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Abstract: Novel ionic liquid materials based on 1-alkyl-4-[5-(alkylsulfanyl)-1,3,4-oxadiazol-2-yl] pyridinium tetrafluoroborate derivatives were synthesized. Ultra-thin ionic liquid films were prepared on silicon wafers by means of spin-coating and their tribological properties were investigated. The wear life increases when the chain length decreases. Under low load, they show good tribological properties which are closely related to the interaction between ionic liquid and substrate surface, especially the film of 1-ethyl-4-[5-(ethylsulfanyl)-1,3,4-oxadiazol-2-yl] pyridinium tetrafluoroborate, it has low friction coefficient and long wear life. So, this kind of ionic liquid can be potentially applied as ultra-thin lubricating coating. [Copyright &y& Elsevier]

The effects of proton radiation (PR) irradiation on the components, friction and wear of Ti:WS 2 /P201 composite lubricating system were mainly investigated. PR irradiation has a great effect on the physicochemical properties of P201 oil, which can not only decompose oil into small molecular but also make it cross-linking and polymerization. More seriously, oil layer with good wettability transfers to a solid-like organic film on sample surfaces after PR irradiation. In addition, PR irradiation has a slight effect on the microstructure of Ti:WS 2 film due to coverage of oil layer. Meanwhile, Ti:WS 2 /P201 system obviously increases the friction coefficient and wear rate, especially extremely shortened life at high irradiation dose. It attributes to P201 oil occurred degradation when suffers from high PR energy, forming polymer with higher molecular weight. The polymer has poor replenishment on sliding contact interface, so destroying endurance of transfer film, which deteriorates the component and property of the system. At the high irradiation dose, the oil nearly loss fluidity, causing severe abrasive wear and tribo-oxidation, further accelerating the failure of the solid-oil materials. [Display omitted] • PR irradiation generates a great influence on the tribological properties of Ti:WS 2 /P201 system constructed by Ti:WS 2 film and P201 oil. • After PR irradiation, P201 oil layer with good wettability transfers to a solid-like organic film on sample surfaces. • PR irradiation degraded P201 oil to form small volatile molecular compound and polymer with higher molecular weight. • The replenishment capacity of oil become poor on contact area, further destroying wear resistance of transfer film. [ABSTRACT FROM AUTHOR]

Abstract: Bronze matrix composites were prepared by the powder metallurgy technology (P/M). The tribological properties of composites sliding against AISI321 stainless steel pins were studied under sea water condition. The alumina had a strengthened effect on the hardness and wear resistance of composites, but it increased the friction coefficient of bronze material. The nickel coated graphite improved the interfacial bonding between the bronze and graphite. The graphite was an effective solid lubricant in sea water. Sample with 3wt% Al2O3 and 3wt% nickel coated graphite showed good tribological properties in sea water. The composites showed different wear mechanisms. Sea water showed lubricating effect and corrosive effect during the sliding process. [Copyright &y& Elsevier]

Abstract: In this study, we report that a layered Ti3AlC2 ceramic exhibited three distinct tribological behaviors at different vacuum degrees. It is firstly found that the layered Ti3AlC2 exhibited intrinsic self-lubricity under vacuum degree from 2.0×104 to 5Pa with the coefficient of friction (CoF) as low as 0.2 and nearly no wear. Under lower 0.1Pa and air atmosphere, however, it showed lubrication failure. Under lower 0.1Pa, The CoF abruptly rose after transitory low friction in initial duration and deteriorated wear occurred in the Ti3AlC2. The CoF sluggishly ascended to stable value from 0.2 to 0.7 in air. The lubricating mechanism of Ti3AlC2 ceramic was proposed. [Copyright &y& Elsevier]

Abstract: The mechanical properties and wear behavior of an Fe70Ni30 alloy with twinned martensite structure obtained by deep cryogenic treatment at −196°c (DCT) were evaluated in comparison with that of coarse-grained (CG) Fe70Ni30 alloy (single austenite phase). The results showed that after the introduction of martensite with nano-scale twins, the Vickers hardness of Fe70Ni30 increased from 145 to 248Hv. The friction coefficient of both samples was almost the same, and it decreased with increasing applied load and increased with increasing sliding speed. The XPS results indicated that oxide protecting film was formed on the worn surface, which may dominate the friction coefficient. The wear rate for both samples increased with increasing applied load and decreased slightly with increasing sliding speed. The wear resistance of DCT-Fe70Ni30 alloy was obviously enhanced. The wear mechanisms were investigated by SEM accordingly. [Copyright &y& Elsevier]

Abstract: The tribological properties of a Fe3Al material in an aqueous solution of 1mol/l H2SO4 corrosive environment sliding against a Si3N4 ceramic ball are studied using an Optimol SRV oscillating friction and wear tester in a ball-on-disc contact configuration. We investigate the effects of load and sliding speed on tribological properties of the Fe3Al material. The worn surfaces of the Fe3Al material are examined by a scanning electron microscope (SEM) and an X-ray photoelectron spectroscope (XPS). It is found that the Fe3Al material exhibits better wear resistance than 1Cr18Ni9Ti stainless steel in the sulfuric acid corrosive environment. The wear rate of the Fe3Al material is on the order of 10−13 m3/m and increases with increasing load, but does not vary below the sliding speed of 0.08m/s then dramatically increases with increasing sliding speed. The friction coefficient of the Fe3Al material is in the range of 0.1–0.28, and slightly increases with increasing load, and does not vary with the increase of sliding speed. The Fe3Al material occurs tribochemical reaction with the H2SO4 aqueous solution in the friction process. Wear mechanism of the Fe3Al material is dominated by microploughing and corrosive wear. [Copyright &y& Elsevier]

Ionic liquids of the alkylimidazolium hexafluorophosphate type were prepared and evaluated as lubricants for the contact of steel/steel. Their tribological properties of the synthetic ionic liquid as the lubricants were investigated on an Optimol SRV oscillating friction and wear tester in ambient condition and on a CZM vacuum friction tester at 1×10−3 Pa. These synthetic ionic liquids show excellent tribological performance and are superior to the conventional lubricant of liquid paraffin containing 2 wt.% of zinc dialkyldithiophosphate (ZDDP) in terms of the friction-reduction ability and load-carrying capacity. The elemental composition and chemical nature of the boundary films generated on the steel surface were analyzed on a scanning electron microscope with a Kevex energy dispersive X-ray analyzer attachment (SEM/EDS) and X-ray photoelectron spectrometer (XPS). The SEM results showed light abrasion and phosphorus on the worn surface after lubrication with the ionic liquids of alkylimidazolium hexafluorophosphates, and the XPS results indicated the occurrence of the tribochemical reaction of ionic liquid with iron during the sliding process, with the formation of FePO4 and FeF2. [Copyright &y& Elsevier]

High entropy alloys (HEAs) are an important candidate for high temperature mechanical systems. Here, effects of atmosphere, temperature and counterparts on the vacuum tribological behaviors of CoCrFeNi HEA fabricated by spark plasma sintering were systematically studied. Comparison of tribological behaviors in vacuum and air indicated that tribo-oxidation is detrimental to the wear resistance of CoCrFeNi HEA within temperature range 25–400 °C, but positive at 600 and 800 °C. The CoCrFeNi HEA obtains relatively low wear in vacuum when low testing temperatures and heterogeneous counterface are selected. The wear resistance of CoCrFeNi HEA in vacuum is superior or comparable to the steel and intermetallics. • The high-temperature tribological behaviors of CoCrFeNi HEA were studied. • Tribological properties of HEA depend on atmosphere, temperature and counterparts. • Tribo-oxidation is negative for the wear resistance below 600 °C but positive above. • In vacuum, surface oxidation, adhesive and mechanical properties determine the wear. [ABSTRACT FROM AUTHOR]