Four-ball Tribometer Research Articles

Effect of lauric diethanolamide on biodegradability and performance characteristics of mineral hydraulic oil

The impacts of lauric diethanolamide as an additive on biodegradability and the performance characteristics such as friction-reducing and anti-wear abilities, corrosiveness, demulsibility and foaming property of a fully formulated petroleum-based hydraulic oil were investigated. The biodegradabilities of the neat oil and the oils doped with different contents of lauric diethanolamide were evaluated on a biodegradation tester, while the friction and wear performances of neat oil and the doped oils were determined on a four-ball tribometer. The corrosiveness, demulsibility and foaming characteristics were evaluated based on the corresponding Chinese standard methods. The results indicated that lauric diethanolamide not only efficiently enhanced biodegradation of unreadily biodegradable mineral hydraulic oil, but also to a great extent improved the friction-reducing and demulsifying abilities of said hydraulic oil, while the anti-wear capacity, corrosiveness and anti-foam property of the hydraulic oil were almost unaffected by lauric diethanolamide.

The potential of hBN nanoparticles as friction modifier and antiwear additive in engine oil

An experimental investigation was conducted to investigate the potential of hexagonal boron nitride (hBN) nanoparticles as friction modifier and antiwear additive in engine oil. In this study, an optimal composition (0.5 vol.%) of 70 nm hBN nanoparticles was dispersed in SAE 15W-40 diesel engine oil by sonication technique. Sample was stabilized using 0.3 vol.% oleic acid as a surfactant. The tribological test was performed using a four-ball tribometer. Surface morphology and its chemical composition were carried out using a profilometer, Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray Spectroscopy (EDX). It was found that the optimized nano-oil could reduce the coefficient of friction and increase wear resistance, as compared with conventional diesel engine oil. Some adhesive and abrasive wear types were identified as predominant wear mechanisms.

Tribological properties and tribochemical analysis of nano-cerium oxide and sulfurized isobutene in titanium complex grease

Although titanium complex grease has captured wide attention, limited studies were carried out to develop an effective lubricant specifically for extreme operational applications. In this study, terephthalic acid-based titanium complex grease was synthesized. The effects of ceria oxide (CeO2) nanoparticles and sulfurized isobutene (SIB) on the tribological performance of titanium complex grease were investigated using a four-ball tribometer. It was found that because of a synergistic effect of SIB and CeO2 nanoparticles on titanium complex grease, the tribological properties were significantly improved. This study provides a promising lubricant for extreme pressure applications.

Tribological Properties of Limonene Bisphosphonates

Limonene was chemically modified by reacting it with dialkyl phosphites of varying alkyl structures under inert atmosphere in the presence of free radical initiators. The reaction gave a mixture of mono- and di-adduct products and was optimized to produce only the di-adduct product limonene bisphosphonate by forcing both limonene double bonds to react completely. The product mixture was carefully characterized using a combination of gas chromatography–mass spectroscopy, infrared spectroscopy, and nuclear magnetic resonance spectroscopy (1H, 13C, 31P). The bisphosphonates were investigated for their physical and tribological properties. The alkyl bisphosphonates displayed density and viscosity that was a function of the alkyl structure (methyl, ethyl, n-butyl) and much higher than the values for the unreacted limonene. They also displayed improved oxidation stability but lower viscosity index and solubility in polyalphaolefin (PAO6) and high-oleic sunflower oil (HOSuO) base oils. Tribological characterization of the neat modified oils on a four-ball tribometer showed improved extreme-pressure weld point by all three di-adducts and improved anti-wear coefficient of friction (COF) and wear scar diameter (WSD) by the n-butyl di-adduct only. The limonene bisphosphonates also displayed improved COF and WSD as additives in PAO6 and HOSuO base oils at low concentrations. The effects of chemical modifications on physical and tribological properties can be explained in terms of increased polarity of the modified products, insertion of heavy atoms (from PO3) into the limonene structure, and complete absence of unsaturation in the modified products.

Tribological Characteristics of Calophyllum inophyllum–Based TMP (Trimethylolpropane) Ester as Energy-Saving and Biodegradable Lubricant

The purpose of this research is an experimental study of Calophyllum inophyllum (CI)-based trymethylolpropane (TMP) ester as an energy-saving and biodegradable lubricant and compare it with commercial lubricant and paraffin mineral oil using a four-ball tribometer. CI-based TMP ester is a renewable lubricant that is nonedible, biodegradable, and nontoxic and has net zero greenhouse gases. The TMP ester was produced from CI oil, which has high lubricity properties such as higher density, higher viscosity at both 40°C and 100°C and higher viscosity index (VI). Experiments were conducted during 3,600 s with constant load of 40 kg and constant sliding speed of 1,200 rpm at temperatures of 50, 60, 70, 80, 90, and 100°C for all three types of lubricant. The results show that CI TMP ester had the lowest coefficient of friction (COF) as well as lower consumption of energy at all test temperatures, but the worn surface roughness average (Ra) and wear scar diameter were higher compared to paraffin mineral oil and commercial lubricant. Before 80°C, CI TMP ester actually has a higher flash temperature parameter (FTP) than paraffin mineral oil and as the temperature increases, the FTP of TMP ester decreases. The worn surfaces of the stationary balls were analyzed by scanning electron microscopy (SEM) and results show that CI TMP ester has the highest wear compared to paraffin mineral oil and lowest wear compared to commercial lubricant. However, CI TMP ester is environmentally desired, competitive to commercial lubricant, and its use should be encouraged.

Synthesis and lubricating properties of neopentyl glycol oligoesters based on rapeseed oil

Purpose – The aim of this work is to synthesize neopentyl glycol oligoesters based on adipic acid and rapeseed oil (NOAR) which may be used as the renewable and environmentally acceptable base fluids to replace mineral oils in the future. Design/methodology/approach – Oligomeric intermediates were synthesized in the first esterification of neopentyl glycol with adipic acid and characterized by Gas Chromatography-Mass Spectrometer (GC-MS) to calculate the average oligomerisation degree. NOAR were synthesized in the second esterification of oligomeric intermediates with rapeseed oil fatty acid. The effects of average oligomerisation degree on the viscosity, viscosity index, pour point, oxidative stability and biodegradability of NOAR were investigated; the tribological properties and thermal stability of NOAR were evaluated by four-ball tribometer and TGA, respectively. Findings – Results show that with the increase of average oligomerisation degree from 2.10 to 4.34, the viscosity of NOAR increased from 101.1 to 182.0 (mm2/s) at 40°C and 18.3 to 30.1 (mm2/s) at 100°, respectively, and their oxidation stability can be improved as well. The yields of NOAR were 83.3-89.4 per cent, and the evaluated properties were as follows: viscosity index of over 200, pour point of below −43°C, biodegradation rate of more than 96 per cent, maximum non-seizure load (PB value) of 784 N, wear scar diameters of 0.40 mm and thermal decomposition temperature of higher than 300°C. Originality/value – This work provides a method to synthesize rapeseed oil-based oligoesters which can serve as the renewable and environmentally acceptable base fluids with tunable viscosity by controlling the oligomerisation degree of esterification.

Synthesis of nano-Cu/graphene oxide composites by supercritical CO2-assisted deposition as a novel material for reducing friction and wear

Copper nanoparticle/graphene oxide (Sc-Cu/GO) composites were prepared by an in-situ chemical deposition with assistance of supercritical carbon dioxide (scCO2). The anchored Cu nanoparticles with diameter of 5–10nm are uniformly distributed on the GO nanosheet surfaces. The tribological properties of the as-prepared Sc-Cu/GO composites as lubricating additive in liquid paraffin oil were evaluated using a four-ball tribometer. The results show that the Sc-Cu/GO nanocomposites as additives in oil have excellent anti-wear and friction-reducing abilities. The base oil mixed with 0.05wt.% Sc-Cu/GO displays the friction coefficient of 0.065 and the wear scar diameter of 0.26mm that are respectively reduced by 27.0% and 52.7% compared with the pure oil, 15.6% and 35% compared with the oil with 0.05wt.% GO, 13.3% and 38.1% compared with oil with 0.05wt.% nano-Cu. In addition, the lubricating performances of the Sc-Cu/GO composites are much better than that of the Cu/GO nanocomposites produced by the traditional deposition method (without scCO2). The excellent lubrication performances of the Sc-Cu/GO composites derive from the synergistic lubricating action of GO nanosheets and Cu nanoparticles during sliding process. The synergistic lubricating actions are discussed and proposed by analyzing the worn surfaces of the steel balls. This work offers an attractive strategy for fabricating graphene-based nanocomposites as energy efficient lubricant additives.

A Novel Nanomaterial of Graphene Oxide Dotted with Ni Nanoparticles Produced by Supercritical CO2-Assisted Deposition for Reducing Friction and Wear.

Graphene oxide dotted with nickel nanoparticles (Sc-Ni/GO) was synthesized by chemical deposition with the assistance of supercritical carbon dioxide (scCO2). The deposited Ni nanoparticles with diameters less than 5 nm are uniformly anchored on the surfaces of GO nanosheets. The as-prepared Sc-Ni/GO composites were employed as lubricating additives in paraffin oil and their tribological properties were tested using a four-ball tribometer. The results demonstrate that the Sc-Ni/GO composites are efficient lubricant additives. Adding 0.08 wt % Sc-Ni/GO into paraffin oil can reduce the friction coefficient and wear scar diameter by 32 and 42%, respectively, in comparison with the pure oil. In addition, Sc-Ni/GO composites exhibit superior lubricating performances than nano-Ni, GO nanosheets, and Ni/GO composites produced without the aid of scCO2. Such excellent lubricating properties of the Sc-Ni/GO composites derive from the synergistic lubricating actions of Ni nanoparticles and GO nanosheets during the rubbing process. The synergistic lubricating actions are closely related to the microstructure of the nanocomposites and the characteristic features of transfer film formed on the contact steel balls. The anchored Ni nanoparticles with smaller size and more uniform distribution on GO surfaces and the thin transfer film formed on the contact balls favor the full play of the synergistic actions.

Preparation and evaluation of tribological properties of oil-soluble rice-like CuO nanoparticles

Purpose – The purpose of this paper is synthesis of oil-soluble non-spherical nanoparticles modified with free phosphorus and sulphur modifier and investigation of their tribological properties as environment-friendly lubricating oil additives. Design/methodology/approach – To study the effect of morphology of nanoparticles on their tribological properties, rice-like CuO nanoparticles were synthesized. To improve the solubility of CuO nanoparticles in organic media, the in-situ surface modification method was used to synthesize these products. The morphology, composition and structure of as-synthesized CuO nanoparticles were investigated by means of transmission electron microscopy, X-ray powder diffraction, thermogravimetric analysis and Fourier transform infrared spectrometry. The tribological properties of as-synthesized CuO nanoparticles as an additive in liquid paraffin (LP) were evaluated with a four-ball tribometer. The morphology and elemental composition of worn steel ball surfaces were analysed by X-ray photoelectron spectroscopy. Findings – It has been found that as-synthesized CuO nanoparticles with rice-like morphology have an average size of 7 and 15 nm along the shorter axle and longer axle, respectively, and can be well-dispersed in LP. Tribological properties evaluation results show that as-synthesized CuO nanoparticles as additives in LP show good friction-reducing, anti-wear and load-carrying capacities, especially under a higher normal load. Originality/value – Oil-soluble rice-like CuO nanoparticles without phosphorus and sulphur were synthesized and their tribological properties as lubricating oil additives were also investigated in this paper. These results could be very helpful for application of CuO nanoparticles as environment-friendly lubricating oil additives, owing to their free phosphorus and sulphur elements characteristics.

Influence of Microalgal Bio-Oil on the Lubrication Properties of Engine Oil

In order to accelerate and expand the application of bio-energy, two kinds of microalgal bio-oils, prepared via co-liquefaction of Chlorella and Spirulina under sub- and supercritical ethanol conditions, were used as partial substitutes for the engine oil CD SAE 15W-40. The friction and wear behaviors of the oils were tested on a four-ball tribometer, referring to the ASTM D4172 standard conditions. The micro-morphology, profiles, roughness and chemical valences of typical elements on the rubbed surfaces were characterized by Scanning Electron Microscopy (SEM), surface profiler and X-ray Photoelectron Spectroscopy (XPS), respectively. The results showed that both of the bio-oils had good lubrication properties. The suitable weight content of the bio-oils in the engine oil was 10%. The lubrication properties of the Bio-Oil (BOsup) prepared in supercritical ethanol were a little better than those of the Bio-Oil (BOsub) prepared in subcritical ethanol. The lubricating mechanisms were ascribed to the combined actions of various lubricating films, including boundary lubrication, and deposited films and tribological chemical reaction films. The stronger tribological chemical effects of BOsup from higher contents of N-containing compounds contributed to its better lubrication properties than those of BOsub.

Effect of Particle Size and Ligand on the Tribological Properties of Amino Functionalized Hairy Silica Nanoparticles as an Additive to Polyalphaolefin

Hairy nanoparticles, which graft organic chains on nanoparticles, have led to a wide variety of advanced materials and have been applied in many fields over the past two decades. In this paper, effects of nanoparticle size and organic chain on the tribological properties of amino functionalized hairy silica nanoparticles (HSNs) were investigated. Silica nanoparticles with different sizes and amino group organic chains were synthesized and dispersed into polyalphaolefin (PAO) via a modified process. The synthesized HSNs were characterized by variety of methods. The tribology properties of those HSNs were investigated using a four‐ball tribometer. The coefficient of friction and wear scar diameter were measured and analyzed. It was found that the HSNs could form a stable homogeneous solution with PAO. The tribological performance of the PAO 100 was enhanced dramatically by adding the HSNs. The data suggested that HSNs with larger size, longer organic chains, and more amino groups gave better antiwear and friction reduction properties than other nanoparticles.

Tribological Study of Ecological Lubricants Containing Titanium Dioxide Nanoparticles

Titanium dioxide (TiO2), belonging to the family of transition metal dichalcogenides (together with molybdenum disulfide (MoS2) and tungsten disulphide (WS2)), is well known for its solid lubricating behaviour. Thin films of TiO2 exhibit extremely low coefficient of friction in dry environments, and are typically applied by mixed in oil, grease or impregnated into porous matrix of powdered materials. Current researches in many areas imply the using of different types of nanoparticles in the composition of oily lubricants. Results of these researches upon the friction couples show that nanoparticles contained by lubricant can improve the tribological properties, the friction-wear reduction and the lubrication effect. When nanomaterials are used to improve lubrication effect, the selection of metal is very important. In this paper, the authors chose for investigating the tribological properties of two samples of TiO2 with the mean diameter of 15 nm (n-TiO2) and 250 nm (m-TiO2), under different friction conditions. The tribological properties of TiO2 nanoparticles mixed in the ecological lubricant oil were investigated using a four-ball tribometer and a block-on-ring tribometer and show the lowering of the friction coefficient in comparison to the lubricant base oil. The finally obtained lubricant is not considered toxic for the environment. The analyses of surface film composition, characterized with the help of X-ray photoelectron spectroscope (XPS) and scanning electron microscopy (SEM) images showed that the deposed nanoparticles form a protective film (TiO3) allowing for an increase in the load capacity of friction couple. XPS and SEM were used to examine the morphology of the wear track, after the four-ball experiment. The main advantage of the nanoparticles is ascribed to the release and furnishing of the nanoparticles from the valley onto the friction metal surface and their confinement at the interface. The TiO2 nanoparticles showed lower frictions coefficient and higher wear resistance as compared to the common TiO2 particles (about 1.5 μm in diameter(c- TiO2)) on a four-ball machine, which were caused by the microstructure of the protective film and serve as perfect intermediate lubricants between the contact surfaces.

Effect of Surface Modification of Acetabular Cup with Embedded Micro-Pits on Friction Properties

This study describes an investigation of the effect on friction when an acetabular cup surface is embedded with micro-pits. The micro-pit is potentially a suitable structure to act as a lubricant reservoir, in order to reduce the level of friction present between the surfaces of a hip prosthesis. The experiments were carried out using a modified four-ball tribometer. Refined, Bleached and Deodorised (RBD) palm olein and additive-free paraffinic mineral oil were selected to provide lubrication. When the palm olein was applied to the acetabular surface, friction in the hip implant decreased. Severe damage on the acetabular surface resulted in lubricant-free test conditions. Meanwhile, the results of tests on the acetabular cup, with 10 to 40 embedded micro-pits on the surface, indicated that friction had decreased. Based on the experiments, surface modification of the acetabular cup with embedded micro-pits, could prolong the biomechanics of hip prostheses.

Formation and tribological properties of hollow sphere-like nano-MoS2 precipitated in TiO2 particles

MoS2 hollow spheres with an average diameter of 165nm were prepared from Na2MoO4 and CH3CSNH2 at 82°C. A simple method was used to obtain smaller hollow spheres (70nm) without any complicated step, except for the addition of TiO2. The tribological properties of MoS2/TiO2 in rapeseed oil were studied using a four-ball tribometer under 350N at 0.383m/s. The effects of load and sliding velocity were also investigated. Wear was significantly alleviated by the produced lubricating film as lubricated with MoS2/TiO2, which was composed of MoO3, Fe2O3, Fe2(SO4)3, TiO2 (trace), and carbon-containing compounds. The tribological properties were also improved because of the decrease in the size of MoS2 and the synergistic effect between MoS2 and TiO2.

Preparation and tribological properties of complex nanoparticle styrene/calcium borate with core-shell structure

Purpose – The purpose of this paper is to develop a potential nanoparticles lubricant additive for solving the problem of the insolubility and stable dispersity; the complex nanoparticles with core-shell structures are less studied in the field. Therefore, this paper determines novel complex nanoparticles and their tribological properties. Design/methodology/approach – According to the conventional preparation method, the complex nanoparticle styrene/calcium borate (PS/O-CaB) was synthesized. The microstructures of the as-obtained samples were characterized by X-ray diffraction infrared spectroscopy and thermogravimetric analysis. Tribological properties of PS/O-CaB used as lubricating oil additive were evaluated on four-ball tribometer. The worn surface of the steel ball was investigated by a three-dimensional non-contact surface profilometer and X-ray photoelectron spectroscopy (XPS). Findings – The results of the structure characteristic indicate two different crystalline forms, namely, Ca2B6O11 and Ca2B2O5, and the average size of calcium borate nanoparticles in PS/O-CaB is about 20-40 nm. Moreover, the good tribological properties are due to a wear resistance film containing both depositions and the tribochemical reaction products which comprise B2O3, FeB and Fe2O3. Originality/value – Novel complex nanoparticles with core-shell structure (PS/O-CaB) were successfully prepared. Moreover, the PS/O-CaB shows excellent tribological capacity such as load-carrying, friction-reducing and antiwear property.

Tribological study of a highly hydrolytically stable phenylboronic acid ester containing benzothiazolyl in mineral oil

A novel long chain alkyl phenylboronic acid ester containing heterocyclic compound, bis (1-(benzothiazol-2-ylthio) propan-2-yl)-4-dodecylphenylboronic acid ester (DBBMT), was synthesized and characterized. The hydrolytic stability of the DBBMT was evaluated and the results show that DBBMT is of outstanding hydrolytic stability compared with normal borate esters, which indicates that the designed molecular structure, by introducing benzene ring to conjugate with the electron-deficient boron and the benzothiazole as a hinder group, is effective on obtaining a hydrolytically stable long chain alkyl phenylboronic acid ester. The tribological properties of DBBMT and ZDDP in mineral base oil were evaluated using a four-ball tribometer, which suggests that the DBBMT possesses comprehensive tribological properties and could be a potential candidate for the replacement of ZDDP. Furthermore, in order to understand the tribological behaviors, the worn surface was analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) spectroscopy. The results indicate that the elements S, B, O and Fe perform complicated tribochemical reactions to form the compact tribological film composed of B2O3, FeS, Fe3O4 and FeSO4.

Synthesis, Tribological and Hydrolysis Stability Study of Novel Benzotriazole Borate Derivative

Benzotriazole and borate derivatives have long been used as multifunctional additives to lubricants. A novel, environmentally friendly additive borate ester (NHB), which contains boron, ethanolamine, and benzotriazole groups in one molecule, was synthesized by a multi-step reaction, and its tribological properties in rapeseed oil (RSO) were investigated by a four-ball tribometer. The hydrolysis stability of the additive was investigated by half-time and open observation methods, and the mechanism of hydrolysis stability was discussed through Gaussian calculation. The novel compound NHB showed excellent performance under extreme pressure, against wearing, and in reducing friction, and its hydrolysis time is more than 1,220 times, which is better than that of triethyl borate. The mass ratio of NHB is bigger than that of the mixed liquid of triethyl borate and ethanolamine. The lone electron of amino N atoms forms a coordination effect with the B atom to compensate for the shortage of electrons in the B atom and to improve the hydrolysis stability of NHB. The surface morphology and the traces of different elements in the tribofilms formed with 1.0 wt.% NHB in were detected with scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy (EDX)and X-ray photoelectron spectroscopy(XPS). The results shown that the additive caused a tribochemical reaction with the steel ball surface during the lubricating process. A mixed boundary lubrication film that contains organic nitrogen and inorganic salts, such as BN, B2O3, FeOx, Fe–O–B, and FeB, was also formed, and the formation of the lubricating film improved the tribological properties of the base oil.

The Tribological Chemistry of a Novel Borate Ester Additive and Its Interaction with ZDDP Using XANES and XPS

A novel borate ester containing heterocyclic group, 2,5-bis((2-((6-octadecyl-1,3,6,-dioxazaborocan-2-yl)oxy)propyl)thio)-1,3,4-thiadiazole (BDOT), was prepared and characterized. Its tribological properties and synergistic effect with zinc dialkyl dithiophosphate were evaluated using a four-ball tribometer. The results show that the novel borate additive possesses excellent anti-wear and friction-reducing properties compared with the performance of ZDDP. BDOT combined with ZDDP has a synergistic effect on the tribological properties, especially for the friction-reducing performance. The chemical state of nitrogen, boron and sulfur in thermal films and tribofilms was analyzed by XPS and XANES. XPS analysis suggests that the additive forms a protective film on the rubbing surfaces which is composed of B2O3, BN, FeSO4, FeS2 and Fe2O3. However, the B K-edge XANES shows that no BN was detected in the film. The synergistic effect between BDOT and ZDDP may be due to the formation of right concentration of FeS and FeSO4 in the tribofilm.

Estudio Comparativo del Poder Lubricante y Estabilidad Oxidativa entre el Aceite de Ajonjolí y Aceite Mineral 360

A comparative study of the lubricant properties and oxidative stability of sesame oil and a mineral oil, without additives is presented. The superior power of vegetable oil lubricant compared to that of mineral oil was verified by preventive wear tests and extreme pressure in a four-ball tribometer. According to atomic absorption test, there are traces of metals in the areas that are in contact with the sesame oil during the development of the preventative wear test. These particles catalyze the oxidation of the oil during the differential scanning calorimetry test, decreasing the oxidation starting temperature. The preventive wear test partially degraded the sesame oil and increased the peroxide value. This change in the oil was not possible to find by Fourier transform with infrared spectroscopy and acidity. The stability of the mineral oil is superior to that of the vegetable oil.

Tribological properties of sodium dodecyl sulfate aqueous dispersion of graphite-derived carbon materials

The graphene oxide nanosheets (GOS) and reduced graphene oxide nanosheets (RGOS) were dispersed in 0.1 wt% anionic surfactant sodium dodecyl sulfate (SDS) aqueous solution to be functionalized with surfactant layers. The tribological properties of GOS and RGOS in 0.1 wt% SDS aqueous solution were studied using a four-ball tribometer. The RGOS and GOS at optimal concentration in SDS aqueous solution improved the anti-wear and friction reduction properties of SDS aqueous solution. GOS show better friction reduction properties than RGOS. The outstanding lubrication performance of GOS could attribute to their stable dispersion, thin laminated graphitic structure with high-lubricity and nanosize characteristics which can enter the contact area easily. Our findings provide the opportunity to use graphene-related materials for water-based lubricant applications.