Good Friction-reducing Properties Research Articles

Investigations on microstructure and wear resistance of Fe-Mo alloy coating fabricated by plasma transferred arc cladding

A wear-resistant Fe-Mo alloy coating was fabricated on the AISI 1045 steel substrate by plasma transferred arc (PTA) cladding, using pure Mo powders as the precursor material. The microstructure, microhardness and wear resistance of the coating were investigated by scanning electron microscope (SEM) with energy dispersive spectrum (EDS), X-ray diffraction (XRD), Vickers hardness and pin-on-disk wear testers, respectively. It was found that the coating presented rapidly solidified microstructure mainly consisting of cellular R-Fe63Mo37 dendrites and a small amount of lamellar R-Fe63Mo37/α-Fess dendrites uniformly distributed in the α-Fess matrix. Based on the eutectic growth and undercooling theories, the possibility of the R/α peritectic coupled growth in the rapidly solidified peritectic Fe-Mo alloy was discussed. The extensive growth of columnar crystallites into the substrate provided good metallurgical bonding at the interface between the coating and the AISI 1045 steel substrate. The results showed that the microhardness and wear resistance of the coating were much higher than that of the AISI 1045 steel substrate. The transferred oxides layer containing MoO3 formed on the worn surface had a good friction-reducing property and also contributed to the wear resistance of the coating.

Investigation on the oxidation behavior of AlCrVxN thin films by means of synchrotron radiation and influence on the high temperature friction

Abstract Friction minimization is an important topic which is pursued in research and industry. In addition to the use of lubricants, friction-reducing oxide phases can be utilized which occur during. These oxides are called Magneli phases and especially vanadium oxides exhibit good friction reducing properties. Thereby, the lubrication effect can be traced back to oxygen deficiencies. AlCrN thin films are being used as coatings for tools which have to withstand high temperatures. A further improvement of AlCrN thin films concerning their friction properties is possible by incorporation of vanadium. This study analyzes the temperature dependent oxidation behavior of magnetron sputtered AlCrVN thin films with different vanadium contents up to 13.5 at.-% by means of X-ray diffraction and X-ray absorption near-edge spectroscopy. Up to 400 °C the coatings show no oxidation. A higher temperature of 700 °C leads to an oxidation and formation of Magneli phases of the coatings with vanadium contents above 10.7 at.-%. Friction coefficients, measured by ball-on-disk test are correlated with the oxide formation in order to figure out the effect of vanadium oxides. At 700 °C a decrease of the friction coefficient with increasing vanadium content can be observed, due to the formation of VO 2 , V 2 O 3 and the Magneli phase V 4 O 7 .

Tribological studies on chemically modified rapeseed oil with CuO and CeO2nanoparticles

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 CeO2nanoparticles 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.

Friction reduction efficiency of organic Mo-containing FM additives associated to ZDDP for steel and carbon-based contacts

The lubricating properties of two different organomolybdenum additives combined with ZDDP were evaluated for different tribopairs involving carbon-based coatings, hydrogenated DLC and nanocrystalline diamond NCD. Their performances were investigated using reciprocating linear tribometer and compared with the traditional additivation MoDTC/ZDDP. The highly sulfurised moly-trimer additive and organic molybdate ester additive displayed good friction reducing properties in comparison with traditional additivation MoDTC for all tribopairs tested, especially organic molybdate ester. XPS and ToF-SIMS surface analyses performed on the tribofilms formed with these different organomolybdenum additives showed the formation of MoS2/MoS2−xOx species exhibiting a solid lubricant character, but preferentially on steel surfaces. HRTEM/EDS analyses confirmed the presence of MoS2/MoS2−xOx sheets embedded inside an oxygen-rich amorphous matrix. This is different from the traditional additivation that leads to the polyphosphate/phosphate glass matrix. Organic molybdate ester is a sulfur- and phosphorus-free additive that appears particularly interesting for achieving low friction while minimizing the S content of the lubricant.

The tribological behaviors of disulfide-type triazine derivatives as additives in biodegradable lithium grease

Two novel disulfide-type triazine derivatives, 6,6'-disulfanediylbis(4-(dibutylamino)-1,3,5-triazine-2-thiol) (coded DTBT) and 6,6'-disulfanediylbis(4-(bis(2-ethylhexyl)amino)-1,3,5-triazine-2-thiol) (coded DTOT), were prepared. A four-ball tester was used to evaluate their tribological performances as anti-wear and extreme-pressure additives in biodegradable lithium grease. The results show that the disulfide-type triazine derivatives possess good friction-reducing properties and excellent anti-wear, extreme-pressure capacities. For further understanding of their tribological behaviors, X-ray photoelectron spectroscopy and scanning electron microscopy are adopted to analyze the tribofilms generated from these additives in biodegradable lithium grease. The results of X-ray photoelectron spectroscopy analysis illustrate that the prepared compounds as additives in biodegradable lithium grease forms a protective film containing FeS, FeS2 (or S-containing organic compounds), Fe2(SO4)3, FeSO4, FeO (or Fe3O4), and N-containing organic compounds on the metal surface during the sliding process.

Tribological Study of Xanthate-Containing Acetic Ester as Additives in Hydrogenated Oil

A novel ester derivative, dodecyl xanthate acetic dodecyl xanthate ester(DXAD) was synthesized and it’s tribological behaviors as additives in hydrogenated oil, were evaluated using a four-ball tester. Results show that the compound possesses good antiwear performance, extreme pressure capacity, and good friction-reducing property. The action mechanism was estimated through analysis of the worn surface with X-ray photoelectron spectroscopy (XPS) and Scanning Electron Microscope (SEM). The results of XPS and SEM analyses illustrate that the prepared compound as an additive in hydrogenated oil forms a protective film containing ferric sulfide and ferric sulfate compounds on the rubbed surface.

Tribological performances of Mo 6S 3I 6 nanowires

A new nanowire-like material with the chemical formula Mo 6S 3I 6 was studied as an additive in a synthetic base oil, a polyalphaolefin (PAO). This material presents interesting friction reducing properties, friction coefficient reaching a value of 0.04 in boundary lubrication. Transmission and scanning electron microscopy, X-ray diffraction, and Raman spectroscopy were used to characterize nanowires before and after friction. The combination of these techniques gave evidence of MoS 2 formation in contact area during friction test. This structural evolution of nanowires explains their good friction reducing properties.

Tribological properties of Mo?S?I nanowires as additive in oil

A new nanowire-like material with the chemical formula Mo6S4.5I4.5 was studied as additive in a synthetic base oil, a polyalphaolefin (PAO). This material presents interesting friction reducing properties, with friction coefficients reaching a value of 0.04 in boundary lubrication. Transmission and scanning electron microscopy, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy were used to characterise nanowires before and after friction. The combination of these techniques gave evidence of MoS2 formation in the contact area during friction tests. This structural evolution of nanowires explains their good friction reducing properties.

Study of the tribological behaviors of S, P-containing triazine derivatives as additives in rapeseed oil

A series of S, P-containing triazine derivatives, 2,4-bis-(diethylamino)-6-( O, O′-dialkyl dithiophosphate)- s-1,3,5-triazine, which are potential environmentally friendly lubricating oil additives, were synthesized. The tribological properties as lubricating oil additives in vegetable oil were evaluated using a four-ball tester. The results show that the series of triazine derivatives possess good antiwear performance, excellent load-carrying capacity. These compounds also show good friction-reducing properties. The action mechanism was estimated through analysis of the worn surface with X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM).