• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2008년도 하계학술발표대회 논문집
• /
• pp.194-202
• /
• 2008

In this study, we investigated the tribology behaviour of two different bearing materials. One of these alloys content is Cu(90)-Sn(10) alloy and is widely used in the automotive industry.The other is Al alloy. This bearing content is Al-Sn-Si-Cu. Therefore, it is required to study on the lublicating characteristics of bearing according to different materials. In this study, compressor bearings made by respectively "PTFE solid lubricant" and "AI alloy with superior load carrying capacity, rubbing and impact endurance", have gone through journal bearing test. Lubrication and abrasion characteristics are evaluated by analyzing the material characteristics of a scroll compressor bearing bush. The AI alloy bearing showed the most excellent lubrication and abrasion characteristics than Cu-Sn alloy under high load condition.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
• /
• pp.918-920
• /
• 2006

Metal sulfide powders such as MnS, $MoS_2$ and FeS are simply used to the machinery processing improvement agent and solid lubricant in powder metallurgy industrial. And then, metal sulfide powders have received relatively little attention from powder metallurgy. Recently, the portable machine is one of the important interfaces between human or human and electronic machine. With the increase of the intelligent activity, the social and industrial demands for information display device and power source are increasing. The transition metal sulfide materials (FeS, ZnS) have received considerable attention due to the large variety of its electric, optical and magnetic properties. Among the metal sulfide, $FeS_2$ is appealing superior material for applications in $Li-2^{nd}$ battery because of high capacity. ZnS is also a famous phosphor material with various luminescence properties, such as photoluminescence (PL) and electroluminescence (EL). So generally used in the fields of display, sensors and laser. Metal sulfide materials, therefore, are provided for most widely application in all industries. In recent years, material researchers have become increasingly interested in studying with synthesis of metal sulfide.

• 한국전산유체공학회지
• /
• 제14권4호
• /
• pp.56-61
• /
• 2009

This study deals with the numerical investigation on two-dimensional lubrication characteristics of micro-dimple shapes fabricated on solid surfaces by using the commercial CFD code (Fluent V.6.3) to examine the influence of micro dimple depth and width on the reduction in friction under the sliding plate condition. In addition, single and multiple dimple arrays are simulated, all for a fixed area fraction of dimple on the surface. As a result, it is found that the existence of micro-dimpled surface makes it possible to substantially reduce the friction forces exerted on the surfaces, and such an optimum dimple depth would be present because the dimple depth larger than the optimum value did no longer affect the reduction in shear stresses, indicating that the reduction of friction is likely to be associated with inner flows of lubricant inside dimples. Moreover, it is observed that at the fixed area fraction, the friction reduction increases with the increase of dimple diameter.

• 한국재료학회지
• /
• 제12권7호
• /
• pp.568-572
• /
• 2002

Plasma sulfnitriding technology was employed to harden the surface of SKD61 steel. The plasma sulfnitriding was performed with 3 torr gas pressure at $580^{\circ}C$ for 20 hours. Plasma sulfnitriding resulted in the formation of very thin $2-3\mu\textrm{m}$ FeS sulfide layer on top of $15-20\mu\textrm{m}$ compound layer, which consisted of predominantly $\varepsilon$- $Fe{2-3}$ N and a second phase of $\Upsilon'-Fe_4$N. In comparision with plasma nitriding treatment, plasma sulfnitriding treatment showed better surface roughness and corrosion resistance due to the presence of the thin FeS layer. which coated microvoids and microcracks on top of the nitrided layer. It was also found that plasma sulfnitrided sample showed better wear resistance due to the presence of the thin FeS layer which acted as a solid lubricant.

• 대한금속재료학회지
• /
• 제50권8호
• /
• pp.549-556
• /
• 2012

The tribological behavior of CrMoN films with respect to surface chemistry was investigated by using X-ray photoelectron spectroscopy (XPS). All of the films were prepared from a hybrid PVD system consisting of DC unbalanced magnetron (UBM) sputtering and arc ion plating (AIP) sources. The tribological property of the films was evaluated by a friction coefficient using a Ball-on-disk type tribometer. The chemistry of wear track was analyzed by energy dispersive spectroscopy (EDS) and XPS. The friction coefficient was measured to be 0.4 for the CrMoN film, which is lower than that of a monolithic CrN film. EDS and XPS results imply the formation of an oxide layer on the coating surface, which was identified as molybdenum oxide phases, known to be a solid lubricant during the wear test.

• 한국기계가공학회지
• /
• 제20권12호
• /
• pp.16-23
• /
• 2021

Pin-to-disc wear testing experiments were conducted to investigate the wear characteristics of commercial oil (5W-40) with nano-diamond particles. The upper specimen was a SUJ-2 high-carbon chromium steel ball with a diameter of 4 mm, and the lower specimen was made of the Al-6061 alloy. The applied load was 5 N, and the sliding speed was 0.25 m/s. The wear tests were conducted at a sliding distance of 500 m. The friction coefficients and wear rates of the Al-6061 specimens were tested using commercial oil with different nano-diamond concentrations ranging from 0 to 0.02 wt.%. The addition of nano-diamond particles to commercial oil reduced both the wear rate and coefficient of friction of the Al-6061 alloy. The use of nano-diamond particles as a solid additive in oil lubricants was found to improve the tribological behavior of the Al-6061 alloy. For the Al-6061 alloy, the optimal concentration was found to be 0.005 wt.% in view of the friction coefficient and wear rate. Further investigation is needed to determine the optimal concentration of nano-diamond particles for various loadings, sliding speeds, oil temperatures, and sliding distances.

• 소성∙가공
• /
• 제32권4호
• /
• pp.180-190
• /
• 2023

This study deals with residual stress prediction and hardness evaluation within cross ball grooved inner race fabricated by cold upsetting process consisted of upsetting and ejection steps. A raw workpiece material of AISI 5120H (SCr420H) is first spheroidized and annealed, then phosphophyllite coated to form solid lubricant layer on its outer surface. To investigate influences of the heat treatment, uni-axial compression tests and Vickers micro-hardness measurements are conducted. Three-dimensional elasto-plastic FE simulations on the upsetting step and the ejection one are performed to visualize the residual stress and the ductile (plastic deformation) damage. External feature of the fabricated inner race is fully captured by using an optical 3D scanner, and the micro-hardness is measured on internal cross-sections. Consequently, the dimensional compatibility between the simulated inner race and the fabricated one is ensured with a difference of under 0.243mm that satisfied permissible error range of ±0.50mm on the grooved surface, and the predicted residual stress is verified to have similar distribution tendency with the measured Vickers micro-hardness.

• 한국재료학회지
• /
• 제12권12호
• /
• pp.941-946
• /
• 2002

Both Cu and Cu-oxide nanopowders have great potential as conductive paste, solid lubricant, effective catalysts and super conducting materials because of their unique properties compared with those of commercial micro-sized ones. In this study, Cu and Cu-oxide nanopowders were prepared by Pulsed Wire Evaporation (PWE) method which has been very useful for producing nanometer-sized metal, alloy and ceramic powders. In this process, the metal wire is explosively converted into ultrafine particles under high electric pulse current (between $10^4$ and $10^{ 6}$ $A/mm^2$) within a micro second time. To prevent full oxidations of Cu powder, the surface of powder has been slightly passivated with thin CuO layer. X-ray diffraction analysis has shown that pure Cu nanopowders were obtained at $N_2$ atmosphere. As the oxygen partial pressure increased in $N_2$ atmosphere, the gradual phase transformation occurred from Cu to $Cu_2$O and finally CuO nanopowders. The spherical Cu nanopowders had a uniform size distribution of about 100nm in diameter. The Cu-oxide nanopowders were less than 70nm with sphere-like shape and their mean particle size was 54nm. Smaller size of Cu-oxide nanopowders compared with that of the Cu nanopowders results from the secondary explosion of Cu nanopowders at oxygen atmosphere. Thin passivated oxygen layer on the Cu surface has been proved by XPS and HRPD.

• 한국철도학회논문집
• /
• 제12권5호
• /
• pp.788-792
• /
• 2009

철도는 그동안 친환경 교통수단으로 알려져 왔다. 그러나 토양환경보전법 제정 이전 수십 년간 인지하지 못하는 토양오염들이 철도 시설 부지에서 유발되어 왔다. 철도차량기지 등에서는 철도차량 유지관리 및 수선을 위해 사용되어진 많은 폐기물과 유기용제들이 부지 내에 투기되어온 것들이 사실이다. 이들 부지의 개발과 활용을 위해서는 과거의 오염지역에 대한 정차가 선결되어야 하는데, 본 연구는 차량기지의 토양 오염현황과 복원 대책을 제안하기 위해 수행되어 졌다. 차량기지 내 폐기물 투기 지역에서는 유류오염물질인 TPH 성분과 몇몇 중금속 성분이 토양오염 기준치를 초과하는 것으로 나타났으며, 기지 내 선로와 분기기에 대한 조사에서는 분기기 하부에서 유류오염물질이 관측되었다. 원위치, 또는 굴착 후 정차 등의 방법이 오염정화를 위해 적용되어질 수 있으며, 현장의 특성을 고려하고, 모의시험을 통해 적절한 정화 방법을 채택할 경우 현장의 오염정화를 완성할 수 있을 것이다.

• 한국결정성장학회지
• /
• 제16권6호
• /
• pp.273-277
• /
• 2006

High velocity of oxy-fuel (HVOF) thermal spray coating is progressively replacing the other classical hard coatings such as chrome plating and ceramic coating by the classical methods, since the very toxic $Cr^{6+}$ ion is well known as carcinogen causing lung cancer, and the ceramic coatings are brittle. Co-alloy T800 powder is coated on the Inconel 718 substrates by the HVOF coating procesess developed by this laboratory. For the study of the possibility of replacing of chrome plating, the wear properties of HVOF Co-alloy T800 coatings are investigated using the reciprocating sliding tester with a counter sliding SUS 304 ball both at room and at an elevated temperature of $1000^{\circ}F\;(538^{\circ}C)$. The possibility as durability improvement coating is studied for the application to the high speed spindles vulnerable to frictional heat and wear. Wear mechanisms at the reciprocating sliding wear test are studied far the application to the systems similar to the sliding test such as high speed spindles. Wear debris and frictional coefficients of T800 coatings both at room and at an elevated temperature of $538^{\circ}C$ are drastically reduced compared to those of non-coated surface of Inconel 718 substrates. Wear traces and friction coefficients of both coated and non-coated surfaces are drastically reduced at a high temperature of $538^{\circ}C$ compared with those at room temperature. These show that the coating is highly recommendable far the durability Improvement coating on the surfaces vulnerable to frictional heat and wear.