Wear最新文献

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.

Fabricating microstructures on the surface is an innovative method to mitigate cavitation erosion (CE), but there are few studies focus on the effects and mechanisms of microstructure spacing on CE performance. This study has prepared a regular dot array-shaped microstructure with different spacings on the surface of samples. The CE experiments were carried out on both the microstructured samples and smooth samples through a magnetostrictive-vibration cavitation facility. Mass loss measurement and microscopic morphology were utilized to reveal CE characteristics. Numerical simulation was used to study the parameters of the flow field. The results clearly show that the microstructure spacing of 0.25 mm, 0.50 mm, and 1.00 mm samples can improve CE resistance. On these microstructured surfaces, the volume fraction of vapor is reduced and the bubbles move away from it. However, when the microstructure spacing enlarges to 1.50 mm, the damage inside the microstructure groove increases, which will reduce the CE resistance of the materials. As the spacing increases, the volume fraction of vapor on the sample surfaces will increase, and the bubbles in the microstructure groove will congregate, resulting in increasing damage. The research provides the dimensional basis for designing cavitation-resistant surface microstructures.

In heat exchanger applications, the random vibration due to fluid excitation can cause mechanical wear between tubes and supports. In corrosive environments, the synergy between wear and corrosion can make wear more severe. Therefore, this paper focused on the effects of excitation amplitude and excitation force ratio (drag force/lift force) on fretting wear and corrosion of 316L stainless steel under random impact-sliding conditions. The results showed that as the excitation parameters increased, the friction coefficient and total wear amount would increase, the open circuit potential (OCP) decreased and the polarization curve self-corrosion potential shifted negatively. All synergistic coefficients in this paper were greater than 1, indicating that there was an obvious positive synergy between wear and corrosion. In the fretting wear and corrosion process, pure wear always played a dominant role. Under impact-sliding conditions, as the excitation force increased, the rate of wear-promoted corrosion increased from 3.0 × 10⁻⁷ to 2.0 × 10⁻⁶ g/h, an increase of 6.67 times. However, the rate of corrosion-promoted wear decreased from 1.1 × 10⁻⁶ to 2.0 × 10⁻⁷ g/h, a decrease of 5.5 times, showing a certain self-limiting property. The total synergy rose slowly with the increase of excitation parameters. The wear mechanism of materials under impact is characterized by adhesive wear, while under impact-sliding conditions, the wear mechanism involves abrasive wear and corrosion wear.

Silicon carbide (SiC) as a difficult-to-process material is hard to achieve ductile grinding completely, and is likely to occur brittle breakage with low processing efficiency, leading to its low performance, therefore, it is necessary to study its removal mechanism to improve the processing quality. The removal mechanism of single grit cutting is well understood. In the real processing of SiC, there are multiple grits at different positions to remove the materials simultaneously, but the phenomenon of materials removal by multiple grits cannot be observed separately. In order to clarify the interference behavior of neighbored grits, current study conducted a neighbored scratch experiment under varied force in sequence. The experiment evidently revealed the deformation, pits, fracture morphology and removal modes under different interference conditions. Since in-situ monitor of materials removal is unable to be realized, a numerical model with different scratch intervals by coupling the smoothed particle hydrodynamics (SPH) and finite element method (FEM) was used to understand the material damage and stress distribution. Based on the observation from experimental and SPH-FEM results, a theoretical model of neighbored scratch stress field is established to explain the mechanism from plastic and fracture mechanics. From the model, the size of the plastic zone and the interval between the neighbored plastic zone are critical to control the interference mode. The interference mode affects the distribution of stress field and realizes the enhancement effect of material removal. Therefore, the materials removal model could be adopted to control the grinding efficiency and quality in industry.

Lubrication conditions are an important factor affecting both the machining efficiency and quality of 4H–SiC. To investigate the tribological behaviors under different lubrication conditions, a series of scratching experiments are conducted under different loads and environments. The X-ray photoelectron spectroscopy (XPS) surveys and atomistic simulations are used to explain the different tribological behaviors. Both experimental and simulation results show that liquid lubrication can significantly reduce the coefficient of friction (COF) and minimize structural damage. Compared to pure water, the H₂O₂ solution is more conducive to the oxidation of SiC atoms and the modification of tribological behaviors. However, the difference in tribological behaviors between H₂O₂ solution and pure water diminishes as the load increases. The XPS surveys show that the liquids lead to higher-order oxidized species of SiC atoms, such as Si₄C_4-xO₂ and Si-O_x-C_y, which are also observed in the simulation results. It is shown that the oxidized species can reduce the direct bonding between SiC and diamond indenter, which is an important reason for the lower COFs in the liquids. Since the liquids can reduce the direct bonding and mechanical interaction between 4H–SiC and diamond, the material removal rate is much lower under lubrication conditions.

The thread-pairs wear has a significant role in the transmission accuracy, operational stability and service life of planetary roller screw mechanism (PRSM). Nevertheless, the previous literatures still lack the investigation on the wear evolution of roller, nut and screw. Hence, an accumulative wear depth (AWD) prediction model is proposed for PRSM with reciprocating motion. The presented model is validated by the measured wear phenomena of thread pairs and the experimental results in the literature. The equivalent sliding wear experiment of PRSM is designed and the sliding wear coefficient of PRSM material is obtained by the equivalent sliding wear experiment. Considering the thread profile error caused by AWD of roller, nut and screw, the load distribution (LD) and sliding velocities on screw-roller (SR) and nut-roller (NR) sides are calculated. More importantly, the interactions between the AWD, LD and sliding velocity are investigated. Furthermore, the effects of axial load on the AWD, sliding velocities in contact regions and load distribution coefficient are analyzed.

In order to modify the wear resistance of Stellite 6 superalloy as wear resistant coating at room temperature-1000 °C, the different contents (1.0, 2.5 and 4.0 wt%) of ZrO₂ reinforced Stellite 6 matrix coatings were fabricated over the Inconel 718 nickel alloy substrate by laser cladding technology. The microstructure, hardness and high-temperature wear behavior of Stellite 6 matrix coatings with ZrO₂ was systematically studied. The sliding wear test were done using a ball-on-disk tribometer against Si₃N₄ at room temperature-1000 °C. The results showed that the ZrO₂ showed obvious fine-grain strengthening and dispersion strengthening effect. The hardness of coatings reinforced by ZrO₂ were 470–540 Hv. A critical valve of ZrO₂ content was existed for the wear performance of Stellite 6 matrix coatings. The coating with 2.5 wt% ZrO₂ had the desirable wear resistance, and the wear rate was in the order of 10⁻⁵ mm³/N.m. This was attributed to the high microhardness and the formation of solid lubricants, as well as the friction film on the sliding surfaces.