Search Results (3,843)

We are witnessing a global commitment to sustainable mobility that requires advanced materials and manufacturing techniques, such as fused filament fabrication (FFF), to create lightweight, durable, and recyclable machine components. Acknowledging that friction and wear significantly contribute to energy loss globally, developing high-performance polymeric materials with customizable properties is essential for greener mechanical systems. FFF inherently drives resource efficiency and offers the geometric freedom necessary to engineer complex internal structures, such as the gyroid pattern, enabling substantial mass reduction. This study evaluates the tribological performance of FFF-printed thermoplastic polyurethane (TPU 82A) specimens fabricated with three distinct gyroid infill densities (10%, 50%, and 100%). Ball-on-disc testing was conducted under dry sliding conditions against a 100Cr6 spherical ball, with a constant normal load of 5 N, resulting in an initial maximum theoretical Hertz contact pressure of 231 MPa, over a total sliding distance of 300 m. Shore A hardness and surface roughness (R_a) were also measured to correlate mechanical and structural characteristics with frictional response. Results reveal a non-monotonic relationship between infill density and friction, with a particular absence of quantifiable mass loss across all samples. The intermediate 50% infill (75.9 ± 1.80 Shore A) exhibited the peak mean friction coefficient of $\overline{\mu }=1.002$ (${\mu }_{\max }=1.057$), which can be attributed to its balanced structural stiffness that promotes localized surface indentation and an increased real contact area during sliding. By contrast, the rigid 100% infill (86.3 ± 1.92 Shore A) yielded the lowest mean friction ($\overline{\mu }$ = 0.465), while the highly compliant 10% infill (44.3 ± 1.94 Shore A) demonstrated viscoelastic energy damping, stabilizing at $\overline{\mu }$ = 0.504. This work highlights the novelty of using FFF gyroid architectures to precisely tune TPU 82A’s tribological behavior, offering design pathways for sustainable mobility. The ability to tailor components for low-friction operations (e.g., μ ≈ 0.465 for bushings) or high-grip requirements (e.g., μ ≈ 1.002 for anti-slip systems) provides eco-efficient solutions for automotive, railway, and micromobility applications, while the exceptional wear resistance supports extended service life and material circularity. Full article

We aimed to address the issue of fretting wear on the rollers and raceways of pitch bearings in wind turbines during shutdown and under intermittent high loads. This study focuses on triple-row cylindrical roller bearings. A finite element wear simulation of the contact area between a single roller and the raceway was established based on Hertzian contact theory and the modified Archard model. The wear coefficient values of the model before and after coating were verified through experiments, with results of k₁ = 3.125 × 10⁻⁸ and k₂ = 4.5 × 10⁻¹⁰, respectively. The effects of normal load, displacement amplitude, and cycle number on the fretting wear behavior of rollers under both uncoated and GLC-coated conditions were investigated. The results show that the GLC (Glassy Carbon-like Carbon) film significantly reduces the friction coefficient and wear. Compared to uncoated rollers, it reduces the maximum wear depth by approximately 90.53% across various normal loads, displacement amplitudes, and numbers of cycles. Additionally, the wear rate of the coated rollers remains consistently low with small fluctuations. The conclusion holds that the GLC film reduces the interface shear force and effective slip amplitude, enhances surface hardness and stability, and improves the fretting wear resistance of pitch bearings by an order of magnitude under complex load and oil-starved conditions. The primary objective of this work is to investigate the mechanisms for enhancing the anti-fretting wear performance of pitch bearings, with the goal of significantly extending their service life and reliability in harsh operating environments. Full article

In this study, a surface treatment of Ti grade 1 was carried out in air with the use of a Yb-fiber laser to increase the friction-wear properties tested in dry contact with α-Al₂O₃. The laser surface treated specimens clearly differ in their surface roughness and wettability, coefficient of friction and resistance to wear, compared to untreated specimens. The microstructure changes induced by laser treatment were investigated using confocal scanning electron microscopy with chemical composition analysis by energy-dispersive spectroscopy, and phase composition by X-ray spectroscopy. It was found that laser surface treatment caused the formation of titanium oxide layers with TiO₂ (rutile, anatase and brookite) as the main constituent, while in the subsurface areas a partial transformation of α-Ti to β-Ti or α′-Ti was thermally induced. Specimens containing β-Ti or α′-Ti in the subsurface area and anatase or brookite in the top layer were characterized by two times lower friction coefficient values and 10 times lower volume wear index Wv in comparison to untreated Ti grade 1. Results clearly confirmed the beneficial effect of laser surface treatment on friction-wear properties of Ti grade 1, but the selection of laser processing parameters was crucial both for resistance to abrasive wear and wettability. Full article

This work presents a comparative study of TiSiC and TiSiCN composite coatings deposited on stainless steel by reactive plasma spraying using mechanically activated powders. Microstructure, phase composition, and hardness were assessed by SEM/EDS, XRD, and Vickers indentation, while corrosion, erosion, and high-temperature tribological behavior were systematically evaluated. The TiCN + SiC + Si system forms a stable TiC_xN_1−x solid solution with amorphous Si₃N₄ grain-boundary phases, leading to densification and enhanced chemical stability. Compared with TiSiC, TiSiCN coatings exhibit higher hardness (2599 N/mm², ≈324 HV), lower erosion loss (<1 mg), and stable friction coefficients (0.45–0.50 at 600 °C) due to protective oxide/nitride tribofilms. Electrochemical tests in 3.5 wt.% NaCl show a >6-fold reduction in corrosion rate (from 0.0506 to 0.008 mm·year⁻¹) relative to bare steel. Overall, TiSiCN coatings deposited at 500–600 A provide an optimal balance of hardness, wear, and corrosion resistance, indicating strong potential for gas-turbine and power-generation components operating in aggressive environments. Full article

To elucidate the corrosion mechanism of orthodontic archwire in fluoride-containing environments, the friction and wear behavior of archwires following corrosion in fluoride-containing oral care products was investigated. Stainless steel archwires were soaked in solutions of fluoride-free toothpaste, fluoride toothpaste, fluoride-free mouthwash, fluoride mouthwash, and sodium monofluorophosphate, followed by friction testing against brackets. The average friction coefficient of the archwire–bracket tribopair increased gradually from 0.17 to 0.28 with prolonged immersion time in the fluoride-containing solution, accompanied by a progressive increase in the wear scar area on the archwire surface. In the fluoride toothpaste solution, the archwire exhibited a corrosion potential and current density of –301.8 mV and 0.348 μA/cm², respectively, indicating a higher susceptibility to corrosion. Analysis of wear debris revealed significant enrichment of fluorine and oxygen elements on the archwire surface after exposure to fluoride-containing solutions, consistent with pronounced corrosion damage. Integration of friction results and surface characterization elucidated the corrosion mechanism in fluoride-containing environments. It was proposed that fluoride ions facilitated the formation of micro-batteries, while active fluoride species accelerated the dissolution of nickel from the archwire surface and promoted oxygen accumulation, thus driving sustained electrochemical corrosion. This progressive surface degradation ultimately exacerbated the friction and wear of the archwire–bracket tribopair. Full article

This study examines the rheological and tribological behavior of bio-based nano-lubricants enhanced with cerium oxide (CeO₂) and multi-walled carbon nanotubes (MWCNTs), alongside the application of artificial intelligence (AI) models for performance prediction. Rheological results confirmed non-Newtonian, shear-thinning behavior across all formulations. CeO₂-based lubricants exhibited significantly higher viscosities at 40 °C (up to ~3700 mPa·s at low shear), which decreased sharply with shear, indicating strong particle interactions. In contrast, MWCNT-based lubricants maintained moderate viscosities (90–365 mPa·s at 40 °C) with improved flowability due to nanotube alignment. At 100 °C, both systems showed viscosity reduction, stabilizing between 8 and 18 mPa·s, which favors pumpability in high-temperature applications. Tribological testing revealed distinct performance characteristics. CeO₂ lubricants showed slightly higher coefficients of friction (0.144–0.169) but excellent wear resistance, achieving the lowest wear rate of 1.66 × 10⁻⁶ mm³/N-m. MWCNT-based lubricants offered stable and lower CoF values (0.116–0.148) while also providing very low wear rates, with MCO6 achieving 1.62 × 10⁻⁶ mm³/N-m. However, ternary blends (C20T80 and M20T80) displayed moderate CoF but significantly higher wear rates (up to 2.92 × 10⁻⁵ mm³/N-m), suggesting that blending improves dispersion but weakens tribo-film stability. To complement the experimental findings, support vector regression (SVR), artificial neural networks (ANN), and AdaBoost algorithms were employed to predict key performance parameters based on compositional and thermal input data. The models demonstrated high prediction accuracy, validating the feasibility of AI-driven formulation screening. These results highlight the complementary potential of CeO₂ and MWCNT additives for high-performance bio-lubricant development and emphasize the role of machine learning in accelerating material optimization for sustainable lubrication systems. Full article

FeCoCrNiNb_xN (x = 0, 0.25, 0.5, 0.75, 1 molar) high-entropy nitride (HEN) films were fabricated on 304 stainless steel and Si wafers using magnetron sputtering to investigate the influence of Nb content on the microstructure, mechanical properties, and tribological performance. X-ray diffraction (XRD) analysis reveals a face-centered cubic (FCC) structure with a preferred orientation in the (200) plane, which transfers to the (111) plane as the Nb content increases. The lattice distortion induced by Nb incorporation enhanced crystallinity, with the Nb_0.5N film exhibiting the highest diffraction peak intensity and interplanar distance. Cross-sectional SEM images displayed columnar crystal structures, while the surface morphology evolved from “cauliflower-like” to smoother clusters with increasing Nb content, reducing average roughness from 7.54 nm (Nb₀) to 4.89 nm (Nb₁). The hardness and elastic modulus initially decrease, then peak at 25.56 GPa and 265.36 GPa, respectively, for the Nb₁ film, attributed to solid solution strengthening and high-entropy effects. Tribological tests demonstrated that Nb₁ achieved the lowest coefficient of friction (0.46), wear volume (1.23 × 10⁻³ mm³), and wear rate (5.11 × 10⁻⁸ mm³·N⁻¹·m⁻¹), owing to NbN phase formation, refined grains, and reduced surface roughness. The wear mechanisms are abrasive and oxidative wear. Full article

Wave Energy Converters (WECs) depend on hydraulic Power Take-Off (PTO) systems in which elastomeric seals must withstand wear, fatigue, and corrosion under harsh marine loading. This study quantitatively compares two commercial polyurethane seals (E1-E2) with custom-compounded Ethylene propylene diene monomer rubber (EPDM) formulations (E3–E5) using reciprocating wear tests (ASTM G133) at 3–10 N and 10–30 mm/s. It is noted that all experiments were conducted under dry conditions at room temperature as a baseline assessment, and the findings provide foundational insight prior to considering lubrication, hydraulic fluid effects, and marine environmental conditions relevant to WEC operation. Coefficient of friction (COF), specific wear rate, and worn-surface morphology were assessed to determine material durability. The commercial thermoplastic polyurethane (TPU) grades exhibited high hardness (93–94 Shore A), low wear rates (2.29–1.93 × 10⁻⁴ mm³/Nm), and shallow wear scars (≤380 µm). Carbon-black-reinforced EPDM (E3) produced the lowest wear rate among all samples (1.45 × 10⁻⁴ mm³ N⁻¹ m⁻¹) and the longest predicted service life (6.2 years), whereas silica-filled and plasticized EPDMs (E4, E5) showed higher wear (2.44–2.88 × 10⁻⁴ mm³/Nm) and broader deformation zones. Archard-based lifetime estimates at 10 N and 30 mm/s ranged from 3.1 to 6.2 years across materials. These results demonstrate that optimized EPDM formulations can serve as cost-effective alternatives to commercial TPUs for medium-load hydraulic sealing applications while providing a quantitative basis for material selection and life prediction. Full article

To prepare a high-performance Fe-based laser cladding coating, herein, various Fe60/WC/Y₂O₃ coatings are deposited on the surface of 42CrMo steel plate via a laser cladding technique. The WC dosage is fixed as 10 wt%, while the dosage of Y₂O₃ ranges from 0 to 7.5 wt%. The influences of Y₂O₃ dosage on the coating hardness, wear resistance, and corrosion resistance are investigated. With the addition of Y₂O₃, the feature peak of WC disappears, and the peaks of M₂₃C₆ gradually weaken, indicating that Y₂O₃ promotes the decomposition of WC and suppresses the formation of new metal carbides. When the dosage of Y₂O₃ is 2.5 wt%, a grid-like structure is formed on the coating surface, suggesting uniform distribution of decomposed W within the Fe matrix. When the Y₂O₃ dosage exceeds 5 wt%, a large amount of CO₂ gas is released, leading to an increase in surface pores. Through a comparison, the optimal dosage of Y₂O₃ is 2.5 wt%, and the resulting 3# coating has the highest hardness of 861.97 HV. Moreover, the 3# coating also shows the minimum friction coefficient and the minimum wear volume, reflecting its superior wear resistance. The polished coating serves as a working electrode, and the corrosion resistance is tested in 3.5% NaCl solution. The sample containing 2.5 wt% Y₂O₃ has the highest corrosion potential and the lowest corrosion current density, indicating excellent corrosion resistance. The enhanced performance is ascribed to the improved surface quality and the formation of a W-reinforced grid structure. The high-performance coating has promising application potential in material and component repair. Full article

This study systematically investigates the effect and mechanism of a TiO₂ nano-lubricant on edge cracking and surface quality during the rolling of Mg/Al composite foils. Initial friction and wear tests identified an optimal nano-lubricant concentration of 3.0 wt.%, at which the system achieved a minimum average coefficient of friction of 0.067. Subsequent rolling tests using this concentration showed that the nano-lubricant reduced rolling force by 5.39–7.54% compared to dry conditions. It also significantly suppressed the initiation and propagation of edge cracks. Furthermore, the surface roughness parameters Ra and Rz were reduced by 16.5% to 24.0%, and the height profile fluctuation range was reduced by 33% to 45%, resulting in a smoother and more uniform surface morphology. The analysis of the underlying mechanism indicates that the superior performance originates from the synergistic effects of the rolling effect, the mending effect, the polishing effect, and the protective film effect. This work establishes that the use of a 3.0 wt.% TiO₂ nano-lubricant is a viable strategy for fabricating high-quality Mg/Al composite foils with minimal defects. It thereby offers both theoretical and practical guidance for the advanced rolling of bimetallic composites. Full article

Background: Cu-based friction materials (CBFMs) exhibit significant application in transportation and mechanical engineering due to their excellent wear resistance, thermal conductivity, and stable tribological performance. Methods: In this study, CBFMs holding a 3D mesh reinforcement structure was prepared under different sintering temperatures and sintering times. The phase, mechanical, and tribological properties were tested, and the wear mechanisms were analyzed. Results: The results showed that with an increase in sintering temperature, compressive strength showed a trend of increasing first and then decreasing, COF showed a decreasing trend first and then an increasing trend, and wear rate showed a decreasing trend that can be attributed to the different strength of the matrix and 3D mesh reinforcement structure at different sintering temperatures. With an increase in sintering time, COF continuously increased and wear rate sustained a decrease. Conclusions: Compared with previous studies, this study revealed the influence mechanism of sintering temperature and sintering time on the comprehensive properties of CBFMs holding a 3D mesh reinforcement structure for the first time. The results can provide data support for the performance improvement of CBFMs holding a 3D mesh reinforcement structure, and lay a theoretical foundation for the further study of powder metallurgy materials. Full article

In order to improve the high-temperature wear resistance of mold copper plates, this study used laser cladding technology to prepare a high-wear-resistant composite coating with Inconel 718 and WC(Tungsten carbide) particles. The phase composition, microstructure, microhardness, and tribological properties at 400 °C were systematically analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Vickers microhardness tester, and high temperature friction and wear tester. The results indicate that the Inconel 718/WC coating is free of pores and cracks and exhibits a metallurgical bond with the substrate. Its phases mainly consist of a γ-Ni solid solution and various hard carbide reinforcing phases, such as MC, M₃W₃C, and W₂C. The average microhardness of the coating reaches 851.7 HV_0.5, which is 11.5 times than that of the substrate (74 HV_0.5). At 400 °C, the wear rate of the coating is 3.48 × 10⁻⁴·mm³·N⁻¹·m⁻¹, only 35.7% of the substrate’s wear rate. The dominant wear mechanism is abrasive wear, accompanied by oxidative wear. The outstanding performance of the coating is attributed to the combined effects of grain refinement strengthening, solid solution strengthening, and second-phase strengthening induced by the various hard carbides. Full article

To extend the service life of sensors in seawater, this work prepared an integrated diffusion-plated Al₂O₃ film using high-power impulse magnetron sputtering (HiPIMS). The tribological properties of the Al₂O₃ film in a marine environment were tested using a tribometer. The morphology and evolution of the Al₂O₃ film before and after the friction tests were investigated by characterization techniques such as field emission scanning electron microscopy (FESEM). The results demonstrate that the Al₂O₃ film exhibits excellent tribological performance in the marine environment, significantly enhancing the wear resistance of the substrate material. Furthermore, with the protection of the Al₂O₃ film, the designed pressure sensor achieved high-sensitivity detection of minute operational forces underwater. When applied to a robotic gripper for manipulation tasks, the coated underwater sensor enabled accurate perception of subtle motion states of the grasped objects. Full article

One of the limitations of additive manufacturing technology is the high surface roughness of finished products caused by the layered structure of the deposition and the effect of adhesion of unfused powder particles. This worsens the fatigue characteristics, wear resistance, and functional properties of the parts, which are especially important for critical applications in medicine, aviation, and mechanical engineering. The paper presents the results of a study on the possibility of using plasma electrolytic polishing for post-processing of products made of additively manufactured Ti6Al4V alloy to form a homogeneous surface with reduced roughness. The morphology, roughness, and tribotechnical characteristics of the surface after processing in a fluoride electrolyte were studied with varying voltage and polishing time. A 90% reduction in surface roughness is achieved by polishing at 300 V for 20 min. The results of tribological tests revealed that after the polishing of the oxidative wear mechanism is maintained, the temperature in the tribological contact zone decreases, and the load-bearing capacity of the surface increases (the Kragelsky–Kombalov criterion decreases). The greatest decrease in the friction coefficient by 2.1 times was observed with minimal surface roughness, when the largest average radius of rounding of the microprotrusions of the friction track microtopology is formed with a low value of the Kragelsky–Kombalov criterion. Full article

Superconducting magnetic bearings are friction-free devices and therefore in principle suitable for long-term operation, as no wear is observed. However, other degradation mechanisms can influence the operation. Up to now, it has not been clear to what extent degradation of either the bulk superconductors or the permanent magnets impacts the overall bearing performance on long timescales. Therefore, we studied the bearing properties of a 20-year-old rotational superconducting magnetic bearing, which was cooled down occasionally in an open liquid nitrogen bath for presentation. Otherwise, the bearing was stored under ambient conditions. To characterize the current status, we measured the bearing’s static and dynamic stiffness in radial and axial directions. Comparing our results to the values measured after the setup of the bearing revealed a stiffness degradation of up to 77%. This decrease is mainly attributed to the degradation of the bearing’s superconducting bulks and the permanent magnets. Analysis of both components showed clear signs of degradation. The permanent magnetic rotor’s magnetic field is around 19% smaller compared to the original state. The superconducting bulks now only inhomogeneously trap magnetic flux. Critical current calculation based on this data revealed a significant reduction compared to the original measurements. Nonetheless, the bearing allows for a stable levitation. Full article