Hard Particles Research Articles

Locally Curved Surface with CoN4 Sites Enables Hard Carbon with Superior Sodium‐Ion Storage Performances at −40 °C

AbstractThe impressive electrochemical performance of sodium‐ion batteries at low temperatures has long been recognized as a promising technical advantage. However, the inadequate transport kinetics of Na+ ions and complex interfacial reactions at the hard carbon anode surface hinder the practical implementation of commercial sodium‐ion batteries. Herein, a novel approach to address this issue by introducing a homogenized functional carbon coating layer with a locally curved configuration is proposed. This coating layer is designed to accommodate single CoN4 sites on the surface of commercial hard carbon particles, resulting in enhanced sodium storage performance at low temperatures. The surface‐modified hard carbon anode material (HC‐Z1) demonstrates a commendable rate performance of 220.6 mAh g−1 at 3 A g−1@25 °C and a substantial reversible capacity of 288.7 mAh g−1 with an 89% capacity retention at 0.06 A g−1@‐20 °C. Furthermore, even at a temperature as low as −40 °C, the reversible capacity remains at 270 mAh g−1 at 0.06 A g−1. Extensive characterizations and theoretical calculations provide evidence that the optimized interface between the electrode and electrolyte effectively enhances the desolvation and migration of Na+ ions, particularly at low temperatures.

A Review on Distribution of Reinforcement and tensile Strength of Aluminum Lithium Alloy based Nano Metal Matrix Composites Fabricated by STIR Casting

Aluminum Alloy (AA) parts are employed in lightweight engineering fields and have poor mechanical, wear, and corrosion resistance. Aluminum Matrix Composites (AMCs) are materials created by incorporating hard reinforcing particles into an aluminum matrix alloy. The new material has improved characteristics, including higher specific stiffness and strength, as well as higher corrosion resistance, elastic modulus, wear resistance, and low weight. Metal Matrix Composites (MMCs) are composite materials in which metal serves as the matrix and hard particles or ceramics serve as reinforcement. MMCs are used to improve the functionality of a wide range of technical materials. It could be used in many different fields, including aerospace, automotive, space travel, and medicine. In this paper, the reviewer investigates the distribution of reinforcement and Tensile Strength (TS) of Aluminum Lithium (Al-Li) Alloy/Nano Al2O3 MMC fabricated by stir casting. Finally, the authors provide a comparative analysis of prior reviewed research papers. After comparative analysis, TiB2/2195 composite has higher Tensile Strength (115.4%) than the other composite such as AA7010-TiB2 (260%), Al2O3 + SiC (72%), A356/SiC (21.87%), and Al-SiC (37%).

Arc erosion resistance of Al2O3–Cu/35Mo composites reinforced by trace graphene oxide

In this study, Al2O3–Cu/35Mo composites were prepared by rapid hot-press sintering-internal oxidation method, and the materials were modified by adding trace amounts of graphene oxide (GO). The results show that the relative densities of the composites are above 99%, the γ-Al2O3 generated by internal oxidation is diffusely distributed on the copper matrix. The incorporation of GO produced a small number of hard MoC particles at the interface, which facilitated the interfacial bonding of the composites. In the 30 V DC, 10–30 A electrical contact test, the anode mass of the composites increases, while the cathode mass decreases. And GO reduces the total mass loss of the electric contact by 63.6%, 38.9%, 51.3% and 20.9%, respectively. A comparison of the electrical contact properties of the two materials showed that the addition of GO dispersed the concentrated erosion of the arc. At 10 A and 30 A, the arc energy is reduced by 75.5% and 12.5%, respectively. With the gradual increase in electric current, GO makes the Al2O3–Cu/35Mo composites more stable during the electric contact process, improves the anti-welding ability of the contact and reduces contact resistance.

Physics based models for characterization of machining performance – A critical review

This paper presents a comprehensive review of the concept of machinability by considering the dynamic, tribological, and thermo-mechanical interactions encountered at the tool-chip-machined surface interfaces. The paper provides a demonstration of the capabilities and gaps of the physics-based models for the characterization of the machining performance and the prediction of machinability of difficult-to-cut materials, including additively manufactured (AM) materials, nanocrystalline (NC) materials, fibre reinforced polymers (FRP), metal matrix composites reinforced with ceramic hard particles (MMC), and ceramic matrix composites (CMC). The utilization of efficient computation methods for accurate prediction of force, torque, power consumption, cutting temperature, deflection errors, vibration amplitudes, chatter stability, and thermomechanical interactions in the tool-workpiece system is discussed. The development of thermally-activated dissolution-diffusion wear models to describe the chemical reactions at the tool-chip-workpiece contact interfaces is also presented. These predictions are critical for identifying multi-objectives optimal machining conditions. The integration of predictive machining models within the framework of digital twins in cyber-physical spaces, for in-process monitoring and adaptive control, is demonstrated. Future research for developing new models that can characterize the machinability of AM and NC materials, by considering the effects of varying material microstructure and anisotropy, is presented for conventional and micro-machining operations.

The production of $B_{4}C$ reinforced metal matrix composite from waste $AZ91$ magnesium alloy using the ball milling method

In this study, the Mg/$B_4$C composite reinforced with boron carbide particles was produced by mechanical milling method using waste AZ91 magnesium alloy chips. The mechanical and tribological properties of the produced composites were investigated through hardness and wear tests. A mixture of AZ91 magnesium alloy chips, aluminum, and $B_4$C powders was milled at a rotation speed of 300 rpm with a ball-to-powder ratio of 20:1 for 3 hours. The milled powders were first cold pressed and then sintered at 550 °C for 3 hours. In density measurement, it was observed that the sample reinforced with B4C exhibited an increase in density. In X-ray diffraction analysis, peaks corresponding to Mg, $Mg_{17}Al_{12}$, and MgO were detected, while the $B_4$C phase could not be identified. On the other hand, $B_4$C particles in the microstructure were revealed in the energy dispersive X-ray spectroscopy analysis. Scanning electron microscope images revealed that the Mg/$B_4$C composite had lower porosity, consistent with density measurements. It was found that the hardness and wear resistance of the Mg/B4C composite were higher than those of the Mg alloy, which can be attributed to the presence of homogenously distributed hard B4C particles within the microstructure.

Enhanced wear resistance of Ni-Mo-TiN composite coating by synergistic effect of tough Ni-Mo matrix and hard TiN particles

To improve the wear resistance of the metallic components, Ni–Mo-TiN composite coating was prepared via pulsed electrodeposition. The microstructure, mechanical, and tribological characteristics were compared to those of Ni–Mo coating. The results revealed that the addition of TiN reduced internal stress within the Ni-Mo-TiN composite coating and mitigated the propensity for crack formation during both the coating preparation and friction testing. Grooves and pits are observed on the Ni-Mo coating, indicating a typical feature of fatigue wear. Owing to the synergistic effect of the tough Ni-Mo matrix and hard TiN particles, the Ni-Mo-TiN coating was characterized by micro-cutting and superior wear resistance. Based on the experimental results, the effects of TiN on the microstructure, mechanical properties, and wear resistance of the Ni-Mo coating were discussed.

Structural evolution and enhanced thermal cycling life of HVAF-sprayed NiCrAlY bond coat modified by YSZ

Thermal barrier coatings with varied bond coat structures were deposited using high-velocity air fuel spraying. Highly hard YSZ particles are introduced into the NiCrAlY bond layer by accelerating to supersonic speeds at low temperatures to change the porous structure of the bond coat. We systematically increased the YSZ content in NiCrAlY bond coats and extensively investigated microstructure, oxidation behavior, thermal cycling life, and residual stress variation of the bond coats suing a combination of scanning electron microscopy, optical microscope, confocal Raman microprobe. Introduction of YSZ particles reduced the porosity of NiCrAlY bond coat from 2.69% to 0.45%, and altered the oxidation behavior of the bond layer. The NiCrAlY mixed YSZ composite structure induced the formation of a complex and thin thermal growth oxide layer on the bond coat during oxidation process, greatly alleviating and reducing the thermal stress generated of the coating and during the thermal cycling test. And the thermal cycling life of the NiCrAlY mixed YSZ composite structure coating is 2.8 times longer than that of the ordinary NiCrAlY coating. This finding highlights the significance of the bond coat structure in enhancing the service life of thermal barrier coatings.

Comparison of Softening Behavior and Abrasive Wear Resistance between Conventionally and Additively Manufactured Tool Steels

Directed energy deposition (DED) is a powerful method for hard‐facing the existing tool components. Herein, three tool steel grades including a newly developed maraging steel (NMS), a cold work tool steel (V4E), and a high boron steel (HBS) are cladded on a hot work tool steel substrate. After tempering, the cladded tool steels are exposed to high temperatures at 600, 700, and 800 °C for 3 h to evaluate their softening resistance. The results show that all three tool steel grades have a significant hardness drop when the softening temperature reaches 700 °C. The investigated NMS has the lowest initial hardness in the tempered state but the best softening resistance. In contrast, HBS has the highest initial hardness but the worst softening resistance among the three steel grades. V4E tool steel has a moderate softening resistance compared to the other two steel grades. The factors contributing to the softening resistance have been discussed. Corresponding conventional tool steels are also adapted as references for comparison. Except for the NMS, the additive manufacturing tool steel samples have a better softening resistance than the conventional counterparts owing to more alloying elements trapped in the matrix. The abrasive wear resistance of the tempered and softened tool steels manufactured by DED and conventional methods is also evaluated and the wear mechanism is discussed. Besides the hardness, the free spacing λ between coarse hard particles is one of the major factors influencing the abrasive wear resistance.

A confined rod: mean field theory for hard rod-like particles

ABSTRACT In this paper, we model the configurations of a system of hard rods by viewing each rod in a cell formed by its neighbours. By minimising the free energy in the model and performing molecular dynamics, where, in both cases, the shape of the cell is a free parameter, we obtain the equilibrium orientational order parameter, free energy and pressure of the system. Our model enables the calculation of anisotropic stresses exerted on the walls of the cell due to shape change of the rod in photoisomerisation. These results are a key step towards understanding molecular shape change effects in photomechanical systems under illumination.

High-temperature dry sliding friction and wear behavior of in-situ (Al3Zr+ZrB2)/AA6016 aluminum matrix composites

Aluminum alloy, a lightweight material, has poor friction and wear properties at high temperatures. Therefore, aluminum matrix composites were prepared by in-situ autogenous method to enhance the high-temperature friction and wear capability of aluminum alloys. (ZrB2+Al3Zr)/AA6016 in-situ aluminum matrix composites were prepared by in-situ reaction with the addition of mixed salts of potassium fluoborate (KBF4) and potassium fluozirconate (K2ZrF6). The materials were characterized by XRD, SEM, and EBSD. The friction and wear properties were investigated mainly by high-temperature friction and wear experiments combined with SEM and XPS. The results show that the wear resistance of (ZrB2+Al3Zr)/AA6016 aluminum matrix composites far exceeds that of their alloys under severe conditions of high temperature. The wear of AMCs first decreases and then increases with increasing temperature. The lowest wear rate was observed at an ambient temperature of 100°C, where the wear rate of AMCs was reduced by a factor of 2.7 compared to that of aluminum alloys. In addition, the enhancement effect of hard and heat-resistant particles was also due to the oxide film generated during friction on the abrasive scar surface layer of AMCs under this condition and the self-lubricating substance (H3BO3). The composite wear mechanism of AMCs was dominated by abrasive, oxidative, and adhesive wear as the test temperature increased.

Numerical simulation study of PDC cutter rock breaking based on CT scanning to construct a rock model and apply a cohesive element to construct a discretization element

To more accurately simulate the interaction between a polycrystalline diamond compact (PDC) cutter and rock, the structural characteristics of basalt were analysed using computed tomography (CT), and a hard particle–matrix–pore three-phase rock model was established due to its structural characteristics. Three-dimensional models of the interaction between PDC cutters and rock were established by using the finite–discrete element method (FDEM). Using Voronoi diagrams to randomize the grid structure and optimize the propagation of cracks. This study revealed that a broken zone near the cutters will form during the rock breaking process, resulting in the affected area being larger than the area in contact with the formation rock. The rock breaking ability of circular cutters is stronger than that of conical cutters. When a conical cutter breaks hard particles, they are mainly striped or forced away from the rock, but circular cutters can divide hard particles into small pieces. The numerical model used in the research institute can effectively calculation results of the process of interaction between PDC cutter and rock, this proves that the application of the cohesive method to simulate rock breaking by PDC cutters is reliable.

Structural and dynamical equilibrium properties of hard board-like particles in parallel confinement.

We performed Monte Carlo and dynamic Monte Carlo simulations to model the diffusion of monodispersed suspensions composed of impenetrable cuboidal particles, specifically hard board-like particles (HBPs), in the presence of parallel hard walls. The impact of the walls was investigated by adjusting the size of the simulation box while maintaining constant packing fractions, fixed at η = 0.150, for systems consisting of HBPs with prolate, dual-shaped, and oblate geometries. We observed that increasing the distance between the walls led to the recovery of an isotropic bulk phase, while local particle organization near the walls remained stable. Due to their shape, oblate HBPs exhibit more efficient anchoring at wall surfaces compared to prolate shapes. The formation of nematic-like particle assemblies near the walls, confirmed by theoretical calculations based on density functional theory, significantly influenced local particle dynamics. This effect was particularly pronounced to the extent that a modest portion of cuboids near the walls tended to diffuse exclusively in planes parallel to the confinement, even more efficiently than observed in the bulk regions.

Insight into the microstructure and properties of Ni–WC composite through vacuum induction melting (VIM): The effects of thermal damage behaviour of cast WC controlled by VIM temperature

Ni–tungsten carbide (WC) composites were prepared using cast WC as hard particles. In this study, the thermal damage behaviour of cast WC particles and its effects on the microstructure and mechanical properties of Ni–WC composites were investigated. Results show that cast WC particles undergo edge dissolution and particle disintegration at 1600 °C and 1800 °C, respectively. The degree of thermal damage to cast WC particles increases from 30.55% to 48.84% when the melting temperature increases from 1600 °C to 1800 °C. In this process, the Ni-based melt gradually erodes the cast WC particles from the edge towards the centre. This leads to severe dissolution of the W2C phase, while the WC phase only dissolves partially. Notably, the degree of thermal damage to cast WC directly correlates with the W content in the melt. An increase in the W content enhances the volume fraction and nano-hardness of the M23(B, C)6 compound, improving the wear resistance of the composites.

Effects of dispersed α-Al2O3 particles into a cold-sprayed aluminium coating on its subsequent oxidation by the PEO process

The present study focused on the use of a duplex surface treatment combining cold-spray deposition and plasma electrolytic oxidation (PEO) to produce an aluminium metal matrix composite coating, including dispersed α-Al2O3 particles, with improved tribological properties. Al/α-Al2O3 composite coatings were first deposited by cold-spray, with various thickness and proportion in α-Al2O3 particles, and, then partially oxidized by PEO under various processing durations and sparking regimes (arcs or soft regime). The feasibility of cold-spraying thick, compact and adherent aluminium coatings containing well-dispersed α-Al2O3 particles (up to 14 vol%) was demonstrated in this work. It was also pointed out that the addition of hard α-Al2O3 particles into the spray composition tends to densify the deposited aluminium coating. This was related to a stronger peening effect which, in turn, decreases the growth kinetic of the subsequent PEO oxide layer. The presence of dispersed α-Al2O3 particles was found to promote the formation of the corundum alumina phase in the PEO oxide layer by triggering the transition to the soft sparking regime earlier. It was also observed that dispersed α-Al2O3 particles remain unaffected throughout the PEO oxide layers formed within the conventional arcs sparking regime while they undergo a morphological transformation within the specific soft sparking regime. This was explained by considering the different type of micro-discharges that initiate during each regime. Finally, sliding wear tests revealed that the incorporation of α-Al2O3 particles into the cold-sprayed coating resulted in a slight decrease in the friction coefficient and the wear rate of the produced PEO layers.

The addition of SiO2-GO hybrid material enhanced the tribological properties of fluorocarbon resin in marine corrosive environments

Fluorocarbon resin (FC), as a commonly used topcoat material for coating systems, is susceptible to the combined effects of seawater corrosion and ocean current erosion when working in marine environments for a long time, often causing hard particle wear and damage. In order to improve the tribological properties of FC resin, graphene oxide (GO) was modified by sol-gel method, and SiO2-GO hybrid nanomaterials and SiO2-GO/FC composite coatings were innovatively prepared. Through a 50 days long-term immersion experiment, the friction coefficient and wear rate of the composite coating were characterized. The study showed that the addition of SiO2-GO effectively reduced the friction coefficient and wear rate of the coating before corrosion immersion. The average friction coefficient of 0.4 wt% SiO2-GO/FC under a 10 N load for 15 minutes was 0.172, and the wear rate was 1.19×10−4 mm3/Nm, a decrease of 69.9% compared to pure FC coating. After long-term immersion, an oxide layer generally appeared between the coating and the substrate. On the 50th day of immersion, FC, GO/FC, 0.2 wt% SiO2-GO/FC, and 0.6 wt% SiO2-GO/FC all lost their protective ability, while 0.4 wt% SiO2-GO/FC maintained basic tribological properties due to its excellent corrosion resistance. This was mainly due to the lubrication characteristics and good dispersibility of SiO2-GO, which endowed the coating with stronger wear resistance. In addition, the maze effect formed by SiO2-GO within the coating reduced corrosion damage, indirectly improving the tribological performance of the coating.

Tribological and corrosive behavior under HCl corrosive environment of diamond-like carbon films with doped H, Cr and WC

Diamond-like carbon films exhibit low friction and strong wear resistance under various conditions. In order to evaluate tribological and corrosion resistant performance of different types of diamond-like carbon films in hydrochloric acid (HCl) environment, DLC, Cr/DLC, H/DLC and WC/DLC films were prepared by unbalanced magnetron sputtering technology. Their microstructure, mechanical properties, tribological properties and corrosion resistance were characterized and studied. The results show that the prepared DLC film exhibits the lowest wear rate in 1 M HCl solution. H/DLC film has an obvious corrosion resistance due to its high sp3 C bond and dense structure. Cr/DLC and WC/DLC films show a lower friction coefficient. In general, tribological failure of DLC film is mainly due to ordinary mechanical wear; while that of Cr/DLC film is mainly attributed to abrasive wear caused by, for example, hard particles and wear products; adhesive wear is found to be responsible for H/DLC film, which is caused by transformation of CH bond to oxygen group at the friction interface. The WC/DLC film is experienced with both local degradation and low resistance to elastic/plastic changes (H/E and H3/E2), and therefore both granular and chemical failures occurred. This study provides a complete and comprehensive understanding of tribological and anti-corrosive performance of diamond-like carbon films in hydrochloric acid environment, and can be used further as a reference for industrial applications.

Dry sliding wear behavior of sinter forged micrometric and nanometric yttrium oxide reinforced AA-7075 matrix composites

This study aims to investigate the dry sliding wear behaviour of AA-7075 based metal matrix composites developed by powder metallurgy route. AA-7075 metal matrix composites have been developed with 1–15 vol% micrometric yttrium oxide particulate reinforcement and 0.1–3 vol% nanometric yttrium oxide particulate reinforcement by sinter forging.The matrix and reinforcing powders were blended together to obtain a homogeneous composite powder mixture which was cold compacted and further sintered under pure nitrogen atmosphere. The sintered compacts were forged in a closed die to attain full density. The hot forged samples were further artificially age hardened to peak hardness. Wear behavior of AA-7075 and its composites at peak aged condition were investigated at various loads and sliding speeds. The coefficient of friction and wear rate were determined with respect to different volume fractions of micrometric and nanometric yttrium oxide additions to AA-7075 alloy matrix. The overall wear at a constant volume fraction was found to be lower for the compositions having nanometric Y2O3 as compared to micrometric Y2O3. Further the basic wear mechanism of pure aluminum 7075 alloy and reinforced composites consisted of adhesive wear with plastic deformation followed by abrasive wear (due to hard reinforcement particles).Material strengthening by precipitation hardening and reinforcement addition and the role of the forging operation and yttria reinforcements in the removal and uniform distribution of oxide layers present on the AA-7075 powder particles were accountable for the improvement in the wear resistance of the composites.

Research on the impact performance of polyurethane coating on the steel structure surface

Focusing on the 3060 Goal, China builds a large energy base in Inner Mongolia. The steel structure facilities are subjected to long-term impacts from hard particles in the desert environment. Damage to the surface coatings of the steel structures resulted in reduced durability, and safety. The impact test of polyurethane coating was carried out by using an automatic ball impactor, the strain field of PU coating under impact load was collected by combining with Digital Image Correlation, the damage degree of PU coating was investigated by using Laser Scanning Confocal Microscopy, and elastic-plastic properties of PU coating were also studied. The results show that at the same impact height, the indentation depth of the substrate was Steel substrate > PU coating-steel substrate bilayer system, indicating that the PU coating played a better role in protecting the steel substrate. The compressive strain area at the impact contact point of the PU coating-steel substrate bilayer system increased with the increase of impact height, and the surface of the coating appeared to have different degrees of cracks and spalling. The dynamic hardness increases and then decreases with the increase of impact height, and the dynamic hardness value is the largest when the impact height is 30 cm.

HVOF-sprayed surface coating with various compositions of Co-NiCrAlY-Al2O3 to minimize sediment erosion in hydraulic turbines

The components of hydropower plants are susceptible to sediment erosion caused by hard particles in the water. These hard particles cause substantial material loss and a reduction in the performance of the hydraulic turbines. The present study deals with the mitigation of sediment erosion in hydraulic turbines by developing a protective coating (CoNiCrAlY-Al2O3 metal-ceramic composite) using a high-velocity oxygen-fuel (HVOF) coating technique. Hardness measurement, surface wettability analysis, and surface roughness measurement were conducted to characterize the coatings, whereas scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS) were performed for metallurgical characterization. The slurry/sediment erosion behavior of bare and coated substrate was investigated using a slurry erosion tester. Experiments were performed for five coating compositions at different impact angles (30° ≤ ϴ ≤ 90°) and velocities (6 ≤ v ≤ 12 m/s). The maximum improvement in erosion performance (reduction in erosion rate compared to bare substrate ≈ 28.12 % at 30°, 9.29 % at 45°, and 11.69 % at 90° impact angle) was obtained for the coating having 12 wt% alumina doped into Co-NiCrAlY. The coating's performance was improved due to increased hardness, high shielding effect, and reduction in impact energy on Al2O3 by using CoNiCrAlY-Al2O3 deposition. The empirical correlation between erosion rate and velocity for both bare and coated substrates has also been proposed.

Micromechanical study of nano-cutting metal-ceramic WC/Cu by diamond tools

In this paper, the effect of the distribution of ceramic particles WC in Cu matrix on the nano-cutting behavior was investigated using molecular dynamics, and the cutting force, friction coefficient, machined surface quality, sub-surface damage depth, atomic displacement and internal defects were systematically studied, and the performance comparison at different cutting speeds was also investigated. It was found that due to the location of the WC phase, the overall removal of the material by the tool can be divided into the following three ways: When WC particles are above the cutting plane, there is less fluctuation in cutting forces and friction coefficients, and less impact on machined surface and subsurface damage; When the WC particles are below the cutting plane, the fluctuation of cutting force and friction coefficient is slow. Meanwhile, shallow craters are produced at the WC location; When the center of mass of WC particles is on the same level as the cutting plane, the cutting force and friction coefficient fluctuate drastically, the quality of the machined surface deteriorates sharply, and at the same time the hard particles pulled out by the tool remain on the machined surface. It was also found that the WC particles underwent different degrees of counterclockwise deflection in the three stages and caused a diversion of the atomic displacement in front of the tool. In addition, different degrees of dislocation plugging are formed between the WC and the tool at different positions, and the density of dislocation lines increases, which makes the substrate near the WC particles strengthened.