Wear最新文献

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.

In this study, we investigated the interactions between BN and B₄C particles in particle reinforced Al matrix composites (PRAMCs) during friction stir processing (FSP), focusing on particle distribution, microstructure evolution, hardness, and wear resistance. PRAMCs were fabricated with BN accounting for 0 wt%, 10 wt%, 20 wt%, 30 wt% and 100 wt% of the reinforcement particles. Optical microscopy (OM) and scanning electron microscopy (SEM) revealed that particle distribution varied through thickness, becoming more inhomogeneous with increasing BN mass ratio. The most uniform distribution was noted 3 mm beneath the surface, particularly in the BN-30%-3 mm sample. This sample also showed improved homogeneity in B₄C distribution, as confirmed by the box-counting (BC) method. The refined grain structure due to particle stimulated nucleation (PSN) and Zener pinning contributed to an average hardness of 96.67 HV in the BN-30%-3 mm sample, significantly enhancing wear resistance. The wear rate in this sample was reduced by 97.2 % compared to the FSP-3 mm sample, likely due to finer grains, higher hardness, and increased reinforcement, which collectively reduced adhesion and fatigue wear.

The development of modern brake systems requires the assessment of multiple aspects. Among these, parameters related to the tribological behaviour, vibration, and particulate matter emission are typically evaluated using inertia dynamometers and tribometers. While these two testing systems have been previously compared regarding emissions and tribological behaviours, vibrations were not compared, nor have all these aspects been examined simultaneously. This study investigates the scale effects between a pin-on-disc tribometer and a reduced-scale dynamometer operating under dragging conditions with two levels of pressure and velocity, and a disc temperature not exceeding 260 °C. Regarding the vibration, the pin-on-disc exhibited higher and broader values in the normal direction, 1.3–15.5 m/s², than the reduced-scale dynamometer, 0.37–0.42 m/s², while the tangential vibrations exceeded those in the normal direction in both systems. The wear rates in the two systems were overall similar, in the range of 1–4 e−14 m²/N. During the tests the disc temperature in the dynamometer increased at a higher rate compared to the pin-on-disc, affecting the tribological and emission behaviours: steady state values were obtained only in the pin-on-disc tests. The particulate concentration values observed during dynamometer tests better correlated with the peak values from pin-on-disc tests rather than with the steady-state values. This study highlights the importance of including transient values in the evaluation of pin-on-disc testing.

Strong-bonding MoB/Cu laminated (MCL) composites are fabricated by the hot-press method at 1030 °C for 1 h under 20 MPa pressure. The microstructure, tribological properties, and elemental microanalysis are systematically investigated. The structure parameters of laminated composites play a key role in the properties of friction and wear resistance. The average friction coefficient is below 0.3 and the wear rate is almost one order of magnitude lower when the measured ratio of copper thickness to MoB thickness is below 4, compared with the sample whose λ equals 13. The primary phases of MCL are Al₂O₃, Cu(Al), and MoB. They helped the lubricating film to form on the worn surface during the wear process. These tribo-films effectively moderate the wear while safeguarding the metal matrix.