Structure and Tribology Property of Carbon Nitride Films Deposited by MW-ECR Plasma Enhanced Unbalanced Magnetron Sputtering

Carbon nitride films were deposited by a twinned microwave electron cyclotron resonance （ECR） plasma source enhanced unbalanced magnetron sputtering system. The results indicate that the structure of the films is sensitive to the nitrogen content. The increase in the nitrogen flow ratio leads to an increase in the sp3 content and an improvement of the tribological properties.

Effect of Cryogenic Treatment on Microstructure and Tribological Property Evolution of Electron Beam Melted Ti6Al4V

Cryogenic treatment was used to improve the tribological properties of Ti6Al4V artificial hip joint implants.Cryogenic treatment at-196℃with different holding time were carried out on Ti6Al4V specimens fabricated using electron beam melting(EBM),and their microstructure and tribological properties evolution were systematically analyzed by scanning electron microscopy(SEM),vickers hardness,and wear tests.The experimental results show that the as-fabricated specimen consists of lamellarαphase andβcolumnar crystal.While,the thickness of lamellarαphase decreased after cryogenic treatment.In addition,it can be found that the fineαphase was precipitated and dispersed between the lamellarαphase with the holding time increase.Vickers hardness shows a trend of first increasing and then decreasing.The wear rate of the specimen cryogenic treated for 24 h is the minimum and the average friction coefficient is 0.50,which is reduced by 14.61%compared with the as-fabricated.The wear mechanism of the as-fabricated specimen is severe exfoliation,adhesive,abrasive,and slight fatigue wear.However,the specimen cryogenic treated for 24 h shows slight adhesive and abrasive wear.It can be concluded that it is feasibility of utilizing cryogenic treatment to reduce the wear of EBMed Ti6Al4V.

Effect of electrical current on tribological property of Cu matrix composite reinforced by carbon nanotubes

Cu matrix composite reinforced with 10%（volume fraction） carbon nanotubes（CNTs/Cu） and pure Cu bulk were prepared by powder metallurgy techniques under the same consolidation processing condition.The effect of electrical current on tribological property of the materials was investigated by using a pin-on-disk friction and wear tester.The results show that the friction coefficient and wear rate of CNTs/Cu composite as well as those of pure Cu bulk increase with increasing the electrical current without exception,and the effect of electrical current is more obvious on tribological property of pure Cu bulk than on that of CNTs/Cu composite;the dominant wear mechanisms are arc erosion wear and plastic flow deformation,respectively;CNTs can improve tribological property of Cu matrix composites with electrical current.

Transfer film effects induced by 3D-printed polyether-ether-ketone with excellent tribological properties for joint prosthesis

Based on the building principle of additive manufacturing,printing orientation mainly determines the tribological properties of joint prostheses.In this study,we created a polyether-ether-ketone(PEEK)joint prosthesis using fused filament fabrication and investigated the effects of printing orientation on its tribological properties using a pin-on-plate tribometer in 25% newborn calf serum.An ultrahigh molecular weight polyethylene transfer film is formed on the surface of PEEK due to the mechanical capture of wear debris by the 3D-printed groove morphology,which is significantly impacted by the printing orientation of PEEK.When the printing orientation was parallel to the sliding direction of friction,the number and size of the transfer film increased due to higher steady stress.This transfer film protected the matrix and reduced the friction coefficient and wear rate of friction pairs by 39.13%and 74.33%,respectively.Furthermore,our findings provide a novel perspective regarding the role of printing orientation in designing knee prostheses,facilitating its practical applications.

Effect of Ellipsoidal Particle Shape on Tribological Properties of Lubricants Containing Nanoparticles

Adding nanoparticles can significantly improve the tribological properties of lubricants.However,there is a lack of understanding regarding the influence of nanoparticle shape on lubrication performance.In this work,the influence of diamond nanoparticles(DNPs)on the tribological properties of lubricants is investigated through friction experiments.Additionally,the friction characteristics of lubricants regarding ellipsoidal particle shape are investigated using molecular dynamics(MD)simulations.The results show that DNPs can drastically lower the lubricant's friction coefficientμfrom 0.21 to 0.117.The shearing process reveals that as the aspect ratio(α)of the nanoparticles approaches 1.0,the friction performance improves,and wear on the wall diminishes.At the same time,the shape of the nanoparticles tends to be spherical.When 0.85≤α≤1.0,rolling is ellipsoidal particles'main form of motion,and the friction force changes according to a periodic sinusoidal law.In the range of 0.80≤α<0.85,ellipsoidal particles primarily exhibit sliding as the dominant movement mode.Asαdecreases within this range,the friction force progressively increases.The friction coefficientμcalculated through MD simulation is 0.128,which is consistent with the experimental data.

Structure and Tribological Property of TiBN Nanocomposite Multilayer Synthesized by Ti-BN Composite Cathode Plasma Immersion Ion Implantation and Deposition

A Ti-BN complex cathode is made from Ti and h-BN powders by the powder metallurgy technology, and TiBN coating is obtained by plasma immersion ion implantation and deposition with this Ti-BN composite cathode. The TiBN coating shows a self-forming multilayered nanocomposite structure while with relative uniform elemental distributions. High resolution transmission electron microscopy images reveal that the multilayered structure is derived from different grain sizes in the nanocomposite. Due to the existence of h-BN phase, the friction coefficient of the coating is about 0.25.

Tribological and rheological performance of lithium grease with poly-a-olefin and alkyl-tetralin as base oils

A new category of lithium greases was synthesized by using poly-a-olefin(PAO8) and alkyl-tetralin as base oil, where the alkyl-tetralins were synthesized by the alkylation of tetralin and olefins. The influence of thickener concentration, alkyl-tetralin content and type of blend oils on the rheological and tribological performance of lithium grease was investigated. The microstructures of soap fibers were measured to reveal the structure-property correlations. The concentration of thickener and alkyl-tetralin content obviously affect the lubricating performance of lithium grease, while the molecular structure of alkyltetralin has no obvious impact on their properties. It was found that alkyl-tetralin could significantly enhance the thickening ability of PAO8 base oils, and decrease the amount of thickeners by 1.5%(mass).Lithium greases prepared using 20%(mass) alkyl-tetralin as co-base oil exhibited high colloidal stability,excellent rheological behaviors and tribological properties.

Well-Dispersed Graphene Enhanced Lithium Complex Grease Toward High-Efcient Lubrication

Graphene as a lubricating additive holds great potential for industrial lubrication. However, its poor dispersity and compatibility with base oils and grease hinder maximizing performance. Here, the infuence of graphene dispersion on the thickening efect and lubrication function is considered. A well-dispersed lubricant additive was obtained via trihexyl tetradecyl phosphonium bis(2-ethylhexyl) phosphate modifed graphene ([P_(66614)][DEHP]-G). Then lithium complex grease was prepared by saponifcation with 12-OH stearic acid, sebacic acid, and lithium hydroxide, using polyalphaolefn (PAO20) as base oil and the modifed-graphene as lubricating additive, with the original graphene as a comparison. The physicochemical properties and lubrication performance of the as-prepared greases were evaluated in detail. The results show that the as-prepared greases have high dropping point and colloidal stability. Furthermore, modifed-graphene lithium complex grease ofered the best friction reduction and anti-wear abilities, manifesting the reduction of friction coefcient and wear volume up to 18.84% and 67.34%, respectively. With base oil overfow and afux, well-dispersed [P_(66614)][DEHP]-G was readily adsorbed to the worn surfaces, resulting in the formation of a continuous and dense graphene deposition flm. The synergy of deposited graphene-flm, spilled oil, and adhesive grease greatly improves the lubrication function of grease. This research paves the way for modulating high-performance lithium complex grease to reduce the friction and wear of movable machinery.

Effect of heat treatment on microstructure,mechanical and tribological properties of in-situ (TiC+TiB)/TC4 composites by casting

To enhance the performance of in-situ synthesized 6vol.%(Ti C+Ti B)/TC4 titanium matrix composites fabricated by casting,a variety of heat treatment processes were carried out.Upon conducting microstructure observations following various heat treatments,it was found that the composites exhibit a basketweave microstructure,consisting of an α phase and a transformed β phase.The sizes of(α+β) phases were found to be refined to varying degrees after the heat treatment processes,while the morphology of Ti B remains largely unchanged and Ti C becomes granulated.Compressive testing revealed that all composites subjected to different heat treatments demonstrate a notable increase in ultimate compressive strength as well as a slight improvement in plasticity compared to the as-cast state.The results of the tribological performance test indicated that the heat-treated composites exhibit lower average friction coefficient,specific wear rate,and worn surface roughness compared to the as-cast composite.Among the heat treatment processes studied,the composite solution heated at 1,150 °C/1 h followed by air cooling,then 950 °C/1 h followed by air cooling,and finally 500 °C/4 h followed by air cooling,demonstrates the highest levels of hardness,compressive strength,and wear resistance.These improvements are attributed to the combined effects of solid solution strengthening,grain refinement,and the pinning of dislocation slip.

Tribological performance under different environments of Ti-C-N composite films for marine wear-resistant parts

The need for reducing the wear in mechanical parts used in the industry makes self-lubricant films one of the sustainable solutions to achieve long-term protection under different environmental conditions.The purpose of this work is to study the influence of C additions on the tribological behavior of a magnetron-sputtered TiN film in air,water,and seawater.The results show that the addition of C into the TiN binary film induced a new amorphous phase,and the films exhibited a dual phase of fcc(face-centered cubic)-TiN and amorphous carbon.The antifriction and wear-resistance properties were enhanced in air and water by adding 19.1at%C.However,a further increase in the C concentration improved anti-frictional properties but also led to higher wear rates.Although the amorphous phase induced microbatteries and accelerated the corrosion of TiN phases in seawater,the negative abrasion state was detected for all Ti-C-N films due to the adhesion of the tribocorrosion debris on the wear track.

Effect of modified MgAl-LDH coating on corrosion resistance and friction properties of aluminum alloy

The in-situ growing approach was utilized in this article to construct the magnesium–aluminum layered double hydroxide(MgAl-LDH)film on the surface of a 1060 aluminum anodized film.To improve the corrosion resistance and friction qualities of aluminum alloy,the MgAl-LDH coating was treated using stearic acid(SA)and thiourea(TU).The aluminum substrate and anodized aluminum film layer corroded to varying degrees after 24 h of immersion in 3.5%(mass)NaCl solution,while the modified hydrotalcite film layer continued to exhibit the same microscopic morphology even after being immersed for 7 d.The results show that the synergistic action of thiourea and stearic acid can effectively improve the corrosion resistance of the MgAl-LDH substrate.The tribological testing reveals that the hydrotalcite film layer and the modified film layer lowered the friction coefficient of the anodized aluminum surface substantially.The results of the simulations and experiments demonstrate that SA forms the dense LDH-TU interlayer film layer by exchanging NO_(3)^(-)ions between TU layers on the one hand and the LDH-SA film layer by adsorption on the surface of LDH on the other.Together,these two processes create LDH-TUSA,which can significantly increase the substrate’s corrosion resistance.This synergistically modified superhydrophobic and retardant hydrotalcite film layer offers a novel approach to the investigation of wear reduction and corrosion protection on the surface of aluminum and its alloys.

Effects of macrosegregation on mechanical and tribological properties of squeeze casting immiscible bearing alloys

The macrosegregation behaviors of Al-Sn-Cu ternary immiscible alloy castings and their effects on mechanical and tribological properties were investigated.The results demonstrate that Sn and Cu segregate in the casting simultaneously,and the mass fraction of the two elements has a"U"shaped distribution.Significantly,positive and negative segregation occur in the casting,with positive segregation appearing on the top and lower surfaces and negative segregation on the remaining surfaces,with the 1/2 surface(hot node location)having the highest degree of negative segregation.Furthermore,the results of Vickers hardness,tensile strength,and elongation show that Sn and Cu cooperatively affect the mechanical properties of castings.The higher the mass fraction of Sn and Cu elements,the higher the hardness,the greater the tensile strength,and the better the elongation.The findings of the step-by-step loading tests demonstrate that the segregation of Sn and Cu significantly impacts the tribological characteristics of the castings.The higher the mass fraction of Sn and Cu on the sample surface,the better the tribological characteristics.

Tribological Properties of Ti-DLC Coatings on Piston-pin Surfaces

A magnetically filtered cathode vacuum arc deposition system was used to deposit Ti-doped diamond-like carbon coatings(Ti-DLC)on pin surfaces to improve the wear resistance of high-power density diesel engine piston pins.The coating structure,composition,and morphology were characterised using field emission scanning electron microscopy(FE-SEM),X-ray photoelectron spectroscopy(XPS),Raman spectroscopy,and other techniques.Friction tests were carried out using a universal tribometer to study the tribological properties of pins with or without coatings under dry friction and oil lubrication.The surface morphology and cross-sectional morphology of the Ti-DLC coating show that the coating has a uniform crosssection and good surface properties.The XPS spectrum shows that the coating contains Ti-C,Ti-C*,sp2-C,sp3-C,and C-O/C=O.Raman spectroscopy shows that there is an amorphous carbon phase in the Ti-DLC coating.The friction test shows that the friction temperature increase of the pin with the Ti-DLC coating is lower than that without the coating,especially under dry-friction conditions.At the end of the test,the difierence in temperature increase is 16.7%.The friction coefficient when using high-viscosity lubricating oil with a coating is relatively lower than that without a coating,especially under low-speed and heavy-duty conditions.In the dryfriction state,the coated surface has better wear resistance than the uncoated surface,which primarily manifests as abrasive wear,and the surface without a coating mainly experiences adhesive wear.

Insight into Hydrolytic Stability and Tribological Properties of B-N Coordination Tung Oil-Based Lubricant Additive in Water

A tung oil-based boron-nitrogen coordination polymer(TWE-BN)was specially designed and synthesized as a highly efficient water-based lubricant additive,which has been beneficial to both energy conservation and conducive to environmental protection.Its hydrolysis stability and tribological properties in water were investigated.To better research the lubricating properties,and thus to understand the interaction between the surface and the lubricating additives.Herein,both experimental and theoretical computations based on density functional theory(DFT)were performed.The addition of TWE-BN reduces the water friction coefficient and wear scar diameter,and the maximum non-seizure load increased from 93 to 726 N.Moreover,the anti-corrosion ability on copper was classified as 1b level.The stainless-steel surface was analyzed using scanning electron microscopy(SEM)and X-ray photoelectron spectroscopy(XPS).In hydrolytic stability testing,TWE-BN was better than nitrogen-free tung oil-based lubricant additive(TWE-B)and remained non-hydrolyzed for at least 15 days,implying the feasibility of tung oil-based boron-nitrogen coordination as highly effective and hydrolytic stability lubricant additives.

Effect of Synthetic Conditions and Thickener Formulation on the Rheological and Tribological Properties of Polypropylene Grease

Polypropylene(PP)grease holds great potential for special industrial applications.In this study,synthetic conditions,thickener content,and the ratio of two different molecular weight PPs were investigated systematically using a rheometer,scanning electron microscope,X-ray diffraction,Fourier transform infrared spectrometer,oscillating tribometer,and 3D surface profiler measurements.The results showed that suitable synthetic conditions are two quenching cycles,and the synthetic temperature and time is 240℃for 12 h.The rheological analysis showed that thickener content and different proportions of the two PP molecular weights have a significant influence on the rheological properties of PP grease.High molecular weight PP(H-PP)has a stronger thickening ability than low molecular weight PP(L-PP).The higher the amount of H-PP in the fixed thickener content or the higher the thickener content with a specific proportion,the higher the viscoelasticity of PP grease.The tribological performance is related to the rheological properties.The proportion of two different molecular weight PPs in the thickener content should be appropriate;excessive H-PP content leads to lubrication failure.

Preparation and tribological properties of surface modified Cu nanoparticles

Cu nanoparticles surface-modified by dioctylamine dithiocarbamate （DTC8） were synthesized using a two-phase extraction route. The size, morphology and structure of resultant surface-capped Cu nanoparticles （coded as DTC8-Cu） were analyzed by means of X-ray diffraction, transmission electron microscopy and infrared spectrometry. The tribological behavior of DTC8-Cu as an additive in liquid paraffin was evaluated with a four-ball machine, and the surface topography of the wear scar was also examined by means of scanning electron microscopy. Results show that Cu nanoparticles modified by DTC8 have a small particle size and a narrow size distribution. Besides, DTC8-Cu as an additive in liquid paraffin has excellent antiwear ability, due to the deposition of nano-Cu with low melting point on worn steel surface leading to the formation of a self-repairing protective layer thereon.

Tribological effects of oxide based nanoparticles in lubricating oils

In order to enhance the tribological properties of lubricating oil, suitable surfactants such as Tween-20, Tween-60, Span-20 and Sodium sodecylbenzenesulfonate were selected and lubricating oils containing CeO2 and TiO2 nanoparticles were prepared. The morphology and size of CeO2 and TiO2 nanoparticles were examined with a transmission electron microscope （TEM）. The tribological properties of the oils were tested using an MRS-1J four-ball tribotester. The research results show that when the proportion by weight of CeO2 nanoparticles to TiO2 nanoparticles is 1：3, and the total weight fraction is 0.6%, the lubricating oil has optimal anti-wear and friction reducing properties. The addition of CeO2 nanoparticles reduces the required amount of TiO2 nanoparticles.

Effect of wear conditions on tribological properties of electrolessly-deposited Ni-P-Gr-SiC hybrid composite coating

The friction and wear properties of the electrolessly-deposited Ni-P-Gr-SiC composites were investigated. The effects of graphite content, load and rotation speed on the friction coefficient and wear resistance of the composite coatings were mainly investigated. The worn surface and cross section of the coatings were characterized by scanning electron microscopy and energy-dispersive X-ray analysis. The results show that the composite coatings reveal good antifriction and wear resistance due to the synergic effect of graphite and SiC particles. The formation of graphite-rich mechanically mixed layer （GRMML） on the surface of Ni-P-Gr-SiC coating contributes to the good tribological behavior of the wear counterparts and SiC particles play a load bearing role in protecting GRMML from shearing easily.

Plasma electrolytic oxidation of magnesium and its alloys:Mechanism,properties and applications

Plasma Electrolyte Oxidation(PEO)process has increasingly been employed to improve magnesium surface properties by fabrication of an MgO-based coating.Originating from conventional anodizing procedures,this high-voltage process produces an adhesive ceramic film on the surface.The present article provides a comprehensive review around mechanisms of PEO coatings fabrication and their different properties.Due to complexity of PEO coatings formation,a complete explanation regarding fabrication mechanisms of PEO coatings has not yet been proposed;however,the most important advancements in the field of fabrication mechanisms of PEO coatings were gathered in this work.Mechanisms of PEO coatings fabrication on magnesium were reviewed considering voltage–time plots,optical spectrometry,acoustic emission spectrometry and electronic properties of the ceramic film.Afterwards,the coatings properties,affecting parameters and improvement strategies were discussed.In addition,corrosion resistance of coatings,important factors in corrosion resistance and methods for corrosion resistance improvement were considered.Tribological properties(important factors and improvement methods)of coatings were also studied.Since magnesium and its alloys are broadly used in biological applications,the biological properties of PEO coatings,important factors in their biological performance and existing methods for improvement of coatings were explained.Addition of ceramic based nanoparticles and formation of nanocomposite coatings may considerably influence properties of plasma electrolyte oxidation coatings.Nanocomposite coatings properties and nanoparticles adsorption mechanisms were included in a separate sector.Another method to improve coatings properties is formation of hybrid coatings on PEO coatings which was discussed in the end.

Effect of Rare Earths on Tribological Properties of Carbon Fibers Reinforced PTFE Composites

Carbon fibers （CF） were surface treated with air-oxidation and rare earths （RE）, respectively. The effect of RE surface treatment on tensile strength and tribological properties of CF reinforced polytetrafluoroethylene （PTFE） composites was invest/gated. Experimental results revealed that RE was superior to air ox/dation in improving the tensile strength, elongation, and the tensile modulus of CF reinforced PTFE （CF/PTFE） composite. Compared to the untreated and air-oxidated CF/PTFE composite, the RE treated composite had the lowest friction coefficient and specific wear rate under a given applied load and reciprocating sliding frequency. The RE treatment effectively improved the interfacial adhesion between CF and PTFE. With strong interfacial coupling, the carbon fibers carried most of the load, and direct contact and adhesion between PTFE and the counterpart were reduced, accordingly the friction and wear properties of the composite were improved.