Search Results (1,936)

High Friction Surface Treatment (HFST) relies heavily on wear-resistant aggregates to ensure roadway safety, yet the conventional evaluation of aggregate abrasion resistance is time-consuming and resource-intensive. In this study, a machine learning framework was developed to predict the abrasion-induced angularity evolution of recycled high-alumina aggregates from their initial morphological characteristics, thereby enabling rapid abrasion-resistance screening. Six regression models were compared under leave-one-group-out cross-validation, and an improved whale optimization algorithm (IWOA) was proposed to tune the Gaussian process regression (GPR) model, incorporating five enhancements and a regularized fitness function to restrain overfitting. The models were trained on 42 samples from six aggregates, whose angularity, Form 2D, micro-texture, sphericity, and F:E ratio were measured with the AIMS II device before and after successive abrasion cycles. The IWOA-GPR model achieved the best performance, with an R² of 0.8909, an RMSE of 150.98, an MAE of 120.55, and a MAPE of 4.60%. The SHAP analysis identified the abrasion revolutions, the initial Form 2D, and the initial angularity as the dominant contributors to the worn angularity. Moreover, the early angularity loss after the first 500 revolutions correlated strongly with the measured Los Angeles abrasion value (r = 0.935), which allows the LAA of a candidate aggregate to be estimated after a single abrasion cycle. The proposed framework therefore provides a rapid and reliable tool for screening wear-resistant aggregates for HFST applications and supports the clean utilization of recycled solid wastes in anti-skid pavements. Full article

Three kinds of surface treatments, including permanganate, molybdate, and phytic acid conversion films, were fabricated on La-Ce mischmetal containing AM60B magnesium alloy. Their effects on the corrosion and tribological behaviors of the alloy in 3.5 wt% NaCl solution were systematically investigated via Mott–Schottky analysis, electrochemical measurements, and friction–wear tests. The results show three surface treatments shift the flat band potential in the negative direction, reduce the corrosion current density, enlarge the electrochemical impedance arc radius, and decrease the friction coefficient, conferring remarkably enhanced corrosion and wear resistance to the alloy substrate. The performance enhancement is ascribed to the formation of uniform, dense conversion films that act as effective physical barriers, which impede the penetration of corrosive species, isolate the substrate from the aggressive aqueous environment, and improve the chemical and electrochemical stability of the alloy–solution interface. The comprehensive performance ranking of the three surface treatments in terms of corrosion and wear resistance is as follows: permanganate conversion film > molybdate conversion film > phytic acid conversion film. Full article

Hydrogels, with their high water content, tissue-like softness, and excellent biocompatibility, are prime candidates for dynamic load-bearing interfaces such as cartilage replacement and implant coatings. However, the toughening structures introduced to enhance damage resistance often compromise surface lubrication: highly dissipative networks, while suppressing bulk crack propagation, frequently increase interfacial friction and accelerate wear. This toughness–lubrication trade-off constitutes a central bottleneck limiting the long-term service of hydrogels under dynamic contact conditions. This review examines the friction and wear behavior of various hydrogel systems and, from the dual perspectives of bulk mechanical reinforcement and surface lubrication regulation, summarizes the core design mechanisms of toughening and hydration lubrication strategies, respectively. Based on this analysis, this review proposes a functional decoupling design principle: hierarchical structures—ranging from homogeneous to heterogeneous—in which the bulk dissipates mechanical load while the surface maintains hydration lubrication, thereby reconciling mechanical toughness with lubrication. Finally, this review surveys cutting-edge applications of such materials in tissue engineering, device coatings, drug delivery, electronic energy-harvesting and storage devices, and soft actuators, providing a reference for the development of hydrogels that integrate excellent mechanical properties with lubrication functionality. Full article

Aluminum matrix composites reinforced with refractory medium-entropy alloy particles are of growing interest for wear-resistant applications, yet the contribution of an oxidized core–shell reinforcement remains largely unexplored. This study investigates the fabrication and tribological performance of Al composites reinforced with WMoNb refractory medium-entropy alloy (RMEA) powder and its oxidized derivative (RMEO). Equiatomic WMoNb powder was synthesized by 150 h high-energy ball milling, forming a single-phase BCC solid solution, then oxidized at 650 °C/4 h, selectively converting Mo and Nb into Mo₄O₁₁ and NbO_0.76 while W remained metallic, yielding a core–shell RMEO structure. Composites containing 2.5–10 wt.% RMEA or RMEO were fabricated by cold pressing/sintering and evaluated by dry sliding wear testing (pin-on-disc, Al₂O₃ counterpart). Both reinforcements reduced friction and wear loss relative to pure Al in a dose-dependent manner; RMEO outperformed RMEA at every ratio, cutting friction and wear loss by ~60% at 10 wt.% and reaching the highest hardness (132 HB) of all compositions. Worn-surface and profilometric analyses revealed a wear-mechanism shift from severe adhesive/abrasive wear in pure Al to a tribo-oxide-mediated regime in RMEO composites. These findings indicate that selective oxidation of refractory medium-entropy alloy powders is an effective strategy for enhancing the wear resistance of Al matrix composites. Full article

In order to enhance the strength and wear resistance of pure copper without obvious sacrifice of high electrical conductivity, Al₂O₃ particle-reinforced copper matrix composites with different volume fractions of Al₂O₃ were fabricated via the oscillatory hot-pressing sintering process. The effects of Al₂O₃ content on the densification, microstructure, mechanical properties, electrical conductivity, and wear behaviors of the composites were systematically investigated. The results showed that oscillatory pressure effectively inhibited pore formation, and Al₂O₃ particles were uniformly distributed within the copper matrix. With the increase in the Al₂O₃ volume fraction, the densification of the composites decreased slightly, while the hardness, compressive strength and wear resistance were continuously improved. By contrast, the electrical conductivity declined marginally and the friction coefficient rose. The 10 vol.% Cu-Al₂O₃ composite exhibited the optimal comprehensive wear resistance, with a hardness of 123 HV and an electrical conductivity maintained at 80.2% IACS. The wear mode of the composites gradually shifts from single adhesive wear of pure copper to the combined effect of abrasive wear and oxidative wear. Full article

Although the duty cycle is an important parameter in pulsed plasma nitriding, its role in simultaneously controlling the microstructure, mechanical performance, tribological behavior, and corrosion resistance of 12Kh18N10T stainless steel remains insufficiently understood. Therefore, this study systematically investigates these relationships under otherwise fixed nitriding conditions. The samples were nitrided at 500 °C, a pressure of 400 Pa, a voltage of 700 V, and a treatment duration of 5 h, with duty cycle (DC) values of 30, 60, and 90%. The surface microstructure and composition were characterized by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction. The mechanical properties were evaluated by instrumented nanoindentation, the tribological properties were evaluated using the coefficient of friction and wear rate, and the corrosion resistance was investigated using potentiodynamic polarization. The maximum nitrided layer thickness of 91.29 μm was obtained at DC30, whereas the layer thickness at DC60 and DC90 was approximately 65.07 μm. Fe₄N and Cr₂N phases were identified in all samples. The DC60 regime provided the highest hardness of 740.6 HV, an elastic modulus of 215.9 GPa, the lowest coefficient of friction of 0.333, and the lowest corrosion current density of 0.000665 mA/cm². The minimum wear rate of 2.276 × 10⁻⁵ mm³/(N·m) was achieved at DC90. These results show that the optimal processing condition depends on the required combination of hardness, wear resistance, coefficient of friction, and corrosion resistance. The obtained results demonstrate that the functional properties of the steel can be effectively tailored by controlling the duty cycle. Full article

The sturdy and stable unique polyhedral structure of FeOOH nanoparticles facilitates stress and load transfer, thereby forming a tighter mechanical interlock at the carbon fiber–matrix interface. In this work, the FeOOH nanocrystal layer in situ grown on flexible carbon fiber cloth was rationally designed and fabricated through hydrothermal synthesis. Then, the non-covalent cation–π bond was constructed at the interface between the iron ion-loaded FeOOH nanoparticles and indole-based poly(hexahydrotriazine) (In-PHT). Owing to the collaborative effects of physical anchoring and chemical bonding, the resultant composite exhibited an outstanding tensile strength of 322 MPa, and the friction coefficient significantly decreased by 63% compared with the composites without FeOOH nanoparticles. Moreover, the resultant worn composite showed an excellent self-healing property owing to the introduction of polyethylene wax (PEW) with a low melting point, and the healed friction coefficient remained almost unchanged. Extensive analyses verify that the phase-separated structure and Fe³⁺–π interactions across multiscale interfaces achieve the combined advantages of wear resistance and durability for recyclable carbon fiber-reinforced poly(hexahydrotriazine) composites (PHT-CFRPs). Full article

SBS-modified asphalt is widely used in high-grade pavements for its excellent rutting and fatigue resistance; however, how its friction behavior evolves under submerged conditions with surface distress remains poorly understood. To address this gap, we developed a rubber–asphalt friction tester to characterize quasi-static rubber–asphalt friction under submerged conditions with three typical distresses: pothole, crack, and surface void. Our results show that friction increases with roughness, load, and water temperature, but degrades progressively under cyclic loading. Among the three distresses, surface void offers the most stable friction performance, whereas pothole exhibits the largest friction loss under repeated loading, identifying them as high-priority repair targets. The positive temperature–friction correlation further implies that wet-skid risks are higher at lower temperatures, providing a basis for seasonal maintenance scheduling. Three-dimensional wear analysis reveals distinct mechanisms: pothole causes localized deep-pit wear, while surface void generates uniform roughening, explaining their contrasting durability. These findings directly support distress prioritization, friction-performance evaluation, and maintenance planning for SBS-modified pavements in rainy environments. Full article

Pitting distress introduces discontinuous surface texture, thereby modifying the friction–adhesion coupling at the rubber–asphalt interface. This study systematically investigates the interfacial friction response of SBS-modified asphalt pavements with three pitting distribution patterns (sparse, medium, and dense) under varying sliding rates, temperatures, and cyclic loading using a custom-developed friction testing apparatus. The results reveal that adhesion-dominated friction is strongly dependent on both texture distribution and operating conditions. With increasing temperature, the dense pattern exhibits the most pronounced adhesion enhancement, with an average friction increase of 55.0%. The sparse pattern shows a continuous decreasing trend in the low-to-medium speed range, but exhibits a strengthening rebound at high speeds, demonstrating the most complex rate sensitivity. Under cyclic loading, among the three pitting patterns tested, the dense pattern exhibits the best friction retention, with an average friction reduction of only 6.2% after 30 cycles, compared to 9.5% for the sparse pattern and 10.8% for the medium pattern. Three-dimensional topography indicates that the medium pattern exhibits a continuous and relatively uniform wavy roughness, while the dense pattern transforms into a high-frequency serrated morphology. However, the wear in both patterns is dominated by homogenized micro-grooves, without the formation of local deep pits or sharp undulations, which favors the maintenance of stable skid resistance under the laboratory cyclic loading conditions tested in this study. Furthermore, a unified regression model with distribution dummy variables and interaction terms (R² = 0.826; cross-validated Q² = 0.646) quantifies the synergistic effect of pitting density and temperature, with the temperature sensitivity increasing six-fold from the sparse to the dense pattern (0.011 to 0.071 N/°C). Full article

This study presents a comparative evaluation of the wear performance of three hot-work tool steels—WCLV (1.2344), Uddeholm Unimax, and Uddeholm QRO 90 Supreme—for die forging applications. The materials were characterized in terms of hardness and bulk chemical composition using Vickers hardness testing and X-ray fluorescence spectroscopy. Tribological behavior was investigated using ball-on-disc tests, while industrial performance was assessed by analyzing forging punches after the production of 16,250 components. Surface degradation was quantified using optical profilometry and three-dimensional roughness parameters. Measured hardness values were 591 HV for WCLV, 622 HV for QRO 90 Supreme, and 639 HV for Uddeholm Unimax. The average friction coefficients were 0.88, 0.92, and 0.77, respectively. Unimax also exhibited the lowest volumetric wear, reaching 0.04683 mm³ (R19 mm) and 0.03384 mm³ (R22 mm), compared with 0.08646–0.13095 mm³ for WCLV and 0.09598–0.13635 mm³ for QRO 90 Supreme. This corresponds to approximately 45–70% lower wear relative to the other steels. Industrial trials confirmed improved surface stability of Unimax punches after service. The observed trends are consistent with differences in alloying content and the expected microstructural response associated with chromium and molybdenum additions. Overall, Uddeholm Unimax demonstrated the most favorable balance of hardness, friction behavior, and wear resistance. Full article

Silver (Ag)-based conductive coatings are widely used in electrical contacts due to their excellent electrical conductivity, low contact resistance, good thermal stability and oxidation resistance, although their susceptibility to sulfidation and environmental corrosion is a concern under certain service conditions. In recent years, significant progress has been achieved in both the manufacture and performance optimization of Ag-based coatings to satisfy the demanding requirements of modern electrical and electronic systems. This review summarizes recent advances in fabrication techniques and processing parameters for Ag-based coatings, including electroplating, electroless deposition, magnetron sputtering, electrospark deposition, thermal spraying, and electrical explosion spraying on metallic substrates, particularly on copper and steel substrates. More attention is given to microstructural design strategies, such as the incorporation and homogeneous dispersion of reinforcement or solid lubricant phases within the Ag matrix, to enhance contact reliability and operational endurance. The performance of Ag-based coatings is analyzed in terms of their physical, chemical and mechanical properties, electrical contact resistance, friction and wear behavior, arc erosion resistance, and environmental durability under different service conditions. Key challenges, including coating degradation under high electrical loads, mechanical wear, and corrosive environments, are highlighted. Future research directions are outlined, focusing on multifunctional coating structures that enhance surface performance and ensure the long-term durability of electrical contacts. Full article

This study investigates the mechanical and tribological behavior of three composites with a ZrO₂ matrix stabilized with 1.75 mol% Y₂O₃ and containing 1 wt.% Al₂O₃, reinforced with TiC (A), TiC + ZrC (B), and TiC + WC + Mo₂C (C). The matrix powder was synthesized by chemical coprecipitation, and the composites were consolidated by spark plasma sintering at 1350 °C. Dry reciprocating sliding tests against 100Cr6 steel were performed at 10 and 25 N. Composite A exhibited the highest HV10 hardness (1268), while the indentation fracture toughness values were similar (6.41–6.57 MPa·m^1/2). Wear resistance did not follow the hardness ranking. At 25 N, composite A exhibited surface fragmentation and a specific wear rate of 2.52 × 10⁻⁶ mm³·N⁻¹·m⁻¹, while composite B showed extensive and heterogeneous transfer of steel-derived material. Composite C exhibited the lowest coefficient of friction and specific wear rate, reaching 0.392 and 7.04 × 10⁻⁸ mm³·N⁻¹·m⁻¹, respectively, at 25 N. EDS mapping revealed an area-integrated Fe content of 0.7 at.% for C, compared with 7.2 at.% for A and B. The superior wear resistance of C was associated with substantially lower steel-derived material transfer and a relatively smooth wear-track surface rather than with the highest bulk hardness. Full article

CrAlN PVD coatings are frequently used to protect cutting tools because of their superior hardness and wear resistance. However, the influence of carbon addition to such coatings remains largely unexplored. Therefore, Cr-Al-C-N coatings were deposited by HiPIMS using a commercial PVD unit equipped with a segmented sputter target. The target consisted of an upper half of Cr and a lower half of Al. Carbon was added under reactive sputtering conditions with the aim of reducing internal stress and introducing a friction-reducing component. A range of different Al-Cr-C compositions could be efficiently explored by varying the acetylene reactive gas flow. Depending on the positioning of the samples, Cr/Al ratios could be varied between about 4/1 and 1/2 while three different levels of carbon concentration (0, 11, and 25 atomic % of total coating composition) were investigated. It was found that an intermediate carbon concentration effectively increased the hardness of Cr-rich coatings, achieving maximum plastic hardness values over 40 GPa. With increasing Al content, hardness drops to below 30 GPa. The cubic CrN phase with mostly 200-oriented grains was detected for most variants. With increasing Al and C contents, a rapid decrease in crystallite size is observed, accompanied by a reduced intensity of the (200) XRD reflection. A turning test on stainless steel showed decreasing flank wear with higher Al contents. However, no improvement associated with carbon addition could be confirmed within the investigated concentration range. Full article

Ni60/WC composite coatings reinforced with various WC contents were fabricated on 45 steels via high-speed laser cladding. First-principles calculations were adopted to investigate the interfacial characteristics between Ni and WC. The microstructures of the coating were analyzed by a scanning electron microscope (SEM). The microhardness and wear resistance of the coatings were evaluated by a Vickers hardness tester and a friction and wear tester. Theoretical calculations indicate that the C-terminated WC (001) crystal plane achieves the most stable bonding with the Ni (111) surface through the hcp site, with an interface energy of 9.57 J·m⁻². The interface is mainly provided by Ni-W metal bonds and Ni-C covalent bonds. The microstructure results show that the WC particles have good metallurgical bonding with the Ni matrix. Thus, the good interface ensures efficient load transfer to hard WC particles. The microhardness rose markedly with the increase in WC content, reaching 760 HV_0.2 for the 40 wt.% WC, which is 1.8 times that of Ni60 coatings. Tribological experiments showed that appropriate WC content could significantly improve the wear resistance of the coating. Full article

This study investigates the tribological performance of three commercial PTFE-based Xylan^® coatings—Xylan^® 1425, Xylan^® 1052, and Xylan^® 1010—applied to 18CrNiMo7-6 steel under dry sliding conditions. Ball-on-Disk tests were conducted at normal loads of 5, 7.5, and 10 N, wear-track radii of 12, 16, and 20 mm, and corresponding sliding velocities of 0.31–0.52 m·s⁻¹. The tribological evaluation was complemented by measurements of coating thickness, surface roughness, nanoindentation, wear-track profilometry, scanning electron microscopy, EDS mapping, and post-test cross-sectional microscopy. All coatings reduced the coefficient of friction from approximately 0.49–0.64 for the uncoated steel to 0.09–0.13, corresponding to an average reduction of 78–80%. Xylan^® 1425 exhibited the highest nanohardness of 57.02 MPa, the highest reduced elastic modulus of 3.33 GPa, and the most favorable elastoplastic indices. It also achieved the lowest wear, with a volumetric loss of approximately 0.03 mm³ under the most severe conditions, representing a reduction of more than 99% compared with the substrate. Xylan^® 1010 provided the lowest friction but showed pronounced plastic deformation, whereas Xylan^® 1052 exhibited fragmentation and increased wear. Post-test cross-sectional microscopy confirmed local exposure of the steel substrate in both coatings. Overall, Xylan^® 1425 provided the best balance of low friction, mechanical stability, coating continuity, and wear resistance. Full article