scholarly journals Characterization and Tribological Performances of Graphene and Fluorinated Graphene Particles in PAO

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 2126
Author(s):  
Yanjie Chen ◽  
Enzhu Hu ◽  
Hua Zhong ◽  
Jianping Wang ◽  
Ayush Subedi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Friction Coefficient ◽  
Wear Rate ◽  
Film Formation ◽  
Low Friction ◽  
Lubrication Film ◽  
Lubrication Performance ◽  
Alpha Olefin ◽  
Average Wear ◽  
Fluorinated Graphene

Graphene has been widely used as a lubricating additive to reduce the energy consumption of engines and improve fuel economy because of its unique crystal structure. Herein, graphene (GR) and fluorinated graphene (F-GR) nanoparticles were prepared by ball milling and liquid-phase exfoliation. The SEM/EDS, HRTEM, XPS, Raman spectrometer, X-ray spectrometer, FTIR were used to investigate the morphologies, surface groups, and crystal structure of two kinds of graphene materials. The influence of loads on the tribological properties of two kinds of particles was investigated in Poly Alpha Olefin (PAO6) using a UMT-2 reciprocating tribometer. Results showed that the crystal structure of GR is better than F-GR. F-GR can improve the lubrication performance of PAO6. For PAO6 containing 1 wt% F-GR at 10 N, the average friction coefficient and average wear rate decreased by 12.3% and 87% relative to pure PAO6, respectively. However, the high load resulted in an inconspicuous anti-wear and anti-friction effect. The influence of F-GR on the tribological behavior of PAO6 was more substantial than that of GR. The friction and wear mechanisms attributed to F-GR quickly entered the interface between the friction pairs. Friction-induced F-GR nanosheets mainly took the tribo-chemical reactions to participate in the lubrication film formation and helped achieve a low friction coefficient and wear rate.

A Mixed-TEHL Analysis of Cam-Roller Contacts Considering Roller Slip: On the Influence of Roller-Pin Contact Friction

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Shivam S. Alakhramsing ◽  
Matthijn B. de Rooij ◽  
Aydar Akchurin ◽  
Dirk J. Schipper ◽  
Mark van Drogen
Keyword(s):  
Friction Coefficient ◽  
Thermal Effects ◽  
Mixed Lubrication ◽  
Contact Friction ◽  
Sudden Increase ◽  
Low Friction ◽  
Pure Rolling ◽  
Lubrication Performance ◽  
Cam Follower ◽  
Film Lubrication

In this work, a mixed lubrication model, applicable to cam-roller contacts, is presented. The model takes into account non-Newtonian, thermal effects, and variable roller angular velocity. Mixed lubrication is analyzed using the load sharing concept, using measured surface roughness. Using the model, a quasi-static analysis for a heavily loaded cam-roller follower contact is carried out. The results show that when the lubrication conditions in the roller-pin contact are satisfactory, i.e., low friction levels, then the nearly “pure rolling” condition at the cam-roller contact is maintained and lubrication performance is also satisfactory. Moreover, non-Newtonian and thermal effects are then negligible. Furthermore, the influence of roller-pin friction coefficient on the overall tribological behavior of the cam-roller contact is investigated. In this part, a parametric study is carried out in which the friction coefficient in the roller-pin contact is varied from values corresponding to full film lubrication to values corresponding to boundary lubrication. Main findings are that at increasing friction levels in the roller-pin contact, there is a sudden increase in the slide-to-roll ratio (SRR) in the cam-roller contact. The value of the roller-pin friction coefficient at which this sudden increase in SRR is noticed depends on the contact force, the non-Newtonian characteristics, and viscosity–pressure dependence. For roller-pin friction coefficient values higher than this critical value, inclusion of non-Newtonian and thermal effects becomes highly important. Furthermore, after this critical level of roller-pin friction, the lubrication regime rapidly shifts from full film to mixed lubrication. Based on the findings in this work, the importance of ensuring adequate lubrication in the roller-pin contact is highlighted as this appears to be the critical contact in the cam-follower unit.

Prediction of Wear Rate Dispersion in Mixed Lubrication

2005 ◽  
Author(s):  
F. Robbe-Valloire ◽  
R. Progri ◽  
B. Paffoni ◽  
R. Gras
Keyword(s):  
Friction Coefficient ◽  
Wear Rate ◽  
Boundary Lubrication ◽  
Mixed Lubrication ◽  
Tribological Behaviour ◽  
Low Friction ◽  
Local Boundary ◽  
Physico Chemical ◽  
Lubricant Films ◽  
Second Category

Mixed lubrication is usually related to the partition of contacts, and these latter may be divided into two categories. The first includes all asperities working in thin lubricated film (physico-chemical film) conditions. This situation corresponds to local boundary lubrication and is characterised by a local friction coefficient around 0.1. The second category contains all other asperity types. Due to the existence of a thick lubricant films asperities belonging to the second category exhibit a low friction coefficient. The global tribological behaviour for a given contact, however, is function of both categories, since it involves asperities from both categories.

scholarly journals MICROSTRUCTURE AND WEAR RESISTANCE OF A COMPOSITE Gr/Al2O3/Al PRODUCED BY RECIPROCATING EXTRUSION

2012 ◽  
Vol 05 ◽  
pp. 646-653
Author(s):  
Z. M. Zhang ◽  
G. P. Zhu ◽  
C. J. Xu ◽  
B. Hu
Keyword(s):  
Friction Coefficient ◽  
Wear Rate ◽  
Extrusion Process ◽  
Pure Aluminium ◽  
Low Friction ◽  
Graphite Particles ◽  
Al Composite ◽  
Alumina Particles ◽  
The Matrix ◽  
Reciprocating Extrusion

A reciprocating extrusion process was used to produce graphite and alumina reinforced pure aluminium composite. The graphite particles (0~5vol%), alumina particles (10 vol%) and pure aluminium particles (balanced) were dehydrated separately at 70°C in vacuum for 3 hours, and then mixed together. A round billet with 50 mm in diameter was prepared by hot pressing at 350°C with the mixed particles and then extruded to a fully-consolidated goblet-like sample at 480°C and 430MPa by reciprocating extrusion. The results showed that all reinforced particles were refined and uniformly distributed in the matrix by reciprocation extrusion severe plastic deformation. The presence of graphite particles caused the reduction in the friction coefficient and wear rate of the Gr / Al 2 O 3/ Al composite. Compared with the composite prepared only by alumina particles (10 vol%) and pure aluminium particles, the friction coefficient and wear rate of the Gr / Al 2 O 3/ Al composite, which contains 5vol% graphite and 10vol% alumina particles, decreased 45.3% and 33.5%, respectively, and thereafter it displays an excellent combination of low friction coefficient (0.37) and wear rate (2.2×10-7mm3/(N.m)), and appears to be more promising.

scholarly journals Friction and Wear Mechanisms of Cu/ta-C Coatings Under PAO-4 and PAO-4 with MoDTC Lubrication

2020 ◽  
Vol 01 (04) ◽  
pp. 183-187
Author(s):  
Decelyne Elly Binjua ◽  
Seock-Sam Kim ◽  
Young-Jun Jang ◽  
Jong-Kuk Kim
Keyword(s):  
Friction Coefficient ◽  
Wear Rate ◽  
Friction And Wear ◽  
Vacuum Arc ◽  
Dlc Coatings ◽  
Base Oil ◽  
Tetrahedral Amorphous Carbon ◽  
Friction And Wear Mechanisms ◽  
Alpha Olefin ◽  
Filtered Cathodic Vacuum Arc

The tribological behavior of various types of DLC coatings in formulated and non-formulated lubricants are needed for proper usage of these coatings. In this research, the friction and wear mechanism of four different DLC coatings in poly-alpha-olefin type 4 (PAO-4) with and without MoDTC were investigated using ball-on-disc tribometer. One ta-C (tetrahedral amorphous carbon) and three Cu/ta-C (copper doped ta-C) with different sputter power of 50 W, 150 W, and 200 W coatings were deposited on silicon wafers by using FCVA (filtered cathodic vacuum arc) technique for this research. The results indicate that ta-C coating on silicon wafer has the lowest average friction coefficient (CoF) and better wear resistance than Cu/ta-C coating when lubricated under PAO-4 oil with MoDTC. Cu/ta-C with sputter powers of 150 W and 200 W exhibited the highest average friction coefficient under PAO-4 oil with MoDTC. Meanwhile, the average CoF for all samples were similar under PAO-4 base oil. In terms of wear, ta-C coating showed the highest wear rate under PAO-4 base oil then followed by Cu/ta-C with sputter power of 50 W. Nonetheless, Cu/ta-C with sputter powers of 150 W and 200 W exhibited significantly low wear rate under PAO-4 base oil compared to PAO-4 oil with MoDTC.

Tribological Properties Between a-C:H Coatings and SiO2 at High Temperature

2020 ◽  
Author(s):  
Noritsugu Umehara ◽  
Kota Konishi ◽  
Motoyuki Murashima ◽  
Takayuki Tokoroyama
Keyword(s):  
High Temperature ◽  
Friction Coefficient ◽  
Wear Rate ◽  
Tribological Properties ◽  
Friction And Wear ◽  
Wear Track ◽  
Severe Damage ◽  
Friction Test ◽  
Low Friction ◽  
Disk Friction

Abstract Tribological properties of a-C:H coatings has been investigated in various friction conditions. It is clear that temperature and mating materials give effects on tribological properties. In this study, we especially focus on the effect of mating material on its tribological properties of a-C:H coatings. Ball-on-disk friction test is conducted between a-C:H coating and 5 kinds of mating material, which is SiC, SiC(O)_800 (SiC oxidized at 800°C), SiC(O)_1050°C, SiC(O)_1300°C, and Quartz glass. It is found that a-C:H coatings shows low friction coefficient and low specific wear rate when O/Si ratio of the element content of mating material is 2, in other words, mating material is SiO2. In the wear scar of a-C:H coating after friction test with SiC, severe damage was confirmed. It is considered that a-C:H coating and SiO2 show low adhesion even at high temperature, which leads low friction and wear. Compared SiC(O) with Quartz, the friction coefficients with a-C:H coatings are respectively 0.013 and 0.038. Even though SiC(O) and Quartz are both SiO2, the tribological properties are different. On the wear track of SiC(O), transferred things from a-C:H coating are confirmed.

scholarly journals Ultralow friction polymer composites incorporated with monodispersed oil microcapsules

Friction ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 29-40 ◽  
Author(s):  
Lin Zhang ◽  
Guoxin Xie ◽  
Shuai Wu ◽  
Shiguang Peng ◽  
Xiaoqing Zhang ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Wear Rate ◽  
Polymer Composites ◽  
Water Emulsion ◽  
Ultralow Friction ◽  
Lubricating Film ◽  
Alpha Olefin ◽  
Lubrication Condition ◽  
Oil In Water Emulsion ◽  
Friction Polymer

Abstract Ultralow friction polymer composites were prepared by adding oil-loaded microcapsules into epoxy (EP) resin. Mono-dispersed polystyrene (PS)/poly alpha olefin (PAO) microcapsules with a diameter of ~2 μm and a shell thickness of ~ 30 nm were prepared by solvent evaporation method in an oil-in-water emulsion. The lubrication behaviors of the EP resin composites with oil-loaded microcapsules have been investigated under different loads and sliding speeds. As compared with the pure EP resin, the friction coefficient of the composite could be reduced to 4% (from 0.71 to 0.028) and the wear rate could be decreased up to two orders of magnitude. It was demonstrated that the released PAO oil from the microcapsules during the friction process produced a boundary lubricating film, which could prevent the direct contact of two rubbing surfaces, and thus leading to an extremely low friction coefficient and wear rate. Moreover, the composites with microcapsules could achieve comparable lubrication properties to the case under the external lubrication condition, while the former case could effectively minimize the lubricant leakage and improve the lubrication efficiency.

Micromechanical Behaviour of Amorphous Hydrogenated Silicon Carbide Films

1993 ◽  
Vol 308 ◽  
Author(s):  
J. Meneve ◽  
R. Jacobs ◽  
F. Lostak ◽  
L. Eersels ◽  
E. Dekempeneer ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Friction Coefficient ◽  
Wear Rate ◽  
Chemical Vapour ◽  
Diamond Like Carbon ◽  
Ambient Atmosphere ◽  
Low Friction ◽  
Hydrogenated Silicon ◽  
Amorphous Hydrogenated Silicon ◽  
Low Wear

ABSTRACTAmorphous hydrogenated silicon carbide (a-Si1-xCx:H) films (x = 0.65 to 1) were deposited by radio frequency plasma assisted chemical vapour deposition (RF-PACVD). Their friction and wear properties were investigated by means of a conventional ball-on-disk apparatus. The results were correlated with film mechanical properties. It was found that adding silicon to a-C:H (also called diamond-like carbon (DLC)) films reduces the hardness, elastic modulus and internal stress values by 15 to 30 %. Scratch testing induces film spallation from stainless steel substrates at low loads (1 N). In the low normal load (1 N) ball-on-disk tests under humid N2 conditions, a-Si1-xCx:H films (0.7 < x < 0.9) combine a very low wear rate of both the film and the counterbody with a steady state low friction coefficient below 0.1. For higher loads (5 and 10 N), however, this low friction coefficient only lasts for a relatively short time. In this case, the harder diamond-like carbon films perform tribologically better because of their higher wear resistance, low wear rate of the counterbody and generally low friction coefficients between 0.15 and 0.35 in a humid ambient atmosphere. In a dry N2 atmosphere, pure DLC films perform tribologically better than a-S1-xCx:H films in all respects.

Effect of Electrical Potential on DPPC Liposome Lubrication for Artificial Joint

2014 ◽  
Vol 905 ◽  
pp. 156-160
Author(s):  
Hai Yu Zhou ◽  
Shan Wei ◽  
Xiao Hui Wei ◽  
Cheng Tao Wang
Keyword(s):  
Friction Coefficient ◽  
Electrical Potential ◽  
Potential Effect ◽  
Negative Potential ◽  
Joint Surface ◽  
Artificial Joint ◽  
Low Friction ◽  
Positive Potential ◽  
Lubrication Performance ◽  
Enhanced Adsorption

This study aimed at investigating positive and negative potential effect on phospholipid lubrication for artificial joint. Surface potentials of CoCrMo in saline were measured once per day for 1 week to simulate corrosion of implanted artificial joint. Both +250 mV and-250 mV were applied on CoCrMo. 2mg/ml DPPC liposome was fabricated to produce lipidic adsorption on CoCrMo. Friction tests were carried out on cartilage vs. CoCrMo and UHMWPE vs. CoCrMo. The results showed that superficial potential of CoCrMo in saline changed from-177 mV at 1stday to 133mV at 7thday. Lubrication performance of DPPC liposome without potential was declined gradually. Liposome@-250 mV sustained low friction coefficient of both tribopairs whereas liposome@+250 mV greatly increased friction coefficient of UHMWPE vs. CoCrMo from 0.041 to 0.076. It demonstrated that negative potential enhanced adsorption of DPPC liposome, and promoted its lubrication. In contrast, positive potential on CoCrMo due to corrosion deteriorated liposome lubrication.

scholarly journals Biotribology of Synovial Cartilage: A New Method for Visualization of Lubricating Film and Simultaneous Measurement of the Friction Coefficient

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2075
Author(s):  
Pavel Čípek ◽  
Martin Vrbka ◽  
David Rebenda ◽  
David Nečas ◽  
Ivan Křupka
Keyword(s):  
Friction Coefficient ◽  
Simultaneous Measurement ◽  
Film Formation ◽  
New Method ◽  
Cartilage Tissue ◽  
Evaluation Procedure ◽  
Synovial Joint ◽  
Friction Forces ◽  
Lubrication Film ◽  
Lubricating Film

A healthy natural synovial joint is very important for painless active movement of the natural musculoskeletal system. The right functioning of natural synovial joints ensures well lubricated contact surfaces with a very low friction coefficient and wear of cartilage tissue. The present paper deals with a new method for visualization of lubricating film with simultaneous measurements of the friction coefficient. This can contribute to better understanding of lubricating film formation in a natural synovial joint. A newly developed device, a reciprocating tribometer, is used to allow for simultaneous measurement of friction forces with contact visualization by fluorescence microscopy. The software allowing for snaps processing and subsequent evaluation of fluorescence records is developed. The evaluation software and the follow-up evaluation procedure are also described. The experiments with cartilage samples and model synovial fluid are carried out, and the new software is applied to provide their evaluation. The primary results explaining a connection between lubrication and friction are presented. The results show a more significant impact of albumin proteins on the lubrication process, whereas its clusters create a more stable lubrication layer. A decreasing trend of protein cluster count, which corresponds to a decrease in the thickness of the lubrication film, is found in all experiments. The results highlight a deeper connection between the cartilage friction and the lubrication film formation, which allows for better understanding of the cartilage lubrication mechanism.

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