Four-ball Friction Tester Research Articles

Tribological Performance of Phosphonium Ionic Liquids as Additives in Lithium Lubricating Grease

Three oil–miscible phosphonium ionic liquids with different structures were synthesized and used as additives for a Poly Alpha Olefin 10 (PAO 10) lithium lubricating grease. Different from other additives, the ionic liquids participated in saponification and were trapped in the entanglement network formed by the thickener. The effects of the ionic liquids on the rheological properties of lithium lubricating grease were characterized through a small-amplitude oscillatory shear (SAOS) measurement. The tribological performances of the lubricating greases were determined on a four-ball friction tester. The addition of phosphonium ionic liquids caused a decrease in the storage (G′) and loss (Gʺ) modulus of lubricating grease. However, the ionic liquids were found to be effective lubricant additives for improving the friction-reducing and antiwear properties of PAO 10 lithium lubricating grease.

The synthesis of magnesium silicate hydroxide with different morphologies and the comparison of their tribological properties

Abstract The tribological properties of magnesium silicate hydroxide (MSH) synthesized at different hydrothermal conditions as lubricant additives were investigated. The morphologies and structures of synthetic MSH were characterized by SEM, TEM, XRD and XRF. The tribological properties of MSH were evaluated using a four-ball friction and wear tester. It is found that different morphologies and structures of MSH are formed through different mechanisms depending on the temperature and reaction-time. Using synthetic MSH as an additive forms a tribofilm on the sliding surface and significantly improve the tribological properties of the oil. MSH with a tubular crystal structure has the best anti-wear property because it is more likely to deposit, adsorb and spread on the friction surface, and thus forms a denser tribofilm.

Tribological properties of lubricating oil with micro/nano-scale WS2 particles

ABSTRACTThe tribological properties of lubricating oil containing micro/nano-scale WS2 (90 nm, 2 µm) and ionic liquid [C7H11F3N2O3S] are evaluated using a four-ball friction tester. Results show that the addition of micro/nano-scale WS2 can improve the tribological properties of the base oil; moreover, adding the ionic liquid as a solvent may lead to a better mixing of the micro/nano-scale WS2 and base oil and promote the dispersion of WS2 in the sample oil. The base oil with 90 nm nano-WS2 and ionic liquid presents the best anti-friction and anti-wear properties at 1 wt.% content. The surface analysis of wear scars reveals that ploughing is the main cause of wear in the three bottom balls. Furthermore, the wear furrows of nano-WS2 as lubricating additive are uniform and symmetrical and can homogenously appear on the friction area. This work proves that the micro/nano-scale WS2 plays an important role in improving the performance of tribological properties of lubricating oil.

Preparation and tribological properties of BN/calcium borate nanocomposites as additive in lubricating oil

PurposeThe purpose of this paper is to investigate the tribological performance and mechanisms of BN/calcium borate nanocomposites (BCBNs) as additives in lubricating oil.Design/methodology/approachBCBNs were prepared by heterogeneous deposition method. And the morphology and structure of samples were analysed by transmission electron microscopy, Fourier transform infrared spectra and X-ray powder diffraction pattern. The maximum non-seizure load (PB) of samples was tested using four-ball friction tester. The average friction coefficients and wear tracks were obtained. In addition, tribological mechanism was also investigated using optical microscope, energy dispersive spectroscopy and X-ray photoelectron spectroscope.FindingsIt was found that the nanocomposites present core-shell nanostructure with the thickness of shell around 12 nm and the diameter of particles 100-200 nm, and tribological tests indicate that the PB value of BCBNs was increased by 113 per cent, whereas the average friction coefficient was decreased by 23.6 per cent and the bloom’s wear area was also decreased by 25.2 per cent.Originality/valueThis paper involves investigation on tribological properties and mechanism of the BCBNs with core-shell structure.

Tribological Properties of Tungsten Disulfide Nanoparticles Surface-Capped by Oleylamine and Maleic Anhydride Dodecyl Ester as Additive in Diisooctylsebacate

Oleylamine (OM) and maleic anhydride dodecyl ester (MADE, synthesized at our laboratory) were adopted as the surface modifiers to prepare OM/MADE-capped tungsten disulfide (WS2) nanoparticles. An X-ray diffractometer and a transmission electron microscope were performed to analyze the microstructure and phase ingredients of the OM/MADE-capped WS2 nanoparticles. Moreover, a four-ball friction and wear tester and a reciprocating tribometer were employed to evaluate the tribological properties of the surface-capped WS2 nanoparticles as the lubricant additive in diisooctylsebacate (DIOS) from room temperature to 150 °C. The morphology of the worn steel surfaces and wear scars and their chemical states were investigated with a scanning electron microscope, three-dimensional profilometry, and an X-ray photoelectron spectroscope. Results show that OM-capped WS2 nanoparticles nearly have no effect on the tribological properties of the DIOS base oil. The OM/MADE-capped WS2 nanoparticles added in the same base stoc...

Effect of nanometer silicon dioxide on the frictional behavior of lubricating grease

Nanometer-silicon dioxide encapsulated in lithium grease is prepared, and the frictional behavior of the lithium grease and nanometer-silicon dioxide–contained lithium grease is compared with respect to the additive content, load, and frictional temperature in this article. The structure and morphology of nanometer-silicon dioxide is characterized by X-ray diffraction and scanning electron microscopy, respectively. Friction and wear tests were conducted on a four-ball friction and wear tester. The morphology of worn steel surface is analyzed by scanning electron microscopy and three-dimensional surface profiler. Results show that the addition of nanometer-silicon dioxide in grease can markedly improve the friction-reducing performance and anti-wear ability of base grease. When the nanometer-silicon dioxide in grease is 0.3 wt%, the friction coefficient and wear scar diameter decrease by 26% and 7% compared with base grease, respectively. The nanometer-silicon dioxide (0.3 wt%)–contained grease exhibits the lowest average friction coefficient at the load of 342 N, which decreases by 39% as compared with that of base grease. The worn surface is quite smooth with few shallow furrows and the wear scar diameter decreases under the lubrication of the grease containing 0.3 wt% nanometer-silicon dioxide. Moreover, it was found that the nanometer-silicon dioxide have been incorporated into the surface protective and lubricious layer by energy dispersive spectrometer analysis.

Synthesis and tribological properties of high purity Ti2SC nanolamellas by microwave hybrid heating

Nearly pure Ti2SC powder has been synthesized by microwave hybrid heating a mixture of TiS2, Ti and C powders using Al powder as an additive. The recipes with different mole ratios of TiS2:Ti:C:Al were examined at temperatures from 800 to 1050 °C. The purity of Ti2SC was sensitive to the final temperature and raw material scale, and the addition of Al considerably reduced the calcining temperature. The nearly pure Ti2SC powder can be fabricated reliably on a large scale by sintering the raw materials with a mole ratio of 1.1TiS2:2.9Ti:1.9C:0.3Al at temperatures from 900 to 1050 °C. The tribological properties of Ti2SC as an additive in 150SN base oil were evaluated by a MMW-1A four-ball friction and wear tester. The results showed that under determinate conditions, the base oil containing 3 wt% Ti2SC sample presented good tribology performance under a load of 300 N. The improved tribological properties of the Ti2SC sample could be attributed to the formation of a tribofilm in the friction process.

Effect of preparation process on elevated temperature tribological properties of composite polyurea grease

Purpose This paper aims to investigate and prepare the composite polyurea greases with excellent thermal stability and tribological properties. Design/methodology/approach In this paper, composite Ba-based (Ba, barium) tetra-polyurea lubricating greases were prepared with two different methods: mixing Ba-based gelatinizer and tetra-polyurea gelatinizer by a physical method; and introducing barium carboxylate into tetra-polyurea molecules by a chemical method. The properties of the products, such as heat stability, water resistance and friction performance, were analyzed with thermogravimetry, water-resistance test and four-ball friction test. Findings The results indicated that the products obtained by chemically introducing barium carboxylate into tetra-urea molecules showed better elevated temperature tribological properties, and the disadvantages of the polyurea greases with high temperature hardening were also obviously improved. The cone penetration rate at 180°C for 24 h is only 3 per cent. The friction coefficient can be decreased to 0.44 and the last non-seizure load value was increased from 560 N to 1,120 N without any other additives. Originality/value The research is significant because the prepared composite grease showed excellent performances, such as the outstanding thermal stability, water resistance and excellent extreme pressure and anti-wear properties, which may be widely applied in steel, metallurgy, bearings and other industrial fields.

Detonation Synthesis and Friction-Wear Test of Carbon-Encapsulated Copper Nanoparticles

Carbon-encapsulated copper nanoparticles were successfully synthesized by preparing an explosive mixture consisting of cupric citrate xerogel, oleic acid, and cyclonite under three operating conditions in the explosion vessel with nitrogen and argon as protective gases. Results obtained through the characterization of the detonation products by X-ray diffraction, transmission electron microscopy, and the four-ball friction test. It showed that the molar ratio of copper to carbon in explosive mixtures exerted considerable influence on the synthesis of carbon-encapsulated copper nanoparticles. The synthesis effect of carbon-encapsulated copper nanoparticles was better when the molar ratio range no more than 0.031. In this range, the particles showed good dispersion and high degree of graphitization of the carbon shell, grain size of approximately 10–30 nm, and carbon shell thickness of approximately 2–3 nm. When the ratio exceeded 0.031, carbon-encapsulated copper nanoparticles were not synthesized, and the products included exposed copper particles and amorphous carbon. A new type of the explosive mixture is presented in the paper, namely, the mass ratio of {Cu [CO(NH2)2]2}(NO3)2, Cu 2} to oleic acid, sorbitan stearate and RDX being 16:27:10:76, suitable for synthesis of carbon-encapsulated copper nanoparticles. After adding carbon-encapsulated copper nanoparticles, the friction coefficient of lubricating base oil decreased with the increase in carbon-encapsulated copper nanoparticle dosage, and the anti-wear ability also increased to varying degrees. To illustrate, when carbon-encapsulated copper nanoparticle dosage was 1 wt%, anti-wear ability was improved by 10.6 %.

Preparation and Tribological Properties of Lanthanum Trifluoride Nanoparticles-Decorated Graphene Oxide Nanosheets

Graphene oxide (GO) nanosheets were decorated with lanthanum trifluoride (LaF3) nanoparticles by a simple solution method to afford LaF3–GO nanohybrids, with which ammonium fluoride and lanthanum nitrate were used as raw materials to synthesize LaF3 nanoparticles. As-prepared LaF3–GO nanohybrids were characterized by X-ray diffraction, Raman spectrometry, transmission electron microscopy, and Fourier transform infrared spectrometry. Moreover, the thermal stability of the as-prepared LaF3–GO nanohybrids was evaluated by thermogravimetric analysis, and their tribological properties as an additive of distilled water were evaluated with a four-ball friction and wear tester. It was found that LaF3 nanoparticles are integrated with the GO nanosheets through electrostatic interaction thereby affording LaF3–GO nanohybrids. In addition, when the as-prepared LaF3–GO nanohybrid was added into distilled water at an optimum mass fraction of 1.5%, it was able to significantly improve the tribological properties of distilled water. This is because LaF3–GO nanohybrids can be deposited on rubbed steel surfaces to form protective and lubricious layers consisting of GO, LaF3, Fe2O3, and FeF3, thereby significantly reducing the friction and wear of the steel–steel contact under water lubrication.

Synthesis and tribological properties of oil-soluble copper nanoparticles as environmentally friendly lubricating oil additives

Purpose – The purpose of this paper is to synthesize oil-soluble copper (Cu) nanoparticles modified with free phosphorus and sulfur modifier and investigate its tribological properties as environment-friendly lubricating oil additives. Design/methodology/approach – To improve the anti-oxidation properties of these nanoparticles, two kinds of surface modifiers, oleic acid and oleylamine were used simultaneously. The morphology, composition, structure and thermal properties of as-synthesized Cu nanoparticles were investigated by means of transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectrometry and differential thermal and thermogravimetric analysis. The tribological properties of as-synthesized Cu nanoparticles as an additive in liquid paraffin were evaluated with a four-ball friction and wear tester. Findings – It has been found that an as-synthesized Cu nanoparticle has a size of 2-5 nm and can be well dispersed in organic solvents. Tribological properties evaluation results show that as-synthesized Cu nanoparticles possess excellent anti-wear properties as an additive in liquid paraffin. The reason lies in that as-synthesized surface-capped Cu nanoparticles are able to deposit on sliding steel surface and form a low-shearing-strength protective layer thereon, showing promising application as an environmentally acceptable lubricating oil additive, owing to its free phosphorus and sulfur elements characteristics. Originality/value – Oil-soluble surface-modified Cu nanoparticles without phosphorus and sulfur were synthesized and its tribological properties as lubricating oil additives were also investigated in this paper. These results could be very helpful for application of Cu nanoparticles as environment-friendly lubricating oil additives.

Bio-lubricants derived from waste cooking oil with improved oxidation stability and low-temperature properties.

Waste cooking oil (WCO) was chemically modified via epoxidation using H2O2 followed by transesterification with methanol and branched alcohols (isooctanol, isotridecanol and isooctadecanol) to produce bio-lubricants with improved oxidative stability and low temperature properties. Physicochemical properties of synthesized bio-lubricants such as pour point (PP), cloud point (CP), viscosity, viscosity index (VI), oxidative stability, and corrosion resistant property were determined according to standard methods. The synthesized bio-lubricants showed improved low temperature flow performances compared with WCO, which can be attributing to the introduction of branched chains in their molecular structures. What's more, the oxidation stability of the WCO showed more than 10 folds improvement due to the elimination of -C=C-bonds in the WCO molecule. Tribological performances of these bio-lubricants were also investigated using four-ball friction and wear tester. Experimental results showed that derivatives of WCO exhibited favorable physicochemical properties and tribological performances which making them good candidates in formulating eco-friendly lubricants.

Tribological synergistic effects between plasma nitrided 52100 steel and molybdenum dithiocarbamates additive in boundary lubrication regime

The interactions and synergistic tribological effects between plasma nitrided 52100 steel and molybdenum dithiocarbamates (MoDTC) additive under boundary lubrication were studied in this work. The tribological behaviors of plasma nitrided and untreated steels under lubrication with different MoDTC concentrations were examined on a four-ball friction and wear tester. The results showed an obvious synergistic effect between plasma nitrided steel and MoDTC additive. The synergistic effect indicated a lower friction coefficient without an induction phase and a higher wear resistance, which was attributed to more amount of MoS2 and absorbed carbon were formed in the tribofilm of the nitrided surface.

Experimental research on tribological performance of water-based rolling liquid containing nano-TiO2

Nano-TiO2 was dispersed in water to study the influences of nanoparticles on the tribological properties of water-based rolling liquid for hot steel. The phase composition and microstructure of nano-TiO2 were investigated by X-ray diffraction and transmission electron microscopy methods. The friction reduction and antiwear properties were measured on a four-ball friction tester, and then hot rolling experiments with lubrication have been carried out. The rolling force and surface roughness were measured. Moreover, the surface elements of the steel lubricated by nano-TiO2 rolling liquid were analyzed by energy dispersive spectroscopy. The results showed that nano-TiO2 as water-based liquid additives can effectively improve the antiwear properties of steel–steel friction pair and reduce the friction coefficient. At the same time, nano-TiO2 shows good lubrication properties during hot rolling. It is inferred from the lubrication and repairing mechanism that TiO2 nanoparticles sediment on the surface of steel, and the lower surface film is formed under high temperature and high pressure. The film possesses excellent antiwear, friction-reducing and repair properties.

Preparation of lanthanum trifluoride nanoparticles surface-capped by tributyl phosphate and evaluation of their tribological properties as lubricant additive in liquid paraffin

LaF3 nanoparticles surface-capped by tributyl phosphate (denoted as TBP–LaF3) were prepared by in situ surface modification route. The size, morphology and phase structure of as-prepared TBP–LaF3 nanoparticles were analyzed by means of X-ray diffraction and transmission electron microscopy. The thermal stability of as-synthesized TBP–LaF3 nanoparticles was evaluated based on thermogravimetric analysis, and their tribological properties as additive in liquid paraffin were evaluated with a four-ball friction and wear tester. Moreover, the morphology of worn steel surfaces was analyzed with a scanning electron microscope, and the composition and chemical state of typical elements on worn steel surfaces were examined with an X-ray photoelectron spectroscope. Results show that as-synthesized TBP–LaF3 nanoparticles possess good thermal stability and excellent anti-wear and load-carrying capacities as well as good friction-reducing ability. This is because, on the one hand, TBP as the surface-modifier is able to improve the dispersibility of LaF3 nanoparticles in liquid paraffin and allows good adsorption of LaF3 nanoparticles on sliding steel surfaces. On the other hand, active P element of TBP can form tribochemical reaction film on sliding steel surfaces. As a result, the boundary lubricating film consisting of adsorbed LaF3 nanoparticles and tribochemical reaction film results in greatly improved friction-reducing and anti-wear abilities as well as load-carrying capacity of the lubricant base stock and gives rise to significantly reduced friction and wear of the steel–steel sliding pair.

Lubricant Potentiality of Degraded Palm Oil and Effect of Free Fatty Acid Addition

Lubricant potentiality of used cooking palm oil was examined through four-ball friction test with modified palm oils of two different types. One category of tested oils was the heat-treated type which is expected as degraded palm oil by heating during cooking. The degraded degree was controlled by the length of heating period, then the acid number, AN, was varied between 0 and 3.5[mgKOH/. For these oils, temperature dependence druing friction test was examined on friction and wear between 40-100 ̊C. Degraded palm oil of higher acid number showed wear much more, and the wear for AN=3.5 showed almost double of non-heat treaed oil, but half of mineral oil, VG32, up to 85 ̊C. Friction coefficient did not show strong dependence of the acid number, and the value was 20%-lower than VG32 between 40-100 ̊ C.The other was the free-fatty acid added type which is expected as degraded palm oil by hydrolysis during cooking where boiled water reacts with palm oil. Four model oils were prepared, and each of them contained one of major palm oil components, such as palmitic acid, stearic acid, oleic acid and linoleic acid, at 10mass% to refined palm oil. For these oils, friction test was performed at 40 and 100 ̊ C to examine the effect of temperature. Addition of stearic acid showed lowest wear and lowest friction at both temperatures among fatty acid added types. The experimental results are discussed with kinematic viscosity, apprent normal stress, and apprent tangential shear stress.

Preparation of Water-Soluble Lanthanum Fluoride Nanoparticles and Evaluation of their Tribological Properties

Water-soluble LaF3 nanoparticles surface-capped by two kinds of dialkyl polyoxyethylene glycol thiophosphate ester (denoted as DTP-10 and DTP-20) were synthesized via a surface-modification method. The morphology and microstructure of resultant surface-modified LaF3 nanoparticles (denoted as LaDTP-10 and LaDTP-20) were characterized by means of X-ray powder diffraction, transmission electron microscopy, and Fourier transform infrared spectrometry, and their thermal stability was examined by thermogravimetric analysis. Moreover, the tribological properties of as-synthesized LaF3 nanoparticles as additives in distilled water were evaluated with a four-ball friction and wear tester, and the morphology of wear scar and the chemical states of some typical elements thereon were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. It has been found that as-prepared LaDTP-10 and LaDTP-20 nanoparticles have a size of 19.6 and 8.5 nm, respectively, and they have good dispensability in distilled water. Moreover, as-synthesized LaDTP-10 and LaDTP-20 nanoparticles as lubricant additives in distilled water exhibit good friction reducing, antiwear, and extreme pressure properties as well as high load-carrying capacity even at a concentration of 1 % (mass fraction). This is because LaF3 nanoparticles can be deposited on sliding steel surfaces to afford a surface protective layer, and they may also tribochemically react with rubbing steel surfaces to generate a boundary lubricating film mainly composed of phosphate, sulfide, sulfate, La2O3, and LaF3. Therefore, it is feasible for LaDTP-10 and LaDTP-20 nanoparticles to be used as water-soluble lubricant additives under harsh conditions.

Characterization and friction performance of Zn/Mg/Al-CO3 layered double hydroxides

Zn/Mg/Al-CO3 layered double hydroxides (LDHs) were synthesized by coprecipitation method and the products were surface modified by oleic acid. The materials were characterized by X-ray diffraction, scanning electron microscopy, wavelength dispersive X-ray fluorescence, Fourier transform infrared spectroscopy, thermogravimetry and differential scanning calorimetry. The tribological property of LDHs in base oil was studied by using a four-ball friction test machine. The results showed that Zn/Mg/Al-CO32−-LDHs had high crystallinity and hexagonal lamellar structure with average disk diameter of about 150nm and the chemical formula was Zn0.40Mg0.28Al0.32(OH)2(CO3)0.16·0.28H2O. The interaction between LDHs and oleic acid molecules was based on chemisorption with a monomolecular layer on the surface of laminate. The friction test results indicated that base oil with 0.5wt% LDHs performed optimal antifriction property and the friction coefficient and wear scar diameter reduced by 68.6% and 24.6% respectively.

Preparation and tribological properties of lanthanum-doped TiO2 nanoparticles in rapeseed oil

Oleic acid (denoted as OA) surface-capped lanthanum-doped titanium dioxide composite nanoparticles, abbreviated as OA/La-TiO2, were prepared via sol-gel method in association with surface modification by oleic acid. The microstructure of as-prepared OA/La-TiO2 was characterized by means of X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectrometry, and their thermal stability was evaluated by thermogravimetry and differential scanning calorimetry. Moreover, the tribological properties of OA/La-TiO2 as lubricant additives in rapeseed oil were evaluated with a four-ball friction and wear tester. The morphology as well as elemental composition and chemical characteristics of worn steel surfaces was investigated by scanning electron microscopy, energy dispersive X-ray spectrometry and X-ray photoelectron spectroscopy. Results showed that as-prepared OA/La-TiO2 particles were of spherical shape and had an average diameter of 20 nm. In the meantime, OA/La-TiO2 particles doped with 1.5% (molar ratio; the same hereafter) and 2.5% of lanthanum could markedly improve the anti-wear and friction-reducing capacities of rapeseed oil. This is attributed to the formation of a complex boundary lubrication film mainly composed of the oxides of iron, titanium and lanthanum as well as the formation of an adsorption film of oleic acid on steel sliding surfaces.

Preparation of Nickel-Based Nanolubricants via a Facile In Situ One-Step Route and Investigation of Their Tribological Properties

Nickel-based nanolubricants containing size-tunable monodispersed nickel nanoparticles were in situ synthesized in poly-alpha-olefin (denoted as PAO6) via a simple one-step thermal decomposition method with Ni(HCOO)2·2H2O as the Ni source, PAO6 as base oil, as well as oleylamine and oleic acid as the surface-capping agents. The size-dependent tribological properties of as-synthesized Ni-based nanolubricants were evaluated with a four-ball friction and wear tester. The morphology of wear scar and chemical states of some typical elements on worn steel surfaces were analyzed by scanning electron microscopy and X-ray photoelectron spectroscopy. The morphology and structure of Ni nanoparticles separated from as-synthesized nanolubricants were characterized by means of transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectrometry. It has been found that, when the volume of PAO6 in the reaction system is adjusted as 80, 40 and 20 mL, respectively, the size (average diameter) of Ni nanoparticles can be tuned from 7.5 to 13.5 and 28.5 nm. Ni nanoparticles separated from as-synthesized nanolubricants consist of face-centered cubic nanocrystal and have good dispersibility in a variety of organic solvents and good thermal stability as well. Moreover, as-synthesized Nickel-based nanolubricants exhibit good antiwear behavior even at a low Ni concentration of 0.05 % (mass fraction). This is because surface-capped Ni nanoparticles in as-prepared nanolubricants are able to release highly active Ni nanocores and O- and N-containing organic modifying agents that can readily form boundary lubricating film on sliding steel surfaces. In the meantime, Ni nanoparticles with a smaller size are of high surface activity and can be readily deposited on sliding steel surfaces to form a stable and continuous protective layer thereon. As a result, both the boundary lubricating film and the chemically adsorbed and deposited Ni layer contribute to greatly improve the antiwear behavior and load-carrying capacity of PAO6 base stock.