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Nanostructures as an inert additive to the lubricant act as a tiny friction reduction element by providing asperity filling, polishing, and film formation mechanism at the nanoscale dimension under the boundary layer regime. Here, we explore the synthesis and tribology application of iron‐carbon‐based nanoparticles encapsulated multiwall carbon nanotubes (Fe‐C‐CNTs). Three Fe‐C nanoparticles phase that is, Fe3C‐CNTs, Fe3C‐Fe‐CNTs, and Fe‐CNTs are synthesised. In particular, the emphasis here is on the effect of nanoparticle phase variation on the tribology property. The tribology property of the prepared nanomaterials is studied by dispersing it in commercially used Servo gearbox oil. The coefficient of friction and wear is found reduced in all dispersions compared to the base gearbox oil confirming the manifestation of nanoscale mechanisms at the tribo‐interface. It is revealed that the phase variation shows more impact on the alteration of friction coefficient compared to the dispersion concentration variation analysed using ANOVA two‐way technique. Further, the diameter and composition analysis of the wear scar is used to comprehend the underlying mechanism of the encapsulated particle phase variation. The findings suggest that the Fe‐CNTs dispersions are efficient in reducing friction to a larger extent but also promote the interface oxidation leading to enhanced wear and roughness whereas, Fe3C‐CNTs and Fe3C‐Fe‐CNTs are chemically stable providing smooth sliding and less wear. [ABSTRACT FROM AUTHOR]

In today’s paradigm petroleum and petro-based chemical products are being extracted and consumed at a substantial rate, proving to be hazardous and detrimental to the earth. Bio based resources are environmentally friendly, energy efficient, economical, and proved to be an alternative to the present mineral oils. This paper documents the research on naturally available mahua seed oil for bio-lubrication, its flash point and fire point, tribological properties namely coefficient of friction and wear scar diameter have been modified by the addition of zinc oxide (ZnO) nanoparticles in different concentrations by weight percentage (0.25, 0.50, 0.75, and 1.0). four-ball tester was used according to ASTMD-4172 standards (60 min under 40 kg running at 1200 rpm). Probe ultrasonicator was used for particle dispersion. It was found that 0.75 wt. % loading of ZnO in mahua oil resulted in a 57.14% drop of coefficient of friction, but a slight increase in the wear scar diameter of 30.60% was observed.

In today’s paradigm petroleum and petro-based chemical products are being extracted and consumed at a substantial rate, proving to be hazardous and detrimental to the earth. Bio based resources are environmentally friendly, energy efficient, economical, and proved to be an alternative to the present mineral oils. This paper documents the research on naturally available mahua seed oil for bio-lubrication, its flash point and fire point, tribological properties namely coefficient of friction and wear scar diameter have been modified by the addition of zinc oxide (ZnO) nanoparticles in different concentrations by weight percentage (0.25, 0.50, 0.75, and 1.0). four-ball tester was used according to ASTMD-4172 standards (60 min under 40 kg running at 1200 rpm). Probe ultrasonicator was used for particle dispersion. It was found that 0.75 wt. % loading of ZnO in mahua oil resulted in a 57.14% drop of coefficient of friction, but a slight increase in the wear scar diameter of 30.60% was observed. [ABSTRACT FROM AUTHOR]

This paper presents and analysis of several 3D amplitude parameters of the texture, measured or calculated for the entire wear scar of the stationary balls used in four-ball tester: Sa, St, Sv, Sp, Ssk and Sku. The authors investigated balls tested in rapeseed oil, rapeseed oil + 1% TiO2 and rapeseed oil +1 % ZnO in order to establish the influence of the testing regime (sliding velocity and force on the main shaft of the tester) on the surface quality at the end of the test, by the help of several amplitude 3D parameters. Qualitatively, the wear process is uniform on the balls in one test, because spread ranges of the discussed parameters are small enough. At low force (F=100 N), corroborating the values of the studied amplitude parameters, it could be concluded that wear processes take place on the peaks of the texture. The Sa parameter is not affected by additivation for v=0.38 m/s and forces from F=100 N to F=300 N. At high sliding velocity, a slope change of both parameters is observed between F=200 N and F=300 N. If the wear is approximately the same at the test end for F=300 N, the roughness of the wear trace increases greatly when the rapessed oil is additivated with, meaning that nano particle of TiO2 agglomerate and participate in the formation of a rougher texture. Lubricant with ZnO keeps the average roughness Sa close to that obtained with nonadditivated rapeseed oil. In order to assess the quality of a surface as close as possible to reality, using 3D parameters, the profilometer pitch should be as fine as possible and the area of investigation as large as possible. However, a trade-off has to be done between the step size, the investigation area and, of course, time to fulfill the study. The Sku parameter shows if there are large isolated peaks and Ssk indicates if the peak frequency is high. For the case of worn surfaces, it is the values of the parameters Ssk, Sku, St, Sp and Sv that are of interest, because high peaks affect the tribological parameters. The surface quality when additivated with 1% TiO2 is much better up to F=300 N. Additivation with 1% TiO2 is recommended for low loads, F=100 N and F=200 N, for point contacts. Study should be completed with the same investigation in severe regime where nano-additives should improve seizure limit of load. [ABSTRACT FROM AUTHOR]

The addition of nanoparticles to lubricant is effective for the reduction of wear and friction in the mechanical system. In this research, the effects of additions of copper oxide nanoparticle nanoparticles on lubrication behavior of biodiesel-diesel fuel blends were investigated by using a four-ball tester. Three fuel blends with the addition of 0, 25, 50 and 75 ppm nanoparticle were tested in steady-state conditions at four different rotational speed of 600, 1200 and 1500 rev/min. the results showed that the friction coefficient decreases with the increase in nanoparticles up to 50 ppm because of filling the friction surface with the nanoparticles and replacement of sliding friction with the rolling effect in the contact zone. On the other hand, the FC was enhanced significantly with 75 ppm nanoparticle addition in fuel blends B10 and B20. However, the results showed that the lubrication of fuel blend B50 with the 75 ppm nanoparticle is better than that of other fuel blends in the same situation. Moreover, it was found that with an increase in biodiesel concentration the friction coefficient was reduced due to free fatty acids, monoglycerides, and diglycerides as the components of biodiesel.

Due to environment concern, the current lubricant such mineral oil-based lubricant is not environmentally friendly as it were not readily biodegradable and toxic. Therefore, the vegetable oil-based lubricant has been promoted in order to replace mineral oil-based. In this study, the performance of lubricant for six different ratios between RBD Palm Olein and Semi-Synthetic oil were tested in different loads and been discussed in different parameters including coefficient of friction, wear scar diameter, surface roughness, flash temperature parameter and wear worn surface. Four-ball tribotester machine used to evaluate performance of sample lubricants using ASTM D4172 standard. From the results, it shows that the sample lubricants for engine oil mixing with RBD Palm Olein reduce in 38% of coefficient of friction compared to pure engine oil. From overall of the results, the performance of lubricant was improved as RBD Palm Olein mixing with engine oil.

The extreme pressure (EP) behavior of grease is related to its additives that can prevent seizure. However, in this study following ASTM D2596 four-ball test method, the EP behavior of greases was modified without any changes to its additive package. A four-ball tester with position encoders and variable frequency drive system was used to control the speed ramp up time or delay in motor speed to demonstrate higher grease weld load and lower grease friction that were fictitious. A tenth of a second delay in speed ramp up time had showed an increase in the weld load from 7848 N to 9810 N for grease X and 6082 N to 9810 N for grease Y. Further increase in the speed ramp up time to 0.95 s showed that the greases passed the maximum load of 9810 N that was possible in the four-ball tester without seizure. The mechanism can be related to the delay in rise of local temperature to reach the melting point of steel required for full seizure or welding, that was theoretically attributed to an increase in heat loss as the speed ramp-up time was increased. Furthermore, the speed ramp up time increased the corrected load for grease X and Y. This resulted in lower friction for grease X and Y. This fictitious low friction can be attributed to decrease in surface roughness at higher extreme pressure or higher corrected load. This study suggests that speed ramp up time is a critical factor that should be further investigated by ASTM and grease manufacturers, to prevent the use of grease with fictitious EP behavior.

The addition of nanoparticles to lubricant is effective for the reduction of wear and friction in the mechanical system. In this research, the effects of additions of copper oxide nanoparticle nanoparticles on the lubrication behavior of biodieseldiesel fuel blends were investigated by using a four-ball tester. Three fuel blends with the addition of 0, 25, 50 and 75 ppm nanoparticle were tested in steady-state conditions at four different rotational speed of 600, 1200 and 1500 rev/min. the results showed that the friction coefficient decreases with the increase in nanoparticles up to 50 ppm because of filling the friction surface with the nanoparticles and replacement of sliding friction with the rolling effect in the contact zone. On the other hand, the FC was enhanced significantly with 75 ppm nanoparticle addition in fuel blends B10 and B20. However, the results showed that the lubrication of fuel blend B50 with the 75 ppm nanoparticle is better than that of other fuel blends in the same situation. Moreover, it was found that with an increase in biodiesel concentration the friction coefficient was reduced due to free fatty acids, monoglycerides, and diglycerides as the components of biodiesel. [ABSTRACT FROM AUTHOR]

The present work deals with the study of tribo-pair interaction in lubricated sliding contacts. By considering the environmental issues, the sunflower oil was extracted from the sunflower seeds and used as a base lubricant. The two types of the nanoadditives, i.e., CuO and CeO2, varying concentrations from 0.10 to 0.50% w/v were used to formulate the nanolubricants. The compatibility/synergism of the nanoadditives was examined from antifriction and antiwear behavior study with four-ball tester. Also, sunflower oil was modified by the chemical method to improve its fatty acid structure. A comparative tribological and compatibility study was also done in modified oil at similar concentration levels with both types of nanoparticles. The tribological test result exhibits 0.10% w/v concentration of the nanoadditive as optimum due to lowest wear scar and coefficient of friction. Higher concentration of the nanoparticles impaired the base oil performance. Different analytical tools were used to characterize the oil modification and worn surfaces. Moreover, the role of subsurface of the contacting material with the tribological performance has been reported. [ABSTRACT FROM AUTHOR]

Magnesium-doped zinc oxide (Zn0.92Mg0.08OO) (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 (l), 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 sizedependent. 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. [ABSTRACT FROM AUTHOR]

The environmental problems that are being caused by the mineral-based lubricants has prompted for exploring the possibility of using vegetable-based oil as a lubricant and this has become a worldwide trend. In the present study, the tribological behavior of the chemically modified rapeseed oil has been studied by using a four-ball tester. The CuO and CeO2 nanoparticles of size less than 50 nm were added to the chemically modified rapeseed oil ranging from 0.1 to 1 wt%. And the friction and antiwear properties were analyzed as per the ASTM standard D4172. The size of the nanoparticles was calculated qualitatively by using Scherrer equation with the help of X-ray diffraction analysis. Tribological results showed that the chemically modified rapeseed oil has good antiwear and friction-reducing properties than the raw rapeseed oil. The addition of oxide nanoparticles at an optimum concentration in the chemically modified rapeseed oil showed the good friction-reducing property nonetheless not good antiwear property. The surface topography of the worn ball surfaces was also studied by using a scanning electron microscope. [ABSTRACT FROM AUTHOR]

Bio-oil from fast pyrolysis of biomass is a low-grade liquid fuel, which can be upgraded through the emulsification with diesel oil. In this study, we prepared two rice husk bio-oil samples with different solid char contents and three bio-oil/diesel-oil emulsion samples with the bio-oil content of 10 wt%, 30 wt% and 50 wt%, respectively. The lubrication properties of these oil samples were evaluated by a four-ball tester. The morphologies of the worn ball surface were observed by scanning electron microscope (SEM). The chemical states of the elements on the worn surface and non-worn surface were analyzed by X-ray photoelectron spectroscope (XPS). The results showed that the bio-oil possessed better extreme-pressure, anti-wear and friction-reducing properties than the commercial diesel oil (number zero). The solid char particles in the bio-oil could improve its lubrication performance. Moreover, the lubrication ability of the emulsions would be enhanced with the increasing of the bio-oil content in the emulsions.

A low cost Machine Grease−2 has too poor anti-seizure properties to be used for lubrication of rolling bearings. To enhance its anti-seizure properties, a mixture of copper oxide, glycerol and ethyl alcohol was introduced into its volume in different proportions and examined using a four-ball tester. The aim of the study was to provide an answer to the question whether the copper oxide, in the mixtures proposed above, would undergo reduction to metallic copper to act as a solid lubricant in Machine Grease−2. These AES and XPS analyses showed the presence of metallic copper in the adlayer formed on the surface of tested balls, which resulted in a three- or fourfold increase in seizure resistance in comparison with pure Machine Grease−2. This confirms that, under the conditions of friction in the tester, copper oxide reduces to metallic copper which works as a solid lubricant. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Bio-oil from fast pyrolysis of biomass is a low-grade liquid fuel, which can be upgraded through the emulsification with diesel oil. In this study, we prepared two rice husk bio-oil samples with different solid char contents and three bio-oil/diesel-oil emulsion samples with the bio-oil content of 10 wt%, 30 wt% and 50 wt%, respectively. The lubrication properties of these oil samples were evaluated by a four-ball tester. The morphologies of the worn ball surface were observed by scanning electron microscope (SEM). The chemical states of the elements on the worn surface and non-worn surface were analyzed by X-ray photoelectron spectroscope (XPS). The results showed that the bio-oil possessed better extreme-pressure, anti-wear and friction-reducing properties than the commercial diesel oil (number zero). The solid char particles in the bio-oil could improve its lubrication performance. Moreover, the lubrication ability of the emulsions would be enhanced with the increasing of the bio-oil content in the emulsions. [ABSTRACT FROM AUTHOR]

Abstract: Four-ball testers are widely used for determining the rolling contact fatigue life of bearing components. The tester simulates the rolling conditions in the bearing where the upper ball and the cup simulate the inner and outer rings, respectively, and the planetary balls represent the rolling elements in the bearing. However, in many studies the upper ball is utilized as the ball whose rolling contact fatigue (RCF) life is investigated, mainly to speed up the fatigue process. In this paper, a four-ball tester is used to study the effect of ball configuration, i.e. upper ball versus the planetary ball, on the RCF life. It was observed that the 52100-steel upper ball''s L 10 life is 7.4 times shorter than that of 52100-steel lower planetary balls. For M50 tool steel, the L 10 life of the upper ball was 5.9 times shorter than that of the lower planetary ball. The lesser number of stress cycles per revolution of tester''s spindle and the skid of lower balls resulting in rolling on multiple rolling tracks are the contributing factors to the longer RCF life of planetary balls. [Copyright &y& Elsevier]

Abstract: The fatigue life of all-steel and silicon nitride–steel ball combinations with a focus on the fatigue life of the steel components was experimentally studied using a four-ball tester. The rolling contact fatigue (RCF) tests were conducted according to the IP-300 standard with a rotational speed of 10,000rpm. The L10 of the AISI M50 tool steel components rolling against silicon nitride (Si3N4) balls were observed to be 6 times shorter than that of all-M50 steel bearing configurations. Also, the L10 life of the AISI 52100/Si3N4 combination was 2.3 times shorter than the L10 of all-AISI 52100-steel systems. Since the RCF life of a rolling system is determined by the life of its first component to fail, the steel/silicon nitride hybrid rolling combinations’ overall advantage over all-steel ones using the currently used steel bearing materials such as AISI 52100 and M50 is questionable. [Copyright &y& Elsevier]

Abstract: Two ashless and non-phosphorus hydroxyl-containing dithiocarbamate-triazine compounds, 2,4,6-tri[N,N-di-n-butyldithiocarmate-(2′-hydroxyl)-propionylthio]-1,3,5-s-triazine (LDBA) and 2,4,6-tri[N,N-di-i-octyldithiocarmate-(2′-hydroxyl)-propionylthio]-1,3,5-s-triazine (LDIOA), were prepared and their tribological behaviors as additives in rapeseed oil (RSO) were evaluated using a four-ball tester. Thermal degradation tests were conducted to identify their thermal stabilities using a thermo-gravimetric analyzer. The worn surfaces of the steel balls were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy (XPS). The results indicate that the additives possess high thermal stabilities and good load-carrying capacities. Moreover, they both have good anti-wear and friction-reducing property at relatively high concentration (>1.5wt%) and under all test loads. The results of XPS analyses illustrate that the prepared compounds as additives in RSO forms a protective film containing inorganic sulfide, sulfate, oxidized compounds and organic nitrogen-containing compounds on the metal surface during the sliding process. [Copyright &y& Elsevier]

Abstract: Increased concerns about environmental damage caused by mineral oil based lubricants, has created a growing worldwide trend of promoting vegetable oil as base oil for automobile lubricants. Coconut oil, which is abundantly available in southern states of India, is reportedly being widely used as two-stroke engine lubricant (2T oil) by autorikshaw 1 [1] A tri-wheeled three seated vehicle powered by two stroke air cooled engine used as a taxi in India. drivers. A survey among the users of coconut oil as 2T oil brought forth complaints of increased engine wear. This paper presents tribological properties of coconut oil evaluated using a four-ball tester and a test rig to test the wear on two stroke engines. The influence of an antiwear/extreme pressure (AW/EP) additive on the tribological performance of coconut oil was also evaluated experimentally. The addition of the AW/EP additive has brought about considerable reduction in wear with coconut oil as 2T oil. [Copyright &y& Elsevier]

Three S-(1H-benzotriazole-1-yl) methyl N,N-dialkyldithiocarbamates were synthesized and their tribological behaviors as additives in rapeseed oil (RSO) were evaluated using a four-ball tester. Thermal degradation tests were conducted to identify their thermal stabilities using thermogravimetric analyzer (TGA). The worn surface of the steel ball was investigated by X-ray photoelectron spectroscopy (XPS). The results indicate that the additives possess excellent load-carrying abilities and high thermal stabilities, but have no antiwear and friction-reducing properties. Based on the results of XPS analysis, it can be seen that tribochemical reactions occur between the synthesized compounds and metal surfaces during the sliding process. [Copyright &y& Elsevier]

The extreme pressure (EP) behavior of grease is related to its additives that can prevent seizure. However, in this study following ASTM D2596 four-ball test method, the EP behavior of greases was modified without any changes to its additive package. A four-ball tester with position encoders and variable frequency drive system was used to control the speed ramp up time or delay in motor speed to demonstrate higher grease weld load and lower grease friction that were fictitious. A tenth of a second delay in speed ramp up time had showed an increase in the weld load from 7848 N to 9810 N for grease X and 6082 N to 9810 N for grease Y. Further increase in the speed ramp up time to 0.95 s showed that the greases passed the maximum load of 9810 N that was possible in the four-ball tester without seizure. The mechanism can be related to the delay in rise of local temperature to reach the melting point of steel required for full seizure or welding, that was theoretically attributed to an increase in heat loss as the speed ramp-up time was increased. Furthermore, the speed ramp up time increased the corrected load for grease X and Y. This resulted in lower friction for grease X and Y. This fictitious low friction can be attributed to decrease in surface roughness at higher extreme pressure or higher corrected load. This study suggests that speed ramp up time is a critical factor that should be further investigated by ASTM and grease manufacturers, to prevent the use of grease with fictitious EP behavior. [ABSTRACT FROM AUTHOR]

• A novel synthesis of FCS/GNP hybrid has been reported. • The formation of hybrid was confirmed using SEM, TEM and Raman spectroscopy. • The tribological performance of the hybrid was investigated using a four ball tester. • An 18% reduction in coefficient of friction was obtained for the FCS/GNP hybrid-2 (10:1) in neat oil. A novel synthesis method of Functionalized Carbon Spheres (FCS) coated with Graphene nanoplatelets (GNP) using a simple sonication technique is reported. The FCS/GNP hybrid nanoparticles were found to be effectively improving the tribological characteristics of lubricating oils. For the synthesis of FCS, Carbon Spheres (CS) synthesized via non-catalytic chemical vapor deposition was functionalized using nitric acid. The hybrid nanoparticles were characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Raman spectroscopy. The tribological behavior of CASTROL-20 W 40 engine oil dispersed with different concentrations of FCS and GNP using ultrasonication was investigated using a four-ball tester. The tribological behavior of FCS and GNP were investigated separately to compare the tribological performance of the FCS/GNP hybrid nanoparticles. The neat oil dispersed with 0.275 wt% of FCS/GNP hybrid nanoparticles in 10:1 ratio shows excellent dispersion and stability for 30 days without the addition of any surfactant. The results indicate that the addition of these hybrid nanoparticles causes a remarkable reduction (~18%) in the Coefficient of Friction (COF) of the neat oil. The optical image of wear scar on the ball immersed in neat oil shows a significant reduction in the Wear Scar Diameter from 425.6 µm to 390.0 µm with the addition of hybrid nanoparticles. The Raman mapping of the wear scar on chromium steel ball reveals that the FCS/GNP hybrid nanoparticles remain unseparated after the tribology test. [ABSTRACT FROM AUTHOR]