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 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 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.

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.

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.

Study on Tribological Properties of Irradiated Crosslinking UHMWPE Nano-Composite

Ultra High Molecular Weight Polyethylene(UHMWPE)has been widely used as a bearing material for artificial joint replacement over forty years.It is usually crosslinked by gamma rays irradiation before its implantation into human body.In this study,UHMWPE and UHMWPE/nano-hydroxyapatite(n-HA)composite were prepared by vacuum hot-pressing method.The prepared materials were irradiated by gamma rays in vacuum and molten heat treated in vacuum just after irradiation.The effect of filling n-HA with gamma irradiation on tribological properties of UHMWPE was investigated by using friction and wear experimental machine(model MM-200)under deionized water lubrication.Micro-morphology of worn surface was observed by metallographic microscope.Contact angle and hardness of the materials were also measured.The results show that contact angle and hardness are changed by filling n-HA and gamma irradiation.Friction coefficient and wear rate under deionized water lubrication are reduced by filling n-HA.While friction coefficient is increased and wear rate is reduced significantly by gamma irradiation.The worn surface of unfilled material is mainly characterized as adhesive wear and abrasive wear,and that of n-HA filled material is mainly characterized as abrasive wear.After gamma irradiation,the degrees of adhesive and abrasive wear for unfilled material and abrasive wear of n-HA filled material are significantly reduced.Unfilled and filled materials after irradiation are mainly shown as slight fatigue wear.The results indicate that UHMWPE and UHMWPE/n-HA irradiated at the dose of 150 kGy can be used as bearing materials in artificial joints for its excellent wear resistance compared to original UHMWPE.

Tribological Properties and Failure Analysis of PTFE Composites used for Seals in the Transmission Unit

The sealing rings are one of the most important components as the sealing devices in the wet clutch unit of a heavy vehicle. The sealing ring, made from PTFE composites, was subjected to serious wear on the sealing surface, but the mating metal surface only had slight abrasion. A specialized test rig was designed for wear research and failure analysis of the sealing ring. The composition analyses of the ring material, working conditions and wear surface characteristics by visual inspection and tribological properties as well as microscopic analysis with scanning electron microscope was performed to determine the wear mechanism and failure causes. Results revealed that the wear of PTFE composites was characterized by abrasion and adhesion after a certain duration testing, and the wear mechanism changed to thermal fatigue and abrasive wear in the stage of intense wear. The thermal deformation and fatigue were primarily responsible for the rapid wear of the PTFE composites for the sealing rings.

Tribological properties of TiAlN-coated cermets

Ti（C,N）-based cermets were coated with TiAlN using multi-arc ion plating technology. Sliding wear tests were performed on the coated cermets. The microstructure and morphologies of the coated cermets before and after friction and wear tests were characterized. The results show that the TiAlN coating surface was smooth and its root mean square roughness was 16.6 nm. The hardness （HK） of TiAlN coating layers reached approximately 3200 and the critical load （Lc） under which the coating failure occurred was 59 N. The sliding wear test results show that the friction coefficients of the TiAlN-coated cermets were lower than that of the cermets without any coating. Under the same load, the adhesion phenomenon of the counterpart materials on the specimens was improved and the mean friction coefficient increased with increasing sliding velocity. When the sliding velocity was 0.26 m·s^-1, the mass of the coated cermets reduced. At the same sliding velocity, the average friction coefficient of the TiAlN-coated cerrnets was lower under a higher load. The wear mechanisms of the TiAlN-coated cermets were mainly adhesive and abrasive wear.

Influence of nano-Al_2O_3-reinforced oxide-dispersion-strengthened Cu on the mechanical and tribological properties of Cu-based composites

The mechanical and tribological properties of Cu-based powder metallurgy （P/M） friction composites containing 10wt%-50wt% oxide-dispersion-strengthened （ODS） Cu reinforced with nano-Al2O3 were investigated. Additionally, the friction and wear behaviors as well as the wear mechanism of the Cu-based composites were characterized by scanning electron microscopy （SEM） in conjunction with energy-dispersive X-ray spectroscopy （EDS） elemental mapping. The results indicated that the Cu-based friction composite containing 30wt% ODS Cu exhibited the highest hardness and shear strength. The average and instantaneous friction coefficient curves of this sample, when operated in a high-speed train at a speed of 300 km/h, were similar to those of a commercial disc brake pad produced by Knorr-Bremse AG （Germany）. Additionally, the lowest linear wear loss of the obtained samples was （0.008 ± 0.001） mm per time per face, which is much lower than that of the Knorr-Bremse pad （（0.01 ± 0.001） mm）. The excellent performance of the developed pad is a consequence of the formation of a dense oxide composite layer and its close combination with the pad body.

Tribological properties of high-entropy alloys:A review

Tribology,which is the study of friction,wear,and lubrication,largely deals with the service performance of structural materials.For example,newly emerging high-entropy alloys(HEAs),which exhibit excellent hardness,anti-oxidation,anti-softening ability,and other prop-erties,enrich the wear-resistance alloy family.To demonstrate the tribological behavior of HEAs systematically,this review first describes the basic tribological characteristics of single-,dual-,and multi-phase HEAs and HEA composites at room temperature.Then,it summarizes the strategies that improve the tribological property of HEAs.This review also discusses the tribological performance at elevated temperatures and provides a brief perspective on the future development of HEAs for tribological applications.

Tribological Properties of Few-layer Graphene Oxide Sheets as Oil-Based Lubricant Additives

The performance of a lubricant largely depends on the additives it involves. However, currently used additives cause severe pollution if they are burned and exhausted. Therefore, it is necessary to develop a new generation of green additives. Graphene oxide（GO） consists of only C, H and O and thus is considered to be environmentally friendly. So the tribological properties of the few-layer GO sheet as an additive in hydrocarbon base oil are investigated systematically. It is found that, with the addition of GO sheets, both the coefficient of friction（COF） and wear are decreased and the working temperature range of the lubricant is expanded in the positive direction. Moreover, GO sheets has better performance under higher sliding speed and the optimized concentration of GO sheets is determined to be 0.5wt%. After rubbing, GO is detected on the wear scars through Raman spectroscopy. And it is believed that, during the rubbing, GO sheets adhere to the sliding surfaces, behaving like protective films and preventing the sliding surfaces from contacting with each other directly. This paper proves that the GO sheet is an effective lubricant additive, illuminates the lubrication mechanism, and provides some critical parameters for the practical application of GO sheets in lubrication.

Corrosion Resistance and Tribological Properties of Laser Cladding Layer of H13 Die Steel Strengthened by Ultrasonic Rolling

Laser cladding is a new surface repair method that can improve the wear and corrosion resistance of substrate surfaces.However,the cladding layer typically exhibits a rough surface,high hardness and large residual tensile stress,and thus requires further machining and finishing.Ultrasonic rolling(U-rolling)is a highly efficient finishing and strengthening process that combines ultrasonic technology with traditional rolling(T-rolling).In this study,an ironbased alloy was coated onto the surface of H13 die steel using laser cladding,and the surface of the cladding layer was polished using U-rolling.The effects of U-rolling on the surface quality,corrosion resistance and friction and wear properties of the laser-cladding layer were investigated and compared with those obtained by T-rolling.The surface roughness of the U-rolled sample was only 1/4 that of the T-rolled sample.The hardness and residual compressive stress of the laser cladding layer after U-rolling were higher than those after T-rolling.Similarly,the surface corrosion resistance of the laser cladding layer after U-rolling was higher than that after T-rolling.U-rolling changed the surface roughness,grain size,and residual stress of the material and thus affected the corrosion resistance of the laser cladding layer.The friction coefficient and wear rate of the U-rolled surface of the cladding layer were lower than those of the T-rolled surface.In addition,the tribological properties of the cladding layer were found to be related to the rolling direction.When the friction direction of the sample was the same as the rolling direction,its friction and wear performance were higher than those when the two directions were perpendicular.

Influence of Lanthanum on Tribological Properties and Microstructure of Laser Clad B+Fe+Si Composite Coatings

The effects of rare earth ferrosilicon on the microstructure and anti-wear properties of laser-clad Fe-based alloy coating were investigated. The composition of Fe, B_4C and rare earth ferrosilicon powders with different contents of lanthanum were clad onto a 45~# carbon steel substrate. Microstructural features, chemical compositions, phase structure, hardness, friction and wear properties by scanning electron microscopy (SEM), X-ray photoelectron microscopy (XPS), hardness tester, block-on-ring friction and wear tester of the clad coating were determined. Experimental results show that the friction coefficient of the clad coating doped with rare earth ferrosilicon is reduced while the wear resistance of clad coating doped with rare earth ferrosilicon is enhanced. When the content of lanthanum increases to 1.92%, the clad coating shows the best anti-wear ability, and as the content of lanthanum exceeds 1.92%, the wear weight loss increases quickly. The rare earth ferrosilicon to be doped in the clad coatings helps to disperse the boride phase (Fe_2B, FeB, B_4C) particles and refine the grain of boride phase. The enhancement of clad coating′s wear resistance is due to the existence of dispersed boride phases.

Structure and tribological properties of Si/a-C:H(Ag)multilayer film in stimulated body fluid

Si/a-C:H(Ag)multilayer films with different modulation periods are prepared to test their potential applications in human body.The composition,microstructure,mechanical and tribological properties in the simulated body fluid are investigated.The results show the concentration of Ag first decreases and then increases with the modulation period decreasing from 984 nm to 250 nm.Whereas the C content has an opposite variation trend.Notably,the concentration of Ag plays a more important role than the modulation period in the properties of the multilayer film.The a-C:H sublayer of the film with an appropriate Ag concentration(8.97 at.%)(modulation period of 512 nm)maintains the highest sp3/sp2 ratio,surface roughness and hardness,and excellent tribological property in the stimulated body fluid.An appropriate number of Ag atoms and size of Ag atom allow the Ag atoms to easily enter into the contact interface for load bearing and lubricating.This work proves that the Ag nanoparticles in the a-C:H sublayer plays a more important role in the tribological properties of the composite-multilayer film in stimulated body fluid condition.

Tribological Properties of DLC Film Prepared by C^+ Ion Beam-assisted Deposition (IBAD)

C ^＋ ion beam-assisted deposition was utilized to prepare deposit diamond-like carbon （ DLC ） film. With the help of a series of experiments such as Raman spectroscopy, FT-IR spectroscopy, AFM and nanoindentation , the DLC film has been recognized as hydrogenated DLC film and its tribologicul properties have been evaluated. The bull-on-disc testing results show that the hardness and the tribologicul properties of the DLC film produced by C^ ＋ ion beam- assisted deposition are improved significantly. DLC film produced by C ^＋ ion beam- assisted deposition is positive to have a prosperous tribologicul application in the near future.

Tribological Properties of Polytetrafluoroethylene Composites Filled with Rare Earths Modified Glass Fibers

Rare earths were used to modify the surface of glass fiber in order to enhance the interfacial adhesion and improve the tribolngical properties of GF / PTFE composites . Three surface modifiers, a coupling agent, rare earths, and a mixture of coupling agent and rare earths, were investigated. It is found that the tensile properties of rare earths modified GF / PTFE composites were improved considerably under the same experimental conditions. The PTFE composites, filled with rare earths modified glass fibers, exhibited the lowest friction coefficient and the highest wear resistance under both dry friction and oil-dropped lubrication conditions. In addition, rare earths modified GF/ PTFE composites showed the highest wear resistance under reciprocating impact load. The worn surfaces observation shows that rare earth elements modifier are superior to coupling agent modifier and the mixture of coupling agent and rare earths in promoting interfacial adhesion between the glass fiber and PTFE, accordingly improve tribological properties of GF / TFE composites due to their outstanding chemical activity.

Synthesis and Tribological Properties of Sodium-Ion-Exchangedα-Zirconium Phosphate

Sodium-ion-exchangedα-zirconium phosphate(Na-α-ZrP)was synthesized by using disodium hydrogen phosphate as the sodium source,which was an efficient ion exchange way.The tribological properties of Na-α-ZrP as an additive in lithium grease were investigated by a four-ball friction tester and a SRV tester,respectively.The synergistic effect of Na-α-ZrP with ZDDP was also studied.Results indicate that Na-α-ZrP can effectively improve the antiwear and friction-reducing properties of lithium grease.Combined with ZDDP,the grease demonstrated excellent anti-wear performance,especially under high loads.The possible wear mechanism was discussed by observing the worn surface using 3D optical profiler,scanning electron microscopy(SEM),energy-dispersive spectrometry(EDS),and X-ray photoelectron spectroscopy(XPS).The simple synthetic method and superior tribological performance make the Na-α-ZrP become a potential choice for lubricant additives.

Influence of Deposition Temperature and Pressure on Microstructure and Tribological Properties of Arc Ion Plated Ag Films

The films deposited at low temperature（LT-films） have increasingly attracted theoretical and technical interests since such films exhibit obvious difference in structure and performances compared to those deposited at room temperature.Studies on the tribological properties of LT-films are rarely reported in available literatures.In this paper,the structure,morphology and tribological properties of Ag films,deposited at LT（166 K） under various Ar pressures on AISI 440C steel substrates by arc ion plating（AIP）,are studied by X-ray diffraction（XRD）,atomic force microscopy（AFM） and a vacuum ball-on-disk tribometer,and compared with the Ag films deposited at RT（300 K）.XRD results show that（200） preferred orientation of the films is promoted at LT and low Ar pressure.The Crystallite sizes are 70 nm-80 nm for LT-Ag films deposited at 0.2 Pa and 0.8 Pa and larger than 100 nm for LT-Ag films deposited at 0.4 Pa and 0.6 Pa,while they are 55 nm-60 nm for RT-Ag films deposited at 0.2 Pa-0.6 Pa and 37 nm for RT-Ag films deposited at 0.8 Pa.The surfaces of LT-Ag films are fibre-like at 0.6 Pa and 0.8 Pa,terrace-like at 0.4 Pa,and sphere-like at 0.2 Pa,while the surfaces of RT-Ag films are composed of sphere-like grains separated by voids.Wear tests reveal that,due to the compact microstructure LT-Ag films have better wear resistances than RT-Ag film.These results indicate that the microstructure and wear resistance of Ag films deposited by AIP can be improved by low temperature deposition.