Mean Wear Scar Diameter Research Articles

Synergistic studies of Schiff base with organoborate as efficient antiwear lubricant additive

Schiff base derived from condensation of 4-aminotriazole with indole-3-carboxylaldehyde has been characterized by Fourier-transform infrared and 1H NMR spectroscopic techniques. The tribological properties of synthesized Schiff base have been evaluated using four-ball tester at optimized concentration (1% w/v) and compared with its individual components. The tribological testing has been performed by varying load for 30 min duration and varying test durations at 392 N load. The synergistic action of Schiff base with commercial borate ester effectively enhances the antiwear properties of base oil and its load-carrying capacity. Pronounced reduction in the values of mean wear scar diameter, friction coefficient (µ), mean wear volume (MWV), and wear rates confirm the synergistic interaction between Schiff base and borate ester. The best tribological properties are shown by synergistic mixture, followed by Schiff base, then indole-3-carbaldehyde, and finally 4-aminotriazole. The surface topography of worn surfaces has been studied by scanning electron microscopy and contact mode atomic force microscopy which show the drastic decrease in surface roughness in the presence of synergistic mixture. The energy-dispersive X-ray analysis of worn surface lubricated with synergistic formulation exhibits nitrogen, carbon, boron, and oxygen indicating the adsorption of additive on the metal surface to form in situ protective tribofilms, which prevent direct metal–metal contact thus reducing friction and wear. The quantum chemical calculations studies show that there is significant interaction of Schiff base additive with the metal surface than those of its individual components and the data correlate very well with the obtained tribological results.

Synthesis, Characterization, and Tribological Evaluation of TiO2-Reinforced Boron and Nitrogen co-Doped Reduced Graphene Oxide Based Hybrid Nanomaterials as Efficient Antiwear Lubricant Additives.

The microwave-synthesized reduced graphene oxide (MRG), boron-doped reduced graphene oxide (B-MRG), nitrogen-doped reduced graphene oxide (N-MRG), boron-nitrogen-co-doped reduced graphene oxide (B-N-MRG), and TiO2-reinforced B-N-MRG (TiO2-B-N-MRG) nanomaterials have been synthesized and characterized by various state-of-the-art techniques, like Raman spectroscopy, powder X-ray diffraction, scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Furthermore, the tribological properties of prepared nanomaterials as antiwear additives in neutral paraffin oil have been evaluated using a four-ball machine at an optimized additive concentration (0.15% w/v). The tribological parameters, like mean wear scar diameter, coefficient of friction, and wear rates, revealed that these nanomaterials have potential to be developed as environmentally friendly sulfated-ash-, phosphorus-, and sulfur-free antiwear lubricant additives. The friction- and wear-reducing behavior of MRG increased upon successive doping of nitrogen, boron, and both nitrogen and boron. Among these additives, B-N-co-doped MRG shows superior tribological behavior in paraffin base oil. Besides this, the load-carrying properties of B-N-co-doped MRG have significantly improved after its reinforcement with TiO2 nanoparticles. A comparative study of the surface morphology of a lubricated track in the presence of various additives has been assessed by SEM and contact-mode atomic force microscopy. The X-ray photoelectron spectroscopy studies have proved that the excellent lubrication properties of TiO2-B-N-MRG are due to the in situ formation of a tribofilm composed of boron nitride, adsorbed graphene layers, and tribosintered TiO2 nanoparticles during the tribocontact. Being sulfur-, halogen-, and phosphorus-free, these graphene-based nanomaterials act as green antiwear additives, protecting interacting surfaces significantly from wear and tear.

The Use of Tertiary-Butyl-Hydroquinone (TBHQ) in Minimizing Oxidation Effects on Palm Oil Based Lubricant Using Four Ball Tribotester

The extended uses of mineral oil based lubricant have continuously troubling the global environment issues. The remaining mineral oil resources also being the most debated issues in renewable energy conferences. Vegetable oils are still offering the highest possibility in replacing the mineral oil resources. This research is concerning on how to eliminate one of the disabilities found in palm oil based lubricant which is oxidation. Palm oil possessed unsaturated double bond in which susceptible to oxidation process. The simplest approach is to blend the palm oil based with anti – oxidant agent homogenously. This research was conducted using double fractionated palm oil (SPL) as lubricant and Tertiary-Butyl-Hydroquinone (TBHQ) as anti – oxidant agent to determine the tribology behavior including the coefficient of friction, wear scar diameter and the surface roughness profile. The experiment was also conducted using four-ball tribotester by following ASTM D4172B standard. Superior Mineral Engine Oil (EO) was used as comparison. The results found that SPL+TBHQ was able to reduce the coefficient of friction and provided lower surface roughness value. However it was unable to minimize the mean wear scar diameter compared to EO. The physical appearances of wear worn are also being observed in this research.

The investigation of different particle size magnesium-doped zinc oxide (Zn0.92Mg0.08O) nanoparticles on the lubrication behavior of paraffin oil

Magnesium-doped zinc oxide (Zn0.92Mg0.08O) (ZMO) nanoparticles of 23 nm particle size have been synthesized by auto-combustion method. The variation in particle size of these nanoparticles has been performed by their further calcination at 800 and 1000 °C for 2 h and the corresponding calcined particles are designated as ZMO-1 and ZMO-2, respectively. The nanoparticles have been characterized by powder-XRD, scanning electron microscopy (SEM), energy dispersive X-ray and transmission electron microscope. The effect of particle size on the antiwear lubrication behavior of paraffin base oil has been investigated on four-ball lubricant tester. The tribological tests of these nanoparticles as antiwear additives have been studied at an optimized concentration (0.5 %w/v) by varying load for 30 min test duration and by varying the test durations at 392 N load. Various tribological parameters such as mean wear scar diameter, friction coefficient (µ), mean wear volume, running-in and steady-state wear rates show that these nanoparticles act as efficient antiwear additives and possess high load-carrying ability. From these tribological tests it has been observed that the lubrication behavior of studied nanoparticles is strongly size-dependent. The best tribological behavior is shown by nanoparticles of the smallest size, ZMO. Being sulfur, halogen and phosphorous free, ZMO nanoparticles have potential to be used as low SAPS lubricant additives. The SEM and atomic force microscopy analysis of the worn surfaces lubricated with ZMO nanoparticles at 392 N applied load for 60 min test duration show drastic decrease in surface roughness. The values of surface roughness of different additives are in good agreement with their observed tribological behavior.

Tribological studies of stearic acid-modified CaCu2.9Zn0.1Ti4O12nanoparticles as effective zero SAPS antiwear lubricant additives in paraffin oil

Stearic acid modified ceramic nanoparticles SCCZTO-6 h, SCCZTO-8 h and SCCZTO-12 h of average sizes 60, 80 and 90 nm were prepared from CCZTO-6 h, CCZTO-8 h and CCZTO-12 h respectively (where CCZTO represents CaCu2.9Zn0.1Ti4O12; 6 h, 8 h and 12 h are the sintering times). The SCCZTO nanoparticles have been characterized by Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). Tribological behavior of these nanoparticles in liquid paraffin oil has been evaluated using a four-ball lubricant tester and compared with conventional high SAPS containing zinc dialkyldithiophosphates (ZDDP). All antiwear tests have been performed using an optimized concentration of the SCCZTO nanoparticles (1% w/v) by varying the load for a 30 min test duration and by varying the test durations at 392 N load. Various tribological parameters such as mean wear scar diameter (MWD), friction coefficient (μ), mean wear volume (MWV), running-in, steady-state and overall wear rates show that all the SCCZTO nanoparticles act as efficient antiwear additives and possess a high load carrying capacity. The best tribological behavior is shown by SCCZTO-6 h, followed by SCCZTO-8 h and then SCCZTO-12 h. The surface morphology and roughness of the wear scar have been studied by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) respectively. AFM and SEM micrographs of the wear scar in the presence of SCCZTO-6 h and SCCZTO-8 h at 392 N applied load for a 90 min test duration show a drastic decrease in surface roughness. Energy-Dispersive X-ray (EDX) analysis of the worn surface under similar experimental conditions in the presence of SCCZTO-6 h nanoparticles exhibits the presence of calcium, copper, zinc, titanium and oxygen on the worn steel surface indicating tribosinterization and/or adsorption of the additive on the rubbing surface resulting in the formation of a strong tribofilm. X-ray Photoelectron Spectroscopy (XPS) of the tribofilm shows the presence of CaO, CuO, Cu2O, TiO2, Fe2O3 and adsorbed carbon in the form of –C–C– and –C(O)O– moieties.

Effect of ambient humidity and hygroscopy on the lubricity of diesel fuels

The lubricity of a selection of multicomponent fuels and pure substances was measured on a high frequency reciprocating rig at different vapor pressures. The objective was to evaluate the effect of air humidity on the wear scar diameter. Specific correction factors depending on the chemical composition of the fuel are proposed to normalize the mean wear scar diameter. The humidity correction factor recommended by the European standard shows an overestimation for most of test fuels, except biodiesel fuels which require higher correction factor. The effect of the water content in the fuel on the wear scar was also studied, showing significant direct correlations for all test fuels. An indirect approach for the estimation of the fuel hygroscopy, based on the combination of the effects of humidity and water content of the fuel on the wear scar, has confirmed that the air humidity affects wear through the humidification of the fuel. The results obtained by the proposed method show that paraffinic fuels are more hydrophilic than diesel fuels but they are less hydrophilic than biodiesel and alcohol fuels, which is consistent with the literature.

Lubricity of ethanol-gasoline fuel blends

In this work the lubricity of several ethanol (hydrated or anhydrous) / gasoline fuel blends was measured by using a conventional HFRR tester. Tests were carried out at 25ºC with no water vapour pressure control, according to the ASTM D6079 standard. According to the results the range of variation of the mean wear scar diameter was small among tested fuels in the range E-20 to E-85, indicating that the addition of ethanol, anhydrous or hydrated, did not impact significantly blend lubricity. The addition of hydrated ethanol (96% v/v) slightly improved blend lubricity in comparison with the addition of anhydrous ethanol. The higher mean wear scar diameters, lower fluid film traces and higher friction coefficients obtained for all tested fuels, in comparison with the typical values for diesel fuels, indicate the necessity of using lubricity additives when gasoline or ethanol / gasoline blends are used in new engine technologies requiring higher pressures in the fuel injection system.

Phosphorous free antiwear formulations: Zinc thiosemicarbazones–borate ester mixtures

Antiwear properties of zinc(II) complexes of salicylaldehyde N(4)-phenyl- p-substituted thiosemicarbazones and their synergic action with Vanlube 289 additive were evaluated in paraffin oil on four ball tester using steel balls of 12.7 mm diameter and the results were compared with those of zinc dibutyl dithiophosphate. On the basis of mean wear scar diameter, mean wear volume, friction coefficient, running-in and steady-state wear rate under optimum conditions, the following order of efficiency emerged: Zinc(II) thiosemicarbazones + Vanlube 289 > Vanlube 289 > ZDDP > Zinc(II) thiosemicarbazones. Among the zinc(II) complexes alone or their synergic formulations, salicylaldehyde N(4)- p-methoxyphenylthiosemicarbazones [Zn(HSTC- p-OMePh)2] exhibits best antiwear properties followed by salicylaldehyde N(4)- p-chlorophenylthiosemicarbazone [Zn(HSTC- p-ClPh)2], salicylaldehyde N(4)- p-methylphenylthiosemicarbazone [Zn(HSTC- p-MePh)2] and salicylaldehyde N(4)- p-phenyl thiosemicarbazones [Zn(HSTC-Ph)2] derivatives. The topography of the wear scar studied by atomic force microscopy and scanning electron microscopy in absence and presence of the additives indicated reduced roughness of the surface in presence of the additives. The admixtures containing zinc(II) complexes and their synergic formulations with Vanlube 289 showed presence of sulfur, nitrogen, oxygen and zinc in the energy-dispersive X-ray analysis of the wear scar.

Lanthanum dithiocarbamates as potential extreme pressure lubrication additives

The extreme pressure lubrication (EPL) properties of bipyridyl adducts of different lanthanum dithiocarbamates of the type LaL3·bipy (where LH = dimethyl dithiocarbamate (Me2DTCH), piperidine dithiocarbamate (PipDTCH), morpholine dithiocarbamate (MorphDTCH), and diphenyl dithiocarbamate (Ph2DTCH); bipy = 2,2′-bipyridyl) have been evaluated with a four-ball lubricant tester using steel balls of 12.7-mm diameter and molybdenum disulfide as a reference additive. Various tribological parameters, viz. mean wear scar diameter, friction coefficient, mean specific pressure, initial seizure load, 2.5-s seizure delay load, weld load, flash temperature parameter, mean Hertz load, pressure wear index, etc., have been determined. The surface topography of wear scar has been studied by atomic force microscopy and scanning electron microscopy. Energy-dispersive X-ray analysis has been performed to give the composition of the wear scar surface. Experimental results indicate that admixtures containing bipyridyl adducts of lanthanum dithiocarbamates in paraffin oil exhibit better EPL properties than paraffin oil alone or with a reference additive (MoS2). In view of very high efficiency, the synthesized compounds can be recommended for their application as EPL additives.

The interest of combining two additives with palm olein as selected lubricant components

PurposeThe purpose of this paper is to study the effect of palm olein, amine phosphate and 4‐nonyl phenoxy acetic acid (NPAA) added to a commercial lubricant in terms of tribological properties such as wear and coefficient of friction.Design/methodology/approachA tribological study on the lubrication performance of a lubricant‐based palm oil (PO) containing anti‐wear and antioxidant combined corrosion inhibitor additive was carried out using a universal sliding wear machine. In this experiment, amine phosphate and NPAA were selected as additive to be mixed with PO (palm olein) in several concentrations and commercial lubricant 20W‐50 for the tests. Various PO blended samples with additional 1 and 3 percent additive were used in this study. The experiments were performed under 252 rpm sliding speed for 2 h where the oil temperature reached 100°C.FindingsThe analysis showed that the average wear coefficient and the mean wear scar diameter (MWSD) which is normalized to the 1.4 KPa water pressure generates lower values for the PO containing additives than 100 percent PO, commercial lubricant and their blended. The coefficients of friction and wear were also lower for the samples with additives compared to other. To consolidate the result, viscosity of used samples is checked and shows the additives improved the viscosity stability. Finally, the overall study concluded that PO‐added additives have the potential to be one of the ingredients in effective lubricant oil.Research limitations/implicationsThe paper is limited to findings based on a Universal Sliding Machine Test under certain conditions. The test has been conducted on the basis of three types of chemical compounds (palm olein, amine phosphate and NPAA) which are designed as a combination of anti‐wear and antioxidant additive. Wear and friction characteristics of the lubricant with and without these additives are analyzed in this paper. However, the film formation and microstructure analysis of the lubricated materials are excluded in this study.Practical implicationsThis paper shows a significant reduction of average wear rate and friction coefficient when palm olein and additive added to the lubricant compared to pure commercial lubricant. In terms of wear scar diameter (WSD), with additional palm olein and additive produces lower WSD which is under the standard limit of diesel lubricity. These results have confirmed that by using palm olein as renewable component together with amine phosphate and NPAA additive would improve lubrication performance as well as improves biodegradability of the lubricant.Originality/valueThis paper emphasises the advantages of synthetic additives that are derived from renewable resources. Since environmental issues are now stringent, many lubricant industries have focused on environmentally friendly lubricant and researches on this particular area become important. The presented tests have been carried out in the above area which is close to those applied in lubricant industry. Thus, the results are reliable and could be very useful both for lubricant designers and the researchers of lubricant and additive formulation.

The tribological behavior of essential oils in low sulphur automotive diesel

This paper presents the impact of essential oils on the lubricity of automotive diesel. Nine essential oils were used as lubricating additives on two low sulfur diesel fuels, at the concentration range of 200–5000 ppm. Tribological experiments carried out on the high frequency reciprocating rig showed that five of nine essential oils used provide satisfactory mean wear scar diameter (WS 1.4) of less than 460 μm, at the concentration levels of 200–5000 ppm. Among the essential oils, those having the higher density and viscosity appeared to have better lubrication performance, exhibiting smaller wear scar diameter (WS 1.4) than the limit of 460 μm. Overall, the five essential oils seem to be better lubricants than others, maybe due to their chemical structure characteristics.

The tribological behavior of alkyl ethers and alcohols in low sulfur automotive diesel

This paper presents the impact of alkyl ethers and alcohols on the lubricity of automotive diesel. Seven ethers and five alcohols were used as lubricating additives on two low sulfur diesel fuels, at the concentration range of 50–2000 ppm. Tribological experiments carried out on the high frequency reciprocating rig showed that six of seven ethers used provide satisfactory mean wear scar diameter (WS 1.4) of less than 0.46 mm, at the concentration levels of 750–1500 ppm. Among the ethers of the same molecular type, those having the oxygen in the middle of the molecule appeared to have marginally better lubrication performance for some concentration ranges. In the case of alcohols, the effective concentration was 750 ppm or higher. Overall, alcohols appear to be better lubricants than ethers at high concentrations, maybe due to their more pronounced polar nature.

Influence of aceto acetic esters and di-carboxylic acid esters on diesel fuel lubricity

This paper presents the impact of acetoacetic esters and di-carboxylic acid esters on the lubrication properties of automotive diesel. Three alkyl acetoacetates and seven di-carboxylic esters were used as lubricating additives on two low sulfur diesel fuels, at seven different concentrations of 50, 100, 500, 750, 1000, 1500 and 2000 ppm. Tribological experiments carried out on the high frequency reciprocating rig (HFRR) showed that only two of the three acetoacetic esters used, provide satisfactory mean wear scar diameter (WS 1.4) of less than 460 μm, at the concentration level of 750 ppm. In the case of di-carboxylic acid esters, the effective concentration was 500 ppm or higher.