Current Issue : October-December Volume : 2025 Issue Number : 4 Articles : 5 Articles
This study investigates the current-carrying tribological properties and wear mechanisms of copper–graphite composites under varying contact loads. Two copper– graphite composites with different graphite content were prepared using the pressure sintering method. Current-carrying tribological tests were conducted at three distinct contact loads. Scanning electron microscopy, X-ray diffraction, laser confocal microscopy, and pin-on-disk tribological testing were utilized to examine the current-carrying tribological properties and the worn morphologies of the materials. The results indicate that, under the three contact loads, the friction coefficient of the copper–graphite materials ranged from 0.3 to 0.5, the wear rate was on the order of 10−13 m3/(N·m), the average voltage drop varied between 0.7 and 1.6 V, and the average electrical noise ranged from 0.2 to 0.9 mV. The wear mechanism included delamination wear and a minor amount of abrasive wear, and the lubricating film formed on the surface was mainly composed of C, PbO, and CuO. Notably, copper–graphite composites with lower graphite content exhibited superior hardness, electrical conductivity, and relative density compared to those with higher graphite content. At a contact load of 0.31 N, the copper–graphite composite containing 30wt% graphite demonstrated the most favorable current-carrying tribological performance, characterized by the lowest wear rate (1.09 × 10−13 m3/(N·m)), voltage drop (0.943 V), and electrical noise (0.234 mV)....
In this work, silicon oxide based coatings with embedded graphene nanoplatelets (content ranging from 1.8 wt.% to 7.2 wt.%) have been developed following the sol-gel route, using AISI430 stainless steel as substrate and dip and roll-to-roll as coating techniques. The tribological and corrosion behaviour of these coatings have been evaluated and compared to bare steel. Concerning tribological behaviour, the coefficient of friction and wear print were significantly reduced with increasing the graphene nanoplatelets content. Regarding corrosion, all coatings showed improved corrosion behaviour compared to bare steel. However, higher concentration of nanoplatelets revealed a negative effect on the corrosion resistance, probably due to aggregation. Taking into account these two counteracting effects, as final part of this work, a bilayer coating with different graphene content has been proposed and fabricated. A top layer, with high graphene nanoplatelets concentration has allowed enhanced tribological properties whereas bottom layer, with no graphene nanoplatelets assures corrosion inhibition under harsh environments....
This study introduces a novel gradient dual-phase structure design in brass, achieved through ultrasonic severe surface rolling (USSR) processing, which enables an unconventional asymmetric bilayer structure—comprising a hardened surface layer (>1 mm thick) and a ductile substrate—distinct from conventional hard-soft-hard sandwich configurations in gradient nanostructured materials. Microstructural characterization reveals a gradient dual-phase (α + β ) structure in the hardened layer, progressively transitioning into a homogenized dual-phase structure in the substrate. This unique architecture endows the USSR brass with exceptional mechanical properties, including a yield strength of 582.4 ± 31.0 MPa, ultimate tensile strength of 775.3 ± 33.9 MPa, and retained ductility (9.3 ± 1.0%), demonstrating an outstanding strength-ductility synergy. The USSR brass also demonstrates superior wear resistance with a 42.32% reduction in wear volume and 40.82% decrease in coefficient of friction compared to its as-received counterpart under oil lubrication. This architectural paradigm establishes a robust framework for engineering high-performance brass that simultaneously achieve an exceptional strength-ductility balance and enhanced wear resistance....
The continuous advancement of technology has led to escalating demands for superior tribological performance in industrial applications, necessitating the enhancement of ceramic materials’ frictional properties through innovative approaches. Solid-lubricant embedding is a widely employed lubrication strategy in metals. However, the challenge of machining holes on ceramic surfaces remains a significant barrier to applying this lubrication technique to ceramics. Gel casting, as a near-net-shaping process, offers several advantages, including uniform green body density, low organic content, and the capability to fabricate components with complex geometries, making it a promising solution for addressing these challenges. In this study, alumina ceramics with small surface holes designed for embedding oil-containing microcapsules were fabricated via gel casting using an N-hydroxy methylacrylamide gel system, which demonstrates lower toxicity compared to conventional acrylamide systems. The fabricated alumina ceramic materials exhibited a high density of 98.2%, a hardness of 16 GPa, and a bending strength of 276 MPa. The oil-containing microcapsules were self-synthesized using hexafluorophosphate ionic liquid as the core material and polyurea-formaldehyde as the wall material. The research results show that under conditions of using an alumina ball, sliding speed of 10 cm/min, load of 5 N, and at room temperature, the material with a microcapsule content of 15 wt% and embedded hole diameter of 1.2 mm reduced the friction coefficient from 0.696 in an unlubricated condition to 0.317. Moreover, the embedding of microcapsules further improved the wear resistance of the alumina....
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....
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