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The tribological behaviors of polycrystalline diamond compact (PDC) under alternating high and low temperature conditions in vacuum environment were evaluated by a ball-on-disk tribometer. The wear surface features and chemical composition were measured by FIB-SEM-Raman-TOF-SIMS microanalyzer (SEM, EDS, Raman), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results showed that the coefficient of friction (COF) was pretty low and stable at atmospheric room temperature condition, while it was much higher and fluctuated in vacuum environment with alternating high and low temperature condition. In atmospheric environment with room temperature, the continuous formation of adsorbed films on the contact surface kept the chemical composition of the friction pair virtually unchanged, and the wear mechanism was a combination of mild abrasive wear and oxidative wear. In vacuum environment with alternating high and low temperature condition, the adsorbed film on the contact surface desorbed and could not continue to form, and the adhesion of Si 3 N 4 materials occurred on the wear area and the Si-C bonds were formed. In addition, a combination of high friction heat, localized flash temperature and Co binder led to the graphitization of diamond. The wear mechanism was a combination of abrasive wear and adhesive wear. The above results showed that the adhesion of Si 3 N 4 and the Si-C bonds led to high friction force, while the graphitization phenomenon weakened the bonding force between diamond grains, and made them more likely to be detached during the sliding. These were the mainly reasons for the severe wear under vacuum environment with alternating high and low temperature condition. [Display omitted] • Evaluation of the possibility of polycrystalline diamond compact (PDC) as a potential material for space drilling bits. • The vacuum environment and the fluctuation of temperature led to an increased wear rate of PDC. • The main wear mechanism of PDC under alternating high and low temperatures in vacuum was elucidated. [ABSTRACT FROM AUTHOR]

This study developed a rapid structure control technique for AlCoCrFeNi/AT13 (Al₂O₃–13 % TiO₂) composite coatings using plasma spraying and dual powder feeding. Four coatings were fabricated: pure HEA, HEA-D (dispersed), HEA-S1 (multilayer with outer HEA), and HEA-S2 (multilayer with outer AT13). The introduction of AT13 altered the internal stress distribution and enhanced corrosion resistance by lowering the electrochemical reaction rate. In layered coatings (HEA-S1, HEA-S2), the AT13 interlayer barrier reduced corrosion tendency. Additionally, pure HEA coatings exhibited adhesive wear. While HEA-D coatings experienced abrasive wear as AT13 particles improved plastic deformation and interface shearing. HEA-S1 reduced strain and wear via an internal AT13 layer. HEA-S2 achieved superior abrasion resistance through an outer AT13 layer, exhibiting typical abrasive wear mechanisms. • Achieved precise control of the AlCoCrFeNi/AT13 composite coating structure. • Examined structural changes' influence on composite coating corrosion performance. • Structural control lead to significant improvements in friction performance. [ABSTRACT FROM AUTHOR]

In modern artillery systems, frictional properties of modular charge significantly impact the operation of artillery feeding system. In this study, Tribology performance between modular charge and aluminum alloy were investigated under simulated environment of artillery. The result indicates that the COF initially increased and then decreases with the temperature dropped from 50 °C to −40 °C. Additionally, COF increased from 0.19 to 0.41 when relative velocity increased from 100 mm/s to 2000mm/s. SEM detection and chemical composition analysis demonstrated that the main wear forms are adhesive wear and abrasive wear. The tribofilm including aluminum titanium oxide and aluminum nitrides generated through tribochemical reaction, which are beneficial for boundary lubrication. This work provides theoretical reference for artillery tribology research. [Display omitted] [ABSTRACT FROM AUTHOR]

The microstructure, mechanical and wear behavior of a high chromium cast iron were studied at different normalizing temperatures (950 °C, 1000 °C, 1050 °C, 1100 °C). The martensite content was proportional to the normalizing temperature except at 1100 °C because of the appearance of retained austenite. As the temperature increased, the primary carbide downsized whereas the secondary carbide content first increased but then decreased, contributing to the superior mechanical properties observed tempered at 1050 °C. The superior hardness and strength improved the surface deformation resistance, including enhanced work-hardening in the matrix and stacking fault locks in carbides, hindering dislocation slipping and material spalling, thus achieving excellent wear properties when normalized at 1050 °C. Moreover, the wear mechanism changed from oxidative/fatigue to abrasive/adhesive wear as the temperature increased. • Mechanical and wear properties of a novel HCCI was studied at normalizing 950-1100 °C. • Primary M 7 C 3 carbides gradually downsized as normalizing temperature increasing. • Grain size, secondary carbide and martensite contents raised first and then reduced. • Strength and hardness were the maximum as 2819 MPa/66.5 HRC as normalized at 1050 °C. • Work-hardening in matrix and stacking fault locks in M 7 C 3 raised the wear resistance. [ABSTRACT FROM AUTHOR]

With the widespread implementation of maglev technology in fields such as rail transit and military, it is imperative to investigate the effects of magnetic fields on fretting damage in metallic materials. This study conducted multi-parameter fretting wear tests on typical ferromagnetic counterparts in the presence of an external permanent magnetic field. Subsequently, the wear behavior and damage mechanism of the fretting interface were elucidated through multi-scale characterization analysis. The results indicated that the operation state of the fretting interface was shifted towards the partial slip regime under the magnetic field. Meanwhile, the external magnetic field transformed the dominant wear mechanism from abrasive wear to adhesive wear. The influence of the external magnetic field on fretting wear has been demonstrated to manifest in dual aspects: Firstly, the Hertzian contact stress at the interface is enhanced by the magnetic field induction force, resulting in a remarkable reduction of about 79.83 % in accumulated dissipation energy; Secondly, the effectiveness of debris being expelled from the worn interface decreased, and the wear progression was further impeded by the accumulated debris, so that the abrasion loss is significantly reduced by about 60.66 %. These findings provide valuable theoretical data and practical reference for the protection of fretting damage in ferromagnetic materials under the action of a magnetic field. • A self-developed fretting wear tester in a magnetic field environment was established. • Fretting wear damage mechanisms were elucidated through multi-scale characterization. • Quantitative analysis of wear resistance was conducted based on dissipated energy. • The material damage mechanisms under mechanical-magnetic coupling were uncovered. [ABSTRACT FROM AUTHOR]

In order to improve the toughness of aluminum matrix composites with high ceramic contents, nacre-inspired Ti (C, N)/Al-Cu composites are prepared via freeze casting and pressure infiltration, and their mechanical properties and tribological behavior are investigated. The prepared composites can maintain excellent compressive strength, hardness and wear resistance when the experimental temperature increases from 25 °C to 300 °C. This can be attributed to the stable load bearing capacity of the Ti (C, N) ceramic layer at high temperature, the high interface binding capability between Ti (C, N) and Al, as well as the high crack growth inhibition ability of "layered network" structures. Moreover, the tribo-oxide layer formed during the wear process can further improve the wear resistance of the composites. [Display omitted] • Nacre-inspired Ti (C, N)/Al-Cu composites showed an excellent wear resistance at 25-300 °C. • Effects of test temperature on mechanical and tribological properties were investigated. • The "layered network" structure of the composites contributes to the strength. • The continuous ceramic layer alleviated the adhesive wear of the composites. [ABSTRACT FROM AUTHOR]

In this study, CoCrFeNiV non-equiatomic high entropy alloys (HEAs) with varying N content were prepared using vacuum hot-press sintering. The effects of N content on the alloy's microstructure, mechanical properties, and tribological behavior at different temperatures were investigated. The results indicate that the N-added alloys primarily maintain an FCC phase. With increasing N content, the σ phase in the alloy gradually decreases, while the VN content increases, leading to grain refinement. This results in a 10.7 % increase in hardness, a 9 % increase in compression strength, and a 56 % increase in compression deformation. Below 400 °C, the primary wear mechanisms are adhesive wear, spalling wear, and slight oxidative wear, while above 600 °C, oxidative wear dominates. The addition of N reduced the wear rates of the alloy by 33.8 %, 8.1 %, and 31.3 % at RT, 200 °C, and 600 °C, respectively, and decreases the coefficient of friction at all temperatures. In summary, N addition improves the alloy's tribological performance at various temperatures. [ABSTRACT FROM AUTHOR]

This study investigates wear mechanisms of coated shafts in journal bearings within liquid lead-bismuth eutectic. Shafts were coated with TiAlN, a-C:H, multi-layer TiAlN with sputtered carbon, and chrome plating. Bearings made from sintered iron with carbon inclusions (DEVA 120 and DEVA 121) were tested in LBE at 200 °C and 50 rpm using a dedicated test rig. The a-C:H coatings failed due to tribofilm wear with DEVA 120, while TiAlN coatings failed from fatigue wear with DEVA 120 but succeeded with DEVA 121. Chrome-plated shafts experienced abrasive and adhesive wear with DEVA 121 but survived DEVA 120 due to transfer layer formation. The study highlights the need to understand wear mechanisms and material compatibility to develop durable coatings for harsh environments. • The a-C:H coated shaft failed due to wear mechanisms associated with tribofilm degradation. • Chrome-plated shafts failed using DEVA 121 due to abrasive and adhesive wear. • TiAlN coated shafts failed using DEVA 120 due to fatigue-related wear. • Poor adhesion of the coating to the shaft leads to failure through delamination. • Multi-layer coatings of TiAlN and sputtered carbon successfully endured testing with DEVA 120. [ABSTRACT FROM AUTHOR]

Tribo-corrosion-fatigue coupling damage greatly affects the service safety of wire rope. A self-made test rig was employed to investigate the influences of fatigue load characteristics (amplitude, stress ratio, maximum) on bending tribo-corrosion-fatigue damage of wire ropes. The tribological properties and electrochemical corrosion of the wire ropes, and the coupling damage and mechanisms were discussed in detail. Results indicate a lower friction coefficient between wire ropes in artificial seawater. The main wear mechanisms in seawater are adhesive wear, fatigue wear, oxidation wear and corrosion wear as compared to abrasive wear, adhesive wear, oxidation wear and fatigue wear in pure water. Lower stress ratios amplify corrosion and adhesive wear. Fatigue fractures are mainly ductile, with stress ratio being a significant factor. Tribo-corrosion-fatigue coupling exacerbates damage in contact ropes compared to fatigue ropes. Seawater increases fatigue rope damage but reduces contact rope damage. Higher fatigue load amplitude and maximum value, and lower stress ratios, increase friction coefficient, deformation, volume loss, wire breakage, and decrease corrosion resistance. These findings provide essential data for assessing wire rope service life under seawater corrosion conditions and ensuring offshore drilling safety. [Display omitted] • The influence of fatigue load on the bending tribo-corrosion-fatigue between steel wire ropes is investigated. • The stress ratio has the greatest effect on the coupling damage (wear, deformation and wire breakage). • Seawater promotes the damage to the fatigue ropes, but inhibits the damage to contact ropes. • The mechanism of tribo-corrosion-fatigue damage is discussed. [ABSTRACT FROM AUTHOR]

In this paper, the fretting wear mechanism of the directionally solidified superalloy (DZ125) surface created by wire electrical discharge machining (WEDM) are studied. Samples with varying surface characteristics are prepared by changing the number of wire cutting (NWC), ranging from one to five times (NWC-1 to NWC-5). Comparative analysis reveals that the NWC-3 exhibits the best surface characteristics. Subsequent fretting wear tests under different displacement amplitudes show increased dissipation energy with greater displacement. Compared with other samples, NWC-3 in the synergistic effect of surface roughness and hardness exhibits excellent fretting wear performance. In addition, the fretting mechanism transitions from mixed slip regime (MSR) to gross slip regime (GSR) as the displacement increases. The wear mechanism transitions from abrasive wear to oxidation wear and adhesive wear. [Display omitted] • The fretting friction behavior and wear mechanism of the surface created by WEDM are studied. • NWC-3 exhibits the lowest dissipation energy and excellent fretting wear performance under identical conditions. • The fretting mechanism of NWC-3 transitions from mixed slip regime to gross slip regime as the displacement increases. [ABSTRACT FROM AUTHOR]

To repair oil drill pipe joints that have failed owing to dry wear and tribocorrosion, graphene-reinforced CoCrFeMo 0.5 NiTi 0.5 high-entropy alloy composite coatings (HEACCs) were developed through high-speed laser cladding. The HEACC containing 1.5 wt% graphene exhibited dry wear and tribocorrosion rates that were 59.18 % and 32.20 % of those observed in the high-entropy alloy coating, respectively. The HEACC exhibited a corrosion current density of 2.475 × 10−7 A/cm2. The HEACC containing 1.5 wt% graphene underwent progressive damage during dry wear owing to the combined effects of abrasive wear, which created furrows; adhesive wear, which led to flaking; and oxidative wear, which formed oxide layers. During tribocorrosion, chloride ions exacerbated surface damage caused by hard abrasives and asperities, intensifying corrosive–abrasive wear interactions. ● Composite coatings of graphene-reinforced high-entropy alloys were prepared via high-speed laser cladding. ● The tribocorrosion rate of the HEACC can reach 2.720 µm3·N−1·mm−1, which is only 32.20 % of that of the HEA. ● The influence of the graphene content on the tribocorrosion performance of HEACCs was investigated. ● The corrosion current density of the HEACC reached about an order of magnitude smaller than that of the HEA. ● The formation of reinforcing phases and the self-lubricating effect of graphene collectively enhanced the tribocorrosion resistance of the composite coating. [ABSTRACT FROM AUTHOR]

This study investigates the high-temperature wear of additive-manufactured Ti6Al4V alloy against GH2132. The wear mechanism transitioned from abrasive and adhesive wear to oxidative wear with rising temperatures. The microstructure characteristics reveal the special hybrid high-temperature wear mechanisms: shear deformation-induced wear hardening and dynamic recrystallization-induced wear softening. At lower temperatures, the thinner oxide layer was easily removed and the worn surface in contact underwent work hardening, reducing the negative effects of thermal softening. At higher temperatures, the thicker oxide layer slightly reduced adhesive of the substrate but failed due to cracking and spalling. Combined with intensified thermal softening, recrystallization softening on the worn surface not only eliminated surface hardening but led to a sharp decline in wear resistance. [ABSTRACT FROM AUTHOR]

High entropy alloy particles reinforced aluminum matrix composites (HEAp/AMC) with mass fractions of 1.5 wt%, 3 wt%, 4.5 wt%, along with pure aluminum, were fabricated via stir-casting. Among these, the 3 wt% HEAp/AMC exhibited the lowest wear rate. The 3 wt% HEAp/AMC were then subjected to room-temperature rolling (RTR) and cryorolling, and their tribological characteristics were investigated. Compared to RTR HEAp/AMC, the wear rate of cryorolled HEAp/AMC decreased from 3.87 × 10−3 mm3/(Nm) to 2.70 × 10−3 mm3/(Nm) at room temperature, which declined to 1.41 × 10−3 mm3/(Nm) in a cryogenic environment. The wear rate in the cryogenic environment decreased by 63.6 % compared to that at room temperature. The wear debris of the HEAp/AMC in the cryogenic environment was substantially refined, indicating a transition from adhesive wear to abrasive wear. • The tribological characterization of rolled HEAps/AMCs at cryogenic temperature was studied for the first time. • Compared to room-temperature rolling, cryorolled HEAps/AMCs exhibited a relatively lower wear rate. • In a cryogenic environment, the HEAps/AMCs exhibited further lower wear rate. • The higher mechanical properties and reduced microstructural defects in cryorolled HEAp/AMC minimized adhesive wear. • The wear debris of the HEAp/AMC in the cryogenic environment was refined considerably. [ABSTRACT FROM AUTHOR]

As wind turbine capacities increase, the demand for improved stability and reliability has intensified. Traditional rolling bearings used as wind turbine main bearings often prove insufficient under conditions of the low speeds, heavy loads, frequent start-stop cycles, and complex load environments, along with significantly high maintenance costs. Sliding bearings offer a promising alternative, yet research on high-performance materials tailored for Wind Turbine Main Shaft Sliding Bearings (WTMSSB) is limited. This study investigates the tribological behavior and failure mechanisms of several sliding bearing materials under complex operational conditions. Multi-condition friction and wear tests were conducted to evaluate the friction coefficient, friction temperature rise, and volume wear rate of Babbitt alloy (ZChSnSb11–6), bimetal CuSn10Pb10, pure PEEK, and the 10 % PTFE-filled modified PEEK composites. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were employed to analyze the microstructural features and elemental distributions on wear surfaces and wear debris. The 10 % PTFE-filled modified PEEK composite demonstrated superior self-lubricating properties and wear resistance under both lubricated and dry friction conditions, showing strong potential for complex load environments. While Babbitt alloy exhibited low friction under oil lubrication, its high wear rate and susceptibility to adhesive failure under dry conditions limit its applicability. Bimetal CuSn10Pb10 displayed consistently high friction and poor wear resistance across all conditions, with a tendency for seizure. This study provides robust experimental evidence for optimizing sliding bearing materials for WTMSSB and offers guidance for future material development and practical applications. • Comprehensive tests reveal tribological behavior and failure mechanisms of sliding bearings under typical wind turbine conditions. • PEEK composites show excellent self-lubrication and wear resistance, offering great potential for wind turbine bearing applications. • Babbitt alloy excels under lubrication but suffers high-temperature softening and adhesive wear, leading to failure in dry friction. • Bimetal CuSn10Pb10 faces high seizure risk and excessive frictional wear under dry friction conditions. [ABSTRACT FROM AUTHOR]

Tool wear is a significant challenge in the milling of difficult-to-cut materials such as Ni-based superalloys, as it directly impacts the machining process and surface integrity. In multi-axis torus milling, the complex and varying cutting conditions of cutter-workpiece engagement make predicting wear particularly difficult. This paper proposes models for predicting the life and flank wear of a torus milling cutter equipped with round cutting inserts in a multi-axis milling process. A novel technique for changing the active segment of the cutting edge, specifically designed for torus milling cutters, was used. The cutter-workpiece engagement (CWE) zone was determined and equal width cutting belts were determined on the torus surface. Analysis of wear mechanisms revealed the uneven distribution of flank wear. Based on cutting tests under defined CWE and high-speed machining conditions, predictive models for tool life and flank wear were developed for each active cutting edge segment. These models were calibrated using multi-axis milling experiments on the Inconel718 superalloy. Results demonstrate that the predictive models achieve high accuracy, with average percentage errors below 15 % for tool life and 13 % for flank wear. The models enable precise predictions of torus milling cutter life and flank wear in multi-axis milling of Inconel718 while utilizing the active cutting edge segment change technique. Analysis of wear mechanisms indicated that abrasive and adhesive wear dominates, and flaking and notching wear was also observed. [ABSTRACT FROM AUTHOR]

Two oil-miscible ionic liquids (ILs) with different anions, phosphate (N 88816 P 4) and phosphorothioate (N 88816 SP 4), were applied in PAO10 as lubricating additives. Adsorption layers and tribofilms formed at the interface With ILs, which facilitated transition from adhesive to abrasive wear and enhanced the tribological performance. Moreover, N 88816 SP 4 outperformed N 88816 P 4 , especially at elevated temperature and under extremely high pressure. As revealed by density functional theory (DFT) calculation and transmission electron microscopy (TEM) analysis, S-containing anions not only enhanced the adsorption of ILs, but also participated into the tribochemical reaction, resulting in a tribofilm consists of iron oxides and sulfides. As the temperature increased, the content of sulfides increased, leading to superior tribological performance. • Two oil-miscible ionic liquids N 88816 P 4 and N 88816 SP 4 with different anions were synthesized as additives for PAO10. • N 88816 SP 4 demonstrated the highest maximum non-seizure load, lowest COF and smallest wear volume at 100 °C. • S participated into the tribochemical reaction and formation of tribofilms, while N and P existed in the adsorption layers. • DFT calculation indicates that S atoms significantly enhance the adsorption ability. [ABSTRACT FROM AUTHOR]

There are still major limitations of their low hardness and insufficient wear resistance so far, although titanium alloys (TC4) are common materials used in key moving mechanical components. Hence, in this study, the Stellite6-Cu/Graphene coatings were prepared to employ laser cladding. The comprehensive characterization methods, such as XRD, SEM, XPS, and Raman spectrum analysis, were conducted to investigate the effect of adding graphene on the microstructure, microhardness, and tribological performances of samples. The main phase component of composite coating consisted of γ-Co solid solution, carbides (such as Cr 23 C 6 , Cr 7 C 3, and TiC), and CuTi x intermetallic compound, which were uniformly distributed into the interdendritic region and played a key role in realizing the grain refinement. This helped to greatly improve the strength and tribological performance of coatings. On a sliding tribo-pair system, the friction and wear properties of the substrate and coatings were studied, and the wear mechanisms of the samples were analyzed. The results indicate that in all composite coatings, the M2 composite coating with 1.2 wt% graphene achieved a twice increase in the microhardness compared with the raw substrate. The excellent lubrication effect of the graphene tribo-film resulted in significant reductions in friction (30 %) and wear (98 %) relative to the substrate under room temperature. At this temperature, slight adhesive wear and slight oxidative wear were the main worn mechanisms. Under a high temperature of 600 °C, the friction coefficient and wear rate were reduced by 55 % and 64 %, respectively, as compared to the substrate. This was mainly caused by the presence of oxidized tribo-film containing massive oxides and few graphene, with the mechanisms of slight abrasive wear and oxidative wear. This work is expected to provide certain data support for applying TC4 alloys in the wear-critical field. [ABSTRACT FROM AUTHOR]

To enhance the current-carrying friction behavior of carbon skateboards, this investigation focuses on developing a new copper-impregnated carbon skateboard containing tungsten disulfide. Its performance was evaluated by various current-carrying friction tests and tribological analysis techniques. As the current increased, the carbon skateboard gradually transformed from fatigue wear and abrasive wear to adhesive wear. The average contact resistance and average friction coefficient of the carbon skateboard containing tungsten disulfide were decreased by 25.11 % and 11.43 % at 40 N, respectively, as compared to a commercial copper-impregnated carbon skateboard of the same type. Furthermore, the presence of tungsten disulfide reduced the formation and adverse effects of spalling pits, improving contact conditions and enhancing stability in the electrical contact resistance and coefficient of friction. [Display omitted] • A copper-impregnated carbon skateboard containing tungsten disulfide was designed. • The presence of WS 2 reduced the formation and adverse effects of spalling pits. • Current-carrying wear behavior of the carbon skateboard with WS 2 was more stable. • The average contact resistance of the carbon skateboard decreased by 25.11 % at. • The wear mechanism of carbon skateboard containing WS 2 was analyzed. [ABSTRACT FROM AUTHOR]

The wear behavior of lamellar Ti-46Al-2Nb-2Cr was investigated by reciprocating sliding at room and service temperatures. The wear scar and subsurface microstructure were studied via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The coefficient of friction (COF) increased with the temperature. However, the wear volume loss first decreased and then increased, due to the formation of a relatively complete tribo-layer at 750 ℃. Abrasive wear, oxidative wear and adhesive wear were activated at elevated temperatures. Reciprocating sliding introduced gradient nano-grained structures covered with tribo-layers. Compared to room temperature, the oxidative tribo-layer and nano-grained layer formed at 750 ℃ were thicker. And the nano-grains were finer. Nano-grains at room temperature and 750 ℃ were related to defects and enhanced dynamic recrystallization, respectively. • At 750 ℃, the wear volume loss and surface roundness of wear scar reach the minima for forming a complete tribo-layer. • At room temperature, abrasive wear is the wear mechanism of lamellar Ti-46Al-2Nb-2Cr. • At elevated temperatures, the wear mechanism is mixed wear mechanisms, including abrasive, oxidative and adhesive wear. • Compared to room temperature, the tribo-layer and nano-grained layer at 750 ℃ are thicker, and nano-grains are finer. • Nano-grains at room temperature are ascribed to defects, while that at 750 ℃ are linked to dynamic recrystallization. [ABSTRACT FROM AUTHOR]

Addressing the problem of fine abrasive particles being closely packed on the surface of conventional grinding tools easily leads to titanium alloy clogging, rapid tool wear and worse surface quality, the small-scale textured grinding tool with uniformly distributed helix groove structures is proposed and fabricated by combining the low-speed wire electrical discharge turning with electroplating techniques. Compared to cylindrical grinding tool, the grinding force, the clogging and adhesive wear phenomenon of titanium alloys processed by textured grinding tool is found much smaller, and the surface roughness is improved especially in rapid wear stage.The effects of tool wear on surface morphology characteristics, surface quality, grinding force and the tool wear form and wear resistance of textured grinding tool are elucidated. [ABSTRACT FROM AUTHOR]

A novel method combining laser-induced modification and abrasive belt grinding (LM&BG) was proposed to prepare wear-resistant surfaces of titanium alloys. Comprehensively investigated the evolution mechanism of material modification and wear resistance of LM&BG samples. It was found that an oxide-ceramic-modified layer with increasing hardness (10 times) was formed by laser modification on the titanium alloy, mainly composed of TiO 2 , with the two phases Rutile-TiO 2 and Anatase-TiO 2. Moreover, the surface roughness after abrasive belt grinding of the modified layer is less than Ra0.1, with a uniform subsurface microstructure. Interestingly, the wear modes of the modified layer shifted from adhesive and oxidative wear to brittle microdetachment, significantly reducing the coefficient of friction, material wear, and subsurface damage, thus improving the wear-resistant capability. [Display omitted] • Proposed LM&BG method to enhance the hardness and wear resistance of titanium alloys. • LM&BG surfaces have good integrity with a roughness of less than Ra0.1. • The oxide ceramic modified layer consists of TiO 2 with a hardness of 35.01 GPa. • COF, wear and subsurface damage were significantly reduced for LM&BG samples. • LM&BG samples shifted from severe wear and deformation to brittle microdetachment. [ABSTRACT FROM AUTHOR]

The MoSi 2 -reinforced copper-graphene composites (Cu-MoSi 2 -GNS) were prepared using mechanical ball milling and spark plasma sintering techniques. The effects of MoSi 2 content on the microstructure, electrical conductivity, mechanical performance, and tribological properties were systematically investigated. Results indicate that the addition of MoSi 2 significantly enhanced strength and hardness, although slightly reducing electrical conductivity. When the MoSi 2 content does not exceed 5 wt%, MoSi 2 is uniformly dispersed, refining copper matrix grains and improving GNS dispersion. Optimal MoSi 2 addition facilitates the formation of a stable subsurface structure with complete mechanical mixture layer, improving wear resistance and self-lubricating properties. The main wear mechanism shifts from adhesive to abrasive wear. At 5 wt% MoSi 2 , the Cu-MoSi 2 -GNS composites exhibits superior mechanical properties, electrical conductivity, and tribological performance. [ABSTRACT FROM AUTHOR]

The effect and mechanism of micro/nano iron powder on properties of Cu-matrix composites are researched. The braking ability under various velocities is tested by means of pin-disk tests. The mechanical behavior, elemental mapping, friction film, and wear debris are explored by Brinell hardometer, multifunctional densitometer, SEM, and EDS. The findings show that the hardness and density are the highest, while the porosity is the lowest for the composite containing nano Fe powder. In addition, it possesses the most stable friction and minimum wear at high velocities from 250–350 km/h. The wear mechanism at different braking speeds is enunciated by investigating the variations of surface, section, abrasive debris, and tribofilm. It changes from severe delamination wear of micro Fe powder to adhesive wear of nano Fe powder. Compared to micro Fe powder, nano iron powder can improve the growth rate of friction film, inhibit the generated rough peaks, and enhance the intensity of tribofilm. This provides reference for the development of high performance brake pads. [ABSTRACT FROM AUTHOR]

Water-lubricated Bearings (WLBs) are the core transmission components of a ship propulsion system, and their wear behavior primarily occurs during the starting and stopping states. To characterize the wear behavior of WLBs, an equivalent experiment is conducted on bush material to obtain the relationship between dimensionless wear coefficient and sliding distance based on the Archard wear model. Then, an experimentally determined transient wear model is incorporated into a tribo-dynamic model to develop a fully coupled Tribo-Dynamic-Wear (TDW) model for the WLBs during repeated start-stop cycles. In this model, the 3D thermal effect, the transient bush worn surface and the geometric imperfection of the journal surface are considered. Numerical results show that the wear rate is more significant at the beginning of the start-up state and the end of the stopping state of the WLB. Meanwhile, it is found that compared to a perfect journal, a reasonable undulation number and undulated amplitude of the journal surface can improve the wear resistance performance of WLBs during repeated start-stop cycles. More specifically, a relatively lower undulation number leads to a smaller wear volume than the perfect journal, and the undulated journal surface has an optimal undulated amplitude that minimizes the wear volume. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the effects of intermolecular potential on adhesive wear behaviors of microcontacts between a rigid flat and an elastic-plastic sphere, using a Finite Element (FE) model. In this model, a separation-dependent adhesive pressure, governed by the Lennard-Jones (LJ) potential, is applied to the surfaces of both the rigid flat and the sphere under combined normal loading and tangential displacement. To assess material damage, the Johnson–Cook (JC) failure and fracture energy criteria are utilized, allowing for element deletion upon reaching the damage threshold. The role of intermolecular potential in the adhesive wear behaviors of spherical microcontacts is evaluated, focusing on wear volume, wear rate, wear morphology and fracture propagation mode under various dimensionless normal loads and adhesive energies. Two fracture propagation modes, namely bidirectional-like and unidirectional-like modes, dependent on normal load and adhesive energy, have been identified. The transition from mild to severe wear regime is found to be closely related to the fracture propagation mode. Additionally, an interesting observation is that relatively high adhesive energy could result in decreased wear volume and wear rate under certain normal loads, which can be attributed to the change in fracture propagation mode caused by the adhesive pressure. [ABSTRACT FROM AUTHOR]

The tribological behavior of TiC/Ni composites is optimized by adding Ta, due to the improved oxidation resistance and hardness. The (Ti,Ta)C particles with core-rim structure are formed, and particle size decreases from 1.03 µm to 0.75 µm by adding 8 wt% Ta, and the hardness increases from 630.43 HV to 669.13 HV. At 20 N load, the primary wear mechanism is oxidation wear and the tribological property is influenced by oxidation resistance. At 50 N load, the main wear mechanism includes abrasive, adhesive, delamination and oxidation wear, and the tribological behavior is mainly influenced by the hardness and oxidation resistance. [ABSTRACT FROM AUTHOR]

In industrial settings, the same friction pair can undergo both fretting and sliding wear depending on the working conditions. This study compares the fretting and sliding wear behaviors of TC4 against GCr15 at various temperatures. The results indicate that in fretting tests, the average friction coefficient decreases with increasing temperature, while in sliding tests, it shows the opposite trend. As the temperature rises, the material transfer is intensified, and a significant amount of Fe 2 O 3 oxide friction layer forms on the surface of TC4 alloy, providing protection to the worn surface and decreasing the wear rate. At 300 ℃, adhesive wear in fretting wear is more severe than sliding wear, with peeling being more pronounced around the wear scar of sliding wear. [ABSTRACT FROM AUTHOR]

The poor wear resistance of titanium alloy makes it challenging to develop high-performance lubricating materials. For the characteristic of highly designable structure, ionic liquids (ILs) are the potential lubricants with excellent physicochemical properties and lubricating performance. Herein, three protic phosphorus-based ionic liquids (PPILs) were designed and synthesized with the exploration of their interfacial lubrication behavior and interaction mechanism on the titanium substrate. The as-synthesized IL lubricants exhibit optimal tribological properties on steel-titanium friction pairs even at high load and temperature. The surface analysis showed that IL can form the lubricating protective film on the titanium-based metal surface, effectively reducing the adhesive wear. Combined with surface analysis techniques (SEM, XPS, FIB-TEM and TOF-SIMS), the lubrication mechanism was discussed systematically. [Display omitted] • Ionic liquid lubrication is explored on the titanium substrate. • Excellent anti-wear and lubricating properties on the titanium alloy surface is obtained. • The tribofilm is generated on the titanium substrate through the self-assembly behavior of PPILs. • Tribochemical reaction can occur for PPILs at titanium-based sliding asperity. [ABSTRACT FROM AUTHOR]

Torsional fretting wear is a commonly wear form in assemblies, while its inherent concealment and debris evolution make it difficult to study. Titanium alloy, widely used in aviation and aerospace, suffer from fretting wear under complex alternating load. In this paper, the effects of laser shock peening (LSP), fretting amplitude, and frequency on cylinder-on-flat torsional fretting wear of TC21 alloy was investigated. The friction torque and fretting loop were illustrated to identify the fretting regime. Results shown that LSP reconstructed surface morphology, increased surface roughness and hardness, meanwhile reduced the wear volume of titanium by more than 30 %. The fretting wear mechanisms varied with amplitude: lower amplitudes led to oxidation and adhesive wear, while higher amplitudes caused oxidation and abrasive wear. The results of wear volume shown that the influence of fretting frequency on wear was related to the difficulty of wear debris discharge. [ABSTRACT FROM AUTHOR]

The GH4169D superalloy, a novel Nickel-based material widely acknowledged for its exceptional high temperature strength and fatigue resistance properties, plays a pivotal role in the production of critical components of contemporary aero-engines. The material, however, falls under the category of a typical difficult-to-cut metallic material due to the substantial cutting forces and significant tool wear experienced during the machining process. In this paper, a method of longitudinal ultrasonic vibration assisted side milling (LUVM) was developed to extend tool life. The investigation primarily involved an analysis of tool wear behaviors, including milling force, tool life, morphologies of tool wear, and various underlying wear mechanisms in LUVM and conventional milling (CM) of GH4169D superalloy. The results demonstrate that LUVM exhibits the advantage of reducing milling forces and prolonging tool life in comparison to CM. Throughout the entire milling process, the maximum milling force of LUVM is consistently smaller than that of CM, displaying a comparatively slower growth trend. At the conclusion of machining, while CM reaches a maximum milling force of 360.3 N, the maximum milling force of LUVM (195.9 N) is significantly lower. The tool life of LUVM is 28.2 min, representing a 33 % increase compared to CM (21.2 min). Material adhesion, coating delamination, and built-up edge (BUE) phenomena can be observed on both the tool rake face and flank face in CM. LUVM contributes to mitigation of bonding phenomena, prevention of BUE formation, and avoidance of abrasive wear in comparison to CM. However, it is prone to lead to tool tip chipping. For CM, the tool wear mechanisms include adhesive wear, oxidation wear, abrasive wear and diffusion wear; whereas for LUVM, the tool wear mechanisms comprise of adhesive wear, oxidation wear and diffusion wear. [Display omitted] • LUVM exhibits the advantage of reducing milling forces and prolonging tool life compared to CM. • LUVM contributes to mitigation of bonding phenomena and prevention of BUE formation compared to CM. • Adhesive, oxidation and diffusion wear patterns are identified as the tool wear mechanisms for LUVM. [ABSTRACT FROM AUTHOR]

The CoCrNi-FeCoCrNi-FeCoCrNiMo gradient high entropy alloy (GHEA) coatings with good metallurgical properties have been successfully prepared on 316 stainless steel by laser cladding (LC). The microstructure, element distribution, microhardness and wear behavior of HEA coating were investigated by SEM, EDS, hardness test and wear test, respectively. The results show that the design of the entropy-varying gradient structure improves the bonding quality of the 316 stainless steel and the FeCoCrNiMo coating. The phase compositions of FeCoCrNiMo HEA coating and CoCrNi-FeCoCrNi-FeCoCrNiMo GHEA coating contain face-centered cubic (FCC) and σ phases. The surface microstructure of the CoCrNi-FeCoCrNi-FeCoCrNiMo GHEA coating is much finer than that of FeCoCrNiMo HEA coating. The microhardness and wear resistance of the CoCrNi-FeCoCrNi-FeCoCrNiMo GHEA coatings are significantly improved compared to the FeCoCrNiMo HEA coatings directly deposited on the 316 stainless steel. The CoCrNi-FeCoCrNi-FeCoCrNiMo GHEA coatings have high hardness of 840HV. Moreover, the results show that the shift in the wear mechanism is evident within the GHEA coatings, from more severe oxidized wear, adhesive wear and slight deformation to abrasive wear, which can significantly reduce the wear rate of the HEA coatings in friction process. [ABSTRACT FROM AUTHOR]

We developed a nickel-boron-graphite (Ni-B-Gr) composite coating with self-lubricating properties and investigated its tribological behavior. We employed an electroless bath to deposit the Ni-B-Gr coatings on AISI 4140 steel. The Ni-B matrix serves as a hard matrix, while graphite (<20 µm) at varying concentrations (0.05 to 0.5 g/L) act as the self-lubricant. We subjected the composite coating to plasma nitriding (PN) at 400 °C for 1 h in a mixture of 25% nitrogen and 75% hydrogen. Our analysis involved microstructural examination, hardness testing, toughness assessment, and tribological evaluations. The PN Ni-B-0.275Gr composite demonstrated a 65% reduction in wear rate and a 25% decrease in coefficient of friction. Furthermore, incorporating graphite altered the wear mechanism, shifting from adhesive to oxidation wear. [Display omitted] • Electroless Ni-B-Gr composite coatings were developed to enhance tribological performance. • Integration of plasma nitriding and graphite improves bonding and wear resistance. • Plasma nitrided Ni-B-0.275Gr coatings exhibit a reduction in wear rate and COF. • Graphite incorporation transforms the wear mechanism by reducing adhesive wear. [ABSTRACT FROM AUTHOR]

The present study investigates the effect of processing method on the tribological behavior of 3D-printed Polylactic acid (PLA)/graphene composite samples. Two different methods, electrochemical (EG) and chemical exfoliation (HG) of graphite, are used to prepare graphene fillers. The PLA/graphene composites are processed using two different solvents, chloroform (CHCl 3) and dimethylformamide (DMF). Various PLA/graphene composite combinations are prepared by varying filler type, solvent type, and filler loading. The 3D printable composite feedstock filaments are prepared using a single-screw Desktop extruder. Fused Filament Fabrication (FFF) is employed to print samples for tribological tests. The coefficient of friction (COF) and wear rate are evaluated using the ball-on-flat reciprocating sliding wear tests. It was observed that COF was reduced by 76 % with 0.5 wt% loading of filler. The wear mechanism has changed from predominant abrasive wear in neat PLA to adhesive wear for composites. Further, the interactive effect of process parameters is studied using ANOVA. The results indicate that filler type and filler loading significantly influence weight loss. The solvent type has a minimum effect. [ABSTRACT FROM AUTHOR]

A novel liquid metal-based SiC/Graphene-Mo hybrid nanofluid (LMNF) has been fabricated. The nanoparticles are uniformly dispersed, and LMNF temperature-viscosity characteristics is stabler in a wider temperature range than traditional hydraulic media. With this, the LMNF tribological performance on Al 2 O 3 and SS316L friction pairs is studied: The LMNF has superior severe-pressure and high-temperature lubrication with the nanoparticle-enabled wear resistance. The SS316L surface forms composite nanofilm with the LMNF, which prevents adhesive wear and mitigates liquid metal corrosion. Comparatively, the nanoparticles function as "micro-bearings" on the Al 2 O 3 surfaces to assist lubrication. These benefits are reflected in the gear pump volumetric efficiency and wear rate of our industry-level hydraulic system, approving LMNF as a potential hydraulic transmission medium in harsh conditions. [ABSTRACT FROM AUTHOR]

Micro-arc oxidation is an effective method to enhance surface wear resistance. This paper comparatively studies the fretting and sliding wear properties of micro-arc oxidation-treated 7075 aluminum alloy at different temperatures. Research indicates that both the untreated and MAO-coated samples exhibit peak friction coefficient values due to adhesion at elevated temperatures. At both room temperature and 150 °C, the fretting wear rate of the MAO-coated sample is lower than that of the sliding wear rate, which can be attributed to distinct surface damage mechanisms and third body behavior under different wear modes. Adhesive wear is more prominent in MAO-coated samples during high-temperature fretting compared to room temperature, while abrasive wear and spalling are more prevalent during high-temperature sliding. [ABSTRACT FROM AUTHOR]

Damage to mechanical components caused by contaminant ingress is a common failure. In response to this issue, this study introduces a synergistic abrasion reduction method based on the combined application of ceramic materials and surface texturing. Using cylindrical thrust roller bearings as an illustration, circular textures were applied to the raceways, and a small number of steel rollers were substituted with ceramic ones. Moreover, alumina was introduced into the lubricant as a contaminant. The frictional and dynamic performance of the "ceramic-textured surface" combination under lubricant contamination conditions was explored and compared with corresponding single abrasion reduction techniques. The synergistic abrasion reduction mechanism of the "ceramic-textured surface" combination was also examined. The findings reveal that under lubricant contamination conditions, the synergistic abrasion reduction method surpasses individual abrasion reduction methods and demonstrates a certain degree of complementarity. Compared with traditional all-steel bearings, textured bearings with four ceramic rollers have reduced the average frictional force by approximately 56.82 %, and the mass loss of the shaft washer and seat washer has been reduced by approximately 81.01 % and 80.86 %, respectively. Rolling elements treated with the synergistic abrasion reduction method exhibit enhanced resistance to abrasive particle wear. This improvement is attributed to the collaborative effects of various mechanisms, including crushing and refinement, capture and storage, grinding and finishing, as well as self-healing and smoothing. • A synergistic wear reduction method to reduce abrasive wear is proposed. • Abrasive wear tests were carried out under rolling conditions. • The surface texture and ceramic materials are added to the rolling bearing as anti-wear measures. • The tribological behavior and dynamic performance of the synergistic anti-wear method were evaluated. • The synergistic wear reduction method exhibits better wear resistance. [ABSTRACT FROM AUTHOR]

Charging connector of electric vehicles faces two working conditions of sliding friction and current-carrying fretting. Traditional Ag coating is difficult to meet the performance requirements. Herein, Ag/graphene composite coatings were prepared by electroplating, and the chemical compositions, crystal phase, mechanical and tribological properties were studied. The results showed that adding graphene increased the hardness, elastic modulus and toughness. Under sliding friction and current-carrying fretting, Ag/graphene coating exhibited low COF and wear, stable and low ECR. The sliding friction mechanism was dominated by abrasive wear, while the current-carrying fretting mechanism was dominated by adhesive and fatigue wear. The worn surface analysis indicated that the superior tribological properties were attributed to the improved mechanical properties and the formation of transfer film. [Display omitted] • Ag/graphene coating was fabricated as electrical contact material for charging connector. • The addition of graphene significantly increased the mechanical properties and toughness. • The tribological behaviors were investigated under sliding friction and current-carrying fretting. • The excellent tribological properties were attributed to the improved mechanical properties and the transfer film. [ABSTRACT FROM AUTHOR]

In this work, heterogeneous functionally graded material (FGM) with SS316LSi and ER70S-6 is deposited using twin wire arc additive manufacturing technique. Tribological, mechanical and microstructural characterization were undertaken for the developed FGM structure. Microstructural analysis revealed acicular ferrite and bainite regions near molten pool boundaries, with "lathy ferrite" formations during solidification. Developed FGM structure exhibited appreciable mechanical strength with an average yield strength of 440±6 MPa, ultimate tensile strength of 714±13 MPa, and 43%±1.23 elongation. Worn surfaces revealed an adhesive wear mechanism. Gradation in wear rate and average coefficient of friction, measured as 9.98 × 10−4 mm 3/N-m and 0.46–0.51, respectively, was observed in the final deposited structure with intermediate values between SS316LSi and ER70S-6. Results reveal that as-deposited FGM exhibits superior wear resistance and mechanical performance compared to SS316LSi and ER70S-6. [Display omitted] [ABSTRACT FROM AUTHOR]

High performance CoCrFeNiW 0.2 and CoCrFeNiW 0.2 + 3 at% C HEAs were prepared by vacuum arc melting, which are promising candidates for extreme environment applications. To study the current-carrying wear behavior of the two HEAs under different current conditions, a pin-on-ring test rig was custom-designed. The microstructures, hardness, wear properties and mechanisms of the HEAs were investigated. The results reveal that the HEAs exhibit outstanding wear resistance in the absence of current, as evidenced by the very low wear rates and the relatively smooth worn surfaces. With the increasing of current intensity, it simultaneously exacerbates the abrasive wear, adhesive wear, oxidative wear and arc erosion. The HEAs show the worst wear resistance due to the melt ejection and arc discharge at 10 A. However, when the current reaches 20 A, the elevated temperature promotes material transfer and the formation of dense and complete oxide film, which has lubricating and protective effect to separate the worn surfaces, resulting in the reduction of COFs and wear rates. The rupture and regeneration of oxide film play an opposite effect on sliding contact friction, and their competitive relationship dominates the wear resistance of the HEAs under the large current. The CoCrFeNiW 0.2 + 3 at% C HEA exhibits superior wear resistance than CoCrFeNiW 0.2 HEA under various conditions because the WC carbide is harder than μ phase particle and can impede plastic deformation of FCC matrix during tribological process more efficiently. [ABSTRACT FROM AUTHOR]

To simulate the variational working conditions of the titanium fastener in the aero-engine, variable cycle fretting wear tests were carried out for normal loading (80/40 N), frequency (100/30 Hz), displacement amplitude (80/40 µm) and operating temperature (500/350 °C) in a self-lubricating composite coating on TC21 titanium alloy substrate, and the fretting wear behavior and wear mechanism were thoroughly investigated. The results shows that the coefficient of friction (COF) and the wear volume present a significant difference under variable cycle fretting conditions. The specimen exhibits a relatively stable COF under variable operating temperature. Whereas for the specimen under variable displacement amplitude presents a lowest wear volume. The adhesive wear is mainly found in the specimens under variable normal loading and frequency. Whereas for the specimens under variable displacement amplitude and operating temperature, abrasive wear and oxidation wear is mainly dominated, respectively. The dissipated energy calculation results demonstrate that the variable displacement amplitude and operating temperature have greater impact on the fretting wear behavior. The microstructure analysis in the cross-section of specimens reveals that the sub-surface is composed of amorphous-nano crystalline layer, plastic deformation layer and the origin coating. Additionally, the wear mechanism of the specimens under variable fretting conditions were deeply revealed. This work can provide essential information on fretting behavior and mechanism under the variational working conditions. • The fretting wear behavior and mechanism of a composite coating were investigated under variable cycle fretting conditions. • The variation of displacement amplitude has a significant effect on fretting wear. • The amorphous-nano crystalline layer provides a protective role and suppresses wear effectively. • This work can provide essential information on fretting behavior and mechanism under the variational working conditions. [ABSTRACT FROM AUTHOR]

Polyetheretherketone (PEEK) carbon nanomaterial-based nanocomposites, incorporating zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D) and three-dimensional (3D) carbon structures have gained prominence as advanced materials with the potential to enhance tribological properties paving the way for a new era in the development of advanced bearings for high-performance machinery applications. This study delves into the forefront of friction and wear analysis, employing all atom molecular dynamics (aa-MD) simulations to engineer PEEK polymer nanocomposites with precision under elevated temperature and higher velocity. The research presents optimization of mechanical strength and tribological properties crucial to meet the demanding requirements of industrial machinery. The addition of C60 fullerenes reduced COF by 16.59% and wear rates by 6.52% due to its spherical shape and lubrication effects. Introduction of carbon-nanotubes further decreased COF by 54.54% and wear rates by 32.5%, offering resistance to abrasive and adhesive wear. S-graphene showed notable performance, reducing COF by 69.40% and wear rates by 75.03%, making it promising for sliding and wear applications. Carbon-nanocones reduced COF by 60.6% and wear rates by 72.06%, slightly higher than S-Gr due to abrasive effects and increased surface contact. These findings underscore the potential of reinforcement dimensionality in enhancing the tribological properties of PEEK based nanocomposites. [Display omitted] • Explored PEEK nanocomposites varying nano sized reinforcement dimensions (0D to 3D). • MD simulation study shows that 0D-3D reinforcements reduce friction and wear. • Studied effects of high temperature and velocity on nanocomposites wear resistance. • Role of PEEK and reinforcement interactions in mechanical/tribological behavior. • This study highlights role of MD simulations in designing polymer nanocomposites. [ABSTRACT FROM AUTHOR]

To achieve low-temperature sintering of B 4 C ceramic, 'sol-gel' method is employed to create a B 4 C@SiO 2 core-shell structure composite. Black phosphorus (BP) is exfoliated through 3 methods to obtain few-layer black phosphorene (FLBP) with sizes ranging from 100 µm to 1 µm. B 4 C@SiO 2 /20BP composite is successfully prepared through cold sintering process at 3 GPa and 90 °C, using NaOH solution as the transient liquid phase. The dry friction properties of B 4 C@SiO 2 /20BP composites with different sizes of FLBP are investigated in a ball-on-disc contact form. The findings reveal that as the FLBP size decreases, the friction coefficient gradually increases, inversely correlating with the wear rate. The wear mechanism shifts from adhesive wear to fatigue wear, leading to a diminishing anti-friction effect of FLBP. [ABSTRACT FROM AUTHOR]

The TiN-ZrO 2 -B 4 C reinforced Cu-metal matrix composites were prepared using powder metallurgy, and the microstructure, properties, and friction mechanisms were investigated when paired with self-made C/C-SiC materials. Appropriate TiN/ZrO 2 ratio (3/5) can enhance the performance of Cu, due to the formation of TiB 2 through the diffusion reaction between TiN and B 4 C, while excessive TiN may weaken it because the continuity of the Cu matrix is destroyed. As the TiN content increases, the Cu-metal matrix composites materials undergo abrasion wear, adhesive and oxidative wear, abrasive and adhesive wear, and adhesive and oxidative wear, respectively. ZrO 2 primarily contributes to mean friction coefficient at low braking speed, while TiN at mid and high-speeds, and B 4 C plays a crucial role in high-speed. [ABSTRACT FROM AUTHOR]

This study explored the evolution of friction-induced vibration (FIV) and wear in high-speed train friction braking through experiments, theoretical analysis, and numerical simulation. Experimental tests revealed that vibration behavior transitions from high-frequency modes at high speeds to low-frequency stick-slip at lower speeds. Theoretical analysis indicated that brake disc speed, coefficient of friction (COF), and contact stiffness affect system stability. Specifically, the system experiences high-frequency vibrations at high speeds due to mode coupling, and the friction block surface primarily undergoes abrasive wear mechanisms. At lower speeds, the system demonstrates low-frequency stick-slip vibrations induced by the combined effects of mode coupling and negative friction velocity slope (NFVS) characteristics, and the friction block surface mainly experiences adhesive wear mechanisms. • FIV in high-speed train braking exhibits diverse mechanisms with speed changes. • The system stability is affected by brake disc speed, COF, and contact stiffness. • FIV is influenced by mode coupling and NFVS from high to low speeds. • The wear mechanism changes from abrasive to adhesive wear during deceleration. • FIV characteristics correlate with wear mechanisms on the friction block. [ABSTRACT FROM AUTHOR]

The Mo–Si–B alloys with good wear resistance are prominent for high-temperature applications. In this work, the effects of ZrB 2 content and test temperature on the tribological properties of the Mo–Si–B/ZrB 2 composites at 25–800 °C were investigated. It indicates that the composites show an enhanced wear resistance, which can be ascribed to the improved hardness and formation of Zr-rich borosilicate layer by introducing ZrB 2 particles. The main wear mechanism is abrasive wear accompanies with adhesive wear at 25–400 °C, where ZrB 2 addition can reduce the wear loss. And adhesive wear dominates at 600–800 °C, where the formed tribo-layer can provide a good self-lubricity and is beneficial for improving the wear resistance of the composites. • Tribological properties and wear mechanism at 25–800 °C were investigated. • The composites show lowest COF and wear rate at 600 °C for good self-lubricity. • The self-lubricity is mainly derived from MoO 3 containing oxides film. • The formation of Zr-rich borosilicate layer improves the wear resistance at 800 °C. • Abrasive wear dominates at 25–400 °C and adhesive wear dominates at 600–800 °C. [ABSTRACT FROM AUTHOR]

In this study, polyetheretherketone (PEEK) based composite coatings reinforced with polytetrafluoroethylene (PTFE) were applied to copper-steel bimetallic plates. The impact of process parameters on the tribological properties of the coatings was investigated. The results indicated that the optimized PTFE/PEEK 2.2 coating exhibited commendable friction reduction and wear resistance performance when subjected to aviation kerosene lubrication. It was observed that the hot-pressing temperature has the most significant influence on the bearing capacity and wear rate of the coatings. In contrast, the hot-pressing pressure primarily affects the average friction coefficient. The primary wear mechanism observed in these coatings is adhesive wear. These findings suggest promising application prospects for the composite coatings in aviation hydraulic pumps, underscoring their potential to significantly improve overall performance. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced plastics (GFRP) are widely appiled for high-value components, but it faces limitations due to the heterogeneity and limited milling tool life. This study investigates the wear mechanism of tools in varying states of wear during the milling of GFRP under different combinations of cutting parameters. The findings demonstrate a significant increase in flank wear values of new tools, initially worn tools, moderate worn tools and severely worn tools associated with the large material removal rate (LMRR), exhibiting respective increments of 56.7%, 59.8%, 74.3%, and 26.5% in contrast to the small material removal rate (SMRR). The wear mechanisms in distinct cutting regions of the tool were systematically classified and characterized. The flank face and tool nose primarily experience abrasion and adhesion, while the rake face and cutting edge predominantly display characteristics of microchipping and abrasive wear. In contrast, the bottom edge is exclusively impacted by microchipping. The deposition of chemical elements on the cutting edge was examined through electron dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). A comprehensive investigation was undertaken to elucidate the progression of tool wear. The findings indicate that the principal factors influencing tool wear in LMRR are adhesive wear resulting from cutting heat and chipping wear arising from substantial cutting loads. In contrast, tool wear during SMRR is predominantly attributed to abrasive wear caused by the presence of fiber-based hard points within GFRP workpieces. The wear characteristics of milling tools during the machining of GFRP are systematically investigated and analyzed. This study holds theoretical significance in guiding the design of tool materials for GFRP milling operations. • Under SMRR conditions, tool mainly suffers from abrasive wear, whereas in LMRR, it primarily undergoes chipping wear. • The rake face of the tool is more susceptible to friction and heat, and oxidative wear is more significant. • A comprehensive description of the evolution of tool wear at different material removal rates is presented. • Thermal effects primarily induce adhesion and edge chipping, whereas the existence of rigid particles results in abrasion. [ABSTRACT FROM AUTHOR]

The pantograph-catenary system plays a crucial role in the current acquisition of Electric Multiple Unit. To obtain better carbon skateboard/contact wire matching properties, this study discusses the current-carrying properties of four different copper-impregnated carbon skateboards with chromium-zirconium-copper alloy contact wires at different currents. The test results demonstrate that the CI-D carbon skateboards are able to withstand higher currents with relatively stable electrical contact resistance and have a lower wear rate. According to tribological analysis, adhesive wear was the main wear mechanism of copper-impregnated carbon skateboards under the test conditions, which micro-analysis revealed as oxidized layers over a wide range of small areas. Small amounts of oxide particles and third-body abrasive debris cause abrasive wear on the carbon skateboard surface. [Display omitted] • Analyzed the friction property of four contact pairs. • Comparing the wear rate and interface temperature performance of contact pairs. • Analyzed the influence of current on current-carrying friction property. • Comparing the matching performance of different friction pairs. [ABSTRACT FROM AUTHOR]

Fretting corrosion behavior and damage mechanism of Zr-4 alloy mated with Inconel 718 alloy under different fretting regimes in high temperature high pressure water were studied. The corresponding running condition fretting corrosion map (RCFM) and material response fretting corrosion map (MRFM) were established. The results showed that the change of fretting regime led to the differences of fretting corrosion behavior and damage mechanism. Based on the damage mechanism, the MRFM could be divided into partial slip regime with only slight surface damage; mixed fretting regime-I dominated by cracks; mixed fretting regime-II dominated by cracks and abrasive wear; and gross slip regime dominated by severe adhesive wear and oxidation. The transformation of fretting regime also resulted in different oxides. • The MRFM presents four regimes: partial slip regime, mixed fretting regime-I, mixed fretting regime-II and gross slip regime. • The MRFM presents slight degration in PSR, cracks in MFR-Ⅰ, cracks and wear in MFR-Ⅱ, adhesive wear and oxidation in GSR. • The main oxides on the worn surface were monoclinic ZrO 2 in PSR and MFR, NiCr 2 O 4 and tetragonal ZrO 2 in GSR. [ABSTRACT FROM AUTHOR]

Recently, 3D-printed Ti-6Al-4 V alloys have been gradually used for medical implants, where surface quality plays a crucial role in bio-tribological resistance. In this study, we designed three Ti-6Al-4 V samples through mechanical grinding, polishing, and sandblasting to explore the effect of surface roughness on the bio-tribological behavior against the Si 3 N 4 counter-ball in a simulated body fluid (SBF) solution. Results indicate an increasing trend in the bio-tribological properties with decreasing surface roughness, with the polished sample exhibiting the lowest wear rate (2.73 × 10−3 mm3/N·m) and superior bio-tribological resistance. Finite element simulation reveals that asperities on the rougher surface sample lead to stress concentration, forming larger asperity fragments, enhancing mechanical interlocking and thus intensifying wear. Additionally, with increasing surface roughness, the wear mechanism of the as-printed Ti-6Al-4 V alloy shifts from abrasive and adhesive wear to a combination of abrasive, adhesive, and oxidative wear. This study provides valuable insights into the effect of surface roughness on the bio-tribological properties of as-printed Ti-6Al-4 V alloys, offering guidance for regulating surface quality in biomedical implants. [ABSTRACT FROM AUTHOR]