Axle gear oils: Friction behaviour under mixed and boundary lubrication regimes (original) (raw)
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Axle gear oils: Friction, wear and tribofilm generation under boundary lubrication regime
Tribology International, 2017
The internal friction torque measurements in Cylindrical Roller Thrust Bearings (RTB) lubricated with axle gear oils under boundary film conditions were performed using an axial rolling bearing test rig generating tribofilms. The X-ray photoelectron spectroscopy (XPS) was used to characterize the tribofilms formed on the bearing rollers and raceways. After the tests, wear debris were found on the oil samples which lubricated the surface of the roller bearing raceways for that surface topography measurements and oil analysis (ferrography) were mandatory to measure and to visualize the occurring wear. The results obtained indicate that axle gear oil formulations and their additive packages have got a significant influence in controlling roller bearing friction and wear under boundary film lubrication.
Axle gear oils: Tribological characterization under full film lubrication
Tribology International, 2017
The tribological properties of five axle gear oils are characterized. Three oils (75W90-A, 80W90-A and 75W140-A), available on the market and labelled as "Fuel Efficient", were selected together with two candidate products (75W85-B and 75W90-B). Their viscosity, film generation and traction properties were measured for three different temperatures under full film lubrication regime. The product formulation and the measured properties promote significant differences under full film lubrication. The film thickness is directly related with the Lubricant Parameter while the traction coefficient depends on the base oil and it decreases with the increase of Viscosity Index and the decrease of Piezoviscosity. So, new lubricants with lower viscosity but holding high VI and low Piezoviscosity are promising for this application.
Friction torque in rolling bearings lubricated with axle gear oils
Tribology International, 2018
As a part of the main research project within the aim of increasing significantly drive axle efficiency, this work focuses on rolling bearing friction torque lubricated with five fully formulated axle gear oils with different viscosity and different formulations. The lubricant tribological behaviour in different rolling bearings was analyzed. A modified Four-Ball Machine was used to test the rolling bearings. The effect of speed, temperature and axial load on rolling bearing friction torque was assessed. Experimental results for the internal friction torque were validated with an SKF model. Direct comparisons in terms of friction torque between axle gear oils when they are lubricating different rolling bearing types are presented and discussed.
Tribotest, 2003
The antiwear and extretnc-pressure properties of six dgerent types of additi7ap (ttiolybdenzini dialkyldithiophosphute, dibenzyl clisulphide, tnolybdtmtti diulkyldithiocurbunzute, zinc diulkylciithioy~hosy~hate, chlorinated paraffin 7 i m , and triaryl pkosphatc) 71~eri~ er~aliiated by stanriard four-ballfriction and 71mr tests. This 7ms fullo7i~d by scanning electron microscopy (S E M) , X-ruy photoelectron spcctroscopy (XPS), iznd X-ray photoelectron itnaging (X P I) analyses of the roorn stiflaces to detrrinine tkc sfrtictiire of the boiindury liibrication filnz und the tnechanistiz of the tribocheniical reaction occurring diiring the friction process. The presence of the udditi7~es in tkP base oil significantly increased the 7 1 d d load and drastically rediiced the 7iiear-scar diutiieter, suggesting antiwear and extrenie-pressiiri. propertitJs of the additiaes. The enkanccd anti7ilear and loadcarrying capacity of the additizle-containing oils 711~s attributed to tke fortnation of a cotnplex botindary lubricationfilni formed bet7ueen the siiyfiices diiring the friction process as a restilt of the tribocheniicul reaction. Thc antiiiwar and extrenic-presstire properties of the udditives 70ere explained based on the X P S iiatu. The studies indicated that tkc lubricating properties of the udditi7)es depend on their chemical nutiire and re-a~fi7)ity 7i)itk metal siiYfUct7s.
Journal of Tribology, 2021
To extend drain intervals and improve efficiency, new engine oils with increased dispersant concentration and reduced viscosity are required. Low viscosity engine oils can increase the prevalence of boundary friction at low temperature and increase its severity at higher temperatures. As a result, combinations of organic and inorganic friction modifiers (FM) will be used to reduce boundary friction across a range of temperatures, also preventing damage to vehicle catalysts. This paper presents an experimental case study of such new generation of fully-formulated engine lubricants with varying concentrations of polyisobutylene succinimide dispersant, organic and inorganic FM. Representative conditions pertaining to those encountered at the top dead centre reversal of the piston compression ring-cylinder liner contact are created, and the generated friction measured through use of a sliding-strip tribometry. Subsequently, X-Ray Photoelectron Spectroscopy (XPS) is used to determine the composition of the formed surface tribofilms in order to explain the observed frictional characteristics. The key interactions and frictional behaviour of the dispersant and friction modifiers are highlighted across a range of operating temperatures.
Multiscale friction in lubricant-surface systems for high-performance transmissions under mild wear
The lubricant-surface system is complex in nature and can significantly affect the frictional performance of high-performance transmission systems. The complexity stems from the coupled mechanical and chemical phenomena that occur at the inter-facial tooth conjunctions. A combined analytical and precision experimental approach is presented to analyse the salient parameters of the lubricant-surface system. A multiscale procedure comprising topographical measurement, pin-on-disc tribometry, atomic force microscopy in lateral force mode, X-ray photo-electron spectroscopy and continuum contact mechanics analysis under mixed non-Newtonian thermo-elastohydrodynamics is used to describe the formation of a tribo-film, as well as wear and frictional characteristics of the lubricant-surface system. The contribution of chemisorbed and physisorbed bonded tribo-film on the boundary coefficient of friction is ascertained at different physical scales. Therefore, the paper presents a novel multiscale analysis, promoting improved understanding of the complex interactions between mechanisms of friction, wear and surface chemistry. Keywords Gear · Tribo · Film · Additive · ZDDP · AFM · Atomic force microscopy · Wear · Friction
Lubricants, 2014
The role of surface protective additives becomes vital when operating conditions become severe and moving components operate in a boundary lubrication regime. After protecting film is slowly removed by rubbing, it can regenerate through the tribochemical reaction of the additives at the contact. However, there are limitations about the regeneration of the protecting film when additives are totally consumed. On the other hand, there are a lot of hard coatings to protect the steel surface from wear. These can enable the functioning of tribological systems, even in adverse lubrication conditions. However, hard coatings usually make the friction coefficient higher, because of their high interfacial shear strength. Amongst hard coatings, diamond-like carbon (DLC) is widely used, because of its relatively low friction and superior wear resistance. In practice, conventional lubricants that are essentially formulated for a steel/steel surface are still used for lubricating machine component surfaces provided with protective coatings, such as DLCs, despite the fact that the surface properties of coatings are quite different from those of steel. It is therefore important that the design of additive molecules and their interaction with coatings should be reconsidered. The main aim of this paper is to discuss the DLC and the additive combination that enable tribofilm formation and effective lubrication of tribological systems.
Influence of tribofilms on failures and friction of gears with particular focus on running-in
Industrial Lubrication and Tribology, 2019
Purpose This paper aims to address the influence of tribofilms and running-in on failures and friction of gears. The operation regime of gears is increasingly shifted to mixed and boundary lubrication, where high local pressures and temperatures occur at solid interactions in the gear contact. This results in strong tribofilm formation due to interactions of lubricant and its additives with the gear flanks and is related to changes of surface topography especially pronounced during running-in. Design/methodology/approach Experiments at a twin-disk and gear test rig were combined with chemical, structural and mechanical tribofilm characterization by surface analysis. Pitting lifetime, scuffing load carrying capacity and friction of ground spur gears were investigated for a mineral oil with different additives. Findings Experimental investigations showed a superordinate influence of tribofilms over surface roughness changes on damage and friction behavior of gears. Surface analysis of...
Reducing Wear and Friction by Means of Lubricants Mixtures
Procedia Engineering, 2013
In this study, two types of lubricants are mixed together in order to maximize wear reduction. Various compositions of mixtures are compared in terms of viscosity index, coefficient of friction and wear scar diameter. Heavy duty engine oil (HDEO) and automatic transmission fluid (ATF) have been used a lubricant condition. The standard procedures used in this study are ASTM D2270 for viscosity test method and ASTM D4172 for four balls tribology test method. Mixture of HDEO and ATF produces better friction resistance as compared to the original HDEO. The benefit of ATF can be used for engine lubrication.