Search Results (79)

Titanium alloys are widely used in aerospace, marine engineering, and biomedical fields owing to their excellent specific strength, corrosion resistance, and biocompatibility. As an important surface modification technique, sandblasting combined with acid pickling can not only eliminate the machining defects in Ti-6Al-4V but also improve its surface morphology, thereby playing a crucial role in enhancing its service performance. By employing advanced characterization equipment, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), a 3D profilometer, and a friction and wear tester, combined with wetting theoretical models and morphological evolution analysis, this study systematically investigated the comprehensive effects of different pressure sandblasting followed by acid pickling on the surface microstructure, wetting behavior, and tribological properties of forged Ti-6Al-4V alloy. The results indicated that the combined application of sandblasting and acid pickling exerted a significant regulatory effect on the surface and interface characteristics of the Ti-6Al-4V alloy. After the combined sandblasting and acid pickling treatment, a distinct micro-pit network structure was formed on the surface of the Ti-6Al-4V alloy, and its hydrophilicity and roughness showed a positive correlation with the increase in sandblasting pressure. Notably, the microstructural evolution exhibited a high degree of internal consistency with the macroscopic wear resistance: the hierarchical micro-pit network exposed after acid pickling exerted an excellent “debris capture” effect, thereby suppressing the severe third-body abrasive wear observed in the solely sandblasted state. This study aims to enhance the surface roughness, wear resistance, and hydrophilicity of the Ti-6Al-4V alloy, providing a cost-effective and industrially applicable method for the surface texturing of titanium alloys. Full article

The effects of Ti/Nb microalloying-induced MC-type carbide precipitation and tempered microstructure evolution on the dry-sliding wear behavior of low-carbon martensitic wear-resistant steels were systematically investigated. Three experimental steels with different microalloying strategies (0.04Ti, 0.1Ti, and 0.04Ti/Nb) were subjected to quenching and subsequent tempering. Microstructural features, carbide characteristics, and mechanical properties were characterized using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), tensile testing, and impact testing, while wear performance was evaluated by pin-on-disk tests under dry-sliding conditions. The results indicate that wear resistance is governed by the combined effects of tempered martensite stability and MC-type carbide precipitation. Low-temperature tempering effectively reduces the wear mass loss of Ti-containing steels by enhancing their resistance to abrasive shear deformation while maintaining sufficient toughness. In contrast, the Nb-containing steel exhibits a stage-dependent wear response associated with the formation and destabilization of oxide-derived third-body debris during sliding. (Nb,Ti)C precipitates act as microscale load-bearing units, contributing to strength enhancement and subsurface damage suppression, but their influence on wear behavior strongly depends on tempering temperature. The dominant wear mechanism is abrasive micro-cutting, accompanied by fatigue-induced spalling and oxidation-assisted damage at later stages. These results demonstrate that wear performance cannot be correlated with hardness alone, but instead requires the coordinated optimization of carbide precipitation and tempered microstructural stability. This work provides microstructural guidance for the design of microalloyed martensitic wear-resistant steels. Full article

Wire arc additive manufacturing (WAAM) demands aluminum feedstock with tightly controlled diameter and high surface integrity. Adding hard TiC nanoparticles is a viable route to enhance the mechanical response of Al wires, yet the associated increase in contact severity can accelerate the wear of wire processing tools, particularly cemented carbide dies. This study elucidates the unidirectional sliding interaction between a TiC reinforced Al WAAM wire, and a WC/Co die material containing 5 wt% Co, using a modified scratch testing configuration under dry and lubricated conditions. Two dominant mechanisms are identified: (i) aluminum adhesion on the die surface and (ii) third body abrasion arising from WC particle pull out, promoted by preferential degradation of the cobalt binder. The presence of TiC nanoparticles reduces both the extent of Al transfer and the intensity of third body abrasion, an effect that is further amplified by lubrication. Consistently, lubrication also diminishes surface defects on the wire after sliding. The results provide a mechanistic basis to balance wire strengthening with tool life and highlight practical levers—nanoparticle reinforcement and lubrication strategies—for mitigating die damage while preserving WAAM wire surface quality. Full article

Starved lubrication poses a critical challenge to hybrid ceramic bearings operating under severe conditions. This study investigates the tribological behavior of carburized 20CrMo steel sliding against Al₂O₃ ceramic balls and GCr15 steel balls under dry sliding, with oil-lubricated tests as a reference. Under oil lubrication, the 20CrMo/Al₂O₃ pair exhibits superior wear resistance, attributed to the high hardness of the ceramic counterpart. Under dry sliding, however, this pair shows a slightly lower friction coefficient but a wear rate approximately three times that of the 20CrMo/GCr15 pair. This counterintuitive behavior stems from two mechanisms: lower contact stress and friction-induced work hardening in the GCr15 pair, which together suppress wear. Further analysis reveals that secondary carbides in the carburized layer detach under repeated high shear stress, acting as hard third-body abrasives and accelerating surface damage. These findings highlight that hybrid ceramic bearings are more susceptible to lubrication failure than all-steel bearings. Under heavy loads and poor lubrication, residual compressive stress plays a key role in governing the tribological behavior of carbides on carburized surfaces. Full article

Incorporating TiAl alloys in engine applications offers benefits including reduced fuel consumption and improved efficiency. However, understanding the wear behaviour of these materials is an important consideration due to their use in harsh environments involving movable parts. This study investigated the wear behaviour and mechanisms of Ti–48Al–2Nb–0.3Si-1Sn (TiAl–S1) together with Ti–48Al–2Nb–0.3Si (TiAl–S0) as a reference alloy against an alumina ball. Scanning electron microscopy (SEM) analysis showed that the addition of Sn refined the lamellar structure from 216 $\mu \mathrm{m}$ to 130 $\mu \mathrm{m}$ and promoted more uniform deformation. SEM observations also indicated that abrasive wear is the dominant mechanism in the TiAl alloys. The TiAl–S1 exhibited lower hardness, resulting in deformation of wear debris and promoting third body acting as a lubricant. SEM-EDS revealed that the tribo-layer and wear debris originated from the TiAl materials rather than the counterpart alumina material. Both alloys demonstrated noble wear resistance, with a wear rate of 7.542 × 10⁻⁶ mm³/Nm for TiAl–S1 and 6.729 × 10⁻⁶ mm³/Nm for TiAl–S0. Even though both TiAl alloys experienced abrasive wear mechanisms, the addition of Sn emerges as a promising alloying strategy, for enhancing ductility without significantly increasing material loss. Full article

Friction braking is the most spread braking system in vehicles, where the morphologies of the disc and the braking pads are essential to ensure that friction reduces rotation speed efficiently. However, modern braking systems are submitted to a complex balance between functionalities: braking ability, resistance to wear, and limited noise emission, i.e., squealing. This article studies the evolution of the morphology of a braking pad in a pin-on-disc configuration to further understand its influence over surface functionalities. Data collected from a pin-on-disc tribometer, and topographies are coupled to perform a multiscale and multiphysics analysis of the braking pad surface. Relevancy of roughness parameters regarding braking ability, surface wear, pad temperature and noise emission is evaluated with a bootstrap-based relevancy analysis. Relevant scales of the pad morphological structures are identified for surface wear (446 µm), braking ability (19.5 µm), pad temperature (2717 and 446 µm) and squealing frequency (1720 and 15.7 µm). Correlations between test bench data and roughness parameters highlighted the role of wear plateaus on the braking pad surface. These plateaus are formed by the damaged surface peaks during braking or by compaction of the third body trapped across the braking pad surface. Full article

In this study, the effect of boron carbide (B₄C), hexagonal boron nitride (hBN), holy super graphene (HSG), and hybrid (B₄C + hBN + HSG) nano-additives on the tribological performance of SAE 5W-30 gasoline engine oil was investigated on Al-Si-based samples (Al 4032) prepared by cutting from a single-cylinder gasoline engine block. The addition of nano-additives regularly increased the kinematic viscosity; the 63.80 mm²/s (BO) value rose to 68.90 mm²/s at the highest level of B₄C and to 70.50 mm²/s in the hybrid oil (≈10.5% increase). The lowest and most stable friction performance was found in the hybrid 0.025 g/25 mL nano-additive oil, which remained between 0.03 and 0.05 during the entire COF test. The EDS mapping and line scan results confirmed the formation of tribofilm by identifying the additive elements (B for B₄C, B and N for hBN, C for HSG) in the wear scar, and the presence of increased O elements showed the restricted formation of tribo-oxidation. The results show that hybrid nano-additive oils provide the most effective friction and wear improvement, especially at low concentrations, while at high additive levels, performance does not show a consistent increase due to particle accumulation and third-body effects. Full article

The growing demand for environmentally responsible lubricants motivates the use of bio-based base stocks and benign solid additives. This study assesses the tribological performance of two Amazonian vegetable oils, Carapa guianensis (andiroba) and Copaifera spp. (copaiba resin) and a paraffinic mineral oil (PNL30) formulated with different zinc oxide (ZnO) particles, namely nanocrystals and microcrystals, at 0.01, 0.05, and 0.10 wt.%. Reciprocating sliding tests, coupled with 3D profilometry, viscosity, and sedimentation analyses, were used to link dispersion stability with friction and wear responses. A preliminary stability screening constrained the practical loading window to ≤0.10 wt.% for reproducible suspensions. Performance depended on the interplay between particle type and base-oil chemistry. Andiroba exhibited the most pronounced gains, with ZnO microcrystals near 0.05 wt.% delivering the best friction outcomes and the largest wear reductions (up to ~35%). In copaiba resin oil, nanocrystals produced small, sometimes non-significant improvements, whereas microcrystals tended to worsen wear consistent with abrasive third-body effects in a less polar matrix. In PNL30, the overall benefits were modest: nanocrystal additions generally increased wear, whereas microcrystals particularly at the highest loading 0.10 wt.% achieved a 36.4% reduction in SWR, representing a measurable and statistically significant improvement in wear resistance. These results highlight that eco-efficient lubricant design should co-optimize particle characteristics and dosage with base-oil polarity and film-forming tendencies, prioritizing dispersion stability alongside tribological targets. Full article

To investigate the effect of surface roughness on the fretting wear behavior of the Inconel 718 alloy, specimens fabricated by selective laser melting (SLM) were polished using SiC abrasive papers to obtain different surface roughness levels. Ball-on-flat tangential fretting tests were conducted under a normal load of 50 N, displacement amplitudes of 50 and 100 µm, and a total of 10⁴ cycles. The results reveal that all test conditions fall within the gross slip regime (GSR). The coefficient of friction was not significantly affected by surface roughness, while the energy dissipation per cycle exhibited a decreasing trend with decreasing roughness. The high-roughness surface (R_a = 0.80 µm) exhibited severe stress concentration, leading to asperity fracture and fatigue delamination. The medium-roughness specimen (R_a = 0.43 µm) developed a dense third-body layer, showing a synergistic mechanism of abrasive and fatigue wear. The low-roughness specimen (R_a = 0.07 µm) maintained a stable contact interface with sufficient debris evacuation, dominated by adhesive and abrasive wear. At a displacement amplitude of D = 100 µm, the wear depth reached −6 µm, indicating the largest material removal and the most severe damage. Full article

During the extrusion of novel nickel-based powder superalloy bars, the die is subjected to elevated temperatures, high pressures, and severe friction, which readily lead to abrasive wear and thermal-fatigue damage. These failures deteriorate the quality of the extruded products and significantly shorten the service life of the die. Frequent repair and replacement of the tooling ultimately increase the overall manufacturing cost. This study investigates the friction and wear behavior of H13 and 5CrNiMo hot-work tool steels under extreme transient high-temperature conditions by combining finite element simulation with tribological testing. The temperature and stress distributions of the billet and key tooling components during extrusion were analyzed using DEFORM-3D. In addition, pin-on-disk friction and wear tests were conducted at 1000 °C to examine the friction coefficient, wear morphology, and subsurface grain structural evolution under various loading conditions. The results show that the extrusion die and die holder experience the highest loads and most severe wear during the extrusion process. For 5CrNiMo tool steel, the wear mechanism under low loads is dominated by mild abrasive wear and oxidative wear, whereas increasing the load causes a transition toward adhesive wear and severe oxidative wear. In contrast, H13 tool steel exhibits a transition from abrasive wear to severe oxidative wear. In 5CrNiMo steel, friction-induced recrystallization, grain refinement, and softening lead to the formation of a mechanically mixed layer, which, together with a stable third-body layer, markedly reduces and stabilizes the friction coefficient. H13 steel, however, undergoes surface strain localization and spalling, resulting in persistent fluctuations in the friction coefficient. The toughness and adhesion of the oxide film govern the differences in wear mechanisms between the two steels. Owing to its higher Cr, V, and Mo contents, H13 forms a dense but highly brittle oxide scale dominated by Cr and Fe oxides at 1000 °C. This oxide layer readily cracks and delaminates under frictional shear and thermal cycling. The repeated spalling exposes the fresh surface to further oxidation, accompanied by recurrent adhesion–delamination cycles. Consequently, the subsurface undergoes alternating intense shear and transient load variations, leading to localized dislocation accumulation and cracking, which suppresses the progression of continuous recrystallization. Full article

Metal–organic frameworks (MOFs) and porous organic frameworks (POFs) have been extensively explored in recent years as lubricant additives for various systems due to their structural designability, pore storage capacity, and tunable surface chemistry. These materials are utilized to construct low-friction, low-wear interfaces and investigate the potential for superlubricity. This paper systematically reviews the tribological behavior and key mechanisms of MOFs/POFs in oil-based, water-based, and solid coating systems. In oil-based systems, MOFs/POFs primarily achieve friction reduction and wear resistance through third-body particles, layer slip, and synergistic friction-induced chemical/physical transfer films. However, limitations in achieving superlubricity stem from the multi-component heterogeneity of boundary films and the dynamic evolution of shear planes. In water-based systems, MOFs/POFs leverage hydrophilic functional groups to induce hydration layers, promote polymer thickening, and soften gels through interfacial anchoring. Under specific conditions, a few cases exhibit superlubricity with coefficients of friction entering the 10⁻³ range. In solid coating systems, two-dimensional MOFs/COFs with controllable orientation leverage interlayer weak interactions and incommensurate interfaces to reduce potential barriers, achieving structural superlubricity at the 10⁻³–10⁻⁴ level on the micro- and nano-scales. However, at the engineering scale, factors such as roughness, contamination, and discontinuities in the lubricating film still constrain performance, leading to amplified energy dissipation and degradation. Finally, this paper discusses key challenges in achieving superlubricity with MOFs/POFs and proposes future research directions, including the design of shear-plane structures. Full article

Ceramic-on-ceramic (CoC) bearings are widely used in total hip arthroplasty due to their extremely low wear rate, excellent chemical stability, and good biocompatibility. They are considered one of the most reliable long-term friction bearing systems. Although frictional instability, lubrication regime transitions, and microstructural damage mechanisms have been widely reported at the experimental and retrieval-analysis levels, current clinical evidence, limited by follow-up duration and event incidence, has not demonstrated a definitive negative impact on the clinical performance of fourth-generation ceramic components, including BIOLOX^® delta. Data from national arthroplasty registries consistently demonstrate excellent survivorship and low complication rates for 4th-generation ceramics in both hard-on-soft and hard-on-hard configurations. The most reported causes for revision, such as infection, dislocation, aseptic loosening, and periprosthetic fracture, are not primarily associated with ceramic-related complications, such as ceramic fracture, excessive wear, squeaking, and revision, related to bearing failure; however, these mechanisms remain highly relevant for the design and evaluation of emerging ceramic materials and next-generation implant systems, where inadequate control may potentially impact long-term clinical performance. This review summarizes recent advances in the tribological research of CoC artificial joints, focusing on clinical tribological challenges, material composition and surface characteristics, lubrication mechanisms, wear and microdamage evolution, and third-body effects. Recent progress in ceramic toughening strategies, surface engineering, biomimetic lubrication simulation, and structural optimization is also discussed. Finally, future research directions are outlined to support the performance optimization and long-term reliability assessment of CoC artificial joint systems. Full article

In this study, the microstructural, mechanical, wear, and corrosion behavior of Ni-Al-Cr and Ni–Al–Cr/SiC composite coatings with different composition ratios, produced by electric arc melting on Inconel 600 substrates, was systematically investigated. Microhardness measurements revealed a significant and consistent increase in the hardness values of the coatings depending on the increase in SiC reinforcement ratio (1%, 3%, and 5%). Wear tests showed that the coated samples exhibited significantly higher wear resistance compared to the pure Inconel 600 substrate. A significant improvement in wear resistance was achieved with the addition of SiC at 1% and 3% weight percentages; the width and depth of wear tracks were significantly reduced with SiC reinforcement. In contrast, increasing the SiC ratio to 5% weight percentage led to a decrease in wear resistance. This was attributed to particle aggregation at high SiC content, weakening of bonds at the matrix-reinforcement interface, and the behavior of SiC particles separated from the matrix as third-body abrasives. Electrochemical corrosion tests have shown that SiC-reinforced coatings form a more stable and permanent passive film, and corrosion resistance increases as the SiC content increases (1%, 3%, and 5%). The results indicate that the SiC reinforcement ratio affects the mechanical and electrochemical properties of Ni-Al-Cr/SiC composite coatings produced by electric arc melting. Full article

Silica-rich dust intrusion is a persistent challenge for lubrication systems in agricultural machinery, where abrasive third-body particles can accelerate wear and shorten component service life. Here, molecular dynamics simulations are employed to elucidate how SiO₂ nanoparticle contamination degrades polyalphaolefin (PAO) boundary lubrication at the atomic scale. Two confined sliding models are compared: a pure PAO film and a contaminated PAO film containing 7 wt% SiO₂ nanoparticles between crystalline Fe substrates under a constant normal load and sliding velocity. The contaminated system exhibits a higher steady-state friction force, faster lubricant film disruption and migration, and consistently higher interfacial temperatures, indicating intensified energy dissipation. Substrate analyses reveal deeper and stronger von Mises stress penetration, increased severe plastic shear strain, elevated Fe potential energy associated with defect accumulation, and reduced structural order. Meanwhile, PAO molecules store more intramolecular deformation energy (bond, angle, and dihedral terms), reflecting stress concentration and disturbed shear alignment induced by nanoparticles. These results clarify the multi-pathway mechanisms by which abrasive SiO₂ contaminants transform PAO from a protective boundary film into an agent promoting abrasive wear, providing insights for designing wear-resistant lubricants and improved filtration strategies for particle-laden applications. Full article

The wheel–rail friction coefficient is a critical factor influencing train traction and braking performance. Low-adhesion conditions not only limit the enhancement of railway transport capacity but are also the primary cause of surface damage such as scratches, delamination, and flat spots. This study employs femtosecond laser technology to fabricate wavy groove textures on U75V rail surfaces, systematically investigating the effects of the wavy angle and texture area ratio on friction enhancement under various medium conditions. Findings indicate that parameter-optimized textured surfaces not only significantly increase the coefficient of friction but also exhibit superior wear resistance, vibration damping, and noise reduction properties. The optimally designed wavy textured surface achieves significant friction enhancement under water conditions. Among the tested configurations, the surface with parameters θ = 150°@η = 30% demonstrated the most pronounced friction enhancement, achieving a coefficient of friction as high as 0.57—a 42.5% increase compared to the non-textured surface (NTS). This enhancement is attributed to the unique hydrophilic and anisotropic characteristics of the textured surface, where droplets tend to spread perpendicular to the sliding direction, thereby hindering the formation of a continuous lubricating film as a third body. Analysis of friction vibration signals reveals that textured surfaces exhibit lower vibration signal amplitudes and richer frequency components. Furthermore, comparison of Stribeck curves under different lubrication regimes for the θ = 150°@η = 30% specimen and NTS indicated an overall upward shift in the curve for the textured sample. The amplitude, energy, and wear extent of the textured surface consistently decreased across boundary lubrication, hydrodynamic lubrication, and mixed lubrication regimes. These findings provide crucial theoretical insights and technical guidance for addressing low-adhesion issues at the wheel–rail interface, offering significant potential to enhance wheel–rail adhesion characteristics in engineering applications. Full article