Search Results (265)

In applications involving repeated high-frequency mechanical impacts, such as cutting, machining, or percussive operations, understanding the surface fatigue performance of advanced ceramics is critical. This study investigated the surface fatigue resistance of duplex oxide–carbide ceramic composites fabricated via spark plasma sintering, complementing prior work on their sliding wear performance. The composites, featuring a hybrid oxide–carbide structure, were tested using a cyclic impact setup with a 10 mm ZrO₂ ball activated with 12 hammers fixed to a rotary disc delivering 500,000 impacts per test. Surface degradation was quantified through three-dimensional profilometry to determine the net material loss and scar depth, while fatigue mechanisms were analyzed using scanning electron microscopy coupled with energy-dispersive spectroscopy. In situ monitoring was implemented using accelerometers to capture vibrational signatures during cycling loading, enabling real-time assessment of material response and damage evolution. The WC-containing composite (S2 AZW) exhibited the lowest surface fatigue wear loss (700 × 10³ µm³), whereas the ZrC-based composite (AZZ1) showed the highest (1535 × 10³ µm³). A distinct inverse correlation was observed between the average peak acceleration and fatigue wear loss. Frequency-domain analysis of accelerometric signals revealed progressive degradation patterns consistent with post-test surface damage, indicating that such signal features may serve as effective in situ indicators for tracking material fatigue in future applications. Full article

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

In this paper, the achieved state-of-the-art understanding regarding the wear behaviour of various PVD (physical vapour deposition) coatings deposited on TiB₂/Ti composites produced by SPS (spark plasma sintering) is presented. The objective of this paper is to investigate the wear behaviour of various PVD coatings deposited on TiB₂/Ti composites manufactured by SPS, when lubricated with hexagonal boron nitride (hBN) as an external solid lubricant in the range from room temperature up to 900 °C in friction contacts under extreme pressure and with oscillation relative motion. Four multicomponent and multilayer coatings were investigated based on AlCrN and TiCrN coatings with TiCrN-AlCrN/AlCrTiN/Si₃N₄ interlayers and various external layers (AlCrN, Si₃N₄, AlCrTiSiN, and AlCrTiSiN gradient with increasing oxygen gradient replacing nitrogen). The wear tests were performed by means of a ball-on-disc SRV friction and wear tester using reciprocating motion of the Si₃N₄ ball sliding against a coated disc from room temperature up to 900 °C. The best protection against wear and oxidation at higher temperatures (even up to 900 °C) was achieved for coatings with AlCrN and AlTiCrN external layers, and hBN lubricant was used simultaneously. Full article

The cage shape plays a critical role in controlling lubricant distribution and replenishment and enhancing lubrication performance within rolling bearings. This study investigates the effect of four tailored cage shapes on lubricant migration and frictional characteristics at both Ball-Cage (B-C) and Ball-Disc (B-D) contacts. Utilizing a bearing cage friction and lubrication test rig (BCFL), adapted from an optical elastohydrodynamic lubrication (EHL) apparatus, the variation in grease films and friction forces was examined under varying entrainment speeds, grease properties, and grease quantities. Cage-induced lubricant redistribution on the ball surface, replenishment at the B-D contact, and the formation mechanism of thicker film thickness were recognized. The influence of cage design for four distinct shapes on mechanisms enhancing grease lubrication efficiency and friction reduction was examined. The findings provide critical insights for designing next-generation self-aligning cage structures with improved lubrication performance and reduced friction force. Full article

Additive manufacturing (AM) has emerged as a promising technology for producing low-cost, customized tooling, particularly for prototyping and small-series injection molding. However, the inherent surface roughness and anisotropic properties of 3D-printed parts pose significant challenges for their direct use as functional mold inserts. This study investigates the effectiveness of various post-processing techniques on 3D-printed plastic inserts made from polyamide 12 (PA12) and glass bead-filled PA12 (PA12GB). The primary objective was to evaluate the impact of these surface treatments on the functional properties and service life of the mold inserts. A comprehensive analysis was conducted, including a detailed characterization of roughness using a confocal microscope, cross-sectional analysis to determine layer thickness, and tribological tests employing the ball-on-disc method to assess wear resistance. The study employed a modular injection mold and tested a range of surface finishing processes, including PostProcess Suspended Rotational Force (SRF) technology, metal decomposition coatings from HVM Plasma, and various methods from DyeMansion (Powershot S and Powerfuse). Results show a significant reduction in surface roughness across all methods. Notably, the vapor-based Powefuse treatment from DyeMansion achieved a surface roughness (R_a) of 1.2797 μm, which is below the typical R_a value of 1.6 μm for conventional metal molds, thereby making it suitable for high-quality molding applications. The tribological analysis provided critical insights into the durability and wear resistance of the treated surfaces, supporting their potential for extended use. This research validates the potential of specific post-processing methods to transform AM parts into functional tooling, enabling cost-effective and rapid prototyping in the plastics industry. Full article

This study examines the effect of an AlTiN/TiSiXN two-layer coating on the tribological performance of HS6-5-2C steel under dry friction conditions. Tribological assessments were conducted using a tribometer and a calotester with a ball-on-disc configuration, involving HS6-5-2C steel discs (both uncoated and coated with AlTiN/TiSiXN) and 100Cr6 steel balls. Analyses, including surface topography, microstructure, and chemical composition, were performed utilising confocal microscopy, atomic force microscopy, and scanning electron microscopy with energy dispersive spectroscopy. The hardness and elastic modulus of the coating and substrate were determined through nanoindentation techniques. The coating exhibited a hardness of approximately 38 GPa and high elasticity, substantially enhancing the tribological characteristics of the system. Notably, the coated specimens exhibited friction coefficients approximately 10% lower than those of the uncoated steel, while wear on the coated discs was reduced by more than 90% in comparison to their uncoated counterparts. Wear rate evaluations of the counter-samples indicated a slightly increased wear of the balls—approximately 21%—when in contact with the coated discs, which can be attributed to the high hardness of the coating. These results substantiate the superior efficacy of the AlTiN/TiSiXN coating in improving wear resistance and reducing friction. Full article

As a functional coating, the wear-resistant Cr coating is of considerable importance in metal plating. In the present paper, S235 steel samples were electrodeposited with 5 µm thick Cr coating at current densities of 15, 27 and 40 A dm⁻². Nanoindentation was performed to measure the hardness of samples with electroplated Cr coating. Under the defined electroplating process conditions, the Cr coating hardness varied as a function of current density: the minimum average H_IT value of 11.4 GPa was measured at a current density of 15 A dm⁻² and the maximum average H_IT value of 12.9 GPa was measured at 40 A dm⁻². Tribological characteristics of coated samples were determined using the ball-on-disc tribo-method with surface evaluation of tribo-track on the confocal and electron microscope. The Cr coating deposited at 15 A dm⁻² had the lowest wear resistance with a wear rate of 12.76 × 10⁻¹⁵ m³ (Nm)⁻¹. The Cr coating deposited at 40 A dm⁻² had the highest wear resistance on the sample with a wear rate of 3.84 × 10⁻¹⁵ m³ (Nm)⁻¹. Full article

This study investigates the structure–property–performance (SPP) relationships of two thermoplastic polyurethanes (TPUs), FILAFLEX FOAMY 70A and SMARTFIL^® FLEX 98A, manufactured by fused filament fabrication (FFF). Disc specimens were produced with varying gyroid infill densities (10–100%) and Archimedean surface textures, and their tribological and surface characteristics were analyzed through Ball-on-Disc tests, profilometry, and optical microscopy. SMARTFIL^® FLEX 98A exhibited a sharp reduction in the coefficient of friction (μ) with increasing infill, from 1.174 at 10% to 0.371 at 100%, linked to improved structural stability at higher densities. In contrast, FILAFLEX FOAMY 70A maintained a stable but generally higher coefficient of friction (0.585–0.729) across densities, reflecting its foamed microstructure and bulk yielding behavior. Surface analysis revealed significantly higher roughness in SMARTFIL^® FLEX 98A, while FILAFLEX FOAMY 70A showed consistent roughness across infill levels. Both TPUs resisted inducing abrasive wear on the steel counterpart, but their stress-accommodation mechanisms diverged. These findings highlight distinct application profiles: SMARTFIL^® FLEX 98A for energy-absorbing, deformable components, and FILAFLEX FOAMY 70A for applications requiring stable surface finish and low adhesive wear. The results advance the design of functionally graded TPU materials through the controlled tuning of infill and surface features. Full article

This article presents studies of surface layers produced by electro-spark deposition (ESD) on cast iron using a W-Ni-Co sintered electrode. To minimize the number of required experiments, a two-factor, five-level Hartley experimental design was chosen. The assessment involved observing the effect of voltage and capacitor capacity during the ESD process (on layer thickness and wear of the sample and counter-sample under technically dry friction conditions). Microscopic and tomographic observations were performed to analyze the thickness and structure of the layers. Image analysis methods were employed to examine the cross-section of the layers. ESD diffusion analyses were performed on the produced layer. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were performed to characterize the microstructure and composition of the coating. In addition, in order to evaluate the performance properties of tungsten coatings, the tribological tests were also conducted on a TRB³ Ball-on-Disc testing device. Hardness tests confirm an increase in the hardness of cast iron with a tungsten layer by over 400 µHV. The tests showed that higher voltages during the ESD process result in thicker layers and reduced wear of the sample with a tungsten layer at the expense of increased wear of the counter-sample (ball). Full article

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 (µ_k), 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. Full article

During the homogenization process of lithium battery slurry, the slurry shearing process causes the surface of the homogenization equipment to wear and generate metal containing debris, which poses a risk of inducing battery self-discharge and even explosion. Therefore, inhibiting wear of homogenizing equipment is imperative, and systematic investigation into the wear behavior and underlying mechanisms of SUS304 stainless steel during homogenization is urgently required. In this study, lithium iron phosphate (LFP) and lithium nickel cobalt manganese oxide (NCM) cathode slurries were used as research objects. Changes in surface parameters, microstructure, and elemental composition of the wear region on SUS304 stainless steel under different working conditions were characterized. The results indicate that in the SUS304-lithium-ion battery slurry system, the potential wear mechanism of SUS304 gradually evolves with changes in load and rotational speed, following the order: adhesive wear (low speed, low load) → abrasive wear (medium speed, high load) → fatigue wear (high speed). Under high-load and high-rotational-speed conditions, oxidative corrosion wear on the ball–disc contact surface is particularly pronounced. Additionally, wear of SUS304 is more severe in the LFP slurry system compared to the NCM system. Macroscopic experiments also revealed that the speed effect is a core factor influencing the wear of SUS304, and the increase in its wear rate is more than twice that caused by the load effect. This study helps to clarify the wear behavior and wear mechanism evolution of homogenization equipment during the lithium battery homogenization process, providing data support and optimization direction for subsequent material screening and surface strengthening treatment of homogenization equipment components. Full article

This study quantifies how pressurized water-immersion aging degrades the tribological response of cross-ply E-glass/polyester laminates by coupling dual-mode testing with surface metrology and factorial ANOVA. Eleven-ply [0/90]s plates were aged at 10 bar for 0, 7, 14, and 21 days, gaining 10% mass (72.2 to 79.4 g), then tested under 20 N in ball-on-disc (50–100 mm s⁻¹; 100–200 m) and reciprocating modes (1–2 Hz; 10–20 m). In ball-on-disc tests, steady-state COF rose from 0.40 to 0.47 (unaged) to 0.49 to 0.52 (14–21 days), and the low-friction run-in largely vanished with aging. Wear scar width and depth increased from 1.38 to 1.90 mm and 75 to 117 µm, respectively. Reciprocating tests showed a non-monotonic trend: moderate aging lowered COF to 0.50, whereas 21 days produced the harshest response (up to 0.78) and the widest/deepest scars (1.15 to 1.95 mm; 40 to 110 µm). ANOVA revealed that, in ball-on-disc tests, the COF was governed by sliding distance (28.70%) and speed (24.64%), with a strong Days × Speed interaction (31.66%); track-depth variance was dominated by distance (42.16%) and aging (32.16%). For the COF under reciprocating tests, aging was the leading main effect (21.21%), with large Days × Frequency (20.36%) and Days × Track (20.03%) interactions. Uniquely, this study isolates the effect of controlled hydrostatic aging (10 bar) and compares two sliding kinematics under identical loads, establishing quantitative thresholds (14 and 21 days) where interfacial debonding and third-body abrasion accelerate. Full article

This study aimed to develop an experimental method for producing artificially aged oil with properties—such as coefficient of friction, average wear scar diameter, and antiwear additive content—similar to those of used oil contaminated with alternative fuel, sampled after 129 h of engine test bench operation. A design of experiment (DoE) methodology was applied to examine the effects of various parameters and identify optimal settings. Friction and wear tests were conducted using an Optimol SRV5 tribometer in a ball-on-disc configuration, while wear scars were analyzed with a Keyence VHX-1000 digital microscope. Oil analysis was conducted with an Anton Paar 3001 viscometer and a Bruker Invenio-S Fourier-transform infrared spectrometer. The DoE results showed that the heating duration had a negligible effect on oil degradation. Aging time primarily affected changes in the friction coefficient and average wear scar diameter, whereas aging temperature was the primary factor influencing the anti-wear additive content. Gaussian elimination identified the optimal aging parameters as 132.8 °C and 103.1 h. These results were confirmed through surface analysis using a ThermoFisher NexsaG2 X-ray photoelectron spectrometer, which showed that the tribofilm composition of the used oil most closely matched that of artificially aged oils prepared at 120 °C for 96 h and 140 °C for 120 h. The strong correlation between the predicted and experimentally confirmed conditions demonstrates the reliability of the proposed method for replicating realistic aging effects in lubricating oils. Full article

In view of the need to increase the durability of working tools exposed to intense friction, this study analysed hybrid coatings (TiAlCN, AlTiCN, AlCrTiN, TiN, CrN) with a DLC (Diamond-Like Carbon) layer, deposited using PVD (Physical Vapour Deposition) methods (arc evaporation and magnetron sputtering). The structural characteristics of the coatings were determined using SEM (Scanning Electron Microscope) and AFM (Atomic Force Microscope) microscopy, as well as Raman spectroscopy, which confirmed the compact structure and amorphous nature of the DLC layer. Tribological tests were performed using a ball-on-disc test, revealing that DLC hybrid coatings significantly reduce the coefficient of friction (stabilisation in the range of 0.10 to 0.14 due to DLC graphitisation), limiting tool wear even under increased load. The SEM-EDS (Scanning Electron Microscope-Energy Dispersive Spectroscopy) microscopic examination revealed that the dominant wear mechanisms are abrasive and adhesive damage, and the AlCrTiN/DLC system is characterised by low wear and high adhesion (L_c = 10⁵ N), making it the optimal configuration for the given loads. Microhardness tests showed that high hardness does not always automatically translate into increased wear resistance (e.g., the AlTiCN coating with 4220 HV showed the highest wear), while coating systems with moderate hardness (TiAlCN/DLC, CrN/DLC) achieved very low wear values (~0.17 × 10⁻⁵ mm³/Nm), which highlights the importance of synergy between the hardness of the sublayer and the low friction of DLC in the design of protective coatings. Full article

This study investigates the critical influence of oxidation temperature on the intrinsic characteristics and surface properties of thermally oxidized Zr2.5Nb alloy. The resulting oxide layers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), surface hardness, and nanoindentation. The tribological behavior of the untreated and thermally oxidized Zr2.5Nb alloy was evaluated via reciprocating ball-on-disc wear tests under a load of 29.4 N. MC3T3-E1 cells were employed to assess the biocompatibility. The results show that oxide layers primarily composed of m-ZrO₂ formed on the alloy surface, with thickness increasing from 2.43 µm to 13.59 µm as the oxidation temperature rose from 500 °C to 700 °C. However, this thickness increase was accompanied by elevated defect density. Compared to the untreated alloy, thermally oxidized samples exhibited significantly enhanced hardness and wear resistance. Notably, oxidation at 600 °C produced a dense 5.31 µm oxide layer with optimal structural integrity, achieving an 85% reduction in wear rate and a superior MC3T3-E1 cell relative activity of 123.07 ± 6.02%. These findings provide foundational data for developing zirconium-based implants with improved stability. Full article