• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1991년도 제14회 학술강연회초록집
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• pp.34-37
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• 1991

Al계 베어링합금은 소착저항력등의 베어링특성이 우수하여 최근에 자동차의 엔진부품에 많이 사용되고 있다. Al계 베어링합금으로는 Al-Sn계, Al-Pb계, Al-Si계 합금이 개발되어 사용되어 왔다. Al-Si계 합금은 높은 강도, 우수한 부식성, 주조성이 향상되는 장점등을 갖고 있다. 또한 Al-Pb계 합금은 Pb가 고체윤활제로 작용하여 소착저항성이 높으며 가격도 저렴한 장점을 갖고 있다. Al과 Pb는 용융상태에서 넓은 용융간극을 갖어 중력편석을 일으키기 때문에 일반적인 주조방법으로 Al계 베어링합금을 제조할 수없다. 또한 Al에 Si이 첨가됨에 따라 높은 경도등의 기계적성질의 향상이 얻어지지만 Al 기지에 Si의 함량이 증가할 수록 편석이 심해져 조대한 Si-rich상이 미세조직에 존재하여 합금이 취약해지는 단점을 갖고 있다. 따라서 본 연구에서는 Al 기지에 Pb의 중력편석을 최소화하고 Al 기지에 조대한 Si-rich상이 생성되는 것을 막기 위하여 Al과 Pb가 공존하는 온도구역에서 높은 교반속도로 용탕을 강제교반하여 액상에서 Pb와 Si을 미세하게 분산시킨 후 수냉되는 동주형에서 급속응고시켜 Pb와 Si-rich 상이 균일하게 분포된 Al계 베어링합금을 제조하였다. 본 연구에서는 Pb의 양을 0%에서 35%까지 변화시켰으며, Si의 양을 0%에서 20%까지 변화시켜서 베어링합금을 제조하였으며, 강제교반속도는 500rpm에서 2500rpm 까지 변화시켜 베어링합금을 제조하였다.

• Tribology and Lubricants
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• 제14권2호
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• pp.35-41
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• 1998

The $WS_2$ solid lubricant synthesized through the vapour phase transport method was coated on the commercial bearing steel (SUJ 2) substrate, and the tribological behaviour of the lubricant was investigated using a ball-on-disk type tester. The $WS_2$ powder was spray-coated at room temperature using compressed air, and the change of friction coefficient was examined in various conditions, i.e., specimen configuration, atmosphere (air and nitrogen), applied load and rotating speed. $WS_2$ coated ball and disk showed the optimum friction coefficient of 0.07 and wear life of 45,000 cycles in the nitrogen atmosphere under 0.3 kgf and 100 rpm, whereas relatively high coefficient of 0.13 and reduced wear life of 4,000 cycles were observed in air atmosphere. The effect of rotating speed on the friction coefficient was not observed both in nitrogen and in air atmospheres. This confirmed that the spray-coated $WS_2$ solid lubricant was effective in reducing the friction coefficient and improving wear life in nitrogen atmosphere, and the oxygen and moisture existing in air could seriously deteriorate the lubrication effect of $WS_2$ coating layer.

• 한국기계가공학회지
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• 제12권4호
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• pp.123-130
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• 2013

Zirconia is well known in industrial applications for its mechanical characteristics. DLC (diamond-like carbon) have high elastic modulus, high electric resistivity, high dielectric constant, high wear resistance, low friction coefficient, bio compatibility, chemically inert and thermally stable. Because of all these physical and chemical properties these types of coatings have become key procedure for thin coating. Friction coefficient of DLC films is already evaluated and the current work is a further advancement by calculating the fracture toughness and wear resistance of these coatings. In the present study DLC thin film coatings are developed on $ZrO_2$ alloy surface using Plasma Enhanced Chemical Vapor Deposition (PECVD) method. Vicker hardness test is employed and it was concluded that, DLC coatings increase the Vickers hardness of ceramics.

• 한국기계가공학회지
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• 제16권2호
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• pp.108-113
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• 2017

The performance of refrigerant oil at the thrust bearing and at the journal bearing of a scroll compressor is a significant factor. This paper presents the friction and anti-wear characteristics of nano-fluid with a mixture of a refrigerant oil and nano powders. The particle size distribution and oxidation stability of nano powders prepared by the electrical explosion method were analyzed by TEM and BET. It was found that the nanoparticles showed a spherical morphology with sizes ranging of 40-60 nm and were covered with graphite layers of 2-4 nm. The thermal conductivity of POE oil was 0.1-0.5W/mk higher than that of POE oil. The coefficient of friction of Cu-POE was found to be 0.1 higher than that of Al2O3. The cooling capacity of the heat pump with nanofluid increased to 3.67%, and the performance was improved by 5.83%.

• 한국분말재료학회지
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• 제13권4호
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• pp.250-255
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• 2006

Wear behaviors of gas atomized and extruded Al-Si alloys were investigated using the dry sliding wear apparatus. The wear tests were conducted on Al-Si alloy discs against cast iron pins and vice versa at constant load of 10N with different sliding speed of 0.1, 0.3, 0.5m/s. In the case of Al-Si alloy discs slid against the cast iron pins, the wear rate slightly increased with increasing the sliding speed due to the abrasive wear occurred between Al-Si alloy discs and cast iron pins. Conversely, in the case of cast iron discs against Al-Si alloy pins, the wear rate decreased with increasing the sliding speed up to 0.3m/s. However, the wear rate increased with increasing the sliding speed from 0.3m/s to 0.5m/s. It could be due to adhesive wear behavior and abrasive wear behavior_between cast iron discs and Al-Si alloy pins.

• 한국자동차공학회논문집
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• 제15권5호
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• pp.139-145
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• 2007

Fretting is a kind of surface damage mechanism observed in mechanically jointed components and structures. The initial crack under fretting damage occurs at lower stress amplitude and lower cycles of cyclic loading than that under plain fatigue condition. This can be observed in automobile and railway vehicle, fossil and nuclear power plant, aircraft etc. In the present study, railway axle material RSA1 used for evaluation of fretting fatigue life. Plain and fretting fatigue tests were carried out using rotary bending fatigue tester with proving ring and bridge type contact pad. Through these experiments, it is found that the fretting fatigue limit decreased about 37% compared to the plain fatigue limit. In fretting fatigue, the wear debris is observed on the contact surface, and oblique cracks at an earlier stage are initiated in contact area. These results can be used as useful data in a structural integrity evaluation of railway axle.

• Journal of Welding and Joining
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• 제21권2호
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• pp.42-49
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• 2003

The protection of steel surfaces against wear is a practical problem far agricultural, mining and manufacturing industries. Commercial processes are available in which a hard tungsten carbides rich steel layer is formed on the surface of carbon steel digging, drilling and gouging tools to improve their wear resistance. The nature of the interaction of the tungsten carbide with the steel matrix is important in determining the wear and corrosion properties of the resulting metal matrix composites(MMC). In the study, WC-12%Co/low carbon steel MMC overlays have been prepared by gas metal arc welding(GMAW) according to size of WC-12%Co grits. The characteristics wear resistance and wear mechanism have been investigated in relation to the experiment conditions each other. After MMC overlay had been tested by rubber wheel abrasion test, it was known that MMC overlay has a excellent wear resistance. Fe$_{6}$W$_{6}$C carbides of matrix in overlays were not important to restrain rubber wheal abrasion wear. Wear loss is proportioned to a applied load according to time. On the case of low load, wear occurred severely in the matrix of overlay more than WC-12%Co grit, on the contrary it is reverse on the case of high load because of fracture of WC-12%Co grits.its.

• Tribology and Lubricants
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• 제9권1호
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• pp.62-69
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• 1993

Friction and wear behavior of a carbon/carbon composite material for aircraft brake material was experimentally investigated. Friction and wear test setup was designed and built for the experiment. Friction and wear tests were conducted under various sliding conditions. Friction coefficients were measured and processed by a data acquisition system and amount of wear measured by a balance. Stainless steel disk was used as the counterface material. Temperature was also measured by inserting thermocouple 2.5 mm beneath the sliding surface of the carbon/carbon composite specimen. Wear surfaces were observed by SEM, and analyzed by EDAX. The experimental results showed that sliding speed and normal force did not have significant effects on friction coefficient and wear factor of the composite. Temperature increase just below the surface was not large enough to cause any thermal degradation or oxidation which occurred at higher temperature when tested by TGA. Wear film was generated both on the specimen and on the counterface at relatively low sliding speed but cracks, grooves, and wear debris were observed at high sliding speed. Friction coefficient remained almost constant when the sliding speed or normal load was varied. It is believed that the adhesive and abrasive components contributed mainly to the friction coefficient. Wear behavior at low sliding speed was governed by wear film formation and adhesive wear mechanism. At high speed, fiber orientation, ploughing by counterface asperities, and fiber breakage dominated wear of the carbon/carbon composite.

• 한국재료학회지
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• 제12권8호
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• pp.608-612
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• 2002

The sliding wear behavior of an iron-base NOREM 02 hardfacing alloy was investigated in the temperature range of $25～250^{\circ}C$ under a contact stress of 103MPa (15ksi). With increasing temperature, the wear loss of Norem 02 in water increased slightly up to $180^{\circ}C$ at which Norem 02 showed the wear loss of 2.1mg. The wear resistance of Norem 02 resulted from the surface hardening due to the strain-induced phase transformation from austenite to $\alpha$'martensite during sliding wear. The wear loss of Norem 02 was smaller in water compared to air at same temperature because the water could be served as a sort of lubricant. The wear mode of NOREM 02 changed abruptly to severe adhesive wear at $190^{\circ}C$ and galling occurred above $200^{\circ}C$. It was caused that the strain- induced phase transformation took place below $180^{\circ}C$ while not above $190^{\circ}C$. Therefore, Norem 02 was considered to be inadequate at high temperature service area.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제28회 추계학술대회
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• pp.106-114
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• 1998

Tribological investigation of ultra thin film magnetic storage disks which have two different kinds of start/stop zone of laser textured bump disk and mechanically textured disk for before CSS test and after CSS test. To measure surface roughness, height reduction before/after CSS test and obtain accurate topographies, AFM(Atomic Force Microscope) which is most powerful recently has been used. The result of statistical analysis showed that both laser textured bump height and mechanically textured zone height have been reduced about 4~7nm after 15000 cycle CSS test. Using commercial Nano-Indenter, ramping load scratch test has been performed to investigate friction characteristic for laser textured zone and mechanically textured zone before/after CSS test.