Anti-wear Performance Research Articles

Dependence of high temperature tribological performance of MoS2-based composites on type of oxides

As a solid lubricating material with excellent anti-friction and anti-wear performance, MoS2 is prone to oxidation in high temperature and atmospheric environment, which leads to the deterioration of lubricating performance and the decrease of service life. The addition of nano-particle oxides can improve the high-temperature lubricating performance of MoS2-based solid lubricating materials to some extent, but the effects of different nanoparticles oxides under the same test condition is still unclear. The effects of nano-particles oxides (TiO2, Cr2O3, Al2O3 and ZrO2) on the tribological performance of MoS2-based composites at 450 °C were compared. It was shown that MoS2-TiO2 exhibited the best high temperature tribological properties, and its average friction coefficient was about 0.26, which was about 26 % and 10 % lower than that of 718 substrate and MoS2, respectively. Here we attempted to propose a new concept of correlative potential to explain the lubricating difference of binary oxides under high temperature. The good tribological performance of MoS2-TiO2 at high temperature was attributed to the low correlative potential of TiO2 nanoparticles and the dense tribo-oxide layer formed at the friction interface that reduce the shearing of the rubbing interface. The research results can provide reference for the selection and design of MoS2-based composites, and also enrich the theory of high temperature tribology.

Morphological Characterization and Tribological Properties of TiCoNi Alloy Coatings on Ti–6Al–4V Alloy via Laser Deposition

The goal of this work is to improve the Ti–6Al–4V alloy's hardness and tribological behavior. Coaxial laser surface cladding was used to develop intermetallic layers of nickel (Ni), cobalt (Co), and titanium (Ti). Laser power of 900 W, beam spot size of 3 mm, powder feed rate of 1.0 g/min, and gas flow rate of 1.2 L/min are the optimized parameters used for laser depositions. The laser scan speeds were adjusted between 0.6 and 1.2 m/min. Investigations were conducted into the effects of powder admixture and laser parameters on the fabricated coatings' microstructure, tribological behavior and hardness. X-ray diffractometry (XRD), energy dispersive spectroscopy (EDS) with Scanning electron microscopy (SEM) was employed for the characterization of the microstructural evolution and phase identification, respectively. Additionally, the tribological experiment was conducted via UMT-2 –CETR reciprocating tribometer, and the coatings’ micro-hardness characteristics were examined using EmcoTEST DURASCAN. The micrographs exhibit no signs of porousness, cracks, or stress introduction, according to the results. For every manufactured sample, good metallurgical adhesion was obtained. By comparing the hardness of the ternary coating (Co–Ni–10Ti deposited at a scan speed of 1.2 m/min, with a hardness of 980 HV) to the substrate (Ti–6Al–4V, with a hardness of 330 HV), a hardness increase of approximately 2.96 times was observed. Furthermore, the Co–Ni–10Ti coating, deposited at a scan speed of 1.2 m/min, demonstrated a 51.1% reduction in the coefficient of friction (COF) compared to the base alloy, indicating superior anti-wear performance. The enhanced properties are attributed to the formation of hard intermetallic compounds such as Ti–Co, Co2Ti, Al5Co2, and Ni3Ti, along with their uniform distribution and finely tuned grain sizes.

Plasma-sprayed high entropy alloy coating with novel MoS2 /resin hybrid sealant: Tribological and corrosion characterization

Sealing treatment provides a strategy for the long-term performance of thermal spray coatings under actual working conditions. However, common sealants are mainly limited to improving the corrosion resistance of coatings, neglecting applications in more complex environments where they are subject to simultaneous corrosion and wear. Herein, a novel organic-inorganic hybrid composite sealant, composed of self-lubricating MoS2 nanoparticles and environmentally friendly waterborne silicone modified acrylic resin (WBS-ACR), was successfully prepared in the pores and micro-defects of plasma-sprayed HEA coatings by one-step hydrothermal method. The results indicate that MoS2 nanosheets are uniformly synthesized in resin materials through precursor hydrothermal reactions. The hybrid sealants are filled densely in the micro-defects of HEA coatings with a maximum penetration depth greater than 180 μm. The tribological and electrochemical results indicate that the hybrid sealant exhibits similar anti-wear performance, but two orders of magnitude lower corrosion currents than that of pure MoS2 sealant. In comparison to the pure resin sealant, the hybrid sealant retains its excellent corrosion resistance while increasing its wear resistance. The superior comprehensive performance of the novel organic-inorganic hybrid sealant could expand the application of thermal spray coatings into new fields.

Strengthening mechanism of different morphologies of nano-sized MSH on tribological performance of phosphate/MoS2 bonded solid lubricating coatings

Magnesium silicate hydroxides (MSHs) with granular, schistose, and tubular morphologies were separately incorporated to enhance the tribological properties of phosphate/MoS2 composite coatings. The nano-schistose MSH demonstrated superior tribological performance due to its effective interactions with the worn surface and frictional synergies with solid lubricants. Incorporation of nano-schistose MSH decreased the friction coefficient of composite coatings by about 34.7% and increased the anti-wear performance of composite coatings by about thirteen times. Nano-schistose MSH facilitated the formation of a friction-induced multi-layer heterogenous slipping structure with layered solid lubricants at the friction interface. Moreover, tribo-chemical reactions between nano-schistose MSH and worn surface promoted the in-situ formation of a cermet supporting film, and this also induced the gradual in-situ formation of a lubrication film on the top of worn surface. Consequently, the contact state between tribo-pairs was timely regulated and the invalidation of the nanocomposite slipping structure was effectively restrained during the friction process. As a result, the service life of the phosphate composite coatings was significantly extended and further abrasion on the worn surface was notably reduced.

Microstructure and performance of (CoCrNi)88Al6Ti6-cBN composite coatings by high-speed laser cladding (HSLC): A novel strategy for synergizing wear-resistance and friction reduction

To enhance the wear-resistance of nickel-based blade surfaces, a (CoCrNi)88Al6Ti6-cBN composite coating was produced on GH4169 substrates using HSLC. The microstructure, microhardness and tribology properties of the coating at 25 and 600 °C were evaluated. The finding demonstrates that the hardness of the cBN composite coating increase by 91.6 HV0.3 attributed to precipitation strengthening, second phase strengthening and dislocation strengthening. Furthermore, the anti-wear performance of the coating increased by 3.72 times at 25 °C and by 3.23 times at 600 °C, respectively. Additionally, the friction coefficient exhibited by the coating diminished significantly by converting a portion of the cBN to hBN under the high temperatures generated by laser and oxides generating.

Competition Between Growth and Removal in Zirconia Nanocrystal-Derived Tribofilms: The Role of Co-additives

Antiwear additives permit energy-efficient lubrication of gearboxes, bearings, and other tribological interfaces. We study zirconia (ZrO2) nanocrystal additives, which readily form protective tribofilms in tribological contacts. Our prior work demonstrated cooperative antiwear performance between ZrO2 and the S- and P-based co-additives in fully formulated hydrocarbon gear oils. Here, we extend that work by examining the growth kinetics of the ZrO2 tribofilms, including the influence of the co-additives. In the boundary lubrication regime for mixed rolling-sliding contacts, the initial phase of ZrO2 tribofilm growth is soon overtaken by removal processes, phenomena whose importance has gone unnoticed in prior work. Tribofilm removal affects the steady-state thickness and morphology of the tribofilm as well as its growth kinetics. The S- and P-based co-additives are incorporated into the ZrO2 tribofilm, and alter the competition between the growth and removal processes, increasing initial net growth rates per contact cycle and contributing to a more polished final interface. This work highlights the significance of removal processes in determining tribofilm antiwear performance, and suggests several routes for improving tribofilm growth kinetics using co-additives.Graphical abstract

The excellent anti-wear and friction-reducing performance of magnesium silicate hydroxide/graphite nanocomposite (MSH-C) as a lubricant additive

Abstract In this paper, MSH-C and MSH-GO composites were prepared by doping MSH with micron-sized few-layer graphene oxide (∼10 um) and nanoscale graphite (∼300 nm), respectively, during the hydrothermal synthesis process. Octadecyltrimethoxysilane (ODTMS) was used as a surfactant to disperse these two types of additives into the fully formulated oil. Tribological tests demonstrated that MSH-C exhibits much more superior tribological properties when compared to MSH-GO. The findings reveal that the oil sample containing 0.5 wt% MSH-C can effectively reduce wear volume (by approximately 26.4%) as compared to fully formulated oil and that the friction coefficient is decreased to ∼0.02. SEM, Raman, FIB-TEM, and TOF-SIMS characterizations and molecular dynamics simulation were used to investigate the tribological mechanism. A tribo-film composed of two layers of different compositions was formed on the worn surface of MSH-C, indicating the synergistic effect of MSH and graphite.

Enhanced mechanical properties and anti-wear performance of Cu45Mn8Ni40Sn7 medium entropy bronze alloy by multi-stage heat treatment

High/ medium entropy brass and bronze alloys exhibit considerable potential for application as structural materials. This study focuses on a Cu45Mn8Ni40Sn7 medium entropy bronze alloy that demonstrates excellent hardness, compressive strength, ductility, and wear resistance through a multi-stage heat treatment technique. The effects of heat treatment on the phase composition, microstructural evolution, mechanical properties, and tribological performance of the alloy were systematically investigated. The alloy, treated by homogenization (820 ℃/4 h)-solution (900 ℃/1 h)-aging (450 ℃/5 h), exhibits a hardness of 362 HV, yield strength of 626 MPa, ultimate strength of 1229 MPa, compressive strain of 47.2 %, fracture toughness of 20.7 MPa·m1/2, and maintains a low wear rate of 1.72×10−5 mm3·N−1·m−1. The processes of homogenization and solution treatment reduce dendrite segregation of elements and eliminate the detrimental lamellar structure at the grain boundaries. During the aging treatment of the alloy, sub-micron scale needle-like precipitates are formed, which play a significant role in enhancing its mechanical properties.

Study on the Lubrication Performance of Graphene-Based Polyphosphate Lubricants in High-Temperature Steel–Steel Friction Pair

In the study, a hybrid lubricant was prepared by introducing graphene into a polyphosphate lubricant. In the tribological test of a steel/steel friction pair at the high temperature of 800 °C, the addition of a small proportion of graphene significantly enhances the lubrication performance of polyphosphate at elevated temperatures. The coefficient of friction and the wear were obviously held down while the surface quality of the high-temperature friction pair was enhanced effectively with the graphene-strengthened polyphosphate lubricant, compared with the dry sliding condition. Through scanning electron microscopy and Raman spectroscopy analysis, the formation mechanism of tribofilm and the antiwear performance of the hybrid lubricant are further explained. This lubricant effectively combines the advantages of both; the combination of polyphosphate melted at elevated temperature with graphene and metal surfaces ensures the self-sealing of the friction contact area and brings better high-temperature oxidation resistance. At the same time, the presence of graphene provides excellent strength to the friction film and ensures the anti-wear and wear-resistant performance of the lubricant at high temperatures.

Lubrication performance of graphene in the sliding electrical contact interface

Electrical contact materials are increasingly widely used, but the existing electric contact lubricants still have lots of room for improvement, such as anti-wear performance and lubrication life. Due to the excellent electrical and lubrication properties, graphene shows great potential in lubricating the sliding electrical contact interface, but there is a lack of relevant research. Some researchers have studied the lubrication performance of graphene between the gold-coated/TiN-coated friction pair at an ultra-low current. However, the lubrication performance of graphene on more widely used electrical contact materials such as copper and its alloys under larger and more commonly used current or voltage conditions has not been reported. In this paper, we study the lubrication performance of graphene in the copper and its alloys sliding electrical contact interface under usual parameters, which is explored through four aspects: different substrates—copper and brass, different test methods—constant voltage and constant current, different normal loads and durability test. The experiments demonstrate that graphene can significantly reduce the friction and wear on brass and copper under the above test methods and parameters, with low contact resistance at the same time. Our work is expected to provide a new lubricant for electrical contact materials and contribute to enriching the tribological theory of graphene.

Effect of Grease Composition on Impact-Sliding Wear

Impact-sliding experiments were performed by using four self-made lithium-based greases, namely Yangtze Grease 1, Yangtze Grease 2, Yangtze Grease 3, and Yangtze Grease 4. The influence of base oil viscosity, thickener content, and morphology of thickener fiber clusters on the lubricating state were visually explored, combined with field-emission microscopy and two-light interference technology. The grease film distribution at the middle section was measured using Dichromatic Interference Intensity Modulation (DIIM) software. All experiments were executed in a completely flooded environment. The results show that among the components of grease, the base oil’s viscosity has the greatest impact on the anti-wear performance of the grease. As the viscosity of the base oil increases, the grease exhibits better anti-wear performance. The grease film thickness under the condition of high-viscosity base oil is about 10 times higher than that under the condition of low-viscosity base oil. Secondly, the content of thickener in the grease needs to be controlled within a reasonable range. The experiments indicate that the effect of thickener content on the grease’s film-forming properties becomes more pronounced at higher speeds. From the experiment using YG 4, it can be seen that a higher thickener content under high-speed conditions increases the thickness of the lubricating grease film by about 10 times. The dimensions of the thickener fibers and the density of their entanglement structure significantly influence the rheological properties and load-bearing capacity of the grease. Larger fiber sizes and higher entanglement densities result in reduced grease fluidity and recovery but enhance its load-bearing capabilities. In order to obtain the best anti-wear performance during impact-sliding motion, the size of the thickener fiber and the density of the entanglement structure need to be controlled within an appropriate range.

Tribological performance and mechanism of graphite, hBN and MoS2 as nano-additives in palm kernel oil-based lubricants: A comparative study

Layered nanoparticles have received considerable interest in tribological applications owing to their outstanding tribological performances, including in vegetable oil-based lubricants. Despite the advantages of vegetable oil-based lubricants over petroleum-based lubricants, the limited manufacturing scale of vegetable oil-based lubricants restricts their more comprehensive implementation in various industries. In order to gain further insights into the exquisite nano-additive properties of layered nanoparticles, this research was conducted to explore the tribological performance of palm kernel oil-based lubricants combined with three different layered nanoparticles, namely graphite, hexagonal boron nitride (hBN), and molybdenum disulfide (MoS2), using a four-ball tribotester. The four-ball tribotester analysis indicated that the wear scars lubricated with graphite, hBN, and MoS2 nanolubricants exhibited a lower coefficient of friction (COF) and wear scar diameter (WSD) than the base lubricant. The findings also showed that the MoS2 nanolubricant had the best friction reduction and anti-wear performance, with a 24.9% drop in COF and a 12.3% drop in WSD. It was followed by the hBN and graphite nanolubricants. To fully understand the lubricating mechanisms involved, the worn surfaces of the tested balls were characterised using various microscopic and spectroscopic methods. Accordingly, the structural changes that occurred during sliding were shown to affect the formation of protective tribofilm. In summary, the findings in this study suggest that the formulated layered nanolubricants possessed exceptional tribological performance, which was contributed by the inherent properties of the individual nanoparticles and the formation of effective tribofilms.

Study on the Tribological Properties of Acid-Doped Polypyrrole (PPY) as Conductive Grease Additive

This study investigated the acid doping of polypyrrole (PPY) using as dopants three solutions: hydrochloric acid (HCl), dodecylbenzene sulfonic acid (DBSA), and 1-butyl-3-methylimidazolium tetrafluoroborate (LB104). Four conductive lubricating greases were prepared with these dopants based on composite lithium-based grease (LCG). The research aimed to explore the physicochemical properties and tribological performance of conductive lubricating greases. Experimental results indicate that acid-doped PPY conductive lubricating greases exhibit lower resistivity and higher dropping points. Moreover, these lubricating greases can form stable boundary lubricating films, demonstrating excellent antifriction and antiwear properties. Among these, the additive with LB104-doped PPY shows superior antifriction and antiwear performance, as well as conductivity, suggesting broad prospects for application in the field of conductive lubrication.

Enamel matrix proteins in promoting saliva lubrication

Anti-wear performance of human enamel in the mouth is closely related to the lubrication of salivary pellicle. It is well known that the inorganic hydroxyapatite (HA) of the enamel plays an important role in the adsorption and pellicle-forming of salivary proteins on the enamel, but the role of enamel matrix proteins remains unclear. In this study, the adsorption and lubrication behavior of salivary proteins on original, heated, and deproteinated enamel surfaces was comparatively investigated using an atomic force microscopy and nano-indentation/scratch techniques. Compared with that on the original enamel surface, the adsorption and lubrication behavior of salivary proteins remains almost unchanged on the heated enamel surface (where the enamel matrix proteins are denatured but the size of HA crystalline nanoparticles keeps constant) but exhibits an obvious compromise on the deproteinated enamel surface (where the enamel matrix proteins are removed and agglomeration of HA crystallites occurs). The HA agglomeration weakens the electrostatic interaction of enamel surfaces with salivary proteins to cause a distinct negative influence on the adsorption and pellicle-forming of salivary proteins. Further, the negative effect is confirmed with a quartz crystal microbalance with dissipation. In summary, by regulating enamel nanostructure for appropriate electrostatic interactions between salivary proteins and enamel surfaces, the enamel matrix proteins play an essential role in the adsorption and pellicle-forming of salivary proteins on human enamel, and then contribute to saliva lubrication, which provides the enamel with an anti-wear mechanism. The findings will promote and assist the design of enamel-inspired anti-wear materials.

Wear and corrosion resistance behavior of hydrophobic surface on Ti-6Al-4V prepared by nitrogen gas-assisted EDM

Despite the widespread use of titanium alloys in various fields, surface defects that arise during the processing of Ti-6Al-4V can significantly reduce their service life. Therefore, developing a new approach to enhance the performance of TC4 alloys, particularly in challenging environments such as high-wear and wet conditions is crucial. This study proposes a novel method to create a hardened surface enriched with TiN using nitrogen gas-assisted electrical discharge machining (NA-EDM). The aim was to assess the impact of surface modification via NA-EDM on anti-wear and anti-corrosion performance across different peak currents and to explore the mechanism behind the surface's hydrophobic properties. The findings show that the NA-EDM process produces fewer surface defects compared to traditional EDM. Moreover, NA-EDM treatment significantly improves surface hydrophobicity, as evidenced by a 21.25 % increase in the contact angle (CA). Furthermore, the NA-EDM-treated surface exhibits enhanced resistance to wear and corrosion, with a notable 14.9 % reduction in wear rate and average friction coefficient.

Alkyl Germanes: Active lubricant additives in PAO-10

Germanium-based functional materials have found wide application in the field of material industry and show promise as lubricant additives due to their good designability and unique chemical properties. In this work, seven examples of stable alkyl germanes were synthesized and employed lubricant additives in PAO-10. These alkyl germanes exhibit good solubility in PAO10 and demonstrate significant improvements in friction-reducing, anti-wear performances and extreme carrying capacity. Notably, the addition of 1 % Bu3GeC8 can reduce the average friction coefficients and wear volumes by about 57 % and 90 %, respectively. The lubrication mechanism was elucidated by contact angle, SEM, EDS, XPS and FIB-TEM. Results revealed that the protective tribofilm comprised a physical absorbed film (carbonaceous species) and a tribo-chemical film (ferrous oxides and GeO2).

Dynamic Directional Ultrasonically In Situ-Generated N,S-Codoped Carbon Dots in Poly(ethylene glycol) for Improved Tribological Performance.

The dispersion stability of nanomaterials in lubricants significantly influences tribological performance, yet their addition as lubricant additives often presents challenges in secondary dispersion. Here, we present a straightforward method for in situ preparation of N,S-codoped CDs (N,S-CDs)-based lubricants using heterocyclic aromatic hydrocarbons containing N/S elements in poly(ethylene glycol) (PEG) base oil by a directional ultrasound strategy. Two types of N,S-CDs were successfully prepared via the directional ultrasound treatment of PEG with benzothiazole (BTA) and benzothiadiazole (BTH) separately. The resultant N,S-CDs have a uniform distribution of N and S elements and maintain good colloidal dispersion stability in PEG even after 9 months of storage. The N,S-CDs can enter the surface gap of the friction pairs and then induce a tribochemical reaction. Benefiting from the synergistic effect of N and S activating elements, a robust and stable protective film consisting of iron sulfides, iron oxides, carbon nitrides, and amorphous carbonaceous compounds is formed, thus endowing N,S-CDs-based lubricants with improved antiwear and friction-reducing performance. Compared with pure PEG, the coefficient of friction (COF) of the N,S-CDs(BTH)-based lubricant decreased to 0.108 from 0.292, accompanied by a 91.2% reduction in wear volume, and the maximum load carrying capacity increased to 450 from 150 N.

Tribological properties and synergistic effects of ionic liquids and silver complexes

PurposeThe purpose of this paper is to solve the abrupt deterioration of lubricant performance in high-temperature conditions.Design/methodology/approachThree silver pyrazolyl methyl pyridine complexes with different morphologies were synthesized. A four-ball tribometer was used to assess the tribological characteristics as an additive for pentaerythritol oleate both independently and compound with 1-hexyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide.FindingsThe results showed that when silver complexes and ionic liquids (IL) act independently, sheet silver complex 1 and rod silver complex 2 exhibit good lubricating performance; the optimal antifriction concentration of the ILs is 0.25 Wt.%. The tribological results of the compounds additive of ILs and silver complexes indicate that the wear scar diameter of compound 1 decreased by 16.914%, the wear volume reduced by 7.44% and the lubrication effect surpassed that of the two substances individually; rod compound 2 exhibited an antagonistic effect, intensifying wear; compound 3’s lubrication effect fell between that of the two individual components.Originality/valueThe compound of sheet silver complexes and ILs effectively solves the agglomeration problem of micro/nano lubricant additives. When the interface fails, self-repair is completed, improving the stability and antiwear performance of the lubricating oil.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2024-0128

C@Ag core-shell structure as lubricating additives towards high efficient lubrication

Efficient cooperative lubrication can be achieved via the introduction of core-shell structure lubricant additives with hard core and soft shell, for obtaining the expected anti-wear performance from the structural changes in the friction process. In this study, C@Ag microspheres with a core-shell structure were prepared by the redox method with carbon spheres as the core and Ag nanoparticles as the shell. Their tribological behaviors as base oil (G1830) additive with different concentrations were investigated in detail. Compared with base oil, the addition of C@Ag particles at 0.5 wt% can reduce the coefficient of friction (COF) and wear volume (Wv) up to 15.5% and 88%, respectively. More importantly, C@Ag particles provide superior lubrication performance to single additive (like carbon sphere (CS) and Ag nanoparticle). C@Ag core-shell particles contribute to the formation of tribo-film by melt bonding of flexible Ag and carbon sphere (CS) toward excellent self-repair performance and high-efficiency lubrication. Hence, core-shell structural nanoparticles with hard-core and soft-shell hold bright future for high-performance lubrication application.

Tribological Effects of Quaternary Ammonium-Functionalized Montmorillonite as Water-Based Additives.

In this study, a water-soluble quaternary ammonium salt (QAS)-functionalized montmorillonite (MMT) was fabricated using a mechanochemical method as a high-performance water lubrication additive. The intercalation of QAS into the MMT layer expands the layer spacing of MMT, but does not affect the hydrophilicity of MMT. The ultrathin layer QAS-functionalized montmorillonite (QAS-MMT) demonstrated excellent water-stable dispersion and can be used as a water-based lubrication additive. Only 0.1% addition can reduce the friction coefficient by more than 71.4% and the wear volume by about 58.8% when compared to water, demonstrating its excellent friction reduction and antiwear performance. The frictional mechanism indicates that the physical adsorption film, together with the chemical reaction film, endows the QAS-MMT additives with outstanding tribological performance, provides excellent lubrication for the contact of steel/steel pairs, and prevents the steel surface from being further worn.