Excellent Anti-friction Properties Research Articles

Tribological Properties of Laser-Cladded NiCrBSi Coatings Undergoing Friction with Ti6Al4V Alloys

This work aims at reducing abrasion between titanium alloy parts, such as drive shafts and support pairs used in aviation. Three different NiCrBSi coatings, Ni40, Ni50, and Ni60, are prepared on surfaces of Ti6Al4V by laser cladding. The microstructural and mechanical properties of these coatings are analyzed by scanning electron microscope (SEM) and a microhardness tester. The tribological properties of the NiCrBSi coatings undergoing friction with Ti6Al4V are tested using a wear testing machine. The results show that the Vickers hardnesses of the Ni40, Ni50, and Ni60 coatings are 490 HV0.3, 609 HV0.3, and 708 HV0.3, respectively. For the above NiCrBSi coatings, more hard phases are produced with increases in the amounts of Cr in the powders, resulting in increases in the coatings’ hardnesses. The wear test results show that the NiCrBSi coatings could reduce the friction coefficients, which gradually decreased with increases in the coatings’ hardnesses. Both the coating-specific wear rates and the friction pair wear losses initially decreased and then increased. The Ni50 coating and the Ti6Al4V friction pair undergoing friction with the Ni50 coating showed the best wear performance, with a specific wear rate and wear loss of 0.51 × 10−7 mm3/(N·m) and 7.8 mg, respectively. The specific wear rates for Ni50 were only 8.4%, 35.4%, and 37.0% of the Ti6Al4V, Ni40, and Ni60, respectively. In addition, the friction pair wear loss was only 36.4%, 52.5%, and 55.3% of that while undergoing friction with Ti6Al4V, Ni40, and Ni60, respectively. The NiCrBSi coatings prepared on the surface of Ti6Al4V show excellent antifriction and wear resistance properties, providing a viable solution for the design of wear-resistant coatings on load-bearing and non-load-bearing titanium alloy parts.

Hydrogels for Lubrication: Synthesis, Properties, Mechanism, and Challenges

Hydrogels have received extensive attention as functional lubricants because of their excellent anti-friction and anti-wear properties, tunable tribological performances, and effectiveness in alleviating lubrication failures caused by the creeping or leakage of conventional liquid lubricants owing to their semi-solid nature. This review summarizes the current research advances in hydrogel lubricants fabricated with various organic and/or inorganic gelators, including organic polymeric or supramolecular hydrogels, inorganic particles-based hydrogels, and organic polymer-inorganic particle hybrid hydrogels. We illustrate not only the design strategies for constructing high-performance hydrogel lubricants but also the tribological behavior and mechanism of different types of hydrogel lubricants and their potential applications in industrial and biomimetic fields. Corresponding outlooks and suggestions for future studies have also been proposed.

Insight into the tribological properties of cylinder liner-piston ring under the nano BNNs/Cu composite additive lubrication

To improve the tribological properties of the cylinder liner-piston ring, a two-dimensional hexagonal boron nitride/copper composite lubricant additive was prepared and characterized in detail. The tribological properties and lubrication mechanism of nano hexagonal boron nitride composites with different concentrations were studied through the reciprocating friction test on the Rtec friction and wear tester. The results show that copper is successfully reduced and attached to the surface of h-BN nanosheets through the self-polymerization of dopamine, and the spherical structure promotes the interlayer slip of the nanosheets during the reciprocating friction process. The appropriate concentration of nano composite additives has excellent anti-friction and anti-wear properties. At 1 Hz and 100 N, the friction coefficient and wear quality of the nano composite additive with a concentration of 2 wt% were reduced by 29.07% and 76%, respectively. The surface Sq value and Sz value of the cylinder liner sample decreased by 68.06% and 74.47%. At the same time, under the condition of high speed and heavy load, the average wear depth of the cylinder liner sample is reduced by 61.3%. The nano composite material additive forms an excellent friction protective film on the wear surface of the cylinder liner, which can better enter the wear surface of the cylinder liner and produce a filling and repairing effect. The research results provide a method for the use of nano hexagonal boron nitride composite additives to inhibit the wear of cylinder liner-piston ring of Marine diesel engines.

LUBRICATION PROPERTIES OF MXenes AND THEIR COMPOSITES: A REVIEW

Friction and wear phenomena are common problems in sliding equipment, so materials with excellent antifriction and wear resistance properties are getting increasingly more attention. Two-dimensional (2D) materials, such as graphene and molybdenum disulfide, have always been the research hotspots on account of their special structures and excellent tribological properties. In 2011, MXene, an important member of the 2D material family, was launched. With excellent properties such as ultra-high strength, rich surface end groups, and relatively low cost, MXenes have great potential as lubricant additives. Although these properties have proved to be the reason why MXenes are impressive, the preparation of MXenes composites and the understanding of their mechanical and tribological mechanisms remain to be further investigated. In addition, the abundant surface end groups of MXenes nanosheets make them relatively easy to be functionalized, which has attracted widespread attention. This review aims to comprehensively understand the tribological properties of MXenes nanolayers and to summarize and sort out recent research progress. First, the preparation of MXenes is reviewed, and then the latest research progress of MXenes in liquid lubrication, solid lubrication, and solid–liquid hybrid systems since the advent of MXenes is summarized. Finally, some current problems are presented and an outlook on the development of MXenes is given.

Preparation and tribological properties of GO supported MoO3 composite nanomaterials

The MoO3/GO composites were synthesized via a hydrothermal method. The performance of these composites as lubricating oil additives was investigated by a multifunctional friction testing machine. And the lubrication mechanism of MoO3/GO in base oil was discussed based on SEM and EDS test data. The results demonstrate that MoO3/GO composites as additives exhibit excellent anti-friction and anti-wear properties. This is mainly due to the synergistic effect between the lubricating film formed by the composite material on the wear surface and the self-healing ability of nano-MoO3, which can effectively fill and repair wear scars while reducing friction and wear on the steel disc surface.

Comparative study on tribological performance and mechanism of eco-friendly solvent-free covalent MXene nanofluids in glycerin and polyethylene glycol

Solvent-free covalent MXene nanofluids (MXene NFs) were prepared as eco-friendly additives to improve the dispersibility of MXene and the tribological performance of lubricants. Here, the tribological properties and tribo-mechanisms of MXene NFs additives in glycerin and polyethylene glycol (PEG 400) were evaluated, and pronounced differences were observed. In glycerin, the excellent anti-friction (28.9%) and anti-wear (98.0%) properties were realized after 0.5 wt% MXene NFs addition, for MXene NFs preferentially adsorbing onto the surface of friction pair and participating in the formation of tribofilm. However, in PEG 400, the poor friction-reducing and negative anti-wear performance were related to PEG 400 exhibiting high affinity towards steel substrate. This work provides a new approach for fabricating eco-friendly additives with excellent dispersion and lubricity.

Synergistic effect of ceria-zirconia nanoparticles and hBN nanosheets incorporation on the corrosion resistance of MoS2 solid lubricant coatings

Molybdenum disulphide is a conventional solid lubricant material due to their layered crystal structure enabling easy shearing resulting in low coefficient of friction. Even though MoS2 is highly lubricating, the corrosive nature of this dry solid lubricant limits its application, especially in oxidizing and humid environment. The present work focuses on the improvement of corrosion resistance properties of MoS2 nanosheets coatings, while maintaining its excellent anti-friction properties by incorporating hexagonal boron nitride (hBN) nanosheets and ceria-zirconia nanoparticles (CZ NPs). A hybrid structure consisting of MoS2, hBN and CZ NPs was prepared as a composite and multilayer coating. The coatings were characterized by FE-SEM, XRD, Raman spectroscopy and XPS. The inclusion of hBN and CZ NPs did not significantly alter the coefficient of friction (CoF) and wear for the composite and multilayer coatings, as determined by the tribological investigations conducted using high frequency reciprocating rig (HFRR). The MH30-CZ composite coatings showed higher CoF compared to MH30-CZ multilayer coatings, with only 7.75 % increase as compared to pure MoS2 coating. The composite structure and multilayer structure showed high long-term corrosion resistance while the latter had the highest resistance to corrosion and oxidation. The hybrid multilayer structure had the lowest corrosion current density and corrosion rate with 167 % enhancement in total impedance. In the hybrid coating, hBN acts as a physical and insulating barrier to the flow of corrosive ions and charge transfer while CZ NPs forms insoluble precipitates which further impedes the corrosion. The galvanic cell formation of MoS2 with steel was suppressed due to the presence of insulating CZ NPs layers. The synergic effect of hBN and CZ NPs resulted in high long-term corrosion resistance of the coating.

Preparation and properties of graphene composite lubricants additive used for cylinder liner in marine diesel burning low sulfur fuel oil

In recent years, abnormal wear issues have emerged in cylinder liner-piston rings (CL-PRs) in marine diesels that burn low-sulfur fuel oils (LSFO). To address this issue, a graphene-attapulgite composite additive was prepared and characterized as detailed in this report. Then, the tribological properties and corrosion resistance of this graphene-attapulgite were investigated when it was used at various concentrations as a multifunctional composite lubricant additive in simulated LSFO lubrication conditions. It was found that the appropriate concentration of the additive in a lubricant produced excellent anti-friction and anti-wear properties. This was when the additive was at 0.25 wt% concentration in normal lubricating conditions, where the friction coefficient and wear mass loss were reduced by 22.7% and 44.1%, respectively. Additionally, the impermeability of the graphene additive was found to improve the corrosion resistance of the lubricant. These findings revealed the mechanism of the graphene-attapulgite additive for friction reduction and corrosion resistance of cylinder liner in simulated LSFO lubrication conditions, which provided an inhibition method to prevent abnormal wear of cylinder liner in marine diesel burning LSFO.

Fabrication of carbon dots intercalated MXene hybrids via laser treatment as oil-based additives for synergistic lubrication

As an emerging two-dimensional material, MXene exhibits excellent anti-friction and anti-wear properties in lubrication systems. However, as an oil-based lubricant additive, their stable dispersion in base oil still faces great challenges. Optimizing the microstructure has been proved to be an effective strategy to improve the stable dispersion of MXene in base oil. In this work, catechol groups functionalized carbon dots are synthesized successfully by pulsed laser irradiation of tannic acid in acetone, and then they are grafted onto MXene surface to obtain MXene@CDs hybrids via chemical bond between catechol groups of carbon dots and Ti–OH of MXene surface. Carbon dots not only increase the layer spacing of MXene nanosheets, reduce self-weight stacking, but also make it easier to slide between layers. When used as oil based lubricating additives, MXene@CDs can reduce the coefficient of friction of PAO 10 from 0.58 to 0.1, and the wear volume is reduced by 91.3%. Due to the shear-induced and self-healing mechanism, the special intercalation structure of MXene@CDs is easily formed a protective film during the run-in period, which not only reduces the contact area of friction couples but also eliminates the polishing effect on the substrate surface, thus enabling synergistic lubrication.

Tribological behavior of thermal- and pH-sensitive microgels under steel/CoCrMo alloy contacts

The tribological behavior of 316L stainless steel/CoCrMo alloy contacts under aqueous lubrication was investigated in this work. Three types of microgels including poly(N-isopropylacrylamide) (PNIPAM), polyacrylic acid (PAA), and poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM-co-PAA) were prepared and used as lubricant additives in aqueous solutions. Tribological tests were conducted using a ball-on-disk reciprocating tribometer, over a range of temperatures, pH, and concentrations of the microgels. The PNIPAM-co-PAA microgels were proven to have excellent anti-friction and anti-wear properties, depending on the temperature and pH values of the solutions. The maximum friction coefficient coincided with the lower critical solution temperature of the PNIPAM-co-PAA microgels at 32 °C. At the same time, the friction coefficient increased with the increase in pH value of the lubricant solution with the PNIPAM-co-PAA microgels. The unique thermal- and pH-sensitive properties of the PNIPAM-co-PAA microgels provided a new strategy for controlling the friction and wear of steel/CoCrMo alloy contacts under aqueous lubrication.

Organic-Sulfonate Functionalized Graphene as a High Temperature Lubricant for Efficient Antifriction and Antiwear in Water Based Drilling Fluid

The lubricity of drilling fluid resistant to high-temperature over 200 ℃ is still one of the technological breakthroughs. In this study, the graphene modified with sodium dodecylbenzene sulfonate (SDBS) was selected as a resistant to high-temperature lubricant. Our results show that the drilling fluids have high stability after aging at 240 °C with the assistance of the SDBS/graphene. Excitingly, the tribological performance test results revealed that the SDBS/graphene exert excellent anti-friction and anti-wear properties. Compared with the base slurry, the friction coefficient and wear rate of the SDBS/graphene slurry are reduced by 76% and 59%, respectively. The deposited film composed of graphene, Al2O3, SiO2, Fe2O3, FeSO4 actualized the protection of the sliding contact zone, proving that the sulfonate group on the SDBS/graphene contributed to prompt the deposition of the graphene and bentonite and then enhanced tribological properties of the drilling fluids. Overall, the graphene modified with SDBS is expected to solve the difficulty to form effective deposited film and poor lubricity of the drilling fluid under high-temperature.

Preparation and tribological behaviors of magnesium silicate hydroxide-MoS2 nanoparticles as lubricant additive

The tribological properties of lubricating oil during service life largely depend on the properties of lubricant additives. Herein, we present a hydrothermal synthesis of magnesium silicate hydroxide (MSH)-MoS 2 nanocomposite and evaluate its tribological performances and repairing properties on worn surfaces as lubricant additive in poly-alpha-olefin (PAO). The microstructure of MSH-MoS 2 powders is MSH nanotubes surrounded by layered MoS 2 . The tribological test results show that the anti-friction performance and wear resistance of the friction pair were improved by 27.7% and 37.4%, respectively, after adding 1.0 wt% MSH-MoS 2 into PAO. More importantly, the worn volume of the friction disk can be repaired by 33.2% after sliding 5 h under the lubrication of PAO with MSH-MoS 2 . The superior tribological performance should be attributed to the formation of robust tribofilm with low shear strength, high hardness, strong resistance to plastic deformation, and high bonding strength on the sliding surface. • Rod-shaped magnesium silicate hydroxide-MoS 2 nanocomposites were synthesized. • The nanocomposites as additives show excellent anti-friction and anti-wear properties. • The nanocomposites show outstanding repairing properties on the worn surface. • A robust tribofilm with low shear strength and excellent mechanical properties was formed.

A study on the effect of the addition of copper nanoparticles on the tribological performance of Polyalphaolefin synthetic oil

Lubrication has become a powerful tool for minimizing friction and wear between mechanical contact surfaces. In order to improve the lubricating properties of base oil, nanoparticles are added. The present study investigates the effect of the addition of Cu Nanoparticles on the tribological behaviour of Polyalphaolefin (PAO4) synthetic oil. Tribo four-ball tester is used to determine the Friction Co-Efficient (COF) for pure PAO4 base oil and also with different concentrations (0.2, 0.4, 0.6, 0.8, 1.0, 1.2, and 1.4 wt%) of Cu nanoparticles. The wear surfaces are examined using a Scanning Electron Microscope (SEM) with Energy Dispersive X-ray Spectroscopy (EDX) and a Tool Makers Microscope. It is observed that Cu nanoparticles, when used as an oil additive, offer excellent anti-friction and anti-wear properties. When 1.0 wt% Cu nanoparticles are added to PAO4 oil, the COF (at the contact point) is lowered by 51.85 percent, and the wear scar diameter is reduced as well when compared to pure PAO4 oil.

Mechanical and Tribological Properties of Polytetrafluoroethylene Composites Modified by Carbon Fibers and Zeolite

Currently, lightweight and high-strength polymer composites can provide weight savings in the automotive and process equipment industries by replacing metal parts. Polytetrafluoroethylene and polymer composites based on it are used in various tribological applications due to their excellent antifriction properties and thermal stability. This article examines the effect of combined fillers (carbon fibers and zeolite) on the mechanical, tribological properties, and structure of polytetrafluoroethylene. It is shown that the introduction of combined fillers into polytetrafluoroethylene retains the tensile strength and elongation at break at a content of 1–5 wt.% of carbon fibers, the compressive stress increased by 53%, and the yield stress increased by 45% relative to the initial polymer. The wear resistance of polymer composites increased 810-fold compared to the initial polytetrafluoroethylene while maintaining a low coefficient of friction. The structural features of polymer composites are characterized by X-ray diffraction analysis, infrared spectroscopy, and scanning electron microscopy.

The preparation of CNT/PMMA composite film on SiO2 substrates

Abstract Microelectromechanical system (MEMS) has been highly valued since the size of the MEMS structure is miniaturized, the spacing between the components is in the nanometer range, and the behaviors of friction and adhesion greatly affect the reliability of MEMS. An atomic force microscope (AFM) was used to observe the surface morphology of carbon nanotube (CNT)/polymethyl methacrylate (PMMA) film, and X-ray photoelectron spectroscopy (XPS) was used to analyze the chemical state of typical elements on the surface of the film. The friction and wear properties of composite nano-films under macroscopic conditions were systematically studied. The research results show that the composite nano-film has excellent anti-friction and anti-wear properties.

Effect of two halogen-free ionic liquids with different anions on the tribological properties of TC4

Two halogen-free ionic liquids (ILs), P888p-DABD and P888p-DOSS, are designed and synthesized to improve the tribological performances of TC4. The difference between the two ILs is the anion: one is composed of sulfonate base anions, and the other is composed of ammonium dibutyl dithiophosphate anions. The thermal stability, tribological performances and anti-corrosion performance of the two ILs were evaluated. The results show that P888p-DOSS has better tribological performance than P888p-DABD and can be used as a lubricant for Si3N4/TC4 friction pair. Based on the three-dimensional (3D) profile, SEM, EDS, and the XPS analysis of the worn surfaces of TC4 discs, the P888p-DOSS has excellent anti-friction and anti-wear properties mainly because of the complex tribochemical reaction between the ILs and TC4 matrix, which forms a protective film with anti-friction and anti-wear performance. This provides theoretical guidance for light alloy lubrication.

Effects of groove-textured surfaces with Sn-Ag-Cu and MXene-Ti3C2 on tribological performance of CSS-42L bearing steel in solid-liquid composite lubrication system

To expand the applications of MXene-Ti3C2 in solid-liquid lubrication system, CSS-42L smooth surfaces (SSs), groove surfaces (GSs), groove with Sn-Ag-Cu composite surfaces (GSs-SAC) and groove with Sn-Ag-Cu-Ti3C2 composite surfaces (GSs-SACT) are prepared. The tribological behaviors of samples under dry friction and oil lubrication are studied. The results show that Sn-Ag-Cu-Ti3C2 has the excellent oil film adsorption capacity. The micro-hydrodynamic effects of oil in the grooves are produced under oil lubrication. The synergistic effects of oil, Sn-Ag-Cu-Ti3C2 and grooves reduce the fluctuation amplitudes of friction force and load, improving bearing capacity of oil film and profile characteristics on the surfaces. GSs-SACT with uniform and smooth profiles shows the tribochemical wear and obtains the excellent antifriction and wear resistance properties.

The influences of lubricant groove shape on the tribological properties of journal bearing under the grease lubrication conditions

Purpose This paper aims to elucidate the effects of lubricant groove shape, vertical load, swing angle and grease injection cycle on the friction and wear performances of journal bearings under the grease lubrication condition. Design/methodology/approach Three different types of lubricant grooves, namely, numeral eight-shaped, axial straight line-shaped and circular blind hole-shaped, were designed and machined in the bearing bush of journal bearings. The tribological behaviors of these journal bearings were investigated on the self-developed reciprocating swing friction and wear tester. Experimental data including the friction coefficient, the friction temperature, the wear loss and wear time were analyzed in detail. The wear morphologies of friction pairs were observed by scanning electron microscope and confocal laser scanning microscope. Findings The load carrying capacity and service life of the journal bearing with circular blind hole-shaped lubricant grooves are not affected. However, the load carrying capacities of journal bearings with numeral eight-shaped and axial straight line-shaped lubricant grooves are declined. The coverage areas of lubricating grease in the bearing bush are associated with the swing angle. The smaller the swing angle is, the more limited the coverage areas of lubricating grease get. Among these journal bearings, the maintenance-free time of journal bearing with circular blind hole-shaped lubricant grooves is the longest because of its large grease storage capacity. Originality/value The journal bearing with circular blind hole-shaped lubricant grooves exhibits the excellent antifriction and wear-resistant properties, making it suitable for the application in the low-speed and heavy-load engineering conditions.

Synergistic Regulation Mechanism of Inorganic Thermal Oxidation Coating and Poly (Vinylphosphonic Acid) (PVPA) Coating for High Load Bearing Superlubricity

A low friction coefficient and high bearing capacity can improve the service life of implants in the human body. In this study, we firstly investigate the mechanical properties of inorganic thermal oxide coatings on titanium alloy (Ti6Al4V). Tribological experiments were performed for different tribo-pairs under uniform conditions. The inorganic thermal oxide coating on Ti6Al4V formed at 300℃ was found to have excellent tribological properties and can effectively improve the bearing capacity of Ti6Al4V. The organic poly (vinylphosphonic acid) (PVPA) on Ti6Al4V has excellent anti-friction properties, which can help achieve superlubricity. An inorganic thermal oxide/organic PVPA composite coating was fabricated on Ti6Al4V to obtain a surface with low friction and high bearing capacity. It is found that the presence of the thermal oxide doubled the bearing capacity of the composite coating compared to that of the PVPA coating alone. This study can serve as a guide for the modification of artificial joints.

Fundamental understanding on low-friction mechanisms at amorphous carbon interface from reactive molecular dynamics simulation

Amorphous carbon (a-C) film arouses enormous interest in both scientific and engineering communities because of its excellent anti-friction property. However, due to the complexity of working conditions and the lack of in-situ characterization technique into sliding interface, the direct comparison between two widely accepted low-friction postulations, including the graphitization and passivation mechanisms, has never been performed experimentally. Herein, using reactive molecular dynamics simulation, we comparatively investigated the friction property and structural information of contacting interface under different passivated or graphitized states. For the passivation mechanism, the low friction behavior attributes to the reduction of both the real contact area and shearing strength of sliding interface due to the passivation of a-C dangling bonds. This is different from the graphitization mechanism, which improves the friction property by decreasing the shearing strength only. However, the graphitization mechanism strongly depends on the size and layer number of graphitized structure, causing the transition of sliding interface from a-C/a-C, a-C/G to G/G, which is followed by the low-friction mechanism evolved from passivation, synergistic effect between graphitization and passivation to graphitization mechanism. These disclose the fundamental understanding of friction-reducing mechanism and guide the design of a-C films and the development of related technologies for tribological applications.