The composite segmented slip ring (CSSR) serves as a critical component for power and signal transmission. It is capable of alternately triggering and interrupting electrical signals, which is used to control the start/stop of associated mechanical operations. As an instantaneous switch, the CSSR faces the critical challenge of avoiding signal control blind spots at key actuation nodes. This study focuses on the tribological and electrical performance of two typical tribo-pairs (QBe2.0/ZrO2 and QBe2.0/QBe2.0) associated with the CSSR. Tribological test results demonstrate that the QBe2.0/QBe2.0 tribo-pair exhibits higher friction coefficient and more severe wear. Arc ablation and material transfer blur the insulation/conduction boundary of the CSSR, which is identified as the direct cause of signal distortion. This research clarifies the relationship between current-carrying tribological behavior and electrical signal transmission failure of the CSSR, providing a theoretical and experimental basis for optimizing the service performance and reliability of CSSR in mission-critical applications.

In this paper, Al-20Si-5Fe-2Ni composites reinforced with varying contents of Mo2BC and Cu-coated Mo2BC were fabricated via vacuum hot-press sintering. The influence of Cu-coated Mo2BC content on the mechanical and tribological properties of the composites was systematically examined. Results revealed that the Cu coating on Mo2BC ceramic particles reacted with the aluminum alloy matrix during sintering, leading to the formation of Al2Cu interfacial bridges. The incorporation of Cu-coated Mo2BC significantly enhanced the overall mechanical properties of the composites, which was attributed to the synergistic effects of interfacial bridging strengthening and the pinning effect provided by the Mo2BC ceramic particles. Moreover, the tribological performance of the Al-20Si-5Fe-2Ni composites was markedly improved. When sliding against GCr15 bearing steel, the primary wear mechanisms of the unreinforced alloy included adhesive, fatigue, and abrasive wear. With the addition of up to 20 wt.% Cu-coated Mo2BC, a smooth and continuous oxide film formed on the worn surface, which exerted a lubricating effect and reduced wear. However, as the content of Cu-coated Mo2BC further increased to 30 wt.%, agglomeration of Mo2BC particles became evident. Under applied shear stresses during sliding, these agglomerated particles were prone to fracture and disperse within the wear track, ultimately resulting in an increased friction coefficient and higher wear rate.

Under severe contact conditions, the tribological behavior of bearing steels plays a decisive role in determining the operational reliability of rolling bearings. In the present investigation, laser shock peening (LSP) was employed to enhance the dry and oil-lubricated tribological performance of Cronidur30 martensitic stainless bearing steel. A series of reciprocating ball-on-disk tribological tests were carried out at an applied load of 20 N. The influence of varying laser energy levels and impact counts on friction response, wear progression, and underlying wear mechanisms was systematically evaluated using 3D profilometry, SEM and EDS. The results show that LSP treatment led to grain refinement in the near-surface region, significant work hardening, the introduction of compressive residual stress, and changes in surface topography, all of which collectively contributed to improved wear resistance. Under dry sliding, the wear rate of the LSP-4J-4 specimen was reduced to 1.797×10⁻⁵ mm³/(N·m), representing a 42.7% decrease compared with the untreated sample, which exhibited a wear rate of 3.135×10⁻⁵ mm³/(N·m). Under oil lubrication, the LSP-4J-3 configuration demonstrated the most favorable wear resistance, achieving a wear rate as low as 4.200×10⁻⁸ mm³/(N·m). This value corresponds to a 58.8% reduction relative to the untreated condition. SEM and EDS results indicated that LSP reduced oxidation and adhesive damage. The overall improvement in tribological performance can be attributed to the synergistic effects arising from enhanced surface hardness, the presence of compressive residual stress, and a surface morphology that facilitates lubricant retention.

The current-carrying frictional pair is the core channel for current transmission and energy conversion between moving components. The current-carrying frictional pair for electromagnetic launch consists of the Al armature and Cu rails. At variable working conditions with a peak velocity exceeding 103 m/s and a peak current surpassing 105 A, the current-carrying tribological damage of Cu rail pairs were investigated. Under the same discharge voltage of 3800 V, the armature final velocity of Al armature decreased from 1515.6 m/s for the first launch to 1233.4 m/s for the 20th launch. The peak current dropped from 347 kA to 241 kA, and the final contact resistance increased from 35.7 mS2 to 176.4 mS2. The damage at the initial position of the rail is dominated by melting and oxidation, a porous transfer film formed on the surface. While the damage at the terminal position is dominated by high-velocity sliding current-carrying damage such as adhesion, oxidation, and abrasive wear, which has lower roughness and less oxidation. The transition of the damage mechanism is related to the change of the Al-Cu contact state from solid-liquid-solid to solid-solid, and the contact states for damage transition is contact load = 13.1 kN, velocity= 1000 m/s, and current = 160 kA. This finding is valuable for understanding current-carrying wear and material protection under extreme conditions.

Improving the tribological performance of bearing steels by laser shock peening (LSP) remains challenging because the beneficial effects of near-surface strengthening must be balanced against the accompanying changes in surface topography, particularly under different lubrication conditions. In this study, LSP was applied to Cronidur30 high-nitrogen martensitic stainless bearing steel to clarify how pulse energy and repeated impacts regulate its surface state and wear response under dry and polyalphaolefin 4 (PAO 4)-lubricated reciprocating sliding. LSP progressively refined the near-surface martensitic structure, promoted dislocation accumulation and carbonitride fragmentation/redistribution, increased the maximum measured hardness from 749.716 to 880.334 HV, and introduced compressive residual stress up to −845.5 MPa. Under dry sliding, LSP-4J-4 exhibited the lowest measured specific wear rate of 1.797 × 10-5 mm3/(N·m), representing a 42.7% reduction relative to the untreated specimen (UT). Under oil lubrication, LSP-4J-3 showed the lowest measured wear rate of 4.200 × 10-8 mm3/(N·m), 58.8% lower than that of UT. The improved wear resistance is attributed to the synergistic effects of martensite-lath refinement, dislocation strengthening, carbonitride/dislocation interactions, increased hardness, and compressive residual stress, which suppress localized plastic deformation, crack initiation, and material removal. Under oil lubrication, LSP-induced surface topography additionally governs lubricant retention and asperity interaction. Although repeated impacts provide further mechanical strengthening, excessive roughening reduces the film-to-roughness ratio, explaining why the lowest measured wear occurred after four impacts under dry sliding but after three impacts under oil lubrication. These results reveal a lubrication-dependent balance between surface strengthening and topographical evolution in LSP-treated Cronidur30 steel.

Owing to their excellent electrical conductivity and self-lubricating properties, copper–carbon current-carrying frictional pairs are widely used in pantograph-catenary systems, carbon brushes, and slip rings. This study investigates the tribological behavior of copper–carbon contact pairs under electrical current at various conditions of contact pressure (p), rotational velocity (v), and current (I). As the test conditions became more severe, the wear area, volumetric wear, and transfer film coverage of the carbon block increased, while the friction coefficient decreased. The self-lubricating effect was found to occur when the product of p × v exceeded a specific threshold. Compared with the critical value of 10.62 MPa m/s for mechanical sliding (0 A), the critical value for current-carrying sliding (2 A) decreased to 8.45 MPa m/s. Transmission electron microscopy (TEM) observations and Raman analysis revealed that amorphous carbon does not contribute to self-lubrication. Instead, nano-graphite sheets within the transfer film play a key role in the self-lubricating effect. It is inferred that frictional heat under high p × v conditions, combined with resistive heating, weakens the interlayer interactions within graphite, facilitating interlayer sliding and thereby producing self-lubrication. These findings provide valuable insights into the mechanism of graphite-based lubrication and guidance for the design of advanced carbon brushes.

MoCoB ceramic shows promising potential for tribological applications, due to their exceptional oxidation resistance and mechanical strength. Therefore, to evaluate its tribological suitability in high-temperature environments, the tribological behaviors of single-phase MoCoB coupling against SiC counterpart from room temperature (RT) to 800 degrees C are systematically investigated. The results revealed that MoCoB could exhibit outstanding wear resistance across the entire temperature range. However, it showed good lubricity only at RT and 800 degrees C, where the coefficients of friction (COFs) were as low as 0.39 and 0.38, respectively. The favorable lubrication at RT was attributed to the formation of SiO2 tribo-film on the MoCoB surface, which was derived from tribo-oxidation reaction of SiC counterpart. At 200 degrees C, the SiO2 film became discontinuous and failed to provide lubrication, resulting in a high COF (0.74). As the temperature climbed up to 400 degrees C, the tribo-oxidation product, MoO3-x, could be detected as well. Nevertheless, the limited amount of MoO3-x can only provide moderate lubrication, and the COF at 400 degrees C still remains relatively high (0.62). At 600 degrees C and 800 degrees C, the primary tribo-oxidation products consisted of CoMoO4 and MoO2. However, the CoMoO4-MoO2 tribo-film could only provide lubrication at 800 degrees C. The dominant wear mechanisms at 600 degrees C were adhesion and tribo-oxidation wear.

In response to the issues of significant differences in service stages, performance, and materials used in current-carrying tribopairs across different fields. This work uses a custom-made microsliding current-carrying friction test machine to study the evolution of surface damage during the current-carrying friction process. The results indicate that during all the testing processes, the contact resistance experiences four stages: the smooth surface stage, the transition stage, the optimal friction surface stage, and the failure stage. Variations in load can affect the duration of these stages. The smooth surface stage and optimal friction surface stage exhibit good electrical conductivity properties. The number of cycles during the smooth surface stage decreases with increasing load, reaching a maximum of 518 cycles at a wire diameter of 0.4 mm and a load of 0.025 N. The number of cycles during the optimal friction surface stage increases with increasing load, reaching 9,955 cycles at a wire diameter of 1.0 mm and a load of 3.2 N. From the perspective of damage, intense electric arc erosion significantly impacts the current-carrying friction process, and it should be avoided throughout the entire service life of the friction pair. From an engineering perspective, the service stages of “short” lifespan friction pairs, such as electrical connectors, should correspond to the smooth surface stage. For “long” lifespan friction pairs, such as pantograph strips and brushes, the service stages should correspond to the optimal friction surface stage; note that the friction pairs should be run-in.

Hydropower flow-passing components in sand-laden flows degrade under cavitation erosion, abrasive wear and, most severely, their synergistic coupling, which can raise material-loss rates by more than an order of magnitude and shorten overhaul intervals to 2-3 years. This review integrates the full chain from environment to intelligent maintenance: coupled damage mechanisms and micro-topographic evolution; the roles of impact angle, sediment concentration, flow velocity and particle characteristics (size, shape and hardness); mitigation by high-performance bulk materials, surface modification, hydrodynamic design and advanced coatings; erosion/life modelling and cross-scale correlation; and data-driven condition monitoring. Cross-condition comparative tables, an erosion-model comparison, and a defined terminology framework are provided to support material selection, anti-erosion design and full-life-cycle management, particularly for installations in high-sediment basins.

Electrical connectors are widely used in the aerospace industry, rail transit, and new energy vehicles. As typical current-carrying frictional pairs, electrical connectors are key components that determine equipment power and signal transmission. With the continuous advancement of electrification, the reliability and performance requirements for electrical connectors have become more stringent. Unlike traditional mechanical wear, the friction and wear of electrical contacts under current-carrying conditions are influenced by force-thermal-electrical coupling effects, leading to more complex failure modes and damage types. Consequently, the failure mechanisms of electrical connector contacts have attracted significant attention in both academic and industrial fields. Ag is one of the most commonly used coating materials for electrical contact surfaces. To investigate the damage mechanisms of Ag-coated electrical contacts, a sliding current-carrying wear test was conducted using ball-disk frictional pairs. Single-point contact was used to simulate the friction and wear of a single-contact finger during the insertion process. During the experiment, the changes in current-carrying properties and the evolution of material damage mechanisms were examined under different current densities. The results showed that the average friction coefficient in the steady state increased with an increase in current density in the contact area. At high current densities (21.4 and 35.7 A / mm(2)), the friction coefficient suddenly changed after a period of smooth operation. Furthermore, as the current density increased, the timing of this abrupt change occurred earlier: at 21.4 A / mm(2), the average friction coefficient during stabilization was approximately 1.01, followed by a sudden drop to about 0.69 at 1 050 s. At 35.7 A / mm(2), the friction coefficient experienced an abrupt change at 700 s, decreasing from 1.1 to 0.72 within 10 s. The oxygen contents in the wear zones of the ball and disk under different operating conditions were compared. Due to passivation from Ni oxidation, surfaces with high Ni content exhibited no significant oxidation (disk samples at current densities below 7.2 A / mm(2)). The degree of oxidation in the wear zone increased after the appearance of Cu on the surface. At 35.7 A / mm(2), the oxidation level of the disk sample was higher than that of the ball sample. Because the ball was ground repeatedly along the same circular path on the disk surface, its exposure to the external atmosphere was limited during grinding friction, resulting in relatively lower oxidation. The current-carrying wear mechanism of the composite coating involved adhesive wear accompanied by abrasive and oxidative wear. Arc ablation was not observed in this study. The temperature increase at the contact interface of the friction pair resulted from the combined effects of frictional heat and Joule heat, with frictional heating predominating at low current densities. When the current density exceeded 7.2 A / mm(2), Joule heat played a dominant role in the temperature rise, which increased rapidly with increasing current density. Temperature increase is the primary mechanism by which current promotes adhesive wear; it softens the contact material and alters the properties of the contact interface. This research not only provides a simple and effective approach for analyzing the current-carrying performance and wear mechanisms of silver-plated electrical contacts under varying current densities but also offers a theoretical foundation for the reliable design and damage protection of silver-plated electrical connector contacts.

In this study, martensitic steel, lower bainitic steel, and nanostructured bainitic steel were fabricated from the same bearing material (GCr15SiMoAl) using three distinct heat treatment processes. Under identical cavitation erosion (CE) test conditions, the mean depth of erosion (MDE) of the nanostructured bainitic steel was 81% and 49% of that of the lower bainitic steel and martensitic steel, respectively. Correspondingly, its erosion rate (ER) was only 79% and 48% of that of the lower bainitic steel and martensitic steel, while the incubation period of CE was 1.36 and 2.74 times that of the lower bainitic steel and martensitic steel, respectively. These results unequivocally demonstrated that the nanostructured bainitic microstructure conferred superior cavitation resistance, enabling the bearing steel to retain exceptional surface integrity even after prolonged exposure to cavitation attack. This outstanding performance stemmed from the synergistic effect of uniformly distributed surface compressive residual stresses and the intrinsic stability of the constituent phases. Additionally, all three steels exhibited similar damage mechanisms: cavitation damage initiated in the form of micropores or microcracks and subsequently propagated along directions of maximum stress concentration.

Conventional tool steels suffer rapid degradation in molten aluminum, necessitating advanced materials with superior corrosion resistance and high-temperature strength. Refractory high-entropy alloys (RHEAs) are promising, yet how co-regulated alloying elements govern phase constitution, mechanical behavior, and corrosion remains unclear. This study investigates Nb and Si co-regulation in Nb42-xTi25Mo10Al20SixW3 (x = 10, 5, 0) RHEAs via thermodynamic calculations, multi-scale characterization, and static immersion tests at 750 degrees C. Increasing Si at the expense of Nb promotes (Nb,Ti)(5)Si-3 silicide formation: discrete precipitates at 5 at.% Si evolve into a continuous network at 10 at.% Si. The 5 at.% Si alloy achieves the highest yield strength (1452 MPa at 750 degrees C) due to dispersed silicide reinforcement, whereas the continuous network in the 10 at.% Si alloy introduces stress concentration. The Si-free alloy (highest Nb content) exhibits the best corrosion resistance, with a corrosion rate 92.1% lower than that of the 10 at.% Si alloy after 24 h, attributed to its homogeneous BCC solid-solution matrix and absence of rapid diffusion channels along phase boundaries. A competitive diffusion-dissolution kinetic model incorporating a diffusion promotion factor (gamma) quantitatively links silicide network continuity to accelerated Al infiltration, with gamma increasing from similar to 1.00 (x = 0) to 1.42 (x = 10). These findings establish microstructure-property relationships and design principles for balancing strength and corrosion resistance in multiphase RHEAs for high-temperature aluminum processing.

To investigate the effect of the initial surface roughness on the performance at the initial stage of the current-carrying friction of an elastic friction pair, experiments were conducted using a self-made current-carrying friction and wear tester. The results indicate that under the experimental conditions, the lifespan of the friction pair decreases as the surface roughness and load decrease. When the surface roughness is Ra 0.2 μm and the load is 0.025 N, the lifespan is the longest, reaching 320 cycles, with an average contact resistance of 0.045 Ω and a standard deviation of 0.009 Ω. During the normal service period of the friction pair, the main wear mechanism is furrowing. As adhesion and tearing occur, the electrical contact performance begins to degrade. The impact of arc erosion on the wear surface is far greater than that of mechanical wear. This provides a reference for the design and manufacture of current-carrying friction pairs represented by connectors.

A copper-10 wt.% graphite composite was paired with QCr0.5 to investigate the effects of normal load on current-carrying friction behavior. Arc discharges were monitored using a high-speed camera and photodiodes. The results indicate that, under the given experimental conditions, normal load predominantly influences the tribological performance of the material. As the c normal load increases, the wear rate decreases rapidly at first and then increases gradually. The optimal normal load was found to be 70 N, at which the wear rate reached a minimum of 0.46 mg/m. Material degradation was found to consist of mechanical damage—mainly plowing and plastic deformation—as well as arc-induced erosion characterized by melting and spattering. With increasing normal load, arc erosion decreased progressively, and the overall damage was minimized at 70 N. Arc erosion contributed to surface wear non-uniformity. Moreover, particular attention should be paid to high-current, long-duration arcs, which can pose serious localized threats to material integrity.

Given the significant impact of the initial surface layer of materials on their tribological performance, this study uses a wire–plate reciprocating friction pair to investigate the effects of surface mechanical rolling process on the elastic current-carrying friction performance. The plate specimens were subjected to rolling processing with varying feed rates under different load conditions, using a self-designed current-carrying friction and wear testing machine. The results show that as the feed rate and load increase, the contact resistance varies within the range of 0.0065 Ω to 0.0310 Ω, with a standard deviation ranging from 0.01 Ω to 0.07 Ω, indicating good electrical conductivity. As the feed rate of the surface mechanical rolling increases, the wear rate of the material significantly decreases. Under all test conditions, the material wear marks exhibit plowing wear, and with the increase in surface mechanical rolling feed rate, the occurrence and intensification of adhesive wear are delayed. When the feed rate is 100 μm and the load is 0.025 N, the material wear rate is the lowest, reduced by 63.1% compared to the untreated condition.

Corrosion of liquid aluminum impedes the development of aluminum-based products and equipment. Modifying microstructures at the matrix-corrosion interface enhances alloy's corrosion resistance. High-boron alloys, renowned for their superior corrosion resistance, are closely associated with their microstructural characteristics. This study aims to elucidate the microstructural evolution and enhanced corrosion resistance of laser-remelted Fe-Cr-B-Mo alloy, with a particular focus on the mechanisms underlying its enhanced corrosion resistance. The results reveal that the laser-remelted layer, featuring homogeneous micro-nano structures, forms continuous periodic layered structures (PLSs) across the entire interface, enhancing corrosion resistance by preventing elemental interdiffusion and pinning interfacial corrosion products. The formation mechanism of PLSs results from solid-liquid interface diffusion couples caused by thermodynamic and kinetic instabilities. Tailored micro-nano structures, coupled with continuous and full-interface PLSs, offer a novel approach to enhancing corrosion resistance against liquid aluminum, potentially facilitating the development of corrosion-resistant Fe-B alloys.

In this study, the PTFE/Cu coating materials has been interface modified by using polydopamine (PDA) and different PDA + metal nanoparticles (PDA + MNPs, M = Ag or Cu), respectively. Then, the effects of different interface modification treatments on the thermal conductivity, interface bonding force and tribological properties of the PTFE/Cu coating materials were investigated. The results showed that the addition of metal nanoparticles to PDA interface modified layer obviously promoted the chemical cross-linking reaction between the PDA and PTFE coatings and improved the interface bonding force of the coatings. Also, the thermal conductivity of the PTFE/Cu coating materials with PDA + MNPs interface modification is improved. The durability of PTFE/Cu coating materials with PDA + AgNPs and PDA + CuNPs interface modification increased 34 % and 48 % respectively, and their wear resistance increased 47 % and 115 % respectively, because of their good interface bonding, dissipate frictional heat and transfer film forming ability.

In response to the need to optimize the performance of copper–graphite current-carrying friction materials, spark plasma sintering (SPS) technology was used to prepare copper–graphite composite materials with different graphite orientations. A self-made current-carrying friction testing machine was used to study the effect of graphite orientation on the current-carrying friction performance of copper–graphite composites. The results showed that as the graphite orientation increased, the current-carrying friction performance of the copper–graphite composites initially improved and then deteriorated. The performance was optimal when the graphite orientation of the 7.5 wt% graphite–copper composite was 90°, primarily constrained by the wear rate. The main wear mechanism was furrowing, and graphite enrichment occurred on the worn surface, where the graphite content on the wear surface was higher than that in the bulk material. The degree of enrichment varied under different wear mechanisms. The graphite content near the entry region of the friction surface was significantly lower than that near the exit region.

In order to improve the wear resistance and corrosion resistance of U75V steel for the application of the rail steel in high-speed railway, different concentrations of Ti (2%, 4%, 6%, and 8% by weight) were integrated into the Ti/h-BN/Fe composite coatings, fabricated on U75V steel substrates through plasma arc cladding. The study explored how variations in Ti concentration affected the coating's microstructure, hardness, residual stresses, tribological behavior, and electrochemical characteristics. SEM analysis showed that the microstructural configurations varied from dendritic to columnar to equiaxed, depending on the Ti content. The surfaces of these coatings were compact and exhibited no visible cracks or defects. Microhardness values escalated from 770.4 HV 0.5 at 2% Ti to 911.2 HV 0.5 at 8 wt.% Ti. Concurrently, compressive residual stresses on the surfaces also enhanced from 611.4 MPa to 755.6 MPa with increasing Ti percentages. The friction and wear test was carried out by using the UMT-2 multifunctional friction and wear tester with a load of 30N, and the results show that friction coefficients and wear rates initially increased, subsequently decreased, and then ascended as the Ti content was incremented. Optimal tribological properties were noted at a Ti concentration of 6 wt.%, where the friction coefficient and wear rate dropped to 0.387 and 3.7 × 10 −3 mm 3 ·N −1 ·m −1 , respectively, attributed primarily to adhesive wear. Moreover, the corrosion resistance varied inversely with Ti levels, demonstrating a decrease followed by an increase. The most effective corrosion resistance was at 6 wt.% Ti, showcasing the highest self-corrosion potential (E oor ) at −0.1972 V and the lowest corrosion current density (j oor ) at 3.1224 × 10 −9 A·cm −2 , signifying superior corrosion resistance at this concentration. The coating with 6 wt.% Ti content exhibits optimal wear resistance and corrosion resistance, thereby providing a theoretical foundation for the potential application of such coatings on railway tracks.

Surface roughness plays a crucial role in determining surface quality, influencing factors such as vibration, noise, assembly precision, lubrication, and wear resistance in bearings. This research examines how surface roughness (Sa) affects the friction and wear characteristics of GCr15 steel under conditions with adequate oil lubrication while varying the applied load. The findings indicate that with an increase in Sa, the friction coefficient of GCr15 steel also increases. As the load rises from 15 N to 35 N, the friction coefficient remains relatively constant. However, higher loads lead to more severe wear of the microprotrusions on the surface of GCr15 steel. The wear area first decreases and then increases as Sa increases. The minimum wear area occurs when Sa is 0.5 μm. Additionally, a back propagation neural network (BPNN) model has been developed to predict the wear performance of GCr15 steel. Validation experiments show that the average prediction error for the BPNN model is 10.64%.