• Title/Summary/Keyword: tribological properties

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Surface and Tribological Characteristics of Air-cooled and Oil-cooled AISI 4140 Steel (냉각공정에 따른 AISI 4140 강의 표면 및 트라이볼로지 특성)

  • Cho, Hak-Rae;Lee, Sang Don;Son, Jung Ho;Chung, Koo-Hyun
    • Tribology and Lubricants
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    • v.32 no.5
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    • pp.160-165
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    • 2016
  • AISI 4140 steel is widely used in various mechanical components owing to its superior mechanical properties. Surface hardening techniques are often used to further improve the properties, particularly for applications with moving components. The aim of this research is to understand the effect of heat treatment process on surface properties and tribological characteristics of AISI 4140 steel. In this work, we prepare two different AISI 4140 steel specimens- one cooled by air and one by oil- and determine surface properties such as surface topography and roughness using a confocal microscope. We also observe the cross-sections of the specimens using a scanning electron microscope to understand the difference in the material structure. In addition, we assess the hardness with respect to the distance from the surface using a micro-Vickers hardness tester. After characterizing the surfaces of the specimens, we investigate the wear characteristics of the specimens under hydrodynamic lubrication. The results show the presence of grooves on the surface of the oil-cooled specimens. It is likely that such grooves are formed during the cooling process using the oil. However, we observe no other significant differences in the surface properties of the specimens. The wear test results show the occurrence of severe wear on the oil-cooled specimens, which may be due to the groove formed on the surface. The results of this work may be helpful to improve surface properties using surface hardening techniques from a tribological perspective.

Optical, Mechanical and Tribological Properties of Boronnitride Dispersed Silicon Nitride Ceramics

  • Joshi, Bhupendra;Fu, Zhengyi;Niihara, Koichi;Lee, Soo-Wohn
    • Korean Journal of Materials Research
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    • v.20 no.8
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    • pp.444-449
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    • 2010
  • Transparent ceramics are used in new technology because of their excellent mechanical properties over glasses. Transparent ceramics are nowadays widely used in armor, laser windows, and in high temperature applications. Silicon nitride ceramics have excellent mechanical properties and if transparent silicon nitride is fabricated, it can be widely used. h-BN has a lubricating property and is ductile. Therefore, adding h-BN to silicon nitride ceramics gives a lubricating property and is also machinable. Translucent silicon nitride was fabricated by hot-press sintering (HPS) and 57% transmittance was observed in the near infrared region. A higher wt. % of h-BN in silicon nitride ceramics does not favor transparency. The optical, mechanical, and tribological properties of BN dispersed polycrystalline $Si_3N_4$ ceramics were affected by the density, ${\alpha}:{\beta}$-phase ratio, and content of h-BN in sintered ceramics. The hot pressed samples were prepared from the mixture of $\alpha-Si_3N_4$, AlN, MgO, and h-BN at $1850^{\circ}C$. The composite contained from 0.25 to 2 wt. % BN powder with sintering aids (9% AlN + 3% MgO). A maximum transmittance of 57% was achieved for the 0.25 wt. % BN doped $Si_3N_4$ ceramics. Fracture toughness increased and wear volume and the friction coefficient decreased with an increase in BN content. The properties such as transmittance, density, hardness, and flexural strength decreased with an increase in content of h-BN in silicon nitride ceramics.

Study on Tribo-chemistry Properties of Some Additives on Base Oils of Friendly Environmentally Lubricants

  • Bin, Ye;De-hua, Tao
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.10b
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    • pp.263-264
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    • 2002
  • The tribological characteristic of several environmentally friendly lubricating base stocks was examined, and the effect of some commonly used additives on th tribological behavior of the lubricating oils was comparatively investigated on a four-ball machine. It has been found that the commercial additives including butene sulfide, wax chloride, zinc dialkyldithiophosphate and ashless P-N type agent helped to improve the friction-reducing and antiwear properties as well as the extreme pressure behavior. Non-toxic nanoscale $(CF)_x$ showed the best friction-reducing ability, though it registered relatively poor extreme pressure properties. The mechanism on friction of nano-scale material is discussed.

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Tribological Characteristics with Purity Zirconia of Compression Ring Materials in Piston (피스톤 압축 링 재료의 지르코니아 순도에 따른 트라이볼로지 특성)

  • Oh, Seong-Mo
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.15 no.5
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    • pp.91-96
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    • 2006
  • The friction and wear properties of ceramics are very important in the applications to engineering ceramic parts such as seal rings, pump parts, automobile meter parts, and so on. In this study, the effects of each other purity on the mechanical and tribological properties of purity zirconia ceramics were investigated. Also in order to determine the effects of sliding distance, sliding speed, contact load, friction coefficient, the amount of worn out material at a certain time, and the prepared composites were measured. Crystalline phases and microstructure were examined with XRD and SEM. The results show that we obtained the good properties of friction coefficient and wear resistance at the purity 99.5% of zirconia. than this of the purity 95% were great at the wear amount of worn out material.

Tribological Properties of Carbonaceous Ingredients such as Natural Graphite, Artificial Graphite, and Cokes in Automotive Brake Friction Materials

  • Kim, Yoon-Jun;Lee, Kang-Sun;Park, Sung-Bin;Jang, Ho
    • KSTLE International Journal
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    • v.10 no.1_2
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    • pp.43-47
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    • 2009
  • Influences of carbonaceous ingredient as a solid lubricant in automotive friction materials on friction properties were studied. Three types of carbonaceous ingredients such as natural graphite, artificial graphite, and cokes were mixed using a constrained mixture design. A 1/5 scale brake dynamometer was used to obtain tribological properties. Results showed that cokes substantially increased the friction coefficient, and natural graphite effectively reduced stick-slip phenomena. This significant difference was attributed to the formation of the friction film on the brake pad which was shown to be strongly dependent on the graphite types. The different crystal structures of the carbonaceous solid lubricants played a significant role in the formation of friction film at the interface.

Tribological Properties of Clay Bonded SiC (점토 결합 SiC 소결체의 마찰 마모 특성)

  • 한상준;이경희;이재한;김홍기
    • Journal of the Korean Ceramic Society
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    • v.32 no.9
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    • pp.1027-1032
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    • 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.

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Tribological Properties of the Aluminum Short fiber and glass fiber Reinforced Tin-Bronze Matrix Composites (알루미나 단섬유 및 유리섬유 보강 청동기지 복합재의 마모특성 연구)

  • 황순홍;안병길;이범주;최웅수;허무영
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1996.04b
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    • pp.13-19
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    • 1996
  • The tribological properties of the aluminum short fiber and glass fiber reinforced tin-bronze matrix composites manufactured by vacuum hot pressing was studied. The effect of the composition and the relative density on the wear properties was examined by a reciprocal type tribo-test machine. The results were discussed by the observation of the microstructure of sintered specimen and worn surface observation using SEM and EDS. Addition of the fibers led to the wear resistance since the metal matrix was reinforced by the fibers. The reinforcement of the fiber seemed to be stronger as the distribution of the fibers was more uniform. Graphite also reduce the wear loss. The pores in the sintered composites seemed to play an important role to improve the wear resistance since the pores provide the places where the solid lubricants locate.

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An investigation of tribology properties carbon nanotubes reinforced epoxy composites (표면 개질된 탄소나노튜브를 사용한 에폭시 복합재료의 마모특성에 관한 연구)

  • Sulong A.B.;Goak J.C.;Park Joo-Hyuk
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.06a
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    • pp.663-667
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    • 2005
  • Surface modified carbon nanotubes were applied into the epoxy composites to investigate its tribological property. Carbon nanotubes reinforced epoxy composites were fabricated by casting. Effects to the tribological property of loading concentrations and types of surface modification of carbon nanotubes were investigated under sliding condition using linear reciprocal sliding wear tester. The results show that the small amount of carbon nanotubes into the epoxy exhibited lower weight loss than the pure epoxy. It is concluded that the effect of an enormous aspect ratio of carbon nanotubes surface area which wider than conventional fillers that react as interface for stress transfer. As increased the contents of carbon nanotubes, the weight loss from the wear test was reduced. And the surface modified carbon nanotubes show better tribological property than as produced carbon nanotubes. It is due that a surface modification of carbon nanotubes increases the interfacial bonding between carbon nanotubes and epoxy matrix through chemical bonding. Changes in worn surface morphology are also observed by optical microscope and SEM for investigating wear behaviors. Carbon nanotubes in the epoxy matrix near the surface are exposed, because it becomes the lubricating working film on the worn surface. It reduces the friction and results in the lower surface roughness morphology in the epoxy matrix as increasing the contents of the carbon nanotubes.

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Tribological Behavior of Lubricating Oil-Based Nanofluids Containing Ag and Carbon Nanoparticles (Ag 및 탄소 나노윤활유의 제조 및 윤활특성 평가)

  • Choi, Cheol;Jung, Mi-Hee;Choi, Young-Min;Oh, Jae-Myung
    • Korean Journal of Materials Research
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    • v.18 no.11
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    • pp.610-616
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    • 2008
  • Oil-based nanofluids were prepared by dispersing Ag, graphite and carbon black nanoparticles in lubricating oil. Agglomerated nanoparticles were dispersed evenly with a high-speed bead mill and/or ultrasonic homogenizer, and the surfaces of the nanoparticles were modified simultaneously with several dispersants. Their tribological behaviors were evaluated with a pin-on-disk, disk-on-disk and four-ball EP and wear tester. It is obvious that the optimal combination of nanoparticles, surfactants and surface modification process is very important for the dispersity of nanofluids, and it eventually affects the tribological properties as a controlling factor. Results indicate that a relatively larger size and higher concentration of nanoparticles lead to better load-carrying capacity. In contrast, the use of a smaller size and lower concentration of particles is recommended for reducing the friction coefficient of lubricating oil. Moreover, nanofluids with mixed nanoparticles of Ag and graphite are more suitable for the improvement of load-carrying capacity and antiwear properties.

Comparison of Tribological Characteristics of ZnO Coatings Prepared by Sputtering and Sol-gel Methods

  • Lin, Li-Yu;Kim, Dae-Eun
    • KSTLE International Journal
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    • v.10 no.1_2
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    • pp.23-26
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    • 2009
  • In this work the tribological characteristics were compared between ZnO coatings on glass substrate prepared by sputtering and sol-gel methods. In order to assess the effects of processing method on the tribological characteristics, the friction and wear properties of the coatings were measured by using a reciprocating type of micro-tribotester. The sputtered ZnO coatings were prepared on a glass substrate at room temperature, $150^{\circ}$, and $300^{\circ}$. The ZnO coatings prepared by sol-gel method were heat-treated in air atmosphere at $550^{\circ}$ for one hour. The crystal structure and surface morphology of the coatings were measured by X-ray diffraction (XRD) and Atomic Force Microscope (AFM), respectively. The experimental results showed that overall the sputtered coatings exhibited better friction and wear properties than coatings prepared by sol-gel method. The sputtered coating grown at room temperature had a relatively low friction coefficient of 0.14 and superior wear resistance compared with the other coatings. Nevertheless, sol-gel method of coating ZnO on glass is beneficial for economical coating of a large surface area.