Wear最新文献

This study presents a comprehensive analysis using an innovative testing method of two wheel steels paired with cast iron and organic composite brake block materials. By conducting tests under consistent conditions and varying in duration, the study examines temperature profiles, friction coefficients, surface characteristics, weight loss, and microstructural changes in wheel samples, emphasizing the distinct behaviour of these materials in braking applications and the damage evolution over time. The results demonstrate that organic composite brake samples outperform those in cast iron, showcasing smoother wheel sample surfaces and stable friction coefficients. Weight loss analysis reveals the environmental benefits of organic composite brakes, emitting fewer particulates than cast iron counterparts. Microstructural examinations uncover the formation of a Thermal White Etching Layer (T-WEL) on wheel samples tested with cast iron samples, leading to cracks and material detachment. Conversely, extended use of organic composite samples led to a "thermal fuse effect", impacting their efficiency and suggesting the need of careful temperature management in sustained braking scenarios. Despite significant differences in wheel steels, the study underscores the critical role of brake material in braking improvements. The findings not only enhance the scientific understanding of brake material behaviour but also introduce an innovative, cost-effective, and fast 4-contact machine testing method.

In order to improve the wear resistance of Inconel 617 alloy, Ni/WC composite coatings were prepared on it by High-Velocity Oxygen Fuel (HVOF) and electron beam remelting techniques. The effects of remelting beam current (16 mA–25 mA) on the macroscopic morphology, physical phase composition and microstructure of remelted coatings were investigated. The effect of microcomposition on the mechanical properties of remelted coatings was analyzed in combination with hardness tests and friction wear experiments. The experimental results showed that good metallurgical bonding was formed for 19 mA, 22 mA and 25 mA specimens after electron beam remelting. The bonding of the 16 mA specimen was a combination of metallurgical and mechanical bonding. The remelted coating generated new phases such as W₂C, M₃B and Cr₂₃C₆. With the increase of remelting beam current, the WC decomposition became more and more serious, and the grain growth tendency was evident. The remelted coatings prepared with different parameters showed a significant increase in microhardness compared to both the substrate and HVOF coatings. Friction wear experiments with SiC balls as counterbodies show that the wear increases gradually with increasing beam flow at 100 N and under dry friction conditions. The wear mechanism of HVOF coatings was abrasive, and the wear mechanism of remelted coatings was mainly abrasive and adhesive. In summary, the 22 mA specimen had a strong metallurgical bond. The hardness and abrasion resistance were improved compared to the substrate and the HVOF coating, i.e., the 22 mA specimen had the best overall performance.

The present study systematically compared the cavitation erosion (CE) and slurry erosion (SE) resistance of 0Cr12Ni9A and 0Cr17Ni4Cu4Nb coatings fabricated by high power laser cladding (HPLC) and the differences in CE and SE resistance were revealed by combining microstructure and mechanical properties. The experimental results indicated that the build rate of HPLC reached 256 mm³/s, which was much higher than that achieved by traditional low power laser cladding (154 mm³/s). Furthermore, the hardness (50 HRC), ultimate tensile strength (1370 MPa), yield strength (1349 MPa) and break elongation (11.5 %) of 0Cr12Ni9A coating were 1.11 times, 1.12 times, 1.25 times and 0.59 times that of 0Cr17Ni4Cu4Nb coating, respectively. The CE and SE resistance of the 0Cr12Ni9A coating were 9.51 times, 0.63 times (attack angle $\alpha$ = 45°) and 1.23 times (90°) than that of the 0Cr17Ni4Cu4Nb coating and 22.87 times, 1.32 times (45°), 1.91 times (90°) than that of the 0Cr13Ni5Mo substrate, respectively. The cladding layers with high hardness and strength exhibits enhanced CE and SE (90°) resistance due to the higher resistance to plastic deformation and failure when facing the vertical impact of cavitation bubble collapse or sand particles. However, the SE resistance (45°) is related to the unit volume fracture energy, with a higher value indicating more effective absorption of kinetic energy from impacting sand particles, resulting in reduced flaky peeling off for improved SE resistance. The high build rate of HPLC and the exceptional CE and SE resistance of 0Cr12Ni9A coating material provide a novel solution to extend the service life of Pelton turbines.

This study investigates the phase transition of austenite into strain-induced martensite during the long-term rolling contact wear. The transformation of the non-ferromagnetic austenite to the ferromagnetic martensite is studied as a function of rolling contact duration under the constant roller load and rotation. X-ray diffraction technique and scanning electron microscopy demonstrate that the intensity and extent of strain-induced phase transformation are progressively growing along the rolling duration. Furthermore, it is also found that the extent of this transformation is non-homogenous with respect to the produced wear track width when the highest intensity can be found near the grove centre, and a progressive decrease is detected towards the wear track edge. Compressive residual stresses are produced in both crystalline phases. However, their nearly unaffected amplitude with the rolling duration for the martensite phase is contrasted with the gradually decreasing amplitude of the austenite phase, which indicates the thermal effect. The surface temperature increases due to friction, plastic deformation and the phase transition. It has been proved that the Barkhausen noise technique integrates signals from the whole wear track width as well as quite deep regions below the wear track surface. Barkhausen noise exhibits continuous and progressive increase with the rolling duration as it is contrasted with the X-ray diffraction. Consequently, the Barkhausen noise technique was found to be the more reasonable experimental technique to study the progressive propagation of the phase transition into the bulk material than the X-ray diffraction.

Wear-failure is the most common damage for power transmission components in the field of engineering materials, constituting approximately one-fourth in service loss. The development of high wear-resistant Al alloys plays a crucial role in reducing energy demand and weight, and then attributes to the achievement of dual-carbon target. Here we report a novel strategy to develop outstanding wear-resistant (the coefficient of friction of 0.31) Al-10 wt%Si alloys at room temperature, based on the formation of multiple parallel {111} twins and hierarchical {111}-{111} double twins by a route of combining ultrahigh pressure solid solution and electropulsing assisted aging (HPEP), which overwhelms all values of Al alloys, even Ti alloys and high entropy alloys reported so far. The microstructure, formation process and wear-resistant mechanism of nano-twinned Si have been clarified by transmission electron microscopy observations, molecule dynamics simulations and the first principles calculations. It demonstrates that the interactive nano-twinned Si structures are mainly introduced through twin-twin collision or the phase/matrix interface prohibition of twin motion, which are effective to restrain atom separation in contrast to eutectic Si perfect crystal, resulting in homogeneous wear-loss and long operation life. Those new results provide insights towards designing wear-resistant materials with high mechanical properties.

Bulk metallic glass (BMG), also known as amorphous alloy, which is almost free of structural defects such as grain boundaries and dislocations, is expected to achieve superior cavitation erosion (CE) resistance due to possessing high hardness, elastic modulus and superior corrosion resistance. Compared with the extensively studied crystalline alloys, the damage mechanism of amorphous alloys under CE remains unclear. Herein, the CE behavior and damage mechanism of a Zr-Ti based BMG in deionized water was systematically investigated. Relevant results showed that Zr-Ti based BMG exhibited robust resistance to CE in deionized water. The incubation period of CE was found to be about 4 h, which was significantly longer than that of stainless steels, copper alloys and titanium alloys. Moreover, grazing incidence X-ray diffraction analysis indicated that crystallization was absent throughout the entire CE process. Differential scanning calorimetry demonstrated an increasing free volume of BMG with prolonged CE time, which further led to the formation of micro-porosity by the free volume aggregation, and eventually gave rise to the CE damage.

The growing interest in gear scuffing research primarily stems from the escalating standards and operation requirements in aero-engines and electric vehicles, particularly under high-temperature, high-speed, and heavy-load conditions. Existing calculation standards for gear scuffing often deviate when evaluating the load-carrying capacity under different rotational speeds or oil temperatures, thus undermining the reliability of gear scuffing assessments. To address this, thirty-five sets of gear scuffing experiments were conducted with different materials, manufacturing processes, and lubrication conditions. A new evaluation method based on the pressure-velocity-temperature (PVT) limit was proposed for assessing gear scuffing resistance. Using a non-dominated genetic algorithm, exponent coefficients for the contact pressure P, sliding velocity V, and lubricant temperature T were determined. The results demonstrated that the proposed PVT limit effectively evaluates gear scuffing resistance across various conditions. The PVT limits across different operating scenarios, under the same material, manufacturing process, and lubrication conditions, showed a maximum deviation of 6.6%. Conversely, the scuffing temperatures calculated using ISO 6336-20-2017 and AGMA 925-A03-2003 standards deviate from experimental results by up to 36.7% and 32.8%, respectively. Further application of the PVT limit to an aero-engine accessory gearbox confirmed the practical applicability of the proposed method.

Amorphous alloy coatings, known for the exceptional wear resistance, have emerged as a key solution for enhancing the wear performance of magnesium alloys under harsh environments. In this study, Fe-based amorphous alloy coatings were deposited on magnesium alloy by cold spraying technology, and the influence of microstructural evolution on the wear performance of coatings under dry sliding wear conditions was discussed. The results showed that a dense adherent oxide layer with a thickness of ∼700 nm comprising nanograins of less than 8 nm was formed at the outmost surface, which played a role of self-lubricating. Underneath, a 1 μm thick nanocrystalline-amorphous layer with nanograins of ∼20 nm dispersed in the amorphous alloy matrix was formed through in-situ crystallization induced by flash temperature. This composite structure prevented the formation of shear bands in amorphous alloys and enhanced the durability. Therefore, the transition from abrasive wear to adhesive wear was a consequence of the microstructural evolution from a dual-phase composite layer to a self-lubricating oxide layer.

The outstanding strength-to-weight ratio and corrosion resistance of titanium have made it the material of choice in the aerospace industry and medicine. The alpha–beta alloy Ti6Al4V is particularly preferred for its excellent mechanical and bio-compatible properties. Despite its advantages, the low thermal conductivity and poor tribological performance of titanium pose significant challenges during manufacturing and in operation. This research offers deep insights into the high strain rate behavior of Ti6Al4V under abrasive load, such as e.g. experienced in machining, by modifying the standard scratch test setup and using optimized Johnson–Cook material parameters to perform Material Point Method (MPM) simulations. The MPM simulations provide accurate predictions of the data gathered through high strain rate scratch experiments. We found an increase in the von Mises stress distribution as well as the normal and tangential forces required to perform a scratch of the same depth as the strain rate increases. The morphology of the scratch profiles also showed an increase in the height of the ridges that form as the scratching speed increases. These findings are in line with the increase in yield strength and work hardening with growing strain rate. This study bridges the gap between simulation models and experimental observations by providing insights for improved machining strategies and surface treatments that can enhance the performance of Ti6Al4V in demanding applications.