CrN, AlCrN, WC/C was investigated under room temperature, normal air pressure and nothing lubricating condition. Therefore this study carried out research on the friction coefficient, micro hardness(Hv), roughness, EPMA on the vapor deposited coating layers on the SCM415 steel.

• Carbon letters
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• 제12권4호
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• pp.249-251
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• 2011

Carbon/epoxy woven composites are prominent wear-resistant materials due to the strength, stiffness, and thermal conductivity of carbon fabric. In this study, the effect of oilabsorption on the wear behaviors of carbon/epoxy woven composites was investigated. Wear tests were performed on dry and fully oil-absorbed carbon/epoxy woven composites. The worn surfaces of the test specimens were examined via scanning electron microscopy to investigate the wear mechanisms of oil-absorbed carbon/epoxy woven composites. It was found that the oil absorption rate was 0.14% when the carbon/epoxy woven composites were fully saturated. In addition, the wear properties of the carbon/epoxy woven composites were found to be affected by oilabsorption. Specifically, the friction coefficients of dry and oil-absorbed carbon/epoxy woven composites were 0.25-0.30 and 0.55-0.6, respectively. The wear loss of the oilabsorbed carbon/epoxy woven composites was $3.52{\times}10^{-2}\;cm^3$, while that of the dry carbon/epoxy woven composites was $3.52{\times}10^{-2}\;cm^3$. SEM results revealed that the higher friction coefficient and wear loss of the oil-absorbed carbon/epoxy woven composites can be attributed to the existence of broken and randomly dispersed fibers due to the weak adhesion forces between the carbon fibers and the epoxy matrix.