Steel Friction Pairs Research Articles

Method of evaluating the coefficient of friction of frost-resistant sealing rubbers

The results of an experimental study of the effect of the normal pressure in the range of 0.1–0.3MPa, a velocity of sliding of 1–100 mm/s, and a bulk temperature of 22 to–27°C on the coefficient of sliding friction of an elastomer–steel friction pair have been presented. Two types of elastomeric materials have been considered, i.e., frost-resistant rubber based on synthetic propylene oxide rubber and this rubber filled with the antifriction additive of ultrafine polytetrafluoroethylene powder in an amount of 1 weight part per 100 weight parts. The results have shown the efficiency of filling rubbers with ultrafine polytetrafluoroethylene; the coefficient of sliding friction at temperatures below–15°C decreases by more than two times.

Effect of the Material and Sliding Rate of the Counterface on the Tribotechnical Properties of a CM(Ti–Mo–BN)–Steel Friction Pair

The effect of the material and sliding rate (1, 2, 4, 6, and 15 m/sec) of the counterface on the tribological characteristics of a (composite Ti–Mo–BN)–counterface (steels 45, 65G, ShKh15, 40Kh, and Kh18N9T, nitrided titanium, and BrO10 bronze) friction pairs in dry friction in air under a pressure of 0.8 MPa is investigated. It is established that, under these friction conditions, the composite in pair with BrO10 bronze is ineffective. During friction of the composite in pairs with steels 45, 65G, ShKh15, 40Kh, and Kh18N9T, an increase in the sliding rate from 1 to 6 m/sec results in an increase of the friction coefficient, linear wear of the friction pairs, mass loss of the composite and counterface, whereas the temperature of the friction surface increases. The highest temperature of the friction surface of the composite is reached in pair with steel 45. The temperature, sliding rate, and pressure applied lead to the synthesis of a secondary film (on the surface of the composite) of such a phase composition and structure that provide (in pair with steel 45) higher tribological characteristics of the composite than those in pairs with the other steels. At all sliding rates of the counterface, the tribological properties of the friction pairs depend not only on the properties of the composite material (chemical and phase composition, structure, and mechanical characteristics), but also on the same properties of the counterface material.

Improving the efficiency of running-in for a bronze–stainless steel friction pair

In this paper, the possibility of the transfer of additives that are in the emulsion mist is shown by the example of the bronze CuSn7Zn4Pb6–stainless steel X10CrNi18-8 friction pair. The additive is first transferred on the processed surface of the part and through it–in the contact zone of the friction pair. It was established that the emulsion mist reduces the roughness of machined stainless steel surface more than three times, and the introduction of additives based on phosphate esters into the emulsion reduces the roughness by 4–4.5 times. Phosphate-based additive remains on the machined surface in significant quantities, even after 30 min working at heavy loads, reducing the instantaneous friction coefficient and the temperature of the friction zone. The mean width of profile elements of the assessed profile of bronze samples decreases by two times and their bearing length ratio decreases by four times. In this case, a decrease in the wear rate of bronze by more than 40% is ensured. This fact indicates the better running-in of the friction pair.

Tribological Investigation of Guanidinium Ionic Liquids as Lubricants for Si 3 N 4 /steel Contacts

Two kinds of guanidinium ionic liquids were synthesized. The thermal stabilities of the ionic liquids were evaluated by a hermogravimetric analyzer. Their tribological properties were investigated and compared with alkyl imidazole ionic liquids and liquid paraffin by SRV friction-wear test. The results show that guanidinium ionic liquids were the best lubricant among the tested lubricants for steel/Al contacts. The images of worn surface were observed using scanning electron microscope. The X-ray photoelectron spectrometer analysis was carried out to explore the lubrication mechanism. The results show that complex tribochemical reactions occurred and the boundary lubrication films were formed in aluminum/steel friction pair interface during the sliding process. ©, 2015, Science Press. All right reserved.

Stick–Slip Friction of Stainless Steel in Sodium Dodecyl Sulfate Aqueous Solution in the Boundary Lubrication Regime

The objective of this study is to correlate the mass and structure of the adsorbed sodium dodecyl sulfate (SDS) on stainless steel surface in aqueous solution with the boundary lubrication behavior, especially the stick–slip phenomenon of the ZrO2/stainless steel friction pair. Surface tension measurement, quartz crystal microbalance (QCM) technique and ball-on-flat friction test were performed in this study. The adsorption isotherm of SDS on stainless steel surface in SDS aqueous solution was measured by QCM, and four-stage adsorption behavior was found at the solid/liquid interface. As the SDS concentration increases, the mass of the adsorbed SDS molecules increases, while the structure of the adsorbed layer changes from monomers to hemimicelles. Tribological properties of ZrO2/stainless steel friction pair in SDS aqueous solution were verified with an UMT-3 tester. Boundary lubrication was emphasized as water-based lubrication easily fails in hydrodynamic lubrication due to its low viscosity. Stick–slip phenomenon was observed in the boundary lubrication of the adsorbed SDS film under certain loading and sliding conditions. Both the static and kinetic friction coefficients were analyzed with respect to the SDS concentration and sliding velocity. The stick–slip phenomenon is related to both of the adsorbed mass and adsorption structure of the SDS boundary film.

Tribological capabilities of chiral nematic liquid crystal additives in mineral motor oil

This article presents the results of experimental investigation of tribological properties of commercial mineral motor oil with chiral nematic (also known as twisted nematic or cholesteric) liquid crystal additives. Cholesteryl stearate and valerate (fatty acid cholesterol esters) liquid crystals were used as oil additives in investigation. Tribological experiments were performed using a block-on-disc-type tribo-test machine at constant experiment time and sliding velocity conditions. The load (contact pressure), concentration of liquid crystalline additive in oil and Rz roughness of steel–steel friction surfaces were taken as variable parameters. The mean coefficient of friction of steel–steel friction pair lubricated by oil with and without liquid crystal additives and near-contact temperature were taken as dependent variables. Regression equations were then derived for each lubricant and tribological efficiency of liquid crystals as oil additives was evaluated. It was established that coefficient of friction of steel–steel friction pair and near-contact temperature are reduced to about a half in the presence of liquid crystal additives. Results of tribological experiments show that tribological efficiency of liquid crystals as oil additives increases with increase in their molecular mass.

Super-low friction of ta-C coating in presence of oleic acid

Abstract Friction tests have been carried out on bearing steel friction pairs coated with a-C:H and ta-C under lubricated conditions with 1-hexadecene and pure oleic acid, respectively. Main results show that ta-C leads to the super-low regime with oleic acid (friction coefficient below 0.01) and that a-C:H is quite well lubricated by 1-hexadecen. Surface analyses by coupling X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) have been carried out in the case of oleic acid with ta-C and a-C:H coatings. Results show that tribochemical reactions have occurred. OH groups terminate the ta-C surface whereas a-C:H is covered by a thin tribofilm and is terminated by oleic acid monolayers. The superlow regime in the case of ta-C is mainly attributed to the presence of the OH-termination.

Experimental research on tribological performance of water-based rolling liquid containing nano-TiO2

Nano-TiO2 was dispersed in water to study the influences of nanoparticles on the tribological properties of water-based rolling liquid for hot steel. The phase composition and microstructure of nano-TiO2 were investigated by X-ray diffraction and transmission electron microscopy methods. The friction reduction and antiwear properties were measured on a four-ball friction tester, and then hot rolling experiments with lubrication have been carried out. The rolling force and surface roughness were measured. Moreover, the surface elements of the steel lubricated by nano-TiO2 rolling liquid were analyzed by energy dispersive spectroscopy. The results showed that nano-TiO2 as water-based liquid additives can effectively improve the antiwear properties of steel–steel friction pair and reduce the friction coefficient. At the same time, nano-TiO2 shows good lubrication properties during hot rolling. It is inferred from the lubrication and repairing mechanism that TiO2 nanoparticles sediment on the surface of steel, and the lower surface film is formed under high temperature and high pressure. The film possesses excellent antiwear, friction-reducing and repair properties.

Tribological Properties of Motor Oil with Nanodiamond Additive tested for steel friction surfaces with different hardnesses – ERRATUM

Synergistic compositions of detonation nanodiamond (ND) particles in the form of 100nm aggregates in combination with molybdenum dialkyldithiophosphate were used as additives to 10W40 oils. Ring-on-disk tribological tests were performed under high load conditions using friction pairs with different hardnesses, namely normalized-normalized (“soft/soft”) and normalized-quenched (“soft/hard”) steel samples. For the “soft/hard” steel friction pair NDs provide significant reduction in both the coefficient of friction and wear as well as demonstrate polishing. For the “soft/soft” steel friction pair, however, no difference in the coefficients of friction was observed when the base oil was used with or without ND. In the test with oil containing the ND additive, the wear scar in the disk was wider, but more shallow, than in the test with pure oil. Current tests indicate that the significance of the reduction of friction and wear of the sliding surfaces in the presence of the ND additive in oil strongly depends on the hardness of the friction surfaces and most probably is connected with ND polishing effect.

Studying colloidal greases with hard nanoparticles of aluminum silicates used to reduce wear of steel friction pairs

Electron diffraction analysis was used to study the dispersion of natural bentonite particles accompanied by the formation of nanoparticles of aluminum silicates and the rheological behavior of these colloidal systems was investigated. Based on these results, an additive to grease has been proposed, which was highly efficient in terms of improving the wear resistance of lubricated steel surfaces. This additive was produced by the chemical disintegration of modified natural aluminum silicates and their homogeneous distribution in the bulk of the grease using the resonance method. The effect of the amount of the antifriction additive to the grease on the wear resistance of steel specimens was studied. Improving the wear resistance of lubricated steel surfaces was due to the use of the antiwear additive that contained available and inexpensive components. The proposed grease is promising for lubricating the rail-wheel contact, especially in high-speed railway transport.

Tribological Properties of Motor Oil with Nanodiamond Additive tested for steel friction surfaces with different hardnesses

ABSTRACTSynergistic compositions of detonation nanodiamond (ND) particles in the form of 100nm aggregates in combination with molybdenum dialkyldithiophosphate were used as additives to 10W40 oils. Ring-on-disk tribological tests were performed under high load conditions using friction pairs with different hardnesses, namely normalized-normalized (“soft/soft”) and normalized-quenched (“soft/hard”) steel samples. For the “soft/hard” steel friction pair NDs provide significant reduction in both the coefficient of friction and wear as well as demonstrate polishing. For the “soft/soft” steel friction pair, however, no difference in the coefficients of friction was observed when the base oil was used with or without ND. In the test with oil containing the ND additive, the wear scar in the disk was wider, but more shallow, than in the test with pure oil. Current tests indicate that the significance of the reduction of friction and wear of the sliding surfaces in the presence of the ND additive in oil strongly depends on the hardness of the friction surfaces and most probably is connected with ND polishing effect.

Effect of Hardness and Position on Wear Behavior of Steel Pairs

In this paper, the effect of hardness and position on the 40CrNiMoA steel and 18Cr2Ni4WA steel friction pairs’ friction coefficient and wear volume were studied without lubrication, at room temperature. The results show that: Under test conditions, the fluctuation in the friction coefficient is bigger, when the up specimen is the harder 18Cr2Ni4WA steel. And when the up specimen is the softer 40CrNiMoA steel, the fluctuation in the friction coefficient is relatively small. When the up specimen is the 40CrNiMoA steel, the hardness of 40CrNiMoA steel is a relatively small impact on the average value of the coefficient of friction.When the up specimen is the softer 40CrNiMoA steel, the coefficient of friction is relatively larger than that when the up specimen is the harder 18Cr2Ni4WA steel. The wear volumes is relate to the position of friction pair. When the up specimen is the harder 18Cr2Ni4WA steel, both sides of the friction pairs has the same wear volumes when the hardness of 40CrNiMoA steel is about 43HRC. When the up specimen is softer 40CrNiMoA steel, and its hardness is about 54HRC, the wear volumes curves of two materials intersect.

Analysis of surface layers and wear products by Mössbauer spectral analysis

The article presents results of Mössbauer analysis conducted in order to identify structural factors which help to increase wear resistance of steel friction pairs. Wear resistance was tested in the regime of dry friction and oxidative wear using an original tribological tester. The device measured wear in conditions of a created and regulated isothermal boundary at a precisely defined distance from contact of rubbing bodies by receiving heat generated by friction. Cleaning elements were also employed to stabilise frictional resistances.Enhanced wear resistance was observed to obtain where temperature of the friction area becomes equal to the specific temperature of a given system.Mössbauer analysis was applied to surfaces of specimens made of C45, 145Cr6 counter specimens, and wear products. Application of Mössbauer analysis helped to identify composition and structures of ferrous compounds generated by friction, including oxidative secondary structures.Factors improving wear resistance in the testing included: presence of greater quantities of FeO and Fe3O4 combined with absence of Fe2O3 in the friction area of ferrous oxides, transfer of wear particles arising from ferrite, martensite and oxides between co-acting surfaces, enrichment of the specimen surface with martensite from the hard counter specimen and martensite generated in effect of diffusion impacts.

Preparation and tribological properties of water-soluble copper/silica nanocomposite as a water-based lubricant additive

Cu/SiO2 nanocomposite was synthesized by sol–gel method. The size, morphology and phase structure of as-prepared Cu/SiO2 nanocomposite were analyzed by means of X-ray diffraction and transmission electron microscopy, and its ultraviolet-visible light spectrum was measured in relation to surface plasmon excitation of Cu particles. The tribological properties of as-synthesized Cu/SiO2 nanocomposite as an additive in distilled water were investigated with a four-ball machine, and the morphology and elemental composition of worn steel surfaces were examined with a scanning electron microscope and an X-ray photoelectron spectroscope. Results show that as-synthesized Cu/SiO2 nanocomposite as a lubricant additive is able to significantly improve the tribological properties of distilled water. A protective and lubricious film composed of Cu and a small amount of FeS, FeSO4 and SiO2 is formed on steel sliding surfaces lubricated by distilled water containing Cu/SiO2 nanocomposite. During friction process Cu nanoparticles can be released from Cu/SiO2 nanocomposite to fill up micro-pits and grooves of steel sliding surfaces, resulting in greatly reduced friction and wear of steel frictional pair via self-repairing. The state and thickness of the film formed on the worn surface is closely related to applied load; and Cu/SiO2 nanocomposite might be a promising water-based lubricant additive for steel-steel contact subjected to moderate load.

Friction reducing and anti-wear property of metallic friction pairs under lubrication of aqueous solutions with polyether added

The tribological behaviors of steel–aluminium and steel–steel friction pairs lubricated by aqueous solution with amine-polyoxyethylene-polyoxypropylene-ether, KE-1, as additives are investigated with the help of universal micro-tribotester. The results show that the lubricant has a good effect on the performances of friction reducing and anti-wear. It demonstrates a better performance to steel–steel friction pair than steel–aluminium pairs for the anti-wear property under same conditions.

Preparation and Evaluation of Tribological Properties of Cu Nanoparticles Surface Modified by Tetradecyl Hydroxamic Acid

Oil-soluble Cu nanoparticles without phosphorus and sulphur elements were prepared using in situ surface-modification technique with hydrazine hydrate as a reductant and tetradecyl hydroxamic acid (THA) as a modifier. The phase composition, microstructure, and chemical structure of as-synthesized Cu nanoparticles (coded as THA-capped Cu or THA-capped nano-Cu) were analyzed by means of X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectrometry. The thermal stability of THA-capped Cu was examined using thermogravimetric analysis and differential thermal analysis. The antiwear ability of THA-capped Cu as an additive in liquid paraffin was examined using a four-ball machine, and the morphology of worn steel balls was examined using a scanning electron microscope, an energy dispersive spectrometer and an X-ray photoelectron spectroscopy. It has been found that THA-capped Cu can be well dispersed in some organic solvents. As-synthesized THA-capped Cu as an environmentally friendly additive in liquid paraffin shows excellent antiwear ability for the steel–steel contact. Besides, Cu nanoparticles are able to deposit and fill up micropits and grooves on steel sliding surfaces under a higher load and hence greatly reduced wear of the steel–steel pair thereat by way of self-repairing of worn surfaces of the steel–steel frictional pair, showing promising application as an environmentally acceptable lubricating oil additive.

Tribological Properties of Lubricating Films on the Al-Si Alloy Surface via Laser Surface Texturing

Dimpled textures were prepared by using a pulse solid laser on the surface of Al-Si alloy. The combination of laser surface texturing (LST) and MoS2 solid lubricant as well as their tribological properties were investigated in this article. The obtained friction and wear data were critically analyzed to investigate how the parameters of texture influence the tribological performance of Al-Si alloy. Furthermore, morphological investigations of the transfer layers on the worn surfaces were performed and the wear mechanisms are discussed. The results show that the combination of LST and solid lubricant improves the tribological characteristics of Al-Si alloy. The friction coefficient of Al-Si alloy: steel friction pairs can be reduced to 0.15 under dry friction. The lubrication mechanism is attributed to a synergetic effect of providing solid lubricant and traps wear debris in the dimples. It was found that the optimum density of structure was 37% for excellent tribological properties.

Effects of Ag-Carried Content in P/Ag Nanocomposites on Tribological Properties of 45 Mild Steel Friction Pairs

In this paper, some Ag-carried palygorskite nanocomposites P/Ag were prepared, their silver content were 1.3%, 4.61%, 9.54% separately. To investigate the effects of the silver content on tribological properties of 45 mild steel pairs, the P/Ag carried different Ag content were used as lubricant additive and their tribological properties were tested on the MMU-10G testing machine. The wear mass loss is used to assess the anti-wear properties of different additives. The surface topographies and main elements are analyzed through SEM and EDS after running for 30 hours. The results show that the friction coefficient and the wear mass loss significantly decrease along with the increase of silver content in the P/Ag: the average friction coefficient of the P/Ag with 9.54% silver reduces about 65% as much as the one with 1.3% silver, meanwhile, the wear mass loss decreases 57% likewise. The surfaces after rubbing 30 hours, some kind of auto-restoration films that contains sort of characteristic elements such as O, Si, Mg, Al, Ag etc. are formed on the surfaces. With the help of this kind of films, the anti-wear properties of the friction pairs are finally improved. The factors that cause the improvement of anti-friction properties of the friction pairs lie in the quality and the silver content of the auto-restoration films formed on the surfaces of friction pairs.

The influence of antiwear additive concentration on the tribological behaviour of a-C:H:W/steel tribosystem

The effect of antiwear (AW) commercial additive concentration on the load-carrying capacity (scuffing resistance) of a-C:H:W/steel tribo-system intended for heavy-loaded machine parts was investigated. For comparison, steel/steel contacts were also investigated. The scuffing resistance has been measured as the limiting pressure of seizure ( poz) using the four-ball apparatus. The method with continuously increasing load was applied. The tribo-systems were lubricated with poly-alpha-olefin as base oil mixed with a commercial zinc dialkyldithiophosphates type of AW additive. The AW concentration was varied in the range of 0.1–5.0 wt%. The results of the tribological experiments performed in sliding contact have shown that, by the application of the a-C:H:W coating, the tribological properties of the system were significantly improved compared with the steel friction pairs. It has also been found that it is possible to reduce the concentration of commercial AW additive below 1.0 wt%. The surface topography of the rubbed surface was investigated with optical microscopy and atomic force microscopy; the elemental chemical nature of the AW film generated on the steel counter-surface (a-C:H:W/steel tribosystem) was investigated with energy dispersive spectrometry, glow discharge optical emission spectrometry, and X-ray photoelectron spectroscopy.

Influence of convective cooling of the external surface of a plane-parallel layer on the temperature distribution on a layer–base tribosystem

An analytic solution of the boundary-value problem of heat conduction for a tribosystem that consists of a plane-parallel layer sliding over the surface of a semiinfinite base with a constant velocity is obtained. For the materials of an aluminum–steel friction pair, we investigate the evolution of temperature and its distribution in the layer and base along the normal to the friction surface.