Understanding the tribological properties of alloy-based sliding electrical contacts is crucial for both fundamental research and practical applications. Here, to explore the friction, wear, and contact resistance of a AgCuNi alloy/Au-electroplated layer during sliding, a ball-on-disk tribometer was coupled with a source meter. The experiments were conducted under various conditions including a current ranging from 0 to 1.0 A, a normal load ranging from 0.5 to 3.0 N, and a sliding speed of 40 mm/s. The results indicate that the wear of the friction pair is aggravated by both the current and the increase in the normal load. When the current was 0.5 A, the wear loss reached its lowest point. However, as the current increased from 0.5 A to 1.0 A, there was an intensification in Ag transfer from the alloy ball to the Au-electroplated layer, resulting in an increase in wear loss. Both the normal load and current have significant effects on both friction coefficient and contact resistance. The variation in contact resistance over time follows a similar pattern to that of the friction coefficient over time. The formation of a transfer film plays a crucial role in determining contact resistance, wear resistance, and friction coefficient. The experiment demonstrates that optimizing the normal load and current can adjust both the contact resistance and friction coefficient, thereby prolonging service life and ensuring the stability of contacts.

To avoid wear and tear of the slip ring due to electrical corrosion, the slip ring needs to undergo the running-in process under atmospheric conditions without current after assembly. To address the urgent demand for long-service capability space conductive slip rings in the aerospace field, the running-in behavior and failure mechanism between the AgCuNi alloy and Au-electroplated layer are investigated using a ball-on-disc tribometer in this paper. The results show that the transfer film composed of Au plays an important role in modifying the friction during the sliding process. With the accumulation of wear debris composed of Ag on the disc, the contact material of the friction pair changed from Au and Au to Au, Ag and Au, so the surface roughness of wear tracks increased. Finally, the transfer film broke, which made the layer fail. This paper reveals the key element failure mechanism that causes transfer film failure in the running-in contact area, which is used to reveal the friction behavior and failure mechanism of slip ring friction pair materials, and provides a basis for the selection of running-in parameters during the running-in process of slip rings before power-on operation.

Interfacial solvation structures are crucial in wide-ranging applications, including lubrication and electrochemical energy storage. As the sole technique capable of in-situ mapping of three-dimensional (3D) solvation structures, 3D atomic force microscopy (3D-AFM) resolves liquid-solid interfaces with angstrom precision. However, conventional analysis via global averaging or manual selection wastes the massive datasets generated by 3D-AFM, rendering the objective resolution of spatial heterogeneities and 3D features of the interfacial solvation structure unattainable. Here, leveraging the high-throughput capacity of unsupervised machine learning to handle massive datasets, we present a general method integrating 3D-AFM for the unbiased interpretation of interfacial force dataset. Applying this method to the graphite-water interface uncovers a previously obscured spatial heterogeneity, achieving a precise spatial partitioning of the interface into two distinct regimes with divergent mechanical responses. Molecular dynamics simulations attribute this heterogeneity to the nonuniform distribution of trace airborne hydrocarbon contaminants. This work not only elucidates the contaminant-mediated modulation of interfacial water structures, but also provides a general paradigm for identifying chemical non-uniformities at diverse solidliquid interfaces.

While ion correlation is known to enhance molecular-scale solvation forces, its capacity to improve macroscale boundary lubrication on engineering surfaces remains unverified. This study demonstrates that multivalent electrolyte-induced ion correlation significantly reduces macroscopic boundary friction, achieving up to a 67% reduction on alumina surfaces. This macroscopic enhancement is driven by interfacial electrochemical properties, where highly charged polar oxide interfaces trigger strong electrostatic correlation to restructure confined solvents into a rigid, load-bearing barrier. Ultimately, this work proves that interfacial ion correlation directly dictates and enhances macroscale boundary lubrication, bridging molecular-level force control with practical tribological applications.

This study presents a numerical framework for analyzing mixed elastohydrodynamic lubrication (EHL) of rough contact surfaces under grease lubrication, motivated by the need for reliable lubrication design in tribological components such as mechanical face seals and rolling bearings operating in space environments. Considering surface roughness effects, the proposed method integrates an EHL model derived from the Ostwald constitutive equation with the Kogut–Etsion (KE) elastic–plastic asperity contact model. The methodology is demonstrated through a case study of a vacuum grease-lubricated double-row angular contact ball bearing employed in a spacecraft antenna rotation mechanism under low-speed and heavy-load conditions. The governing equations were non-dimensionalized and solved numerically to obtain the lubricant film thickness and pressure distributions under various rotational speeds and axial preloads. The friction torque generated by viscous shear of the lubricant and asperity contact, and the asperity load ratio, were also determined. The novelty of this work lies in two aspects: (i) the integration of the Ostwald grease rheology model and the KE elastic–plastic asperity contact model into a unified mixed EHL framework; and (ii) a systematic investigation of grease-lubricated bearing behavior at low rotational speeds (11.5–55.2 rpm) with explicit consideration of surface roughness. The results indicate that rotational speed and axial preload exert limited influence on film thickness. The film pressure along the rolling direction increases with speed, whereas the asperity contact pressure decreases with speed and increases with preload; the asperity load ratio follows the same trends. The fluid pressure exhibits a single peak on the inlet side of the contact, and no outlet film constriction is observed in the thickness profile. The friction torque decreases with increasing speed, and the asperity load ratio follows the same trend. These findings demonstrate that appropriate adjustment of preload and an increase in rotational speed can reduce both friction torque and the asperity load ratio, thereby improving lubrication conditions and extending bearing service life.