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The plasma electrolytic oxidation (PEO) coatings were prepared on low carbon steel from silicate electrolyte without and with Al nanoparticles, respectively. The structure, composition, anti-wear and anti-corrosion properties of the PEO coatings were investigated. The results indicated that the Al nanoparticles in the silicate electrolyte turned into alumina during the PEO process and reduced the amount of iron oxides in the coating. The PEO coating prepared from silicate electrolyte with Al nanoparticles showed enhanced wear resistance due to the formation of alumina. Furthermore, the coating was characterized by sealed pores on the surface, different from the open pores on the surface of PEO coating prepared from silicate electrolyte without Al nanoparticles. The modified structure and the changed composition of PEO coating by introducing Al nanoparticles in the electrolyte significantly improved the corrosion resistance of the coating, demonstrated by the electrochemical corrosion and salt spray tests. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) have emerged as potential lubricants in 2001. Subsequently, there has been tremendous research interest in ILs from the tribology society since their discovery as novel synthetic lubricating materials. This also expands the research area of ILs. Consistent with the requirement of searching for alternative and eco-friendly lubricants, IL lubrication will experience further development in the coming years. Herein, we review the research progress of IL lubricants. Generally, the tribological properties of IL lubricants as lubricating oils, additives and thin films are reviewed in detail and their lubrication mechanisms discussed. Considering their actual applications, the flexible design of ILs allows the synthesis of task-specific and tribologically interesting ILs to overcome the drawbacks of the application of ILs, such as high cost, poor compatibility with traditional oils, thermal oxidization and corrosion. Nowadays, increasing research is focused on halogen-free ILs, green ILs, synthesis-free ILs and functional ILs. In addition to their macroscopic properties, the nanoscopic performance of ILs on a small scale and in small gaps is also important in revealing their tribological mechanisms. It has been shown that when sliding surfaces are compressed, in comparison with a less polar molecular lubricant, ion pairs resist "squeeze out" due to the strong interaction between the ions of ILs and oppositely charged surfaces, resulting in a film that remains in place at higher shear forces. Thus, the lubricity of ILs can be externally controlled in situ by applying electric potentials. In summary, ILs demonstrate sufficient design versatility as a type of model lubricant for meeting the requirements of mechanical engineering. Accordingly, their perspectives and future development are discussed in this review. [ABSTRACT FROM AUTHOR]

Titanium boride (TiB 2 ) particles with different sizes were introduced into the hybrid Nomex/PTFE fabric composites to explore the high-temperature tribological properties. The thermal, mechanical and tribological properties of the filled fabric composites were investigated. Results showed that the presence of TiB 2 improved the thermal and mechanical properties obviously. High-temperature friction and wear tests also proved that the anti-wear ability of TiB 2 filled fabric composites was enhanced sharply without sacrificing the friction coefficients. Meanwhile, the effects of fillers content and size, applied load and temperature on tribological properties and wear mechanisms were also investigated. XRD and XPS were employed to analyze the worn surfaces and demonstrate the fabrication of tribofilm composed of TiO 2 and B 2 O 3 , which played a vital role in the excellent tribological behaviors. [ABSTRACT FROM AUTHOR]

Rotational speed has an important influence on the performance of coating materials. The a-C:Ta composite coatings were prepared by controlling the substrate rotational speed during deposition process using PVD technique. The results showed that the coating transformed from dense structure to columnar structure. Due to the changes of deposition time and the vapor incident angle of the sputtering ions, the sp2 hybrid structure increased and the C–Ta bonds contents decreased as a function of the rotational speed, which led to the improvement of adhesion force. The average friction coefficient of the composite coatings did not fluctuate significantly for the amorphous carbon matrix and the transfer films formed during friction, while the wear rates were gradually increased. The sample at 0.5 rpm possessed the lowest wear rate, which was mainly associated with the cooperative behavior of the dense structure and the formation of TaC nanoclusters in the composite coating. [ABSTRACT FROM AUTHOR]

The PEEK fabric-reinforced polyimide resin containing microcapsules with excellent mechanical and lubrication properties is reported. The GO-COOH/TiO 2 @PAO double-wall microcapsules (Capsule) were prepared by interfacial condensation polymerization of titanium butoxide (TBT) and self-assembly between GO-COOH and TiO 2 shell. A double crosslink of chemical bond (amide or ester) and hydrogen bond were constructed between microcapsules and polyimide (PI) to improve the mechanical properties of PEEK fabric-reinforced polyimide resin (PEEK/PI). It was identified that the addition of Capsules induced a 12.98% decrease in friction coefficient and 56.85% in the wear rate of the composites. This superior frictional behavior was primarily attributed to the combined effect of the boundary lubrication of PAO6, load-bearing effect of TiO 2 and PEEK fabric, and friction-reducing of GO-COOH. • Developed a novel containing oil microcapsules applied in lubrication. • The chemical bond and hydrogen bond was constructed between microcapsules and polyimide. • The microcapsules demonstrate good lubrication. • Regular fluctuations were observed in the friction curve of the samples containing microcapsules. [ABSTRACT FROM AUTHOR]

The poor dispersion stability of nanoparticles in oils limited their application. To address this problem, diverse of nanoparticles were introduced to supramolecular gels to fabricate a new lubricant (Nano-Gel). The results of molecular dynamics simulation show that gelators adsorbed onto the surface of nanoparticles at the non-covalent interaction. Besides, the intricate networks of supramolecular gels show spatial confinement to nanoparticles, which improved the dispersion stability of nanoparticles. Compared with supramolecular gels lubricant, Nano-Gel shows good anti-friction and anti-wear properties. The excellent tribological properties would be contributed to the self-repairing and tribo-film formed by nanoparticles and gelators. The Nano-Gels provide effective solution to the application of nanoparticles in lubricating oil, which have great values to prolong the life of mechanisms. [Display omitted] • The manuscript reported a new lubricant that diverse of nanoparticles were introduced to supramolecular gels. • The supramolecular gels realized the long-term dispersion stability of different nanoparticles in lubricants. • Dispersion stability mechanism of nanoparticles in supramolecular gels were penetrated by molecular dynamic simulations. • Nanoparticles as lubricant additives improved the anti-friction and anti-wear performances of supramolecular gels. [ABSTRACT FROM AUTHOR]

Elucidating the tribological behaviors of CoCrNi-based high-entropy alloys (HEAs) at cryogenic temperatures is crucial for their practical application. This work uncovers the correlation between the wear-induced microstructural evolutions and tribological properties of single-phase CoCrFeNiMn HEA and heterogeneous CoCrFeNiAl HEA upon two contact conditions at 173 K. When CoCrFeNiMn HEA matches with GCr 15 rather than Si 3 N 4 , low contact stress and high flash temperature suppress the inhomogeneous deformation initiated by martensitic transformation and in turn create a gradient nanograined tribo-layer activated by high-density dislocations and nano-scale deformation twins, which progressively accommodates the frictional strain and reduces wear by an order of magnitude. Instead, the tribological properties of the CoCrFeNiAl HEA sliding against Si 3 N 4 are slightly superior to those sliding against GCr 15 , owing to the elevated contact stress and reduced flash temperature thicken the protective recrystallized nanocrystalline tribo-layer. Our findings offer guidance for optimizing the tribological properties of HEAs in cryogenic environments. [ABSTRACT FROM AUTHOR]

The (CrAlTiNbV)N x coatings are fabricated by controlling the substrate bias via magnetron sputtering method. Under low substrate bias, the coating tends to form a loose columnar crystal structure with (200) preferred orientation. However, when the substrate bias increases, the coating transforms into a dense nanocrystalline structure, and the (111) orientation is enhanced. As the substrate bias increases, the residual stress and hardness of the coating gradually increase, while the adhesion strength decreases slightly. Friction tests show that the coating possesses the lowest average friction coefficient (about 0.06) and wear rate (8.7 × 10-9 mm3/N·m) in 4050# aviation lubricant, which is achieved under the substrate bias of -96 V and -126 V, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • MXene@Fe 3 O 4 @PNA reduce the COF of water from 0.559 to 0.218, the wear volume decreased by 78.7%. • The excellent lubricating properties are attributed to the tribofilm and hydration layer. • MXene@Fe 3 O 4 @PNA can be heated to 73.1 °C and 123 °C in water and dry state under infrared light. Improving the tribological performance of water via designing nanomaterials as lubricant additive has garnered mounting interest. In this work, the poly-(N-isopropylacrylamide) microgel is grafted onto Fe 3 O 4 nanoparticles surface (Fe 3 O 4 @PNA) via free radical polymerization. Then, the Fe 3 O 4 @PNA can self-anchored on the MXene nanosheets via hydrogen bonding interaction to obtain MXene@Fe 3 O 4 @PNA composite. The as-prepared MXene@Fe 3 O 4 @PNA can effectively reduce friction and wear when used as a water-based lubricant additive. Compared with pure water, the average coefficient of friction (COF) and wear volume decrease by 61% and 78.7%, respectively. The lubrication mechanism was analyzed by focused ion beam technique-TEM (FIB-TEM) and X-ray photoelectron spectroscopy (XPS). The outstanding tribological performance of MXene@Fe 3 O 4 @PNA is attributed to the synergistic lubrication effect of MXene and Fe 3 O 4 @PNA. Interlayer shear of MXene and spherical Fe 3 O 4 @PNA can make MXene@Fe 3 O 4 @PNA play a full role of sliding friction and rolling friction mechanism, which can induce tribo-chemical reactions to form a protective film on the contact area of the friction pair. In addition, the hydrophilic groups of the MXene@Fe 3 O 4 @PNA can adsorb a large number of water molecules and form a hydration layer, reducing the agglomeration of nanosheets and acting as a boundary lubrication film. Moreover, the as-prepared MXene@Fe 3 O 4 @PNA exhibit excellent photothermal conversion performance in both underwater environment and dry state. Based on this characteristic, infrared light can be collected efficiently and stored quickly. Then, convert and utilize it. Therefore, the multifunctional MXene@Fe 3 O 4 @PNA has a broad application prospect as a water-based intelligent lubrication additive. [ABSTRACT FROM AUTHOR]

Abstract High concentration hydrogen peroxide solutions (HCHP) have been attractive as potentially future fuels. However, preparing inner moving-parts with both good compatibility and tribological properties under HCHP remains to be a challenge. Here, the high entropy alloys (HEAs)/Si 3 N 4 tribol-pair with compatible alloy and self-lubricating counterpart was researched. The wear-mechanisms and alloy-structure effects were studied. As a result, the realization of lubricated friction depends on whether the condition meet V formtion (formation velocity of colloidal films)- V attrition (attrition velocity of colloidal films)> V pit (increase velocity of pit depth and amount). HEAs with poorer corrosion resistance and higher strength could more easily achieve effective lubrication. The component inhomogeneity of different structures could promote the corrosion behavior. Graphical abstract Image 1 Highlights • Tribological properties of high entropy alloys under 90 wt. % H 2 O 2 solutions are studied. • The wear-mechanism variations and alloy-structure effects are exploited. • Wear mechanisms depend on the competition between V formtion , V attrition and V pit. • High entropy alloys with poor corrosion resistance and high strength easily achieve lubrication. [ABSTRACT FROM AUTHOR]

TiN-doped Sialon matrix composites are potential candidates for high temperature applications due to their excellent mechanical and tribological properties. The objectives of this work are to thoroughly research the mechanical properties and tribological behaviors of the TiN reinforced Sialon composites and reveal their toughening and wear mechanisms. Results show that the fracture toughness can be obviously enhanced by doping TiN. The fracture toughness of the composite with 10 wt% TiN reaches the maximum value of 6.2 MPa m 1/2 and 4.4 MPa m 1/2 at 25 °C and 800 °C, respectively. Moreover, TiN reinforced Sialon composites exhibit excellent tribological properties at a wide temperature range. Especially for the composite with 30 wt% addition of TiN at 200–800 °C, the friction coefficient reduces to 0.46–0.60, and the wear rate decreases about 15–50 times as compared to the material without TiN. In addition, the toughening and wear mechanisms are revealed on the basis of the crack propagation behavior and tribological properties. The crack propagation behavior indicates that crack deflection is the principal toughening mechanism. The enhancement of heat-conducting property, mechanical properties, and the tribo-chemical reaction are the main friction-reducing and anti-wear mechanisms. [ABSTRACT FROM AUTHOR]

As is well known, it is hard to prepare ceramic-Ag composites, owing to the lower melting temperature of silver. In this paper, Si 3 N 4 -based composites reinforced with in situ formation of Ag particles were successfully fabricated by sintering Si 3 N 4 and AgNO 3 , and their microstructure, elevated-temperature mechanical and tribological properties were investigated. It can be found that Ag particles about 1 µm were uniformly dispersed into the Si 3 N 4 matrix and there was no outflow of silver during the sintering. Meanwhile, S 3 N 4 /Ag composite containing 5.1 wt% silver exhibited the best fracture toughness, 7.05 MPa m 1/2 and 6.12 MPa m 1/2 at 25 °C and 600 °C, respectively, and the plastic deformation and crack bridging of silver were responsible for the high toughness. Besides, the friction coefficient and wear rate of composites were continuously reduced as the silver content increases. Especially at 200 °C, the friction coefficients reached the lowest value due to the formation of an amorphous silicon oxide film. And the wear resistance was enhanced by the cooperative strengthening effect of silver toughening and lubricating. [ABSTRACT FROM AUTHOR]

Ti:WS 2 films with duplex-layer structure were deposited by magnetron sputtering. The mechanical properties and tribological performance of Ti:WS 2 film were improved after Ti incorporation. Ti:WS 2 /P201 hybrid system constructed by combination of Ti:WS 2 film and P201 oil displays a synergistic lubricating effect, significantly prolonging lubricating lifetime compared to the single film. It is attributed to the effectively repairing function in some wear areas owing to the debris acted as an additive in oil. However, the AO irradiation can decrease the tribological performance of Ti:WS 2 /P201 hybrid system to different extent, depending on dose of irradiation. The high-dose AO irradiation rapidly deteriorates the tribological properties of the hybrid system, dramatically shortening the lubricating lifetime. It is found that the AO irradiated oil caused the severe tribo-oxidation reaction with the increase of sliding distance, resulting in forming numerous W oxides and carbide. Finally, failure mechanism of Ti:WS 2 /P201 hybrid system under AO irradiation were revealed. • Ti:WS 2 films with duplex-layer structure were deposited, showing better mechanical property and tribological performance after Ti incorporation. • Ti:WS 2 /P201 system constructed by combination of Ti:WS 2 film and P201 oil, significantly prolonging lubricating lifetime, which attributes to the effectively repairing function in wear areas owing to the debris acted as additive. • AO irradiation decreases the tribological performance of Ti:WS 2 /P201 system to different extent, depending on dose of irradiation. • The high-dose irradiation rapidly deteriorates the tribological properties which mainly atrributed to tribo-oxidation reaction. [ABSTRACT FROM AUTHOR]

Poor interfacial adhesion and inferior UV resistance severely inhibit the development of hybrid Meta-aramid/Polytetrafluoroethylene (Nomex/PTFE) fabric composites for distinguished solid self-lubrication materials, especially under high exterior load and long-term UV irradiation conditions. Herein, glycidyl polyhedral oligomeric silesquioxanes (POSS) nanoparticles are covalently grafted onto the hybrid Nomex/PTFE fabric with a polydopamine/polyethylenimine (PDA/PEI) intermediate layer. The microstructure and chemical characteristics of Nomex and PTFE fibers before and after modification are investigated and the results manifest an obvious increase in surface functional groups and roughness, as well as resin compatibility. Tensile and peeling testing results show that the obtained fabric composites, denoted as hybrid-fabric@PDA/PEI-POSS composites, exhibit 24.3% and 46.8% enhancements in tensile and interfacial bonding strength without discernable decrease in pristine hybrid-fabric strength. In addition, the PDA/PEI-POSS hierarchical coating imparts the hybrid-fabric with excellent UV-shielding properties. As a result, the tribological performance of hybrid-fabric@PDA/PEI-POSS composites presents an obvious improvement under high load and UV irradiation conditions. [ABSTRACT FROM AUTHOR]

This research into environmentally-friendly ionic liquids (ILs) used a series of choline amino acid ILs ([Ch][AA] ILs) prepared from choline cations and several amino acid anions. Their physicochemical and tribological properties were tested, and the results showed that [Ch][AA] ILs had good lubricating properties for different friction pairs at room temperature (RT). Their toxicities were checked against three aquatic organisms: brine shrimp, zebrafish and green algae. The results showed that they have a remarkably low toxicity. Versus traditional IL 1-butyl-3-methyl imidazolium tetrafluoroborate (L-B104), the [Ch][AA] ILs had comparable or even better physicochemical and tribological properties. More importantly, they had the environmentally features of biodegradability and non-toxicity. [ABSTRACT FROM AUTHOR]

AlMgB 14 based composites are promising candidates for use as cutting tool etc. In this respect, tribological behavior is one of the most important performances among all the criteria. In this work, a novel AlMgB 14 -30 wt% Si composite (referred to as BMAS30) was prepared by Spark Plasma Sintering. and its tribological property was investigated under different counterface materials (316 L and Si 3 N 4 ) and loads in ambient environment. Besides, the fracture toughness and the hardness were measured. We found that BMAS30 has a good fracture toughness of 5.90 MPa m 1/2 and a super-high hardness of 27 GPa. In terms of the tribological properties, BMAS30 shows good tribological properties when sliding against 316 L, i.e., a lower friction coefficient of 0.19–0.28 and wear rate of 7.00–8.00 × 10 −6 mm 3 /N m, while it presents a relatively high friction coefficient of 0.35–0.46 and wear rate of 3.80–9.00 × 10 −5 mm 3 /N m when sliding against Si 3 N 4 . In the former case, large numbers of Si grains pull-out pits formed on the worn surface that can store wear debris, which is conducive to lower the friction and wear; the latter produces severe fatigue fracture under high Hertz contact stress and thereby aggravates the friction and wear. [ABSTRACT FROM AUTHOR]

In aerospace, some moving parts will meet with simultaneous high temperature and vacuum environments. In this study, the tribological behavior of a nickel alloy matrix solid lubricant composite was contrastively investigated under both air and vacuum conditions from room temperature to 800 °C. Results showed that both the friction coefficient and the wear rate of the composite were highly dependent on testing temperature and atmosphere. The friction coefficient in vacuum was lower than that in ambient air. The compositions of the frictional surfaces were analyzed, based on which, the mechanism of friction and wear was proposed. [ABSTRACT FROM AUTHOR]

In this paper, the tribological behaviors of 20 and 40 vol% in situ TiB 2 reinforced TiAl-based composites sliding against SiC balls were investigated in artificial sea water, and TiAl alloy was also studied as a comparison. The results showed that the TiAl-TiB 2 composites are lubricated in artificial sea water and TiB 2 is effective to improve the wear resistance of the TiAl alloy. Also, it was found that the tribological behaviors have a dependency on the applied loads and sliding speeds. Worn surface morphologies and composition together with electrochemical behaviors of the materials were evaluated and related to the tribological behaviors. [ABSTRACT FROM AUTHOR]

Al matrix composites reinforced with Ti 3 AlC 2 and Cu coated Ti 3 AlC 2 were prepared by hot-press sintering approach. It was confirmed that Ti 3 AlC 2 displayed poor wettability with Al, resulting in the poor interfacial bonding strength between Ti 3 AlC 2 and Al matrix. However, Al 2 Cu layer could be formed due to the reaction between Cu and Al during the sintering process, when Cu coated Ti 3 AlC 2 was incorporated in Al matrix. Because of the formation of enhanced Al 2 Cu interface, the mechanical and tribological properties were significantly improved. The Al 2 Cu layer could bridge Ti 3 AlC 2 particle and Al matrix effectively, which contributed to absorbing energy when load was applied, to provide better mechanical properties. Moreover, Ti 3 AlC 2 particle could exhibit powerful pinning effect to inhibit two-body abrasion and adhesion wear, which was favorable for forming smooth tribo-oxidation surface to yield low friction coefficient. The wear mechanism was believed to be oxidation and fatigue wear. [ABSTRACT FROM AUTHOR]

WS 2 films with duplex-layer structure were deposited by magnetron sputtering. The tribological differences of as-deposited, AO-irradiated WS 2 films and WS 2 /P201 hybrid system were mainly investigated for the same film. In comparison with as-deposited WS 2 film, AO-irradiated WS 2 film exhibits the lower initial friction coefficient and lower wear rate, and longer service longevity. Meanwhile, WS 2 /P201 hybrid system significantly extended service life further. It is found that the generated WS 2 debris act as lubricating agent with different participation states and air isolation in the different lubricating systems affect the tribological property of WS 2 film. Eventually, different lubrication mechanisms for AO-irradiated WS 2 film and WS 2 /P201 hybrid system in vacuum were revealed. [ABSTRACT FROM AUTHOR]

The thermal stability of polymer matrix composite could effectively improve by incorporation of highly thermally conductive ceramic materials into polymers. In present work, hybrid PTFE/Nomex fabric/phenolic composite specimens were prepared with zirconium diboride (ZrB 2 ) particles for the improvement its high-temperature tribological performances. The thermal stability of hybrid PTFE/Nomex fabric/phenolic composite was investigated by TGA. The result showed that the thermal stability was improved because of addition of ZrB 2 particles. In addition, it was found that 9 wt% ZrB 2 reinforced hybrid PTFE/Nomex fabric/phenolic composite exhibited optimal tribological performances compared to unfilled fabric composite under all test conditions. [ABSTRACT FROM AUTHOR]

We report a new type of zwitterionic gelator, which cannot only gelate base lubricating oils by supramolecular self-assembly, but be used as additive in oils for significantly improved the tribological performances. The self-assembly mechanism is confirmed by NMR. The as-prepared zwitterionic gels have good thermoreversible and thixotropic characteristics, which make them as potential high performance semi-solid lubricants. The tribological results showed that the gel lubricants possessed excellent friction-reducing and anti-wear properties compared with blank 500SN and Li-base grease with 2 wt% MoS 2 . The morphologies of the worn surfaces were analyzed by scanning electron microscope (SEM). The lubrication mechanism is proposed according to in-situ electrical contact resistance and the surface composition analysis at the worn surfaces. [ABSTRACT FROM AUTHOR]

Tribological properties of AlCoCrCuFeNi and AlCoCrFeNiTi 0.5 alloys under 90% H 2 O 2 solution rubbing against 1Cr18Ni9Ti steel, ZrO 2 ceramic and SiC ceramic were investigated. The tribological behavior is dependent on the counterparts and the structure of high entropy alloys. The high entropy alloys exhibit significantly lower friction coefficient and wear loss sliding against SiC ceramic than 1Cr18Ni9Ti steel and ZrO 2 ceramic, which can be attributed to the lubricating colloidal film formed by tribo-chemical reaction between H 2 O 2 and SiC. Moreover, the AlCoCrFeNiTi 0.5 /SiC tribo-pair preserves better tribological properties than AlCoCrCuFeNi/SiC tribo-pair, as results of high strength and hardness of AlCoCrFeNiTi 0.5 alloy. [ABSTRACT FROM AUTHOR]

The tribological behaviors of the (W 0.67 Al 0.33 )C 0.67 –Co/fluoride (CaF 2 , BaF 2 , CaF 2 /BaF 2 ) composites against SiC ball from room temperature to 600 °C were investigated. A marked increase in the friction coefficient resulting from fluoride oxidation was observed as the temperature increased. The composites containing BaF 2 or (Ca, Ba)F 2 displayed better integrated wear resistance over a wide temperature range compared with (W 0.67 Al 0.33 )C 0.67 –Co/CaF 2 . The high temperature tribological characteristics of the three composites were distinct, which originated from the composition difference on the worn surfaces. First, the SiO 2 /SiC film formed on the worn surfaces of the composites with BaF 2 or (Ca, Ba)F 2 was favorable for their wear resistance. Second, the oxidation of WC matrix was an important factor influencing the wear resistance of the composites. When mixture oxides of WO 2 and WO 3 appeared on the surface, wear is severe. In addition, single WO 3 formed on the worn surfaces, appeared more adhesive to the underlying substrate and decreased the wear rate. [ABSTRACT FROM AUTHOR]

Purpose - The aim of this paper was to inhibit the serious corrosion of conventional ionic liquids, a series of new ionic liquids (ILs) containing the triazole functionality, as the anti-corrosion groups were synthesized in this work. Design/methodology/approach - It is well known that nitrogen and sulfur containing organic compounds have been traditionally used as corrosion inhibitors. Among them, triazole derivatives are most often used as corrosion inhibitors. To alleviate the corrosion of the ILs and further improve the anti-wear property, the authors prepared a series of imidazolium ILs modified with the triazole functionality in the present study. Findings - The corrosion behavior of the ILs was evaluated with the iron disk corrosion test and their tribological properties were investigated on an Optimol SRV IV oscillating friction and wear tester at elevated temperatures. The results showed that the ILs with the triazole functionality could effectively reduce the corrosion and exhibit a smaller friction coefficient and wear volume than the unmodified counterpart. The ILs containing the triazole functionality can be used as the single component anti-corrosion base oils even at elevated temperatures. Originality/value - The results showed that the ILs with the triazole functionality could effectively reduce the corrosion and exhibit a smaller friction coefficient and wear volume than the unmodified counterpart. The ILs containing the triazole functionality can be used as the single component anti-corrosion base oils even at elevated temperatures. [ABSTRACT FROM AUTHOR]

The tribological behavior of nanocrystalline Fe 88 Si 12 alloy in vacuum environment has been investigated compared with coarse grained counterpart. The results demonstrated that the friction coefficient of the Fe 88 Si 12 alloy reduced with the decrease of both grain size and oxygen partial pressure. The wear resistance of the Fe 88 Si 12 alloy improved more effective in vacuum than in air as the grain size decreased. As the hardness and oxidation activity of the Fe 88 Si 12 alloy decreased, the wear mechanism changed from adhesion and oxidation to plastic deformation and adhesion when the grain size and oxygen partial pressure decreased. [ABSTRACT FROM AUTHOR]

Ni 3 Al matrix composites with addition of silver and barium salt (BaCrO 4 , BaMoO 4 ) were fabricated by powder metallurgy. It was found that from room temperature to 800 °C, Ni 3 Al matrix composite with addition of Ag and BaCrO 4 offers the continuous lubrication properties, and its friction coefficient ranges from 0.29 to 0.38; Ni 3 Al matrix composite with addition of Ag and BaMoO 4 also offers the favorable lubricating properties; the friction coefficient ranges from 0.28 to 0.35 in a wide temperature range. The low friction coefficient in a wide temperature range could be attributed to the synergistic effect of Ag and barium salts. [ABSTRACT FROM AUTHOR]

In this paper, the dry-sliding tests of Ti 3 AlC 2 /SiC tribopairs were conducted from 25 °C to 1000 °C in both air and argon atmospheres for confirming the roles of tribo-oxidation and laminate structure of Ti 3 AlC 2 . The characteristics of the worn surfaces of the Ti 3 AlC 2 were contrastively examined and the corresponding tribological mechanisms were discussed. Ti 3 AlC 2 showed distinctive tribological behaviors and mechanisms in the two atmospheres. Here, the tribo-oxidation film played a very vital role for the tribology of Ti 3 AlC 2 . In air, Ti 3 AlC 2 showed moderate wear at 25–400 °C and Ti 3 O 5 was the major phase of the tribofilms. At 600–1000 °C, the wear-resistant tribo-oxidation films, consisting of TiO 2 and Al 2 O 3 , were believed to be responsible for the negligible wear. In argon, Ti 3 AlC 2 exhibited heavy wear in the whole temperature range. Abrasive and adhesive wear caused the poor tribological performances at 800 °C and below. At 1000 °C, Ti 3 AlC 2 displayed plastic flowing and large furrows under the shear stress. [ABSTRACT FROM AUTHOR]

The mechanical and tribological properties of the Fe–15.88Al–5.46Cr (wt.%) based composites reinforced with 15, 25, 35 wt.% novel W 0.5 Al 0.5 C 0.5 particulates (referred to FA15, FA25 and FA35), produced by hot-press sintering, were evaluated. The hardness of the composites increased with the W 0.5 Al 0.5 C 0.5 content but the bending strength firstly decreased and then increased. The wear resistance of the composites was dramatically superior to Fe–15.88Al–5.46Cr alloy (FA0) without mass density gain. Interestingly, the wear resistance increased with W 0.5 Al 0.5 C 0.5 concentration from 15 to 25 wt.%, but then slightly declined when W 0.5 Al 0.5 C 0.5 content was up to 35 wt.%. It is also surprised that FA25 displayed the lowest friction coefficient, while that of other composites was much higher than Fe–15.88Al–5.46Cr alloy. These abnormal mechanical and tribological behaviors would be associated with the microstructure of the composites and the composition of the worn surfaces. The wear mechanism of the composites was abrasion and oxidation wear. [ABSTRACT FROM AUTHOR]

Ag films, deposited by arc ion plating, had been exposed for 43.5 h in real low earth orbit (LEO) space environment by a space environment exposure device (SEED) aboard the China Shenzhou-7 manned spaceship. The structure, morphology, composition and tribological property of the Ag films after the space environment exposure (SEE) were investigated using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscope (XPS) and ball-on-disk tribometer, respectively. Depth XPS and XRD analysis revealed that after the SEE, the surface layer of Ag films was partially oxidized to Ag 2 O, the cracking and flaking phenomena could be observed from the film surface by FESEM, and so the Ag films lose its metallic shine and became gray. As a result, the tribological performance was deteriorated and the high/unstable friction was obtained. [ABSTRACT FROM AUTHOR]

Producing fabric composites with improved high-temperature tribological property is highly desired for their use in practical application, yet still challenging. Herein, we employed MoSi 2 as anti-oxidant and filled it into the hybrid PTFE/Nomex fabric/phenolic composite. The high-temperature tribological properties of the fabric composites were evaluated on a pin-on-disk tribometer. The results showed that the MoSi 2 filled fabric composites displayed much lower wear rates in high-temperature environment, comparing to that of unfilled fabric composite. Moreover, the antiwear property of the MoSi 2 filled fabric composite can be further improved by treating the fabric with air-plasma, as the bonding strength between the fabric and resin was evidently enhanced. The wear behaviors and the corresponding wear mechanisms of the composites were discussed based on the characterizations. [ABSTRACT FROM AUTHOR]

Abstract: The tribological behavior of a Ni3Al alloy prepared by hot-pressed sintering was investigated at dry friction and sea water condition against AISI 52100 steel ball in ambient environment and at varying loads. The tribological results suggested that the Ni3Al alloy has the better wear resistance properties compared to Ti–6Al–4V alloy at dry friction and sea water conditions, and the Ni3Al alloy possesses the excellent wear resistance properties under sea water environment. Sea water plays a significant role in the improvement of tribological properties of the Ni3Al alloy, which has lubricating, cooling, and corrosive effects on the friction pairs. [Copyright &y& Elsevier]

To improve the tribological properties of WS film both in vacuum and in humid air conditions, its microstructure was optimized by doping different concentrations of Cu via radio frequency co-sputtering method. The film microstructure and composition were investigated by field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, grazing incidence X-ray diffraction and high-resolution transmission electron microscopy. It was verified that Cu was presented in amorphous phase in the WS matrix and could also induce amorphization and densification of the composite films gradually. The film microstructure changed from coarse columnar platelet structure at low Cu content (0-5.8 at.%) to transition structure with two separate layers at increased Cu content (11.5-16.2 at.%) and to a featureless structure at high Cu content (above 24.4 at.%). The mechanical and tribological properties of films were evaluated using the scratch tester and ball-on-disk tribometer, respectively. It was found that the incorporation of a suitable content of Cu dopant could significantly improve the film toughness, but excess amount of Cu dopant lead to high brittleness. All the composite films exhibited much lower wear rate and longer wear life than those of pure WS film both in vacuum and in humid air conditions. The wear mechanisms were proposed after correlating the mechanical performance with film microstructure. [ABSTRACT FROM AUTHOR]

• Preparation of gallate ionic liquids (GAILs). • Their lubricating performances for copper and aluminum friction pairs are discussed. • The GAILs show prominent friction reduction and wear resistance properties. • The properties are attributed the formed physicochemical adsorbing films. In this study, four kinds of GAILs were prepared and used to lubricate copper and aluminum friction counterfaces. Their physicochemical and tribological properties were systematically investigated. The results showed that the GAILs have better performances with regard to viscosity-temperature characteristic, corrosiveness and hydrolytic stability as compared with the two traditional halogen-containing IL lubricants L-B104 and L-F104. Moreover, the most prominent nature of the GAILs are their excellent friction reduction and wear resistance properties as lubricants for copper and aluminum friction counterfaces, while traditional halogen-containing ILs are generally found to be unsuitable for lubricating these counterfaces. The excellent tribological properties of the GAILs are conjectured to be largely attributed to the physical/chemical adsorbed films formed by the GAIL molecules on the friction surfaces, which is further verified by QCM and XPS analysis results. [ABSTRACT FROM AUTHOR]

[Display omitted] • The (CrAlTiNbV)N x high-entropy coatings are prepared by magnetron sputtering method. • All coatings exhibit columnar growth morphology and own a single FCC structure. • The S-38 owns a friction coefficient of 0.096 and wear rate of 1.8 × 10−7 mm3/(N·m). • The excellent wear resistance of S-38 is mainly attributed to its dense structure. (CrAlTiNbV)N x high-entropy nitride coatings are deposited via tuning nitrogen flow rates, and evaluating their influence on the microstructure, mechanical and tribological properties of the coatings. All deposited coatings exhibit columnar growth morphology and own a single face-center-cubic structure. As the nitrogen flow rate increases, the preferred orientation of the coating gradually transfers from (1 1 1) to (2 0 0) and (2 2 0), and then changes back to (1 1 1) with the nitrogen flow rate continues to increase. The S-38 sample possesses the optimal plastic deformation resistance and adhesion strength. Friction and wear results show that the (CrAlTiNbV)N x coating deposited at nitrogen flow rate of 38 sccm owns the best tribological properties with a friction coefficient of 0.096 and wear rate of 1.8 × 10−7 mm3/(N·m) in 4050# aviation oil. [ABSTRACT FROM AUTHOR]

Ester oils (1,4,5,8-4C n) were synthesized through esterification of naphthalene-1,4,5,8-tetracarboxylic acid with aliphatic alcohols. The molecular structures were confirmed with 1H NMR, 13C NMR, FT-IR and elemental analysis. Their KV, VI, FP, PP, oxidation and thermal stabilities, friction reducing and anti-wear performances were measured. The results demonstrate that the 1,4,5,8-4C n have obviously higher thermal and oxidation stabilities than the existing esters DOS, PIS and Phe-3C i8. They also have predominant tribological behavior at both 50 °C and 120 °C. Analyzing from the results of ECR, QCM and XPS, it could be concluded that strongly and orderly physicochemical adsorption of the 1,4,5,8-4C n molecules on the sliding surfaces is the critical factor for these oils to demonstrate excellent tribological performance for steel contacts. • Naphthoate oils were prepared and evaluated as lubricants for steel/steel contact. • The oils have high thermal and oxidation stabilities. • The oils exhibited predominant tribological property. • The predominant property owns to physiochemically adsorbed film formation. [ABSTRACT FROM AUTHOR]

A novel and simple method for the preparation of two-component gel lubricant and some evaluation of its physicochemical and lubricating properties are reported. The addition of two-component gelator including bis(2-ethylhexyl) sulfosuccinate and cholesterol to white oil can result in self-assembly to form a gel. The gelation mechanism was characterized by the combination of atomistic molecular dynamics simulation and experiment. It not only has excellent thermal stability, but also possesses thermal reversibility, creep recovery and thixotropic properties. Noticeably, the gel can significantly enhance lubricous and AW performances of base oil. Obtained by FIB-TEM, EDS, XPS and QCM characterization, we speculate that the gelator forms an effective adsorption and tribochemical reaction film, so it can protect the contact surface from being worn. Image 1 • The manuscript reports a novel, simple and low cost method for the preparation of two-component gel lubricant. • The AOT and cholesterol added to food grade white oil can result in self-assembly to form a gel. • The obtained gel lubricants have excellent lubricity, wear resistance and higher load carrying capacity. • The gel lubricants are green and non-toxic, provide potential application in the field of food or drug processing. [ABSTRACT FROM AUTHOR]