Current Issue : January-March Volume : 2026 Issue Number : 1 Articles : 5 Articles
Electric propulsion requires engines and transmission systems that run at higher speeds compared to combustion engines. For improving sustainability and environmental protection, biodegradable oils are suggested for the lubrication of high-speed gears that require particularly quick wetting of the steel surfaces. Newly developed promising candidates include short-chained polyalphaolefins. In the present work, a study on the applicability of such oil is presented and discussed with respect to different aging levels based on biodegradable properties. It focuses on the wettability of metallic surfaces investigated through time-resolved contact angle measurements. Carbon steels with different carbon contents and microstructures are selected as the most commonly used materials for gears. Effects of steel composition, surface roughness and oil oxidation are studied. The results show that in most cases, the application of biodegradable polyalphaolefins is not critical; however, a combination of steels with inhomogeneous microstructure, high surface roughness and aged oil can be critical because of limited wetting....
Copper matrix self-lubricating composites are critical for high-temperature industrial applications. In this study, Cu-Ni-Sn-Mo-Gr composites with 3–7 wt.% graphite were fabricated via spark plasma sintering (SPS). The influence of graphite content on microstructure, mechanical properties, and tribological behavior from room temperature (RT) to 500 ◦C were systematically investigated. The results demonstrate that increasing graphite content progressively reduces density, hardness, and yield strength, whereas it significantly enhances high-temperature tribological performance. The composites with 7 wt.% graphite addition achieve outstanding self-lubricity and wear resistance across the RT-500 ◦C, achieving an average friction coefficient of 0.09 to 0.21 and a wear rate of 1.32 × 10−6 to 7.52 × 10−5 mm3/N·m. Crucially, temperature-dependent lubrication mechanisms govern performance: graphite-dominated films enable friction reduction at RT, while synergistic hybrid films of graphite and in situ-formed metal oxides (Cu2O, CuO, NiO) sustain effective lubrication at 300–500 ◦C....
The present study aims to examine the tribological and mechanical integrity of AISI 316/420 stainless steel tribosystem under boundary lubrication with artificial seawater for application in a marine environment. The tribological performance was evaluated through sliding friction tests using a ball-on-disc configuration, at contact pressures ranging from 520 MPa to 1400 MPa. The influence of working contact pressure on the kinetic friction coefficient (μk), wear rate (K), and worn surface damage was studied. Their interaction with the corrosive medium was evaluated using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyses to investigate the wear mechanisms. Microhardness testing was also employed to assess the effect of friction and wear on the mechanical properties of the tribosystem. The results showed that friction and microhardness increased with contact pressure, while the wear rate decreased due to strain hardening. The wear mechanisms included abrasion, adhesion, delamination, and localized oxidation. This study offers new perspectives on the tribological response of stainless steel materials in marine engineering systems, providing valuable insights for material selection and design in corrosive and high-load applications....
Additive manufacturing techniques, such as selective laser melting (SLM), enable the production of intricate and integrated components made from metallic materials with inherent porosity. The pores, typically perceived as defects, are commonly observed on the surface or within the matrix of SLM-formed components. However, it is noteworthy that these pores can function as reservoirs for lubricants to enhance tribological performance in specific applications, such as porous bearings. In this study, the optimum conditions for fabricating Cu-15Ni-8Sn alloy porous bearings via SLM technology were investigated. By regulating laser power and hatch space during SLM processing, Cu-15Ni-8Sn alloy porous bearings were successfully obtained. The resulting oil bearings exhibited an oil content exceeding 18% and a radial crushing strength surpassing 370 MPa. At reduced laser power (80 W) and increased hatch spacing (0.9 mm), average friction coefficients of 0.1 and 0.13 were observed, with volumetric wear values of 10.3 mm3 and 96.7 mm3, respectively. The friction mechanism is a combination of abrasive wear and delamination wear....
CoCrFeNiMn HEA-based composites with Cr3C2, 15% Ag, and different mass fractions of CaF2/BaF2 eutectic fluoride were fabricated by spark plasma sintering. The tribological properties and wear mechanism of the composites were investigated from RT to 800 ◦C. The friction coefficients of CoCrFeNiMn-Cr3C2-Ag-CaF2/BaF2 composites decrease from RT to 800 ◦C except for 400 ◦C. At 800 ◦C, with the increasing mass fraction of the eutectic fluoride, the friction coefficient of the composite decreases from 0.53 to 0.25. The wear rates of the composite with 15% CaF2/BaF2 eutectic fluoride decrease significantly at high temperatures. The CoCrFeNiMn-Cr3C2-Ag-15%CaF2/BaF2 composite exhibits the lowest wear rates at 400 ◦C, 600 ◦C, and 800 ◦C, which are 4.47 × 10−6 mm3/N·m, 5.15 × 10−6 mm3/N·m, and 2.42 × 10−6 mm3/N·m, respectively. At low temperatures, the tribological mechanisms of the composites are micro-plowing and micro-cutting, and Ag is formed as a lubricating film to reduce the friction coefficient. At high temperature, fluorides form a transfer film on the wear scar surface, providing a lubricating effect. Also, the oxide layers and chromate are formed on the worn surfaces of the composites, which are beneficial for improving the wear resistance. Based on the mechanical properties and tribological behavior, the CoCrFeNiMn- Cr3C2-Ag-15%CaF2/BaF2 composite demonstrates the best comprehensive properties....
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