Excellent Tribological Properties Research Articles

Design of 3D printed metal frame nested porous polyimide composites

Abstract Porous polyimide (PPI) can store oil, but the mechanical properties are also weakened by the pores. To solve this problem, a 3D printed metal frame-PPI nested composite (MFP) was proposed. The composite material has a binary pore structure (ordered submillimeter-level metal frame macropores and disordered micron-level PPI micropores). PPI material is filled in the metal frame, and the oil could be filled into the micropores, improving the mechanical and tribological performances. The preparation method was optimized and the mechanical, oil content, tribological properties of MFP were investigated. The experimental results showed that MFP enhance its ability to resist external deformation and has excellent mechanical properties and tribological properties. As the density of PPI filled in the metal frame increases, PPI is tightly bonded to the metal. Under the PPI filling density of 1.1 g/cm3 and sintering temperature of 330°C, MFP could be well formed, and the friction coefficient is the lowest (0.035). MFP exhibits excellent mechanical and tribological performances.

Friction, wear, and anti-scuffing behaviors of zinc phosphate film on cylinder liners

Zinc phosphate chemical conversion coating possesses excellent tribological properties, which has attracted increasing attention. In this work, the friction, wear and anti-scuffing performance of zinc phosphate film applied on the cylinder liners were studied using a self-designed friction and wear experimental apparatus, which can sufficiently simulate the working conditions of the piston ring and cylinder in a real engine. The experimental results indicate that comparing with the uncoated cylinder liner, the friction force and total wear losses of friction pairs for the zinc phosphate coating are reduced by 8% and 27.5%, respectively, which is attributed to the formation of the protective film containing metal oxides and iron phosphate. In the scuffing test, uncoated cylinder liner exhibits better anti-scuffing performance because of the spalling of the cast iron graphite. On the contrary, the zinc phosphate coating particles remaining on the worn surface after oil-cut off are peeled off and acted as the abrasive at the contact interface, which accelerates the plastic deformation of friction pairs and the cast iron graphite is covered by the plastic flow of the material.

Micro-structures and dry sliding wear properties of novel AlCrFeNiMo0.5-x(WC) high entropy alloy-ceramic composite coatings

Based on the problems of micro defects (cracks, pores, etc.), uneven distribution of strengthening particles, and poor bonding between strengthening particles and metal matrix in practical engineering applications, the new AlCrFeNiMo0.5-x(WC) (x = 0, 5, 15, 30 wt%) composite coatings have been designed, and further prepared using laser cladding. Their micro-structures, micro-hardness and dry sliding wear properties were deeply explored. They exhibited the dendritic morphologies and consisted of BCC1, BCC2, and carbide phases. The AlCrFeNiMo0.5-30 wt%(WC) coating had the highest hardness (772 HV), which was approximately 5 times that of Q235 steel substrate. With the increase of WC content, dry sliding wear properties showed an increasing trend, that is, AlCrFeNiMo0.5-30 wt%(WC) coating had the lowest friction coefficient (0.50) and wear rate (9.23 × 10−6 mm3/(N · m)), exhibiting excellent tribological properties, which was attributed to the coupling effect of hard carbide and ductile BCC phases. It would be a promising wear-resistant coating material under dry sliding environment. This study not only has significant theoretical significance for understanding the failure patterns and performance evolution of new high entropy alloy/WC composite coating materials in dry sliding environments, but also demonstrates important value for expanding the application of new high entropy alloy/WC composite coating materials in practical engineering.

In Situ Polymerized Self-Healing Microcapsules as Multifunctional Fillers toward Phosphate Ceramic Coatings.

The protective efficacy of chemically bonded phosphate ceramic coatings (CBPC) is notably diminished owing to the presence of micropores and inadequate self-healing capacity in prolonged corrosive environments. Consequently, it is imperative to augment the corrosion and wear resistance of phosphate ceramic coatings while imbuing them with self-healing capabilities. In this work, a novel self-healing phosphate ceramic coating (MC-PTx@CBPC, x = 0.5, 1.0, 1.5) is designed by urea-formaldehyde (UF) in situ polymerization of nanoscale microcapsules encapsulated with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) and evaluated in detail for corrosion and wear resistance. The corrosion inhibition efficiencies of all formulated MC-PTx@CBPC (x = 0.5, 1.0, 1.5) coatings exceed 90%, with the impedance modulus at the lowest frequency (|Z|f=0.01) showing enhancements of 1-2 orders of magnitude compared to pure CBPC. Moreover, the self-healing function becomes active during prolonged immersion. This can be primarily ascribed to the formation of a unique micronanostructure facilitated by nanoscale microcapsules and micrometer-sized alumina ceramics, bonded via the AlPO4 phase. This structure enhances both the hydrophobicity and the bonding strength of the coating. Specifically, following prolonged immersion, the encapsulated PFDTES is liberated from the microcapsules, undergoing hydrolysis and subsequent polymerization upon contact with the electrolyte to form a protective thin film. This film efficiently obstructs the ingress of corrosive agents. Furthermore, the special micronanostructure enhances the hardness of the coating and the releasing PFDTES can form a lubricating film at the interface of abrasion, thus reducing the wear rate and friction coefficient of the MC-PTx@CBPC (x = 0.5, 1.0, 1.5). Therefore, MC-PTx@CBPC (x = 0.5, 1.0, 1.5) possesses excellent corrosion protection, tribological properties, and self-healing capabilities, which provide thought-provoking ideas for phosphate ceramic coatings to protect metals in harsh environments.

Effect of B addition on the microstructure and tribological properties of laser cladding FeCoCrNiCu composite coatings

The high-entropy alloy coatings of FeCoCrNiCuBx (x = 0, 0.1, 0.3, 0.5, x values are molar ratios) were prepared on the surface of Q235 steel by laser cladding. The microstructure, microhardness, and surface energy of the FeCoCrNiCuBx coatings were investigated, and the tribological property and wear mechanism of the composite coatings at room temperature (RT) and 600 ℃(HT) were analyzed. The FeCoCrNiCu coating consists of a single FCC-type solid solution. When x = 0.3, 0.5, the composite coatings appear the Cr2B phase. The x = 0.5 (B5) coating has the lowest surface energy (27.45mN/m), which is one of the reasons it has excellent tribological properties. The tribological properties of FeCoCrNiCuBx composite coatings were improved at both RT and HT. The B5 coating has excellent tribology at both RT and HT. At RT, the wear resistance of the B5 coating (wear rate is 8.54 ×10−5 mm3/N∙m, coefficient of friction (COF) is 0.51) was improved by 54.79%, 50.89%, and 12.86% compared with x = 0(HEA), x = 0.1(B1), and x = 0.3(B3), respectively, the COF reduced by 42.69%, 41.39%, 22.73%. At HT the wear resistance of the B5 coating (wear rate is 6.69 ×10−5 mm3/N∙m, COF is 0.24) was increased by 71.53%, 52.91%, and 49.42% compared to HEA, B1, and B3, respectively, the COF reduced by 29.41%, 25.00%, 17.24%. The wear mechanisms of coatings that add B element at RT are abrasive wear and fatigue wear, and at HT are mainly oxidative wear, moderate abrasive wear and fatigue wear.B2O3 melts at HT to form a low-viscosity liquid that forms a lubricating film that isolates the contact surfaces and reduces direct contact and adhesion. This is the main reason for the excellent friction properties of B5 coating at HT.

Preparation and Tribological Performance of Multi-Layer van der Waals Heterostructure WS2/h-BN

Van der Waals heterostructures with incommensurate contact interfaces show excellent tribological performance, which provides solutions for the development of new solid lubricants. In this paper, a facile electrostatic layer-by-layer self-assembly (LBL) technique was proposed to prepare multi-layer van der Waals heterostructures tungsten disulfide/hexagonal boron nitride (vdWH WS2/h-BN). The h-BN and WS2 were modified with poly (diallyldimethylammonium chloride) (PDDA) and sodium dodecyl benzene sulfonate (SDBS) to obtain the positively charged PDDA@h-BN and the negatively charged SDBS@WS2, respectively. When the mass ratio of PDDA to h-BN and SDBS to WS2 were both 1:1 and the pH was 3, the zeta potential of PDDA@h-BN and SDBS@WS2 were 60.0 mV and −50.1 mV, respectively. Under the electrostatic interaction, the PDDA@h-BN and SDBS@WS2 attracted each other and stacked alternately along the (002) crystal plane forming the multi-layer (four-layer) vdWH WS2/h-BN. The addition of the multi-layer vdWH WS2/h-BN (1.0 wt%) to the base oil resulted in a significant reduction of 33.8% in the friction coefficient (0.104) and 16.8% in the wear rate (4.43 × 10−5 mm3/(N·m)). The excellent tribological property of the multi-layer vdWH WS2/h-BN arose from the lattice mismatch (26.0%), a 15-fold higher interlayer slip possibility, and the formation of transfer film at the contact interface. This study provided an easily accessible method for the multi-layer vdWH with excellent tribological properties.

Topology optimization of AISI 4140 steel with surface texture filled by multi-solid lubricants for enhancing tribological properties

AbstractWind power gears will be excessively worn due to lubrication failure during operation. Herein, the tribological properties of rubbing pairs are improved by filling solid lubricants into surface texture. In texture design, three types of topological textures (Circle (C), Hexagon (H) and Circle/Hexagon (CH)) were obtained by cell topology optimization, and then three cases with 20%, 30%, and 40% density were designed for each texture. Next, SnAgCu and TiC were deposited in texture of AISI 4140 steel (AS) to obtain 9 kinds of self-lubricating surfaces. Among them, AS with 30% CH density (AS-CH30) exhibits excellent mechanical and tribological properties. Compared with AS-C and AS-H, the maximum equivalent stress of AS-CH was decreased by 10.86% and 5.37%, respectively. Friction coefficient and wear rate of AS-CH30 were 79.68% and 78% lower than those of AS. The excellent tribological performances of AS-CH30 can be attributed to the synergistic effect of topological surface and solid lubricants. Topological surface can not only reduce fluctuation of equivalent stress, but also promote the stored lubricants to be easily transferred at the contact interface to form a 200 nm lubricating film containing solid lubricants (mainly), oxides and wear debris.

Surface crack propagation of electroplated chromium coating and cotton fabric with dry friction

Electroplated chromium coatings are commonly used to improve the wear resistance of metal parts in the cotton textile industry, and surface crack is an important feature. This study investigates the tribological properties and surface crack propagation of the electroplated chromium coating in dry friction contact with cotton fabric. It is found that the coating has excellent tribological properties, with the friction coefficient eventually stabilized at 0.11 and the average wear rate of 0.0038 mm3/h. The cotton fabric mainly exhibits a polishing effect on the coating during friction, and the failure of the coating is in the form of delamination failure within the coating. Crack propagation is mainly due to the friction of cotton fabric, the main cracks of the mesh crack structure hardly propagate, while the short cracks extending on the main cracks undergo propagation behavior. Short cracks propagate vertically along the friction direction and eventually develop into the main crack level. The tangential stress generated by friction acts on the crack tip, which is the main cause of crack propagation. The plastic zone generated at the crack tip affects the distribution of the stress field and the effect of the plastic zone on crack propagation is analyzed.

Improve the thermal properties of oil‐loaded polysulfone microcapsules by optimizing copper layer for self‐lubricating polyamide

AbstractThis work reports polymer/metal double‐shell microcapsules with polysulfone (PSF) and copper as walls for application in self‐lubricating polymer. First, polyalphaolefin 40 (PAO40) was selected as lubricant oil, and PAO@PSF single shell microcapsules were prepared. A critical issue for the formation of copper layer is the sensitization of PSF shell, which can affect not only the adhesion between PSF shell and copper layer, but also the density of copper layer. The sensitization conditions were discussed in detail, and the corresponding effect on the formation of copper layer was evaluated. PAO@PSF/Cu microcapsules obtained under optimal sensitization condition were characterized by scanning electron microscopy (SEM), thermogravimetric analyzer (TGA), x‐ray energy dispersive spectrometer (EDS) and fourier transform infrared spectroscopy (FTIR). A uniform and compact copper layer improved the thermal properties of microcapsules. PSF/Cu microcapsules maintained relatively complete spherical shape when were heated to 300°C, while the PSF microcapsule softened and deformed at 200°C. The self‐lubricating polyamide 6(PA6) composites containing PAO@PSF/Cu microcapsules were fabricated at 230°C, microcapsules maintained complete structure and uniform distributed in the polymer matrix. Coefficient of friction (COF) and wear rate of PA6 composites were tested under different friction conditions. Compared with pure PA6, 15 wt.% PAO@PSF/Cu microcapsules could reduce the COF by 79.5%, and the wear rate was decreased by 98.3% under 300 rpm sliding speed and 50 N friction load.Highlights PSF/Cu double‐shell oil‐loaded microcapsules were designed and prepared. The copper layer effectively improved the thermal properties of microcapsules. The self‐lubricating PA6 composite exhibited excellent tribological properties.

Quality control of NiCr-Cr3C2-hBN@Ni coating on thin-walled GH4169 alloy surface prepared by plasma spraying

As equipment lightweight trends progress, thin-walled structures have seen extensive application in critical aerospace components. Nevertheless, the aero-engine tail nozzle flaps are exposed to the harsh operating conditions of high-temperature friction, so there is an urgent requirement to prepare wear-resistant, self-lubricating coatings with a wide range of temperatures for their protection. Due to the poor rigidity and weak strength of thin-walled workpieces and complex forms of structural stresses, the processing is extremely difficult. In order to solve the thermal deformation problem of coating workpieces prepared by spraying on the surface of thin-walled workpieces, the effects of spraying path, cooling airflow, and spraying interval on the thermal force field of thin-walled workpieces to prepare NiCr-Cr3C2-hBN@Ni coating are investigated in this study using finite element simulation. As a result, the deformation and stress of thin-walled workpieces can be minimized by adding back-side cooling air during the spraying process and moving the cooling air with the gun in a set interval, with the maximum warpage and maximum stress being less than 2.366 mm and 0.177 GPa, respectively. During the spraying process by simulating the optimum spraying process, no significant warpage of the substrate occurred and the coating was sprayed with uniform thickness. Typically, the thickness error rate is 16.7 %, and the coating hardness reaches 15–20 GPa, with excellent tribological properties in a wear rate of 10−5 mm3·N−1·m−1 and 10−6 mm3·N−1·m−1, which protects the workpiece effectively.

Tribological Properties of Hard TiB2 Thin Films Prepared at Low Temperatures Using HiPIMS

Magnetron-sputtered WS2 composite thin films are solid lubricants with excellent performances. However, the low hardness of the WS2 thin films necessitates the further improvement of their wear resistance. For this purpose, an effective strategy is to alternately deposit or code posit WS2 and a hard phase, such as TiB2, to form hard lubricant thin films. Herein, a TiB2 thin film was prepared under the same conditions as those used for depositing the WS2 thin film with a dense structure and excellent tribological properties. Because of the high deposition energy of high-power impulse magnetron sputtering (HiPIMS), the TiB2 thin film possesses a dense structure and leather-like flat surface (hardness = 24.17 GPa). The friction coefficient of the film under different loads ranges between 0.6 and 0.8. The wear rate of the thin film increases with load, mainly because of fatigue wear and abrasive wear. Under high loads, obvious furrow-like wear marks are observed. At different sliding frequencies, except 8 Hz, the friction coefficient of the film ranges from 0.6 to 0.8. The main wear mode is fatigue wear, particularly at increasing sliding frequencies. Although the film possesses a relatively high friction coefficient, its wear resistance is excellent (minimum wear rate = 1.96 × 10−6 mm3/(N·m)).

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.

Friction‐Reducing and Anti‐Wear Mechanism of BP/Nano‐Fe3O4 Nanocomposite as a Lubricant Additive in Soybean Oil

ABSTRACTAs an emerging two‐dimensional material, black phosphorus (BP) has excellent tribological properties, but the poor dispersion of BP in oil inhibits its application in friction to some extent. Surface modification is one of the effective methods to solve the dispersibility of BP, and the use of nano‐Fe3O4 dotted on the surface of BP improves the dispersion stability of BP in soybean from 3 days to about 15 days. Compared with pure soybean oil, friction coefficient and wear rate of the addition of 0.12 wt% BP/Fe3O4 are reduced 65% and 78%, respectively. To elucidate the excellent tribological mechanisms of BP/Fe3O4 as additives in soybean oil, the compositional and structural characterisation of the abrasion mark surface was studied accordingly. On the one hand, soybean oil reacts with BP/Fe3O4 to form a composite tribo‐film during the scraping process. This tribo‐film composed of amorphous carbon, iron oxide and phosphorus oxide nitrides prevents direct contact between the sliding interfaces. On the other hand, BP and Fe3O4 nanoparticles form a mechanical rollerball structure, which can further reduce interfacial friction and wear through synergistic lubrication. The results provide new insights into the design of additives in biomass lubricating oils and propose new application prospects for BP in the field of lubricating additives.

Enhancing the tribological performance of hydroxypropyl methylcellulose composite coatings through nano-sized metal and oxide additives: A comparative study

Cellulose, due to its excellent mechanical and tribological properties and eco-friendliness, is suitable for environmentally friendly applications. However, its application is limited due to susceptibility to wear and damage under stress during usage. This study introduces nanosized aluminum, copper, alumina, and copper oxide into composite materials to tackle the challenges of wear and damage. This approach aims to improve the tribological performance of Hydroxypropyl methylcellulose (HPMC) composite coatings significantly. The additive particles enhanced the load-bearing capacity and wear properties of cellulose-based composite coatings. The velocity accommodation mode was provided by nano-metals through S3M2 (interaction of metal particle additives through a third-body mechanism), while for nano-oxides, it was S3M4 (expulsion of nanoparticles from the wear mark to the outer contact zone). Due to the higher specific stiffness and strength of oxides, nanofillers in the composite offered better load resistance than nano-metals, resulting in a smaller actual contact area during wear. Therefore, metal oxide nanofillers enhanced tribological properties more effectively than metal nanoparticles. Finally, detailed explanations of the tribological evidence and discussions on the mechanism were conducted.

Tribological property of dendritic fibrous nano silica composite particle as lubricant additive

In this study, a novel Dendritic Fibrous Nano Silica (DFNS) solid-liquid composite lubricant additive (DFNS@ILs) was prepared by the simple of bi-continuous microemulsion polymerization and vacuum impregnation adsorption ionic liquids (ILs) method. The microstructure and chemical composition were characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The oil lubrication properties of the DFNS@ILs were investigated and the results showed that the DFNS@ILs additive had the most excellent tribological properties when compared to the pure PAO6 oil, commercially available ZDDP and nano-silica. Moreover, DFNS@ILs have long-term stability as lubricant additives. Based on the analysis of the wear surfaces, it is concluded that the excellent performance of DFNS@ILs additive are owing to the synergistic lubrication effect of DFNS and ILs as well as the formation of transfer film, which makes it a promising lubricant material.

Observation of anomalous low friction and wear behavior of polyimide in alkaline environment under high load

Polyimide (PI) was first discovered to exhibit excellent tribological properties in alkaline environments. PI is widely used because of its low thermal expansion coefficient, excellent mechanical properties, and resistance to high and low temperatures. The high manufacturing cost of PI makes its waste recycling a hot topic. The most common way of recycling is to hydrolyze PI in strong alkaline environments (C(OH−)>2 mol/L). Therefore, the intuition is that the friction performance of PI decline in highly corrosive environments. However, this paper found a counter-intuitive phenomenon. PI exhibits excellent tribological properties in alkaline environments. This paper studied the behavior of ball-on-disk contact between ceramic ball and PI disk tribopair in an alkaline environment. Results show a very low coefficient of friction (COF, 0.013) and wear rate (1.4 × 10−6 mm3/NM) in sodium hydroxide (NaOH) solution with pH = 13 under the average Hertzian contact pressure of 60 MPa. The COF and wear rate decreased by 80% and 63.4%, respectively, compared with those in solutions with pH = 7. The worn surface was characterized to explore the tribological mechanism. NaOH reacts with PI to form a polymer containing sodium ions during the friction process. The polymer adheres to the friction surface and improves the friction performance of PI. The chemical reaction breaks the C–N–C chemical bond of PI, thereby reducing the molecular rigidity and improving the adhesion of the PI surface. This paper provides a new modification method for improving the tribological properties of PI.

Thermal-sprayed ceramic/fluoropolymer coatings with tight bond and self-lubrication: Microstructure, tribological properties, and lubrication mechanism

Ceramic/fluoropolymer composite coatings capable of controlling friction and wear have attracted the attention of numerous researchers. However, their practical applications are significantly limited by the complex fabrication process and weak interfacial bonding between ceramics and fluoropolymers. Herein, the robustly bonded Al2O3/Polytetrafluoroethylene (PFA) composite coatings were fabricated via a straightforward technology, and a comprehensive investigation was conducted to scrutinize their microstructure, tribological behaviors, and lubrication mechanism. Results show that forming an interdiffusion layer between Al2O3 and PFA splats could be responsible for robust interfacial bonding. The generation of a well-covered unique lubricant film at the frictional interface enables the coefficient of friction to be reduced by 83.7 % to 0.13, and the specific wear rate correspondingly diminished from 2.69 × 10−4 mm3 N−1 m−1 to 4.93 × 10−6 mm3 N−1 m−1. The lubricant film is composed of numerous spherical structures and a layer of amorphous material. The development of the hybrid coating with a simple and efficient preparation method, strong bonding, and excellent tribological properties offers significant potential for applications in the field of tribology.

Enhanced wear resistance in (CoCrNi)94Al3Ti3 medium-entropy alloy at high temperatures via nano-Al2O3 reinforcing phase

High-entropy or medium-entropy alloys are emerging as promising materials for high-temperature applications due to exceptional properties. In this study, the nano Al2O3 reinforced (CoCrNi)94Al3Ti3 medium-entropy alloy (MEA) composites were prepared using spark plasma sintering (SPS). The nanohardness (7.0 GPa) and elastic modulus (255.3 GPa) of (CoCrNi)94Al3Ti3-2 wt% Al2O3 (2AMEA) are notably higher than MEA, reducing the wear rate by about 50% at 25 and 400 °C compared to the MEA. Meanwhile, 2AMEA forms a continuous strip-like oxide glaze tribo-layer at 800 °C, porviding excellent antioxidative and tribological properties. This study proved the feasibility of enhancing high-temperature wear resistance of medium-entropy alloy via nano-Al2O3.

Synergistic lubrication effects of Sn–Ag–Cu and MXene–Ti3C2 to improve tribological properties of M50 bearing steel with microporous channels

Purpose This paper aims to study the synergistic lubrication effects of Sn–Ag–Cu and MXene–Ti3C2 to improve the tribological properties of M50 bearing steel with microporous channels. Design/methodology/approach M50 matrix self-lubricating composites (MMSC) were designed and prepared by filling Sn–Ag–Cu and MXene–Ti3C2 in the microporous channels of M50 bearing steel. The tribology performance testing of as-prepared samples was executed with a multifunction tribometer. The optimum hole size and lubricant content, as well as self-lubricating mechanism of MMSC, were studied. Findings The tribological properties of MMSC are strongly dependent on the synergistic lubrication effect of MXene–Ti3C2 and Sn–Ag–Cu. When the hole size of microchannel is 1 mm and the content of MXene–Ti3C2 in mixed lubricant is 4 wt.%, MMSC shows the lowest friction coefficient and wear rate. The Sn–Ag–Cu and MXene–Ti3C2 are extruded from the microporous channels and spread to the friction interface, and a relatively complete lubricating film is formed at the friction interface. Meanwhile, the synergistic lubrication of Sn–Ag–Cu and MXene–Ti3C2 can improve the stability of the lubricating film, thus the excellent tribological property of MMSC is obtained. Originality/value The results help in deep understanding of the synergistic lubrication effects of Sn–Ag–Cu and MXene–Ti3C2 on the tribological properties of M50 bearing steel. This work also provides a useful reference for the tribological design of mechanical components by combining surface texture with solid lubrication. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2023-0381/

Evaluation of rheological properties and tribological properties of choline/acetylamino acid ionic liquids at different frequencies

With the increasing average lifespan of human beings, the wear and tear caused by daily activities on joints will also escalate. Consequently, there is a growing focus on the development of green, environmentally friendly, and biocompatible non-toxic lubricating materials. The presence of dual chemical active centers in natural amino acids results in anions and cations that lead to precipitation and poor lubrication effects in traditional choline amino acid ionic liquids. In this study, nine types of choline acetyl-amino acid ionic liquids ([Ch][Ac-AA]ILs) were synthesized using acetylated amino acids (Ac-AA) as anions and choline (Ch) as cations. The physicochemical properties and tribological behavior of [Ch][Ac-AA]ILs at different frequencies were evaluated. The results demonstrated that [Ch][Ac-AA]ILs exhibited excellent tribological properties and maintained effective lubrication even under high-frequency friction conditions compared to sodium hyaluronate (HA-T). This performance was attributed to the carbon chain length and functional group composition of [Ch][Ac-AA]ILs' anions. Energy dispersive spectroscopy and X-ray photoelectron spectroscopy analysis revealed that the superior lubrication performance of [Ch][Ac-AA]ILs was associated with the formation of chemical reaction films and physical adsorption films on the surface of friction pairs. This research enriches our understanding of [Ch][AA]ILs-based lubrication systems while providing valuable insights for selecting joint lubricants suitable for different activity frequencies.