Papers by Keyword: Self-Lubrication

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Authors: Yuan Fa Ding, Wen Guo Huo, Xiang Dong Su, Lan Zhang
Abstract: A new self-lubrication concept based on the techniques including of dry grinding and solid lubricating was proposed for green grinding process. And a kind of self-lubrication grinding wheel was designed with solid powder lubricant and centrifugal impeller inside. The self-lubricating was achieved by the blow out of the solid powder lubricant from the inner cavity of the wheel by the centrifugal force to the grinding surface. The experiments were conducted to study the friction and wear properties of the new cylindrical wheel samples manufactured by the proposed concept. The results showed that the flow channel diameters of 1 to 1.5 mm are the best for the blowing out of the solid lubricant to realize the continuous lubricating. After grinding, the surface coating is even, and the sizes of the abrasive particles are relatively uniform with no peeling into blocks. Although there is a certain wear loss of the grinding surface, the wear rate of the particles on the sample wheels is less than that of the traditional grinding wheel. The computational simulation of the self-lubrication wheel is conducted with the RSM method with FLUENT software to analyze the flow field in the wheel cavity of solid lubricant inside, which is meaningful for the study of the motion of the solid lubricant and useful for optimum design of the wheel design to realize the best self-lubricating performance.
Authors: Hisashi Sato, Wei Wei, Kazuaki Oguri, Motoko Yamada, Yoshimi Watanabe
Abstract: Reduction of frictional coefficient at sliding position can improve wear resistance of material. In previous studies, Cu-based composites containing graphite particles have been reported. Since graphite is better lubrication material, the Cu-based composites containing graphite particles have better wear property comparing with the pure Cu. However, these composites are mainly fabricated by sintering method and its strength is relatively low. In this study, Cu-based composites containing graphite particles are fabricated by centrifugal mixed-powder casting. The centrifugal mixed-powder casting is novel centrifugal casting method combined with powder metallurgy. Using this casting method, the Cu-based composites containing graphite particles are successfully obtained. The graphite particles are distributed in the Cu matrix and no casting defects are observed. Moreover, wear resistance of these Cu-based composites are much better than pure Cu, and the frictional coefficient between these composites and bearing steel as the counter part is reduced by dispersion of the graphite particles. Furthermore, it is found that the optimum area fraction of the graphite particles to improve the wear resistance of the present Cu-based composite is from 15% to 21%.
Authors: Ying Han, Yan Jun Wang, Shou Ren Wang
Abstract: Metal ceramic preforms were fabricated by vacuum sintering method in this work. Ti-Fe-Cr-W-Mo-V powder was used as the basic material, TiH2 and CaCO3 were used as the composite pore-forming material and Al2O3 was used as dispersal particles. The influences of fabricating parameters on infiltrating qualities and mechanical properties were discussed. The friction and wear behaviors under high temperature were investigated by pin on disk wear tester. Moreover, the microstructure and the worn surface morphology of the preforms and the composites were analyzed using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The experimental results showed that the composite, which was sintered at 1230 oC with a holding time of 60min and was infiltrated by melt solid lubricant under a pressure of 5 MPa at 750 oC, exhibits good friction and wear behavior. The composites composed of metal ceramic hard phase and multi-lubricant soft phase with an interpenetrating network exhibit good self-lubricating properties, high obdurability and wear resistance over a range of temperature at 400-700 oC.
Authors: Yan Jun Wang, Bin Wang, Li Ying Yang, Shou Ren Wang
Abstract: High speed steel based ceramic preforms with three-dimensionally interpenetrated micropores were fabricated using the mixture of TiH2, CaCO3 and stearic acid as pore-forming agent. A self-made vacuum high pressure infiltration furnace was used to infiltrate the preforms with Pb-Sn based solid lubricants to create almost fully dense self-lubrication composites. The microstructure and properties of HSS-based self-lubrication composites were investigated as a function of sintered porosity. A quantitative analysis of microstructure was correlated with crushing strength,microhardness and wear rate to understand the influence of pore size, shape and distribution on mechanical and tribological behavior. Crushing strength and microhardness decreased with an increase in porosity. Meanwhile the decrease in microhardness with increasing porosity was slightly. The friction coefficient of HSS-based self-lubrication composites decreased with increasing the volume fraction of lubricant due to the self-lubrication and unique micropore structure. Within the range of lubricant volume fraction from 0% to 14%, the wear rate of the composites decreased steadily with the increase of lubricant content in the composites. Micropore structure and lubricant volume fraction play an important role in determining wear resistance of the composites whereas the measured bulk properties seem to be of minor importance.
Authors: Bogdan Wendler, Tomasz Moskalewicz, Marcin Kot, Slawomir Zimowski, Aleksandra Czyrska-Filemonowicz, Wojciech Pawlak, Adam Rylski, Katarzyna Wlodarczyk-Kowalska, Piotr Nolbrzak, Marcin Makowska
Abstract: A series of nanocomposite, self-lubricating coatings designed for dry friction at different temperatures based on amorphous carbon or amorphous MoS2 or amorphous MoO3 matrix was deposited by magnetron sputtering onto high-speed (HS) steel or Ti6Al4V alloy substrates and characterized with use of LM, SEM, TEM and HRTEM microscopy as well as with use of several other techniques. The nanocomposite nc-MeC/a-C(:H) carbon-based coatings (where Me=Cr or Ti or W) were composed of different nanocrystalline phases of a given transition metal of a size of several nanometers embedded in an amorphous hydrogenated or hydrogen-free carbon matrix. The nanocomposite MoS2(Ti,W) coatings were composed of Tiα or Wα or TiS2 nanocrystallites of 3 nm ÷ 10 nm diam. embedded in a semi-crystalline MoS2 matrix with MoS2 clusters of 3 nm÷8 nm diam. The magnetron sputtered MoO3 based coatings after deposition were composed of Ag nanocrystallites of 50 nm÷100 nm diam. embedded in an amorphous fractal-type matrix composed of MoO3 clusters of different size from very small to relatively great ones (not exceeding, however, 400 nm diam.). These amorphous clusters after 3 hours annealing in the ambient atmosphere under normal pressure at 300 °C transform into nanocrystalline MoO3 ones or after same annealing at 450 °C into crystalline silver molybdate Ag2MoO4 ones. The coatings preserve their resistance to wear and their low friction coefficient to approximately 250 °C in case of carbon-based coatings or to 350 °C in case of MoS2-based ones or to 550 °C in case of MoO3-based coatings. Several mechanical and tribological chracteristics of the coatings are given in the paper as well.
Authors: Wen Feng Ding, Jiu Hua Xu, J.L. Huang, Z.Z. Chen, H.H. Su, Y.C. Fu
Abstract: Self-lubrication CBN abrasive composite blocks and corresponding grinding wheels were made through the sintering process of CBN grains, graphite particles and Cu-Sn-Ti alloy at 920° for 30 min. The mechanical strength of the composite blocks was measured by means of the three-point bending experiments. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD) were employed to characterize the fracture morphology and the interfacial microstructure of the composite blocks. Dressing experiments were carried out and the graphite film on the CBN grain surface was observed. The results obtained show that the bending strength of the composite blocks with 5 wt.% graphite particles reached 116 MPa, which met the mechanical requirements of the working layer of the grinding wheels. Chemical joining has taken place at the interface of CBN/Cu-Sn-Ti and graphite/Cu-Sn-Ti during the sintering process. Graphite film has been formed and spread to the grain surface after dressing.
Authors: Jian Rong Sun, Chang Sheng Li, Hua Tang, Zhi Cheng Guo, Jin Ying Zi Liu
Abstract: The composites of Ni-W-Cr-Fe-Cu-MoS2-Graphite with nano-MoS2 were prepared by powder metallurgy. Its tribological properties were investigated using the UTM-2 Nano+Micro Tribometer from room temperature to 600°C. The effects of amount of MoS2 and Ni-W-Cr prealloy powder, load, and temperature on the tribological properties were investigated and discussed. The results indicated that the addition of 43~45wt.% Ni-W-Cr prealloy powder had a strengthening effect on the hardness, anti-press and tensile strength. The tensile strength of the composite decreases with the addition of Nano-MoS2 and graphite, and the friction coefficient decrease with increase of the additives over the wide temperature range of 25°C∼600°C. The friction coefficients and wear rates of the composites reach the optimization value at 2.5wt.% MoS2,While its wear rates increase with the increasing temperature and load.
Authors: Sui Yuan Chen, Xin Rong Li, Yu Ning Bi, Daniel Wellburn, Jing Liang, Chang Sheng Liu
Abstract: Using 663-tin bronze, Ni, W, nanoAl2O3, MoS2, graphite, CaF2, and Ni coated graphite as the matrix alloy powder, in which copper-coated carbon fiber of 5%, 7%, 9%, 11% and 13% in volume fraction were added as the reinforcing phase, a novel type carbon fiber/copper-matrix self-lubricating composite materials was prepared by means of powder metallurgy. The results indicate that the mechanical properties of the composite materials are improved after adding copper-coated carbon fibers. The composite materials reach optimal overall mechanical performance under testing when the volume fraction of the added copper-coated carbon fibers is 11%.: with a hardness of 57.8 HV and a compressive strength of 222 MPa. The addition of carbon fiber also improved the friction and wear properties of the composite materials. Increasing the volume fraction of fiber, was found to increase the wear resistance and improve self-lubricating performance. A volume fraction of 11% gave a friction coefficient of 0.09 and abrasion loss of 4mg.
Authors: Bolesław Giemza, Artur Król, Tadeusz Kałdoński
Abstract: In the article one investigation’s results regarding the influence of work parameters of the porous bearings on the process of oil ageing is presented. Firstly stand tests were performed for the porous bearings sintered of iron powder Höganas (Sweden) and impregnated by protection oils, often used by porous bearings manufactures. Stand tests were performed until the seizure of the bearing was achieved – loss of self-lubricating capability. Then oil was extracted from all bearings and the degree of oil ageing was observed by two methods: investigation of IR spectrums and total acid number. After that all results were compared with those achieved for fresh oils.
Authors: Y.T. Pei, P. Huizenga, Damiano Galvan, Jeff T.M. de Hosson
Abstract: Advanced TiC/a-C:H nanocomposite coatings have been produced via reactive deposition in a closed-field unbalanced magnetron sputtering system. In this paper, we report on the tribological behavior of TiC/a-C:H nanocomposite coatings in which ultra-low friction is tailored with superior wear resistance, being two properties often difficult to achieve simultaneously. In-situ monitoring the wear depth at nanometer scale reveals that the self-lubricating effects are induced by the formation of transfer films on the surface of ball counterpart. In addition, the CoF of TiC/a-C:H nanocomposite coatings decreases with decreasing relative humidity. This phenomenon can be interpreted in terms of water molecule interactions with the wear track. The influence of the volume fraction and grain size of TiC nanocrystallites on the coating properties has been examined. A superior wear resistance at a level of 10-17 m³/(N m lap) has been achieved under the condition of super-low friction and high toughness, both of which require fine TiC nano-particles (e.g. 2 nm) and a wide matrix separation that must be comparable to the dimensions of the nano-particles.
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