Wear最新文献

In this work, wear mechanisms of electrodeposited Ni–W and Ni–W/Al₂O₃ coatings sliding against Si₃N₄ and AISI 52100 steel have been comparatively studied. For both Ni–W and its composite coatings sliding against Si₃N_4, worn morphology shows the tribochemical reaction (tribooxidation) followed by abrasive wear is the dominated mechanism. Comparing with Ni–W coatings, the protective oxide layer is slower peeled off at tribooxidation stage and wear debris are easier squeezed on the Ni–W/Al₂O₃ during abrasive wear stage. The incorporated Al₂O₃ provide load bearing effect during microploughing and improve the wear resistance. As sliding against AISI 52100 steel, wear rate of Ni–W/Al₂O₃ is several times higher than that of Ni–W coatings. Conformity between surfaces of the Ni–W coating and counterbody leads to mild smoothening wear, while the plastic deformation dominated delamination makes severe wear of Ni–W/Al₂O₃. Deformation resistance of the coatings and transition of counterbodies materials from ceramic to hard metal are responsible for the different wear mechanisms. For Si₃N₄ ceramic, low thermal conductivity leads to tribooxidation followed by abrasive wear of both Ni–W and Ni–W/Al₂O₃ coatings. Relatively high deformation resistance of Ni–W coatings is responsible for the conformity as the premise for mild wear sliding against AISI 52100. Low deformation resistance of composite coatings induced by weak interfaces between Al₂O₃ and Ni–W matrix makes delamination sustained.

High-speed train brake discs, relying on surface friction for braking, can reach up to 600 °C, significantly increasing wear and adversely affecting performance and lifespan. Here, we propose a facile approach employing ultrasonic shot peening with the addition of cobalt (Co) particles (termed UEG) to creates a dense Co-containing coating on the 24CrNiMo steel. Friction tests show that UEG samples exhibit more stable friction coefficients and lower wear rates at temperatures ranging from 25 to 600 °C. Experimental and analytical results reveal a higher dislocation density in the UEG-treated samples surface and the formation of a dense Co-enriched tribofilm, effectively enhancing wear resistance. The findings indicate that UEG has considerable promise for enhancing the wear resistance of brake discs in high-temperature environments.

This paper reviews the behaviour of CVD diamond coatings when subjected to solid particle erosion. The high hardness, elastic modulus and strength of diamond coatings make them attractive options for use in components employed in erosive environments. Nevertheless, despite the disparity in properties between diamond and many common erodents such as silica, which can result in extensive damage to the impacting particles, repeated particle impacts can generate damage to the coating resulting in sudden and catastrophic failure. The factors affecting the erosion behaviour of diamond coatings are described, as well as the common features of erosion damage in diamond coatings, together with the mechanisms by which they were formed. Such understanding can assist in the design of coated components for use in erosive environments.

Polymer composites are increasingly used as frictional components due to their self-lubricating properties. However, they tend to exhibit severe wear during the running-in stage, thus significantly impairing their service life. In the present work, a dual-pin-on-disk (DPOD) method is developed in order to reduce the running-in wear of a polytetrafluoroethylene/alumina (PTFE/Al₂O₃) composite when sliding against GCr15 bearing steel by introducing an assistant polymer component during the running-in stage. The results show that the running-in wear rate of the main polymer pin is reduced by up to 77.26 %. This is because the assistant pin causes excess wear debris to be released into the wear track and provides a higher shear force, thereby promoting the tribological chemical reactions and facilitating the generation of tribofilms on the worn surfaces. In addition, the processed polymer achieves a wear rate similar to that of the conventional single pin condition (∼3 × 10⁻⁷mm³/Nm) in the subsequent steady-state stage. The results of the present work are expected to increase significantly the wear life span and application prospects of the polymer composites.

Boron nitride nanosheets (BNNS) possess extensive potential applications across various fields. However, their limited dispersibility in liquids constrains their effectiveness as lubricating additives. In this study, a streamlined sugar-assisted mechanochemical exfoliation technique was employed to concurrently exfoliate and functionalize BNNS. This approach enabled the covalent grafting of sucrose molecules onto BNNS, enhancing their dispersion in water. The application of water containing sucrose-modified BNNS (S-BNNS) facilitated an ultralow coefficient of friction (COF = 0.001) at the Si₃N₄-Si₃N₄ interface. Additionally, using S-BNNS nanosheets as lubricating additives in water achieved superlubricity with a significant surface roughness (Ra ≤120 nm). We explored the correlation between surface roughness and superlubricity, revealing that tribological performance was enhanced by the formation of a tribofilm composed of S-BNNS and a silica layer at the interface through tribochemical reactions. The exceptional anti-wear properties and significantly reduced shear strength of S-BNNS within the tribofilm substantially contributed to achieving the ultralow COF, thus enhancing lubrication performance.

In this study, the reducibility from silicate minerals is determined and its effect on their tribological properties as lubricant additive is introduced firstly with magnesium silicate hydroxide (MSH) and biocarbon-modified magnesium silicate hydroxide (MSH@C) as operating medium. The differentiated reduction effects induced by MSH and MSH@C are clarified through worn surface analysis, and related tribological tests are conducted on a four-ball machine under different conditions. Results show that biocarbon surface-coating on MSH will enhance the reducibility of MSH and results in better lubrication performance (wear reduced by 10.487 % and friction reduced by 11.321 % under boundary lubrication while wear reduced by 16.566 % and friction reduced by 33.871 % under mixed lubrication compared with MSH) by reducing Fe₂O₃ to Fe₃O₄ more effectively on worn surfaces. Besides, the reduction mechanisms of MSH and MSH@C on iron oxides are explained.

The development of high-performance water-based lubricating additives with excellent properties has been the focus of research recently. Herein, carbon-based nanomaterials made of spherical fullerenol and lamellar graphene oxide (GO) were explored as water-based lubricating additives to enhance tribological properties via the response surface method systematically. The antiwear mechanisms of the carbon-based nanomaterials were revealed through simultaneous wear surface characterizations and molecular dynamics simulations. Results showed that the spherical fullerenol and lamellar GO had superdispersion stability in the water-based lubricants. Fullerenol and GO could play a superior synergistic role to considerably enhance the antiwear properties of the water-based lubricants. Particularly, the wear rate decreased by almost 93 % when the water-based lubricant was supplemented with fullerenol and GO (0.1 wt% each) at the load of 1.5 N and sliding speed of 30 mm/s. The antiwear mechanisms indicated that an excellent antiwear effect was produced by the stable tribofilms containing GO and fullerenol, which combined with hydration layers synergistically exerting a bearing capacity.

Poly-ether-ether-ketone (PEEK) and PEEK composites are widely used polymers in many engineering applications where dry sliding is required. In this study, the influence of sliding velocity and applied load values on the friction and wear behavior of pure PEEK, 30 wt% glass fiber reinforced PEEK (PEEK-30GF), 30 wt% carbon fiber reinforced PEEK (PEEK-30CF) and 10 wt% carbon fiber+10 wt%graphite +10 wt%poly-tetra-fluoro-ethylene (PTFE) filled PEEK (ie. High (H) pressure (P) and velocity (V) resistant PEEK (PEEK-HPV)) composites rubbing against AISI 304 stainless steel disc was investigated. The experiments were carried out at room temperature under dry sliding conditions in a pin-on-disc wear rig. The applied loads ranged from 30 to 250 N, while the sliding velocities ranged from 1.0 to 4.0 m/s. At these load and velocity ranges, the friction coefficient-wear rate relationship of pure PEEK and composites was established and evaluated. In addition, the operating load-velocity limits of each material were determined and stated. The lowest coefficient of friction and wear rate were obtained in PEEK-HPV, PEEK-30CF, PEEK-30GF composites and pure PEEK polymer, respectively. In addition, it was observed that the coefficient of friction (CoF) decreased and the specific wear rate (SWR) increased with the increase in sliding velocity and applied load in all PEEK materials. The wear rate values of PEEK-HPV and PEEK-30%CF composites are in the range of 10⁻⁷ - 10⁻⁶ (mm³/Nm), while the wear rate values of pure PEEK and PEEK-30%GF are in the range of 10⁻⁶ - 10⁻⁵ (mm³/Nm). It was determined that carbon fiber, graphite and PTFE additives added to PEEK polymer as hybrid were very effective in reducing the wear rate of PEEK composite (PEEK-HPV). An adhesive wear mechanism was observed in PEEK-HPV and PEEK-30CF composites both at low load and velocity values and at high load and velocity values.

This study developed a numerical model that coupled transient lubrication and wear in misaligned main bearings under dynamic loading conditions. This model accounts for variations in oil film thickness attributable to journal misalignment, elastic deformation, wear, and temperature fluctuations during the operational cycle of the bearing. Validation of the model's accuracy is achieved through comparisons of bearing temperature, and wear depth. An extensive analysis is conducted on the temporal evolution of temperature, contact pressure, oil film pressure and thickness, wear depth, and wear loss. Comparative assessments between misaligned and aligned bearings are performed. The findings reveal that in cases of journal misalignment, wear depth and contact pressure predominantly accumulate on the edge side, with the maximum wear depth, peak oil film pressure, peak asperity contact pressure, and temperature significantly exceeding those in aligned conditions. Furthermore, to underscore the importance of incorporating temperature in the coupling model, a comparative analysis of lubrication and wear characteristics between isothermal and thermal models across varying radius gaps is conducted. It indicates the necessity of factoring in temperature effects when assessing lubrication and wear properties. It is observed that bearing temperature tends to decrease correspondingly with wear progression.

Recently, energy and environmental crises have aggravated sharply, which results in the eco-friendly and high-efficiency polyethylene glycol (PEG) lubricating oils getting increasingly attention in lubrication. Advancing in PEG-based lubricating oils, especially their high-performance nano-additives is vitally important for energy conservation and reducing pollution. Therefore, a kind of surface and core dual-designed carbon dots (Zn,Cu,Fe-CDs_-N) modified by ionic liquid groups ([AMIm][N(CF₃SO₂)₂]) and doped by polymetallic atoms (Zn, Cu, and Fe) were first synthesized and creatively used as the nano-additives for the PEG200 base oil. Adding 1.0 wt% of Zn,Cu,Fe-CDs_-N can endow the PEG200 base oil with optimal friction-reduction, anti-wear, and load-supporting performances, the maximal increase amplitudes of approximately 46.6 %, 66.3 %, and 125.0 %, respectively. Additionally, the tribological properties of Zn,Cu,Fe-CDs_-N are without any weakening even under high load and long-time operating conditions, exhibiting good practicability and application prospects. Theoretical and experimental studies have illustrated the excellent tribological behaviors of Zn,Cu,Fe-CDs_-N assigned to the synergy of film-forming and nano-lubrication effects.