Anti-wear Properties Of Lubricants Research Articles

МОДЕРНИЗИРОВАННАЯ МАШИНА ТРЕНИЯ

The study objective is to increase the information value, accuracy and reliability of the experimental assessment results of extreme pressure and antifriction properties of the tested materials. A brief analysis of the work on the creation of test tribo-technical equipment is given. The difference between the designs of friction machines for testing using Reichert and Timken tests is shown. The design of an upgraded friction machine for determining extreme pressure, antifriction and anti-wear properties of lubricants is presented. In the proposed installation, the radial force on the friction unit ("roller - ring" or "bar – ring") is generated by a mechanism of even loading, and the assessment of extreme pressure lubricants is determined at the moment of gripping the rubbing samples, at which the motor shaft stops. As a result of upgrading the machine, it became possible to measure the friction force, the normal load and to read the friction factor, both for the lubricants under study and for friction pairs consisting of structural and instrumental materials. The results of comparative tests on the upgraded friction machine for lubricating and cooling liquids with different contents of extreme pressure, antifriction and anti-wear additives are presented. 
 A new friction machine design based on Reichert machine is developed, which allows testing structural and lubricating materials for friction and wear using both Reichert and Timken tests. At the same time, the accuracy of determining tribo-engineering characteristics of the tested materials is increased. It is found that as a result of equipping the friction machine with an even loading system and force measuring sensors, it becomes possible to determine extreme pressure and anti-friction properties of lubricants and structural materials, as well as to estimate the value of the friction factor.

Viscosity Variations and Tribological Performances of Oleylamine-Modified Fe3O4 Nanoparticles as Mineral Oil Additives

In order to improve the flowabilities and anti-friction and anti-wear properties of lubricants, the viscosity variations and tribological performances of oleylamine-modified Fe3O4 nanoparticles as mineral oil additives were systematically investigated via rotational parallel plate rheometer, ball–disc reciprocating tribometer, non-contact three-dimensional surface profiler, scanning electron microscope, energy dispersive X-ray spectrometer and X-ray photoelectron spectroscopy. Spherical monodisperse Fe3O4 nanoparticles were synthesized and dispersed into mineral oils to obtain lubricants with mass fractions of 1%, 3%, 5%, 8%, 10% and 20%, respectively. These lubricants have excellent stabilities within 12 months. Interestingly, the dynamic viscosity and kinematic viscosity of the lubricants first decrease and then increase with the increase in Fe3O4 content, and the lubricants’ viscosity is at a minimum when the mass concentration is 5%. The tensile curves also show that with the mass fraction increase, the lubricants’ tackiness and adhesion have the same change law, and both reach the lowest point when the mass concentration is 5%. Meanwhile, Fe3O4 nanoparticles can improve the tribological properties of the base oils. It is worth noting that the maximum reduction in the wear volume at 25 °C is up to 93.8% compared with base oils when the additive concentration of the Fe3O4 nanoparticles is 5 wt%.

Improving of the tribological properties of attapulgite base grease with graphene

AbstractWith the rapid development of industry, individuals paid increasing demanding on the friction‐reducing and antiwear properties of lubricants under harsh service conditions. Here, the attapulgite base grease and attapulgite greases with grephene were successfully synthesised. The tribological behaviours of the greases were comparatively investigated using a SRV‐IV tribometer with the ball‐on‐disk configuration. The results show that the attapulgite grease with graphene presents better friction‐reducing and antiwear properties than the attapulgite base grease, especially at high load, frequency and temperature. The friction‐reducing and antiwear mechanism was determined through the analysis of worn surfaces and tribofilms formed on it. The results revealed that a tribofilm composed with Fe, Fe3C, Fe2O3, FeOOH, Al2O3, SiO2, graphene, attapulgite and organic compounds was formed on the worn surface, which is responsible for the excellent tribological properties of the attapulgite grease with graphene. Thus, as‐prepared attapulgite grease with graphene shows great potential in the lubrication for mechanical equipment operated under harsh conditions.

PH‐dependent lubrication mechanism of graphene oxide aqueous lubricants on the strip surface during cold rolling

The tribological performance and lubrication mechanism of graphene oxide (GO) aqueous lubricants with different pH levels on the strip surfaces during cold rolling were investigated. And triethanolamine (TEA) was used to adjust the pH levels of GO lubricants. The morphology of GO and physical characterization of GO lubricants were carried out. Four‐ball tribological tests and cold rolling experiments were conducted to obtain the tribological behaviors of GO lubricants on the strip surfaces. To figure out the lubrication mechanism, the surfaces of the rolled strips using GO lubricants were analyzed utilizing a series of experiments. The increase in the pH value of lubricants changed the intrinsic structure of GO, resulting in better dispersibility and wettability. The change of physical characteristics significantly improved the antifriction and antiwear properties of lubricants, and the alkaline lubricant (pH 9.0) exhibited the best lubrication performance. A diameter–height ratio (λd) applied by a calculation method was proposed to approximatively ascertain the lubrication regime during the cold rolling. The λd and the surface quality of the rolled strips indicated that the lubrication regime was the boundary lubrication when using the alkaline lubricant. Moreover, GO particles in the alkaline lubricant could repair the strip surface by mending effect and form the physically adsorbed layers. The layers prevented direct contact between rolled surfaces, further amending the surface quality of the rolled strips.

ВЛИЯНИЕ ДВУХСЛОЙНОГО ПОКРЫТИЯ «АЛМАЗОПОДОБНЫЙ УГЛЕРОД + TIN/ ALTIN» НА ТРИБОЛОГИЧЕСКИЕ ХАРАКТЕРИСТИКИ МАСЕЛ ПРИ ГРАНИЧНОЙ СМАЗКЕ

The application of monocrystalline carbon to steel surfaces of rubbing bodies significantly increases the anti-friction and anti-wear properties of lubricants. (Research purpose) The research purpose is in choosing the optimal intermediate layer material based on the evaluation and comparison of the physical, mechanical and tribological characteristics of two-layer coatings obtained using titanium nitride and titanium aluminitride, respectively, as a solid intermediate layer, and compare them with each other. (Materials and methods) The cylindrical surfaces of 100Cr6 steel rollers with a diameter of 8 mm were coated with titanium nitride and titanium alumonitride, using the latest technologies, and on top of these coatings by pulsed condensation of carbon plasma with additional bombardment with argon ions - monocrystalline carbon. The micromechanical and microgeometric characteristics of the studied surfaces were evaluated using NanoScan-4D and SNeox devices. Pure base oil PAO-4, oil with the addition of oleic acid as a surface-active additive, and zinc dialkyldithiophosphate as a chemically active additive were used as a lubricant. (Results and discussion) The use of intermediate layers of titanium nitride and titanium aluminitride improves the adhesion of the carbon coating, which has a positive effect on its wear resistance. The main role in the antifriction effect of two-layer coatings is performed by a thin-layer carbon coating. (Conclusions) The article shows that the use of composite coatings from monocrystalline carbon + heat-resistant coating in friction units operating in the boundary lubrication mode serves as a reserve for improving the lubricating properties of oils, without requiring chemically active additives containing elements that negatively affect the environment. As an intermediate coating, the best result was shown by titanium aluminitride, it is more resistant to wear, and also provides lower friction.

Carbon-based tribofilms from lubricating oils.

Moving mechanical interfaces are commonly lubricated and separated by a combination of fluid films and solid 'tribofilms', which together ensure easy slippage and long wear life. The efficacy of the fluid film is governed by the viscosity of the base oil in the lubricant; the efficacy of the solid tribofilm, which is produced as a result of sliding contact between moving parts, relies upon the effectiveness of the lubricant's anti-wear additive (typically zinc dialkyldithiophosphate). Minimizing friction and wear continues to be a challenge, and recent efforts have focused on enhancing the anti-friction and anti-wear properties of lubricants by incorporating inorganic nanoparticles and ionic liquids. Here, we describe the in operando formation of carbon-based tribofilms via dissociative extraction from base-oil molecules on catalytically active, sliding nanometre-scale crystalline surfaces, enabling base oils to provide not only the fluid but also the solid tribofilm. We study nanocrystalline catalytic coatings composed of nitrides of either molybdenum or vanadium, containing either copper or nickel catalysts, respectively. Structurally, the resulting tribofilms are similar to diamond-like carbon. Ball-on-disk tests at contact pressures of 1.3 gigapascals reveal that these tribofilms nearly eliminate wear, and provide lower friction than tribofilms formed with zinc dialkyldithiophosphate. Reactive and ab initio molecular-dynamics simulations show that the catalytic action of the coatings facilitates dehydrogenation of linear olefins in the lubricating oil and random scission of their carbon-carbon backbones; the products recombine to nucleate and grow a compact, amorphous lubricating tribofilm.

Theoretical justification of influence electric field on antiwear properties of lubricants

In the article the ground of application mathematical dependences of influence electric-field is resulted on antiwear properties of lubricating materials which set intercommunication between the basic physical parameters of tribosystem and electric field

Reproducing the Kinematic Conditions for Automotive Valve Train Wear in a Laboratory Test Machine

The positions of maximum wear on the surfaces of automotive cams and followers have been found to be characterized by low velocities of the point of contact over the surface in question, in combination with significant sliding velocities and thin oil films. The modelling of these critical conditions has now been extended to examine the significance of low contact velocities in two internationally accepted engine tests for the evaluation of the anti-wear properties of lubricants in valve train systems. Calculations of the contact dwell times and the corresponding sliding distances against the opposing surfaces indicate that the particular susceptibility to wear and surface distress in these systems arises from the extreme values of these parameters experienced by particular points on the surfaces during each rotation of the cam. The conditions on the follower surfaces appear to be more severe than on the cams in this respect. It is shown that kinematic conditions representative of the more severe parts of the operating cycles of the engine tests can be reproduced in a modified Amsler two-disc machine, thus enabling the use of small, flat test specimens, which are accessible to a wide range of advanced surface analysis instruments, to facilitate the study of lubricant anti-wear additive film formation.

Apparatus for determining the anti-wear properties of oils and materials

This paper describes an apparatus employing radioactive tracers which permits the wear of the friction pair, its temperature, and the oil temperature to be measured continuously and simultaneously. The correlation of the variations in these parameters also makes possible the observation of short duration phenomena and hence more accurate conclusions concerning the anti-wear properties of lubricants and materials. The apparatus allows both rapid determinations for certain analyses and a study of the progress of the wear process and its transient aspects to be made.

The anti-wear properties of lubricants and the influence of various factors on the anti-wear properties of petroleum oils : M. D. Bezborod'ko, G. V. Vinogradov, N. T. Pavlovskaya and I. G. Tsurkan — Izvest. Akad. Nauk, S.S.S.R.,Otdel.Tekh. Nauk, No. 12 (1958) 104–114; (10 fig., 8 ref.). Published as: R.A.E. Library Transl. 830, Ministry of Supply, London, W.C. 2

The anti-wear properties of lubricants and the influence of various factors on the anti-wear properties of petroleum oils : M. D. Bezborod'ko, G. V. Vinogradov, N. T. Pavlovskaya and I. G. Tsurkan — Izvest. Akad. Nauk, S.S.S.R.,Otdel.Tekh. Nauk, No. 12 (1958) 104–114; (10 fig., 8 ref.). Published as: R.A.E. Library Transl. 830, Ministry of Supply, London, W.C. 2