Lithium Grease Research Articles

Investigation of tribological properties of lithium grease with SiO2 nanoparticles

The aim of the work was to investigate the effect of the SiO2 nanoparticles concentration in the lithium grease and of contact pressure on the spinning friction coefficient in the contact zone between a steel plate and a ball. The invvestigations were carried out using the a tribotester for the spinning friction torque in the contact between the ball and the plate. Ball rotated relative to the plate axis at a constant speed and was loaded by the a force increasing in a stepwise manner for the consecutive series. The contact zone was lubricated with a pure lithium grease - pure or with the grease with suspended SiO2 nanoparticles. The friction coefficient decreased with the increase of contact pressure for the pure lithium grease. For the concentration □ = 6wt.% of SiO2 nanoparticles in the grease friction coefficient decreased and for the other concentrations it increased with the increase of the contact pressure. If the values of average contact pressure were below 550 MPa, the friction coefficient values for pure lithium grease were higher than those for lithium grease with suspended SiO2 nanoparticles. For higher values of the contact pressure, the values of the friction coefficient for the pure lithium grease could be lower, equal or higher than those for lithium grease containing SiO2 nanoparticles depending on the value of SiO2 the concentration.

Study on Rheological Properties of Different Brands of Grease

The rheological properties of seven kinds of lithium greasewere tested by Anton-paar MCR 302 rotational rhemeter, and the Herschel-Bulkley rheological equation gives the calculation formula of apparent viscosity and analyzes its rheological porperties. The results show that the rheological property of lubricating grease decreases with the increase of shear rate and decreases with the increase of temperature. Different kinds of lubricating grease show different elastoplasticity under the same experimental conditions, and composite lithium-based grease shows the best performance.

Quasi-Static Rheological Properties of Lithium-Based Magnetorheological Grease under Large Deformation.

This paper investigates the quasi-static rheological properties of lithium-based magnetorheological (MR) grease under large deformation. Three types of lithium-based MR grease comprising different mass ratios of carbonyl iron (CI) particles and lithium-based grease were prepared. The dependence of the magneto-induced stress–strain curves for MR grease on CI particles content, shear rate, and shear deformation under quasi-static monotonic shear conditions were tested and discussed. The results demonstrate that the shear rate dependence of the maximum yield stress is significantly weakened by the magnetic field, and this weakening is further enhanced as the CI particles content of MR grease increases. In addition, to evaluate and characterize the behavior of the cyclic shear–stress curves of MR grease under quasi-static condition, cyclic shear tests under different controlled conditions, i.e., CI particles content, shear rate, shear strain amplitude, and magnetic field strength, were conduct and analyzed. The magneto-induced shear stress of MR grease with higher CI particles content shows a sharp decrease during the transition from loading to unloading. Moreover, the experiment results also show that the damping characteristics of MR grease are highly correlated with CI particles content, shear strain, and magnetic field strength.

Automated Dielectric Thermoscopy Characterization of Water-Contaminated Grease

Machine maintenance is important for improving machine uptime and reliability, and for reducing costs. Grease is used in most rolling element bearings, and one common failure criterion is water contamination, so developing a sensor that can detect water content automatically without human input could be a useful endeavor. The temperature dependence on the dielectric properties of water-contaminated grease is investigated in this article with computer logged instrumentation. This method has been termed dielectric thermoscopy (DT). Several off-the-shelf (two lithium, one lithium complex, and two calcium sulfonate complex) and one unadditivized lithium grease are tested with varying amounts of water contamination from 0% to approximately 5%. Another grease is tested with small increments of added water from 0% to 0.97% to test the resolution of the measurement. The purpose is to use the capacitance temperature slope (termed dielectric thermoscopy) to show correlations to the water content of the grease sample and investigate whether any grease types will pose problems in the measurement. A small, custom-made fringe field capacitance sensor with an integrated temperature sensor has been used for this characterization, and data are logged automatically with laboratory equipment and a personal computer (PC). A useable and positive correlation to water content and the DT measurement of roughly 0.5 pF per 10 °C and percentage of water was found, although it was found that some greases have different behavior than others.

Friction-Induced Hardening Behaviors and Tribological Properties of 60NiTi Alloy Lubricated by Lithium Grease Containing Nano-BN and MoS2

Hardened 60NiTi alloy, which possesses a unique set of desirable properties, has been considered as an attractive candidate for the bearing materials used in space mechanisms. However, the typical hardening process (quenching from high temperatures with a high cooling rate) may result in quench cracking, especially in casting parts. With this in mind, the feasibility of friction-induced surface hardening of 60NiTi under the lubrication of lithium-based greases containing nanoparticles was explored in our research. In addition, the tribological properties of 60NiTi alloy lubricated with lithium-based greases containing different proportions of nanoparticles were investigated. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive spectroscopy (EDS) were used to characterize the surface of worn 60NiTi. An obvious friction-induced hardening effect on the 60NiTi alloy disc surface was identified, which was due to the formation of a hard metastable Ti3Ni4 phase and B2TiNi phase during the friction process. The lubrication effects of all of the modified grease were superior to those of the base grease, and the antiwear properties were closely related to the types of single nano-additives and the proportion of composite nano-additives.

ANALYSIS OF THE POSSIBILITY OF REPLACING THE ВНІІНП -286M LUBRI-CANT ON THE AERO SHELL GREASE 33 IN THE HIGH LIFT DEVICES OF THE WING OF THE AN-FAMILY AIRCRAFT

The problem of ensuring the lubrication of gearboxes of high lift devices in aircraft of the AN family is considered. Modern aircraft are equipped with a large number of electromechanical elements with the possibility of remote control. In all these cases, there is a mechanical component, and accordingly, the relative movement of one element relative to another, all this causes the presence of friction processes in these mechanical systems. To ensure reliable, continuous, long-term operation of friction pairs using lubricants. In the work of aeronautical engineering is a special feature - work in different operating conditions. These can be critical conditions associated with node overloading, sudden changes in temperature, the use of low-quality lubricant. In modern conditions, the issue of the quality of materials for the production and maintenance of aeronautical engineering is not at a high level. First of all, this is due to improper transportation, storage, reloading and refilling of lubricant. Under these conditions, lubricants are able to accumulate moisture. This phenomenon leads to watering of the lubricant, and, accordingly, changes in the physicochemical properties of lubricants due to their watering. All this leads to increased wear of parts of the units, as well as to an early replacement of the lubricant when it is flooded, which significantly increases operating costs. In turn, analysis of the effect of different water concentrations on anti-wear and anti-friction properties of lubricants considered in the work, showed that the use of Aero Shell Grease 33 lubricant reduces wear of 30ХГСА steel (leading and lagging surfaces), regardless of water concentration ЕРА ВНІІНП -286M. The state of use of the lubricant is analyzed to ensure reliable operation of the wing mechanization gearbox. The correct approach when choosing a lubricant is quite complicated and important. It is proposed to replace the ВНІІНП -286M lithium grease with Aero Shell Grease 33. The effect of different water concentrations on the antiwear and antifriction properties of lithium greases is analyzed.

THE EFFECT OF THE TYPE OF WALL MATERIAL AND GREASE COMPOSITION PAIRING ON SHEAR STRESSES IN BOUNDARY LAYER

The paper presents the results of research on the influence of fillers introduced into plastic greases on the rheological properties of the boundary layer of the resultant lubricant compositions. The fillers were PTFE and MoS2 powders. They are added to lubricants to improve their tribological properties; however, these fillers also affect the rheological properties of the composition. This affects the change of the shear stress value in the lubricant during its flow in the lubrication system. Knowledge of this value, especially during the flow of the lubricant composition in the boundary layer, has a significant impact on the operation of automated central lubrication systems in which these compositions can be used. Measurements were carried out by means of a rotary rheometer (Rheotest 2.1). Tests were performed on lithium and bentonite greases (without additives) as well as compositions of these greases containing various percentage of the fillers mentioned above. Test results showed that both the type of grease and the type of filler introduced into this grease affect the rheological properties in the boundary layer of the produced lubricating compositions.

Impact of silicate contaminants on tribological and thermal transport performance of greases

This work investigates the effects on thermal transport and tribological performance of incorporating silicate particles – emulating pollutants – within various greases: lithium thickened (MB), soap complex thickened (SB) and silica thickened (UB). Silicate particles (200–300 µm) were homogeneously dispersed, by a mechanical method, within the selected greases in concentrations of 1.5 g/10 ml. For tribological evaluation a four-ball tribotester was employed according to ASTM D2266 standard test method for wear preventive characteristics of lubricating greases. For the silica thickened grease (UB) the WSD increased by ~15%; for the lithium soap and the complex soap thickened greases, the changes were almost negligible due to the behavior of their soap thickener and base oil. For the thermal transport evaluation, a guarded hot-plate method-based apparatus was used to characterize the thermal conductivity of greases with and without silicate particles, showing an enhancement range of 25–70% in thermal conductivity with the addition of 1.5 g/10 ml of silicate particles. Thermal conductivity measurements offer an accuracy of ~5%. It was shown that MB and SB greases have a positive impact on the thermal conductivity as silicates are added; UB reflected a negative effect on the thermal conductivity as silicates were mixed within the grease. These results show that silicate contaminants may be able to thermal properties of greases while not affecting significantly their tribological performance.

Tribological Properties of ZnS(NH2CH2CH2NH2)0.5 and ZnS as Additives in Lithium Grease

The layered compound ZnS(NH2CH2CH2NH2)0.5 was evaluated as an additive in grease with different concentrations by using a four-ball tribometer. Results show that ZnS(NH2CH2CH2NH2)0.5 grease has good load bearing ability and excellent anti-wear properties. ZnS(NH2CH2CH2NH2)0.5 revealed better wear resistance than that of ZnS under all test conditions. The reason for this may be that the two-dimensional structure of ZnS(NH2CH2CH2NH2)0.5, with larger interspaces, facilitates an easier sliding process, improving the anti-wear performance. The mechanism was estimated through analysis of the worn surface with SEM, EDS, 3D, and XPS. XPS analysis results show that the tribofilm was mainly composed of FeS, ZnS, ZnO, FexOy, Feu(SO4)v, and ZnSO4. Owing to the simple synthetic method and superior tribological properties as a grease-based additive, ZnS(NH2CH2CH2NH2)0.5 holds great potential for use in demanding industrial applications in the future.

Synergistic effects of phosphate ionic liquids and octadecylaminen‐oleoyl sarcosinate as lubricating grease additives

AbstractA detailed study on the synergistic effects of phosphate ionic liquids (ILs) and rust inhibitor (octadecylaminen‐oleoyl sarcosinate (T711)) in the complex lithium grease (G) at room temperature and 100°C is presented in this paper. The results indicate that the hybrid additives (T711‐ILs‐G) showed better friction‐reducing and antiwear properties than single additives (T711‐G and ILs‐G). In the case of T711‐ILs‐G, the presence of T711 can prevent rustiness of the worn surface so the ILs can easily react with the exposed substrate surface and form tribological films on the sliding surfaces.

Facile Synthesis of Uniform Calcite Microcubes and Their Enhanced Tribological Performance in Lithium-Based Commercial Grease

This study describes a facile synthesis of calcium carbonate (CaCO3) monodispersed fine particles from an abundant indigenous and economical source (quicklime) and its enhanced tribological performance as a green additive in commercial lithium grease (CLG). The effects of various experimental parameters on particle morphology were thoroughly examined, and the conditions were optimized. The synthesized uniform particles were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometry, and thermogravimetric (TG) /differential thermal analysis (DTA), and their results confirmed the calcite structure of the synthesized particles. The friction and wear studies were carried out under the applied load of 0.863 N at an ambient temperature for 5 min. The tribological performance of various amounts (1–7%) of cubic-CaCO3 (CCC) particles in CLG showed that 5 wt. % of CCC was the optimum concentration as additive in the present case. For comparison purposes, a commercial CaCO3 powder was used and a decrease in the friction coefficient of CLG was observed to be 33.4% and 16.4% for 5 wt. % CCC and commercial CaCO3 additives, respectively. The significantly enhanced antiwear and antifriction performance of the optimum CCC-CLG in comparison with the blank and commercial CaCO3-additized CLG was quite encouraging, and extensive studies in a real machine-operating environment are in progress for evaluation of the CCC-CLG blend to be used as an economical, green, and high-performance lubricant in mechanical components.

Lithium lubricating greases containing carbon base nano-additives: preparation and comprehensive properties evaluation

The aim of this research is to investigate the enhancement of lubricating and sealant properties, increase of the life time, and reduce of wear traces for lubricants and sealant greases. For this purpose, carbon dot (C-dot) nanoparticles (NPs) were synthesized successfully to add to the lithium based grease in 0.1, 0.2, 0.4, 0.6, 0.8 and 1 wt%. To better understand the effect of NPs on the properties of lithium based grease, carbon nanofiber (CNF) and Nano-Fullerene (C60) were also used in the mentioned weight percentages to add to the lithium based. NPs were well dispersed in the phase of base grease by the use of ultra-sonication. Variety of tests were done on the lithium base grease and all of the fabricated nano-greases and their results were then compared with each other. Using NPs did not remain any corrosive tracks for all of the nano-greases and caused the improvement in all their properties. Prepared nanogreases were also resistant to fuel, water, and aqueous alcohol in a specific period of time. CNFs with weight percentages in the range of 0.4–0.8 showed to be the optimum NPs content to be added to the lithium based grease in terms of improved properties.

Tribological Properties of Magnesium Ion-exchanged α-Zirconium Phosphate as a Solid Lubricant Additive in Lithium Grease

Magnesium ion-exchanged a-zirconium phosphates (Mg-α-ZrP) with particle sizes of 600 and 80 nm were prepared through the sealed ion-exchange and one-step hydrothermal synthesis methods, respectively. It was found that larger particles of Mg-α-ZrP had a higher load-carrying capacity than that of smaller particles, whereas smaller Mg-α-ZrP particles had better anti-wear properties than that of larger Mg-α- ZrP particles under mild loads. The correlation between the particle size of the sample and the surface roughness of the friction pair thus seems to be a key factor influencing the performance.

Effect of temperature on rheological properties of lithium-based magnetorheological grease

This paper investigates the impact of temperature on the rheological properties of magnetorheological (MR) grease containing carbonyl iron suspended in lithium-based grease Lithium-based MR grease with 70% weight fraction of carbonyl iron is firstly prepared by mechanical mixing. The apparent viscosity and shear stress as a function of shear rate under different temperatures and magnetic field strengths are measured and discussed. It is found that the influence of temperature on apparent viscosity reduces with the increase of magnetic field strength. The dynamic properties of MR grease are obtained under oscillatory shear test. The influences of strain amplitude, driving frequency and magnetic field on the dynamic properties of MR grease at different temperature are discussed. The results demonstrate that the enhancement of temperature leads to the increase of storage modulus and the reduction of the loss factor. Microstructural variation of grease matrix at different temperature is proposed as an explanation of the rheological changes of MR grease.

Study on the Properties of Wire Rope Grease Added with Lithium Grease

Hydrocarbon grease is used to lubricate and protect wire rope usually, but there are some problems have been found during lubricating process, such as high and low temperature working conditions resistance and waterproof performance and so on, in this paper we try to employ lithium grease to lubricate wire rope, according to the experiments, it comes a conclusion that lithium grease has the advantages which hydrocarbon grease doesn’t have by comparing the performance of both, the properties of wire rope grease have been successfully improved by adding some lithium grease, and the percentage of addition is a key factor.

Normal force of lithium-based magnetorheological grease under quasi-static shear with large deformation.

An experimental study was conducted to explore the normal force of lithium-based magnetorheological (MR) grease under quasi-static shear. Firstly, MR grease with various carbonyl iron (CI) particles content was prepared. Then the influence of magnetic field strength, CI particles content, shear rate and temperature on the normal force–strain curves for MR grease under a quasi-static monotonic shear condition were investigated. The results exhibit that the normal force of MR grease under quasi-static monotonic shear decreases first and then maintains constant along with the increase of shear strain, and the critical strain is affected by the magnetic field strength and CI particles content. Finally, the normal force versus shear strain curves under different magnetic fields and shear strains were obtained by using quasi-static cyclic shear. It was found that the normal force of MRG-70 under quasi-static monotonic shear exhibits peak phenomenon at the beginning of the unloading stage, and the peak value increases with the enlargement of shear strain. Furthermore, when the strain amplitude is higher than 40%, normal force exhibits an abrupt change during the transition from the loading stage to the unloading stage.

Tribological behavior of zirconium phosphate‐1,4‐dimethylpiperazine compound as lubricant additives

AbstractZirconium phosphate compound, [C6H16N2]0.5Zr‐(H0.5PO4)2•H2O designated as ZrPO4‐DES8 have been synthesised hydrothermally in the presence of 1,4‐dimethylpiperazine (DMP). In this study, small (0.5‐0.8 μm) and large (8‐10 μm) ZrPO4‐DES8 particles were obtained by varying the amount of H3PO4 in the HF ‐ ZrO2‐P2O5‐DMP‐H2O hydrothermal system. The tribological properties of ZrPO4‐DES8 particles as additives in lithium grease were evaluated by using a ball‐on‐disk reciprocating tribometer under different concentrations, loads, and frequencies. The results illustrated that ZrPO4‐DES8 particles improved the lubricating performance of grease substantially. The small‐sized particles exhibited better and more stable friction reduction and anti‐wear performance than larger ones during sliding. The characterisation of a possible wear mechanism was given by observing the worn surface under a three‐dimensional optical profiler, a scanning electron microscope and energy dispersive X‐ray analysis. The simple synthetic method and superior tribological properties make the ZrPO4‐DES8 become a choice for lubricant additives.

Lithium Based Grease with Additives as an Alternative Lubricant for Conventionally Oil Lubricated Journal Bearings of Sugarcane Crushing Mills

The purpose of this work was to examine the tribological issues related to failure of heavily loaded split journal bearings sugarcane crushing mills. . It was also identified that hydrodynamic fluid film was not formed due to low speed of journal. Regime of lubrication for such journal bearings is thin film lubrication. In such situations journal and bearing surface has physical contact and adhesive or abrasive wear may occur. For such situations grease lubrication can be adopted for journal bearings. Suitability of Lithium Grease with additives as lubricant for sugarcane crushing mills is verified using four ball tester machine.

Wear Behaviors of Three Typical Bulk Metallic Glasses in Bearing Applications

In bearing applications, the development of new materials has become a focus of scientific research in order to make bearing systems smaller and rotate more accurately. Bulk metallic glass (BMG), which has high strength, stiffness and resistance to corrosion, is becoming a promising candidate for bearing and shaft materials. When used as shafts, the friction feature of BMG needs to be evaluated comprehensively. In this work, the friction and wear properties of Ni-based, Zr-based, and Cu-based BMGs sliding against brass lubricated with lithium grease were investigated, using traditional bearing materials (GCr15 steel) as comparison. The results showed that the wear mechanism of the BMGs was primarily abrasive, supplemented by an adhesive wear behavior when sliding against brass plates, just like GCr15 steel. The wear loss of the friction pair (brass plates) increases when the applied normal load increases and the sliding speed decreases. Compared with GCr15 steel, BMGs exhibit better friction performance at low sliding speed, and Ni-based BMG always exhibits a smaller wear loss, especially under large load and low sliding speed. The wear loss of brass plates against Ni-based BMG pin is 24.3% lower than that against GCr15 steel under an applied load of 10 kg, which indicates that Ni-based BMG is an attractive bearing and shaft material for industrial application.

The importance of spectrum loading in 2% milled MoS2 powder greases using four ball wear test

PurposeLoading condition and minimizing friction and wear using molybdenum disulfide grease in aircraft engine bearings are the focus of this research. The relationship between the milled and unmilled MoS2 (molybdenum disulfide) greases to its tribological properties, such as coefficient of friction, wear and chemical-mechanical properties of tribofilms, is examined for constant extreme pressure loading and spectrum or actual loading.Design/methodology/approachIn this study, the design of experiments (DOE) approach was used to analyze the different loadings and speeds at a specific duration of 36,000 revolutions to examine the lithium base grease wear behavior with milled and unmilled MoS2 powder. Load is treated as variable that simulates actual conditions under 1,200 and 600 rpm rotational speeds using the four-ball test with chromium steel ball bearing aircraft grade E52100.FindingsThe results indicated that ball-milled MoS2 grease tests showed reduction in wear and friction under all conditions, especially spectrum or actual loading. Unmilled MoS2 powder exhibited worse wear outcomes than the milled one. The SEM and AES analyses indicated that a tribofilm is formed on the wear surface of the milled powder grease, especially at variable loading and initially at lower loads in the ramp-up tests that significantly enhanced the contact characteristics and prevented abrasion at higher loads.Originality/valueThis research indicated that the wear resistance in actual loading might be due to frictional heating generated during the ramping-up conditions where it provided a protective film that enhanced the steady-state friction for the duration of the test. Several researchers used ASTM standards to work on constant loading conditions. This is the first time that reduced milled MoS2 powder showed significant improvement in grease performance.