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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]

Purpose – The purpose of this paper is to investigate the tribological properties of Si3N4 sliding against Dy-sialon ceramics lubricated by two novel phosphazenes bridged fluorophenoxycyclotriphosphazene (coded as L-2P) and metal halide-stabilized linear phosphazene derivatives (coded as LMZn-3). The traditional phosphazene tetrakis (3-trifluoromethylphenoxy)-bis(4-fluorophenoxy) – cyclotriphosphazene (X-1P) was also tested as the reference. Design/methodology/approach – The lubricity characteristics of phosphazene derivatives were evaluated on an Optimol SRV oscillating friction and wear tester. The morphology of the worn sialon surface was analyzed with a scanning electron microscope (SEM) and X-ray photoelectron spectroscope (XPS). Findings – The two novel phosphazenes are effective lubricants for Dy-sialon and show superior tribological properties to traditional phosphazene X-1P and glycerol. Among all lubricants, linear phosphazene LMZn-3 exhibits the lowest wear volume loss at 20°C or 100°C. Moreover, LMZn-3 and L-2P show much better antiwear ability than X-1P under higher load than 60N. The decreased friction coefficient and wear volume of Dy-sialon ceramics under lubrication of the phosphazene lubricants are attributed to the tribochemical products mainly consisting of organic oxyfluoride or carbonfluoride species and silicon fluoride. Research limitations/implications – The paper deals with only limited compounds. The paper works on the subject progressively to explore more combinations for better tribological properties. Practical implications – The phosphazene derivatives present better tribological performance used as base oils and additives. Originality/value – There are few data about other phosphazene with different structures, such as bridged cyclotriphosphazene and metal halide-stabilized linear phosphazene, used as lubricants for ceramics materials. [ABSTRACT FROM AUTHOR]

Abstract: The tribological properties of Ni-17.5Si-29.3Cr alloy against Si3N4 were studied on a ball-on-disc tribotester between room temperature and 1000°C. The effects of temperature on the tribological properties of the alloy were investigated. The worn surfaces of the alloy were examined using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results indicated that the tribological behavior of the alloy expressed some differences with increase in testing temperature. At low and moderate temperatures (below 800°C), the alloy showed excellent wear and oxidation resistances, and the wear rate of the alloy remained in the magnitude of 10−5 mm3/Nm; but at elevated temperature (800–1000°C), the wear and oxidation resistances decreased, and the wear rate of the alloy increased up to 10−4 mm3/Nm. The friction coefficient decreased from 0.58 to 0.46 with the rising of testing temperature from 20 to 600°C, and then remained nearly constant. The wear mechanism of the alloy was mainly fracture and delamination at low and moderate temperatures, and transformed to adhesive and oxidation at elevated temperatures. [Copyright &y& Elsevier]

Abstract: The tribocorrosion property of a Ni-17.5Si-29.3Cr alloy against a Si3N4 ball was studied in comparison with AISI321 stainless steel using a ball-on-disk reciprocating tribotester in 1M sulfuric acid (H2SO4) solution. The effects of load and sliding speed on the tribocorrosion properties of the alloy were investigated. The results indicated that the wear rate of the alloy increased while the friction coefficient decreased with increasing load. The wear rate of the alloy increased linearly with increasing sliding speed and the friction coefficient increased in the initial stages and then remained constant with increasing sliding speed. The wear mechanisms were mainly microploughing, uniform corrosion and pitting corrosion. Under the experimental conditions of the present study, the Ni-17.5Si-29.3Cr alloy showed excellent corrosion-resistence and anti-wear ability compared with AISI321 stainless steel. [Copyright &y& Elsevier]

Abstract: TiO2, SiO2, hydroxyapatite (HA), TiO2–HA and SiO2–HA thin films with good biocompatibility were grown on Ti–6Al–4V (coded as TC4) substrate by sol–gel and dip-coating processes from specially formulated sols, followed by annealing at 500°C. The chemical states of some typical elements in the target films were detected by means of X-ray photoelectron spectroscopy (XPS). High-resolution scanning electron microscopy (SEM) is applied to characterize the surface and cross-sectional morphologies of obtained films. Various phases of the films were characterized by XRD. The tribological properties of thin films sliding against an AISI52100 steel ball were evaluated on a reciprocating friction and wear tester. As a result, the target films were obtained. Compared with the TC4 substrate, all the sol–gel ceramic films are superior in resisting wear. Among all, HA film shows the best resistance while SiO2 film shows the worst wear resistance both under higher (3N) and lower load (1N). TiO2 shows a good wear resistance under lower load but higher load. Compared with TiO2, the wear resistance of the dual film TiO2–HA can be improved under 3N but deteriorated under 1N. Compared with SiO2, the wear resistance of SiO2–HA is improved both under 3N and 1N. Compared with HA, the wear resistances of dual films are deteriorated both under 3N and 1N. Under 0.5N, a very long wear life for TiO2–HA is also obtained, illustrating that the lower wear resistance of dual films is closely related to the applied load. SEM observation of the morphologies of worn surfaces indicates that the wear of TC4 is characterized by abrasive wear. Differently, abrasion, plastic deformation and micro-crack dominate the wear of ceramic films. The superior friction reduction and wear resistance of HA films are greatly attributed to the slight plastic deformation of the film. Sol–gel is a potential method being applied to implant materials for wear protection according to proper process designs. The single HA film and the dual TiO2–HA film is suggested for biomedical application from the point of view of wear protection. [Copyright &y& Elsevier]

Abstract: The friction and wear behavior of a steel-on-steel contact lubricated by two novel synthetic linear phosphazene oligomers with different side branches and by perfluoropolyethers (PFPE) was comparatively investigated on an oscillating friction and wear tester. The thermal stability of the lubricants was investigated by means of thermogravimetric analysis. The worn surfaces were analyzed by means of scanning electron microscopy, energy-dispersive spectrometry, and X-ray photoelectron spectroscopy. It was found that the two synthetic linear phosphazene oligomers were more effective than PFPE in increasing the wear-resistance of the steel-on-steel frictional pair. The phosphazene oligomer having aromatic rings had better friction-reducing ability and higher thermal stability, and that having fluoropolyether gave higher load-carrying capacity. Tribochemical reaction was involved in the sliding of steel against steel under the lubrication of the lubricants, with the generation of a protective layer composed of inorganic fluoride FeF2 and organic compounds consisting of C, F, O, N and P. The protective layer originated from the tribochemical reaction together with the adsorbed boundary lubricating layer containing organic compounds played an important role in improving the friction and wear behavior of the steel-on-steel system. [Copyright &y& Elsevier]

Abstract: Oleic acid (OA) capped PbS nanoparticles were chemically synthesized and characterized by means of Fourier transform-infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray electron diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The triboligical properties of the capped PbS nanoparticles as additive in liquid paraffin was investigated using a four-ball machine. The lubricating mechanisms were discussed along with the analyses results of XPS and scanning electron microscope (SEM). Results show that OA-capped PbS nanoparticles, with an average diameter of about 8nm, are able to prevent water adsorption, oxidation and are capable of being dispersed stably in organic solvents or mineral oil. OA-capped PbS nanoparticles as an additive in liquid paraffin perform good antiwear and friction-reduction properties owing to the formation of a boundary film. [Copyright &y& Elsevier]

Abstract: The friction and wear behavior of a steel-on-steel contact lubricated by phosphazene-type additive tetrakis(3-trifluoromethylphenoxy)-bis(4-fluorophenoxy)-cyclotriphosphazene (X-1P) and novel synthetic bridged cyclotriphosphazenes was investigated on a oscillating friction and wear tester. The thermal stability of the lubricants was investigated by means of thermogravimetric analysis. It was found that bridged cyclotriphosphazenes give lower wear volume loss and higher thermal stability than X-1P. In particular, the bridged cyclotriphosphazene with aromatic-ring side branch structures has the best antiwear ability and thermal stability among the investigated lubricants. The worn surfaces were analyzed by means of scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). It was found that tribochemical reaction was involved in the sliding of steel against steel under the lubrication of the synthetic lubricants, with the generation of a protective layer composed of inorganic fluoride FeF2 and organic compounds consisting of C, F, O, N and P, which contributed to improve the friction and wear behavior. [Copyright &y& Elsevier]

High oriented ceria-stabilized zirconia (CSZ) thin films were prepared by the sol-gel method using zirconium oxychloride octahydrate and cerium chloride hexahydrate as starting materials. The morphology and microstructure of the films were investigated via X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The films contained only tetragonal phase and showed nanoscale uniformity. Tribological properties were investigated by using a one-way reciprocating tribometer. Under low load (0.05 N), the films displayed excellent tribological properties in sliding against Si3N4 balls. The friction coefficient was as low as 0.15–0.19 and the wear life was more than 5000 sliding cycles. The tribological properties of CSZ/AISI52100 steel system was inferior to CSZ/Si3N4 system. The wear mechanism of CSZ films in sliding against Si3N4 under low load was fatigue wear, slight abrasion and scuffing, whereas that of in sliding against AISI52100 steel was abrasive wear and plastic deformation. [Copyright &y& Elsevier]

TiO2 thin films were grown on a glass substrate by sol–gel and dip-coating processes from specially formulated sols, followed by annealing at 460 °C. Thermogravimetric analysis (TGA) and differential scanning calorimetric analysis (DSC) of dried sols were performed to explore the thermal events occurring during the annealing process of the sol–gel TiO2 films. The chemical states of some typical elements in the target films were detected by means of X-ray photoelectron spectroscopy (XPS). The morphologies of the original and worn surfaces of the samples were analyzed by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM). The tribological properties of TiO2 thin films sliding against AISI52100 steel and Si3N4 ball were evaluated on a reciprocating friction and wear tester. As the results, the target film was obtained and reaction may have taken place between the film and the glass substrate. TiO2 films are superior in reducing friction and resisting wear compared with the glass substrate. SEM observation of the morphologies of worn surfaces indicates that the wear of glass is characteristic of brittle fracture and severe abrasion. Differently, abrasion, plastic deformation and micro-crack dominate the wear of TiO2 films. The superior friction reduction and wear resistance of TiO2 films are attributed to slight plastic deformation as well as good adhesion of the film to the substrate. [Copyright &y& Elsevier]

Cyclotriphosphazene lubricants were synthesized and the relationship between their structures and tribological properties was investigated using an optimol SRV oscillating friction and wear tester and one-way reciprocating friction tester. The elemental composition and chemical nature of the antiwear films generated on 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). It was found that aryloxyphosphazene with polar substituent as a lubricant of steel–steel and steel–aluminum pair gave low wear, while aryloxyphosphazene with nonpolar group on the phenyl pendant led to high wear. Phosphazene provides poor lubricity for the steel–aluminum system under low load (0.5–3 N). The XPS analytical results of the antiwear films generated on the steel and aluminum surface indicate that phosphazene reacted with steel or aluminum counterface and formed a surface protecting film consisting of fluoride and organic compounds containing O, C, F, N, and P during friction. This contributes to reduce the friction and wear of steel–aluminum system. [Copyright &y& Elsevier]

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]

Purpose – The purpose of this paper is to study the influences of test conditions to the tribological behavior of LaF3 nanoparticles as an additive to a polyalphaolefin (PAO). Design/methodology/approach – An Optimol-SRV4 oscillating friction and wear tester (SRV) were used to investigate the tribological properties of LaF3 nanoparticles as an additive in a polyalphaolefin (PAO). The 3-D morphologies and wear loss volume of the worn scar were measured using a surface profilometer. The chemical state and the intensity of La and F elements on worn surface after friction test was investigated with X-ray photoelectron spectroscopy to interpret the possible mechanisms of friction-reduction and anti-wear with LaF3 nanoparticles. Findings – The experimental results show that LaF3 nanoparticles added to PAO exhibit excellent load-carrying capacity, anti-wear and friction-reduction properties. LaF3 nanoparticles deposited on the worn surface under lower test temperature during the friction test, and higher applied load, higher test frequency and longer test duration are propitious to the deposition of LaF3 nanoparticles accumulated on the rubbing surface. Under higher temperature, a complicated tribo-chemical reaction occurred during the friction process, the tribo-chemical reaction product of La2O3 deposit on worn surface, which also exhibits good lubricating performance. Originality/value – This paper investigates the tribological properties of LaF3 nanoparticles as green oil additive in poly-alpha-olefin (PAO) under variable temperature, applied load, sliding speed and sliding duration. The results could be very helpful for the further applications of LaF3 nanoparticles additives in industry. [ABSTRACT FROM AUTHOR]

Abstract: In order to improve the tribological properties of titanium-based implants, sodium hydroxide (NaOH), hydrogen peroxide (H2O2) solutions, sol–gel hydroxyapatite (HA) film, thermal treatment and combined methods of NaOH solution/HA film, H2O2 solution/HA film are used to modify the surfaces of Ti–6Al–4V (coded TC4). The chemical states of some typical elements in the modified surfaces were detected by means of X-ray photoelectron spectroscopy (XPS). The tribological properties of modified surfaces sliding against an AISI52100 steel ball were evaluated on a reciprocating friction and wear tester. As the results, complex surfaces with varied components are obtained. All the methods are effective in improving the wear resistance of Ti–6Al–4V in different degrees. Among all, the surface modified by the combined method of NaOH solution/HA film gives the best tribological performances. The friction coefficient is also greatly reduced by the modification of NaOH solution. The order of the wear resistance under 3N is as following: Ti–NaOH–HA>Ti–NaOH>Ti–HA>Ti–H2O2–HA>Ti–H2O2 >Ti–500; under 1N is Ti–HA, Ti–NaOH–HA>Ti–NaOH. For Ti–H2O2, a very low friction coefficient and long wear life over 2000 passes is obtained under 1N. SEM observation of the morphologies of worn surfaces indicates that the wear of TC4 is characteristic of abrasive wear. Differently, abrasion, plastic deformation and micro–crack dominate the wear of Ti–HA; slight abrasive wear dominate the wear mechanism of Ti–NaOH and microfracture and abrasive wear for Ti–NaOH–HA and Ti–H2O2–HA, while the sample modified by thermal treatment is characterized by sever fracture. The superior friction reduction and wear resistance of HA films are greatly attributed to the slight plastic deformation of the film. NaOH solution is superior in improving the wear resistance and decreasing the friction coefficient under relative higher load (3N) and H2O2 is helpful to reduce friction and wear under relatively lower load (1N). Combined method of Ti–NaOH–HA is suggested to improve the wear resistance of Ti–6Al–4V for medial applications under fretting situations. [Copyright &y& Elsevier]

A novel polyelectrolyte‐grafted multiwalled carbon nanotubes (MWCNTs‐g‐PILs) which possesses a hard backbone of MWCNTs and a soft shell of brush‐like poly (ionic liquids) (PILs) has been synthesized via the surface atom transfer radical polymerization (ATRP). Chemical structure and the grafted PILs quantities of MWCNTs‐g‐PILs were determined by FTIR, TGA, and XPS. TEM and FE‐SEM observations indicate that the nanotubes were coated with a PILs layer, exhibiting core‐shell nanostructures with the PILs chains as the brush‐like or hairy shell and the MWCNTs as the hard backbone. Furthermore, the effect of counter‐anions on the solubility of MWCNTs‐g‐PILs was investigated. The results indicate that relative solubility of MWCNTs‐g‐PILs in various solvents could be switched by anion exchange. This tunable solubility results in the formation of the cycle of reversible phase‐transition. Tribological property of MWCNTs‐g‐PILs as additives in base lubricant 1‐methyl‐3‐butylimidaaolium hexafluorophosphate (LP104) was evaluated using an Optimol SRV oscillating friction and wear tester, confirming that MWCNTs‐g‐PILs are the excellent antiwear and friction‐reducing additives, which can amend the tribological properties of base lubricant significantly. This is attributed to the good dispersibility and core‐shell structure of MWCNTs‐g‐PILs. These results reported in this work may open primarily toward constructing a bridge among carbon nanotues (CNTs), ILs, and lubricant additives and secondarily to prove that CNTs (modified CNTs) as lubricant additives are promising candidates. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7225–7237, 2008 [ABSTRACT FROM AUTHOR]

Abstract: SiO2, TiO2, and hydroxyapatite (HA) thin films with good biocompatibility were grown on Ti–6Al–4V (coded as TC4) substrate by sol–gel and dip-coating processes from specially formulated sols, followed by annealing at 500°C The chemical states of some typical elements in the target films were detected by means of X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) and high-resolution scanning electron microscopy (SEM) are applied to characterize the original unworn films. The tribological properties of thin films sliding against an AISI52100 steel ball were evaluated on a reciprocating friction and wear tester. As the result, the target films composed of nano-particles ranging from 30nm to 100nm around were obtained. All the sol–gel ceramic films are superior in resisting wear compared with the TC4 substrate. Among all, HA film shows the best resistance while SiO2 film shows the worst wear resistance both under higher (3N) and lower load (1N). TiO2 shows good wear resistance under lower load (1N). SEM observation of the morphologies of worn surfaces indicates that the wear of TC4 is characteristic of abrasive wear. Differently, abrasion, plastic deformation and micro-fracture dominate the wear of ceramic films. The superior friction reduction and wear resistance of HA film is greatly due to the slight plastic deformation of the film. It is supposed that the deformation of the HA film is closely related to the special arrangement of the nano-particles and microstructure. HA film is recommended for clinical application from the point of wear resistance view. [Copyright &y& Elsevier]

Abstract: The tribological properties of Fe3Al composites with 40, 60 and 80wt.% Fe3AlC0.5 under dry sliding against AISI52100 steel at ambient conditions were studied. Effects of load and sliding speed on the tribological properties were investigated. Worn surfaces of the composites were analyzed by scanning electron microscopy. It was found that wear rate of the composites were in the magnitude of 10−4–10−3 mm3/m. The composites with 60 and 80wt.% Fe3AlC0.5 had much lower wear rates than that containing 40wt.% Fe3AlC0.5. The wear rate of the composites increased with increasing load, and decreased at first with increasing sliding speed and then those of the composites with 40 and 80wt.% Fe3AlC0.5 dramatically increased and that of the composite with 60wt.% Fe3AlC0.5 slightly increased. Friction coefficient of the composites was in the range of 0.47–0.60 and independent of the carbide content and the load, whereas it increased at first with the increasing sliding speed and then tended to be a constant value. Wear mechanism of the composites was microfracture and the friction behavior related to wear debris layer on the worn surfaces. The composite with 60wt.% Fe3AlC0.5 had the best tribological properties. [Copyright &y& Elsevier]

The tribological properties of FeAl intermetallics under dry sliding against AISI52100 steel at ambient conditions were studied on an Optimol SRV oscillating friction and wear tester in a ball-on-disc contact configuration. Effects of load and sliding speed on tribological properties of the FeAl intermetallics were investigated. The worn surfaces of the FeAl intermetallics were examined with a scanning electron microscopy (SEM) and an X-ray photoelectron spectroscopy (XPS). It was found that the FeAl intermetallics had better wear resistance than the AISI52100 steel. An adhered oxide debris layer was formed on the worn surface in friction. Area and thickness of the friction layer varied with variety of sliding speed but did not vary with load. The oxide layer contributed to decreased wear but increased friction. Wear rate of the material increased with the load, but dramatically decreased at first and then slightly decreased with the sliding speed. The friction coefficient of the material was 0.45–0.60, and did not change with the load, but increased with sliding speed at first, and then tended to be a constant value. Wear mechanism of the material was transformed from microfracture to surface fatigue with increase of sliding speed. [Copyright &y& Elsevier]

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]

Carbon nanofibers were applied into the pores of the porous anodic oxide film (AOF) on aluminum to improve the wear properties of the alumina film. This encompassed an initial formation of an ordered porous AOF by re-anodizing in oxalic acid and a subsequent development of the carbon precursors within the pores via the polymerization of acrylonitrile within the pores of AOF. After polymerization, a series of heat-treating conditions convert the polyacrylonitrile (PAN) polymer structure into a quasi-graphic structure. The sliding wear and friction properties of self-lubrication films were measured by means of a ball-on-plate apparatus using a steel ball as a counterface. The results showed that self-lubricating treatment could improve the wear properties of porous anodic film more efficiently. [Copyright &y& Elsevier]

Two kinds of thiophosphate, tri-n-octyl thiophosphate and tri-n-octyl tetrathiophosphate, were synthesized. The tribological behavior of the synthetic compounds and tricresyl phosphate as additives in rapeseed oil for steel-steel frictional pair was investigated with a four-ball machine. The relationship between the additive structure and tribological properties was explored, while the lubrication mechanisms of the additives were investigated as well. Thus the worn surfaces of the steel ball lubricated with the additive-containing rapeseed oil were analyzed by means of X-ray photoelectron spectrometry and scanning electron microscopy, and the elemental compositions and distributions in the worn steel surfaces were observed and determined with an EPMA-810Q electron probe micro-analyzer. It has been found that the synthetic thiophosphates as additives in rapeseed oil at proper concentrations show better tribological properties than tricresyl phosphate. Tribochemical reactions were involved for steel–steel frictional pair lubricated with the rapeseed oil containing thiophosphates, with the formation of a boundary lubricating and protecting film composed of glyceride of rapeseed oil and tribochemical reaction products of the lubricants. This contributes to improve the tribological properties of the rapeseed oil base stock. [Copyright &y& Elsevier]

[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]