Effect Of Lubricant Additives Research Articles

Effect of lubricant additives of Cu, Fe and bimetallic CuFe nanoparticles on tribological properties

Friction and wear reduction are widely sought to promote energy savings and reliability of moving machine components. Here, a combination of MST2 experiments and molecular dynamics (MD) simulations unveils the detailed lubrication mechanisms and presents quantitative wear descriptions of Cu and Fe nanoparticle (NP). The MD simulations results indicate that average value of friction force is reduced approximately 57.15% after the addition of Cu NP and these results is similar to the experimental results. In addition, bimetallic CuFe NP (Cu–Fe or Cu@Fe NP) shows superior performance than pure Cu NP, and the tribological properties of bimetallic CuFe NP change with structures. Bimetallic CuFe NP can be prepared and investigated by experimental methods, but the effects of different structures of bimetallic CuFe NP on lubrication are not sufficiently studied. The superior structure of bimetallic CuFe NP with higher load-carrying capacity and better tribological properties is predicted by MD simulations. Results from simulations suggest that there is an optimal NP structure and size that will minimize friction and wear for a given surface roughness.

Double-Layered Porous Rayleigh Step Slider Bearings Lubricated with Couplestress Fluids

Objective: To examine the performance of double-layered porous Rayleigh step slider bearings lubricated with couple stress fluid and to compare it with the performance of single layered porous Rayleigh step bearing. Methods: Based on the Stokes micro continuum theory of couple stress fluids, the modified Reynolds equation governing fluid film pressure is derived. Its analytical solution is and the closed form expressions for the fluid film pressure, frictional force and load carrying capacity are obtained. Findings: The numerical results for bearing characteristics such as pressure, load carrying capacity, frictional force are plotted graphically to study the effect of doublelayered porous facing. The effect of permeability of the porous layer is to decrease the load carrying capacity as it gives an easy path for the lubricant to pass through. This adverse effect can be compensated by introducing double layered porous facing with different permeabilities and the results presented here in this paper clearly shows the increase in load carrying capacity and decrease in co-efficient of friction for the double layered porous bearings as compared to that of single layered porous bearings. Novelty: Original research was conducted on double-layered porous Rayleigh step slider bearings with couple stress fluid by considering the effects of lubricant additives in the porous region and the results are compared with that of single layered porous bearings. Keywords: Rayleighstep slider bearing; permeability; Doublelayered porous; couple stress fluid Microcontinuum

Tribological properties of MoS2 and CaF2 particles as grease additives on the performance of block-on-ring surface contact

Recently, the performance effects of lubricant additives on greases have been actively investigated. In order to improve their properties of anti-friction, load-carrying capacity, wear resistance, corrosion resistance, and temperature-enhancing, some additives are added to greases. Determining the appropriate additive ratios is one of the most important research topics in tribology. In this study, friction, wear, and contact temperature were analyzed by adding MoS2 and CaF2 additives to the lithium soap grease. The experiments were carried out at different revolutions (200, 500 and 800 rpm), additive ratios (0.25, 0.5, 1, 1.5 and 2 wt%) and contact loads (72, 108 and 144 N) using a block-on ring tester. The structure and morphology of additives analyzed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of additives on surface morphology and roughness were also characterized with the scanning electron microscopy (SEM) and profilometer. In addition, energy dispersive spectrometry (EDS) was used to detect the elements present on the wear scar surfaces. Results reveal that the MoS2 and CaF2 additives can improve the wear resistance of lithium grease and reduce the friction coefficient. In this experimental study, suitable additive ratios that are anti-wear and friction-reducer were found to be in the range of 1–1.5 wt% for both additives. Besides, both additives continued their friction-reducing characters at over the room temperatures. While the MoS2 additive oil gives the lowest friction and wear values, the same ratio of CaF2 additive oil shows a more stable operation.

Effects of lubricant additives on tribological properties of poly-acetal under boundary lubrication

The objective of this study was to elucidate the effect of lubricant additives on the tribological properties of poly-acetal (POM) and steel materials under boundary lubrication. To investigate the effects of lubricant additives on the tribological properties of POM and structural changes at the friction interface, friction tests and surface analyses were conducted using friction modifiers and anti-wear additives among the lubricant additives under uniform atmosphere conditions other than the additives. The test materials used were POM ring specimens and S45C discs as mating materials. This test was conducted using a ring-on-disk friction test configuration in which the POM ring was rotated by a motor while the POM ring was pressed against the S45C disc at a constant load. As a result, it was found that lubricant additives inhibited the friction-reducing effect of POM regardless of the type of additives. In addition, it was inferred that the friction-reducing effect of POM was due to the POM transfer film formed on the steel material.

Performance evaluation of esters and graphene nanoparticles as an additives on the rheological and lubrication properties of water-based drilling mud

In the practice of drilling horizontal, directional, and unstable well profiles, the friction produced by bit balling, wellbore instability, cavings, and dog-legs resulted in excessive torque and drag. The friction along with high torque and drag, which results from the drill string, casing, and wellbore contact, leads to pipe stucks, overpulls during tripping-outs, and even closure of the oil and gas well. Heat generated from metal contact between casing and drill string is the cause of wear of drill string and casing. Oil-based drilling fluids are identified to produce minimum friction and torque than that of water-based drilling fluid/mud (WBM). However, the use of oil-based drilling fluids is becoming obsolete due to stringent environmental regulations. Therefore, it is critical to identify and design a water-based drilling mud with lubricant additives that are environmentally friendly, cost-effective, and give better lubrication similar to oil-based and synthetic-based drilling fluid. The objective of this study is to investigate the effect of two additives PC60 (the product of the reaction of glycerol ​+ ​tall oil fatty acid) and graphene nanoparticles on the rheological and lubrication properties of water-based drilling fluid. All together total 14 drilling fluid samples have been prepared for the detailed analysis. Extensive experimental work has been done to study the effect of lubricant additives (PC60 and graphene nanoparticles) on the rheology and lubrication of various WBMs with different additive concentrations (1, 2, and 3% by volume) at 30, 60, and 90 ​°C. All samples were investigated for their rheology, viscoelastic behavior, and lubrication properties before and after hot rolling. The experimental data generated in this work have been successfully utilized to find various fitting parameter for the Bingham plastic rheological model, followed by a discussion on foaming tendency of the samples and effect of pH on the rheological stability of drilling fluid. Subsequently, a relationship between the coefficient of friction (in the presence of different lubricant additives in the mud) and rheological properties (plastic viscosity and yield point) of different drilling fluid samples have been proposed. • Rheological/lubrication properties of water-based drilling muds (WBMs) investigated. • The effect of two additives ester and graphene nanoparticles on WBM studied. • Ester-based WBMs shown better rheological performance/stability after hot rolling. • A relationship between coefficient of friction and rheological properties proposed. • Ester-based WBMs exhibit more foaming tendency than nano-graphene-based WBMs.

Effect of Lubricant Additives on the Oxidation Characteristics of Diesel Engine Particulate Matter

Three common lubricant additives, including an antioxidant, detergent, and an antifoamer, were added to diesel fuel to perform a diesel engine bench test. Particulate matter samples underwent thermogravimetric analysis to investigate the effect of lubricant additives on the particulate matter oxidation process, characteristic temperature, and activation energy. The results showed the following. Different lubricant additives result in different variation trends in the thermogravimetric curve of a particulate matter sample by varying the rotating speed and torque. When the rotating speed was stable, as the torque increased, the ignition temperature of the particulate matter of Fuel C declined rapidly during the initial stage and then increased rapidly. When the torque was stable, as the rotating speed increased, the ignition temperature of the particulate matter of Fuel C increased initially and then declined. The particulate matter of Fuel C had the lowest level of activation energy at approximately 57.89 J·mol−1. The particulate matter of Fuel A had the highest level of activation energy at approximately 74.10 J·mol−1. When the fuel has a higher cetane number, the combustion chemical reaction rate is faster and results in a more complete reaction. The active substance contact surface increases, which facilitates particulate matter oxidation.

Effects of Lubrication and Temperature on the Tribological Behavior of a Magnesium Alloy under Contact Sliding

This paper aims to experimentally investigate the effects of lubrication and temperature on the tribology behavior of a magnesium alloy, AZ31B, sliding against 86CrMoV7. The effects of lubricant additives, including oil film improver and extreme pressure (phosphorous donors), on the friction coefficient and surface morphology in the sliding zone were studied. It was found that the relatively lower surface hardness of the material significantly affects the wear of the materials in the sliding zone. The lubricant with oil film improver and extreme pressure can reduce friction. Temperature rise brings about lower friction due to the lubricant additives.

The multiple roles of a chemical tribofilm in hydrogen uptake from lubricated rubbing contacts

A newly developed in-situ technique has been employed to investigate the effect of lubricant additives and water contamination in oil on hydrogen intrusion into the steel. Hydrogen in oil-lubricated contacts is generated as a result of tribochemical reactions. The hydrogen uptake measurement results indicated that tribofilm formation can impede hydrogen ingress, in the substrate, by impeding the formation of fresh metal surfaces. This reduces the generation of hydrogen atoms by preventing the decomposition of hydrocarbon molecules. A uniform tribofilm across the wear track also acts as a physical barrier for hydrogen permeating through the tribo-contact. The water contamination in the oil negatively influenced tribofilm properties and therefore led to higher permeation of hydrogen into the steel.

The effect of lubricant additives on the tribological performance of oil and gas drilling applications up to 200 °C

Abstract Adding lubricant additives is a predictable method to decrease the frictional resistance in oil and gas drilling applications. In this work, tribological studies were carried out for drilling fluid with/without lubricant additives at different temperatures up to 200 °C and environmental pressure of 3.45 MPa. In pure fluid, additive A exhibited higher load capacity, compared to additive B at 200 °C. In drilling fluid, at 75 °C, all additives decreased the COF. However, at 125 °C and 175 °C, the additives did not decrease the COF but decreased the standard deviation of the COF values. SEM/EDS analyses were used to investigate the wear mechanisms and it was deduced that the viscosity of the drilling fluid played an important role in determining the friction and wear performance.

Effect of lubricant additives on the tribological behavior of aluminum alloy against steel

Abstract This study aims to understand the impact of various lubricant additives on the friction- and wear behavior of aluminum alloys against steel. Employing the aluminum alloy Al 6061 and the steel AISI E 52100 as representatives, we studied the effects of the main additives typically found in fully formulated lubricants individually by formulating model lubricants consisting of base oil and just one additive at a time. The additives we studied include sulfurized olefin, complex alkyl phosphate amine, alkyl phosphite, overbased calcium sulphonate, zinc dithiophosphate (ZDP), and calcium sulfonate detergents. For each model lubricant, as well as for the base oil and the fully formulated oil, we performed ball-on-disc experiments with aluminum alloy balls on steel discs. We obtained the friction coefficient, determined the wear volume of the aluminum alloy, and analyzed the composition of the wear surface. We found that all additives except calcium sulfonate detergents promote the formation of aluminum oxide. Among all individually tested additives, zinc dithiophosphate provides the best wear resistance, while sulfurized olefin provides the lowest friction. The lowest friction combined with the second lowest wear rate was actually observed for a fully formulated oil (containing an optimized mixture of several additives).

Effects of Lubricant Additives on Tribological Properties of DLC Films

Effects of Lubricant Additives on Tribological Properties of DLC Films

The Effect of Lubricant Additives on Hydrogen Permeation Under Rolling Contact

This study describes the effects of lubricant additives on the permeation of hydrogen into high-strength-bearing steel in rolling contact conditions. Oil-lubricated tests were conducted in a hydrogen atmosphere under high temperature/pressure. Trioctylphosphate and zinc dialkyldithiophosphate (ZDDP) were used as lubricant additives. Thermal desorption spectrometry (TDS) was performed to measure the amount of permeated hydrogen immediately after the rolling contact tests. TDS analysis suggested that ZDDP is very efficient at preventing hydrogen permeation into the substrate. Auger electron spectroscopy revealed the generation of a protective chemical tribofilm containing zinc, sulphur, oxygen and phosphorus at the interface. This tribofilm should be responsible for the lower rates of hydrogen permeation into the bearing steel.

Effect of Lubricant Additives on the WDLC Coating Structure When Tested in Boundary Lubrication Regime

Improvements in coating deposition technology enable the mass production of high-quality diamond-like carbon (DLC) coatings at an industrial scale and also increase their use in lubricated contacts. However, the understanding of the interactions of different lubricant additives with this material is not yet fully developed. This study focuses on several fundamental aspects of the tungsten-doped DLC coating (denoted as WDLC) behaviour under boundary lubrication conditions with model lubricants. The effect of lubricant additives on the coating structure change is discussed in terms of carbon structure and the tungsten dopant. Electron energy-loss spectroscopy, XPS and Raman spectroscopy characterization for the upper carbon layers indicate that the WDLC coating interacts chemically with selected lubricant additives. The study provides information on both coating and additive optimization under boundary lubrication.

Tribological performances of ZDDP and ashless triphenyl phosphorothionate (TPPT) as lubricant additives on Ti–N and Ti–Al–N coated steel surfaces

In recent years, there has been much attention on the effects of lubricant additives on the friction and wear properties of surface coatings. However, little research has been conducted to investigate the influence of antiwear additives on the tribological performances of titanium nitride (Ti–N) and titanium aluminium nitride (Ti–Al–N) coatings. It has been reported that introducing aluminium into Ti–N coatings enhanced their oxidation resistance. In this study utilising a pin on cylinder tribometer, lubricants containing zinc dialkyl dithiophosphate (ZDDP) or a more environmentally friendly alternative, ashless triphenyl phosphorothionate (TPPT), were used. Experimental results revealed that ZDDP and TPPT helped to reduce wear on both coatings through the formation of a tribofilm, although it was also found that both additives increased the friction coefficient on both surfaces. Based on overall findings, this paper suggests the use of TPPT as a suitable ZDDP replacement for providing wear protection on Ti–N and Ti–Al–N coatings.

Effect of ZDDP and ashless triphenyl phosphorothionate (TPPT) as lubricant additives on tribological performance of Cr–N coatings

In recent years, there has been significant attention paid to the effect of lubricant additives on the tribological properties of advanced surface coatings. However, not many research papers have addressed the influence of additives on the tribological performance of chromium nitride (Cr–N) coatings. In this study, lubricants containing zinc dialkyl dithiophosphate (ZDDP) or triphenyl phosphorothionate (TPPT) were used to conduct tribological tests based on a disc on cylinder tribometer. The wear scars formed on the Cr–N coated discs were analysed using surface sensitive analytical techniques such as field emission scanning electron microscope and energy dispersive X-ray spectroscopy. Results showed that both ZDDP and TPPT (to a lesser extent) enhanced friction reduction compared to pure base oil on the Cr–N surface. Results also indicated that both antiwear additives helped to improve wear protection on the Cr–N coating. At the same treat rate, TPPT gave better antiwear performance than ZDDP.

Lubricants for Metal Belt Continuously Variable Transmissions

This paper reviews the effects of lubricant additives and base stock used in metal belt continuously variable transmissions (CVT) fluids on the CVT transmission torque capacity. Additive formulation composed of phosphorus anti-wear agent, calcium detergent, and dispersant improved the friction coefficient between the metals. The analysis on the post-test surface suggests that the friction behavior strongly depends on the local morphology of the tribofilms derived from lubricant additives. Examining the effect of base stock on the torque capacity in actual belt CVTs revealed that SN (synthetic naphthene) exhibited 10% higher torque capacity than that of PAO (polyalphaolefin). It is believed that the difference in the torque capacity is due to the difference in the oil-film shearing force generated by the relative sliding between the belt and pulley.

Effect of Lubricant Additives on the Tribological Properties of Nanostripe Surfaces

Effect of Lubricant Additives on the Tribological Properties of Nanostripe Surfaces

Experimental study of the influence of a pour point depressant additive on particle size distributions in diesel engine exhausts

Many studies have been performed on diesel engine particulate matter emissions, but the influence of lubricants on emissions has only been considered a few times, and the effects of lubricant additives have yet to be investigated. We studied the influence of a pour point depressant additive (PPD) on particle emissions and particle size distributions from a four-cylinder turbocharged, inter-cooled engine with CF-4 15W-40 lubricant, using diesel or diesel containing the PPD. Changing the working conditions changed the number of particles emitted and the location of the peak particle size(s) emitted. The number of particles first increased and then decreased as the engine speed increased. Particle emissions were optimal at low engine speeds and high load, increasing with increasing engine speed.

Tribological Properties of Metal V-Belt Type CVT Lubricant

The priority for lubricant performance for metal V-belt-type CVT (B-CVTFs) should be the improvement of transmittable torque capacity between the belt and pulley plus excellent antishudder properties for lockup clutch used in B-CVTs. This study intends to investigate the effect of lubricant additives for improving these performances of B-CVTs. In addition, surface analysis techniques were utilized to gain a novel insight into the chemical composites and morphology of the tribofilms. As a result, it is vital for greater torque capacity to give higher boundary friction coefficient between the metal contacting interfaces, and the process of boundary lubricant film formation derived from antiwear additives used in B-CVTFs strongly impacts on the torque capacity. Moreover, it is found that a sort of lubricant formulation gave an excellent antishudder performance for wet clutch with keeping higher friction coefficient between the metals, which would result in improving the performance of B-CVTs.

Tribological performance evaluation of a hydrogenated diamond-like carbon coating in sliding/rolling contact – effect of lubricant additives

In this article, a systematic study is carried out to assess the influence of lubricant additives on the durability of a hydrogenated diamond-like carbon (DLC) coating under mixed rolling/sliding contact is provided. Experiments were performed in a mini traction machine using a DLC (15 at.% hydrogen) coated disc on an uncoated steel ball at 50 per cent sliding/rolling ratio and in a motorized cylinder head (Ford Zetec) cam/follower test rig. Five different lubricants containing zinc dialkyldithiophosphate (ZDDP) and/or friction modifiers (Moly Dimer (MD)/Moly Trimer (MT)) were used. This study reveals that the lubricant additives have a strong influence on the coating durability while ZDDP additive effectively reduces wear to extremely low levels. The addition of the MT additives only has a marginal effect on wear, whereas the MD additive substantially reduces the performance. The mechanisms by which the additives affect the wear in this ultralow-wear regime are discussed.