Friction Coefficient Research Articles

INFLUENCE OF DIFFERENT FACTORS ON THE STABILITY BY ROLLING PROCESS IN THE WIRE BLOCK

One of the leading trends in the development of modern metallurgical manufacturing is the improvement of wire rod production using wire blocks. For existing continuous rolling mills, it is important to maximize the use of equipment capabilities both to improve the quality of products and to reduce the loss of metal and other resources for the adjustment and realize of technological modes at production. Effective technical solutions require scientific justification based on research results. To assess the boundary conditions of the stable rolling process, the average integral of the longitudinal forces at the plastically deformed metal is used. In physical terms, the vector of this force, which opposes the movement of the metal, cannot be directed along the motion of the sample, so the values of the force itself cannot be positive. The assessment of the longitudinal stability of the strip in the rolls (the possibility of a stable rolling process) is as follows: the process is implemented at negative values of the force value, zero value is the limit, at positive values the process is impossible. Analysis of the deformation process in the wire block of rolling mill 200 proved that the specific stresses in the stands should be insignificant because the resource of the forces that draw the metal into the rolls is limited. A more significant influence on the longitudinal stability of the process is the back tension. To ensure the stability of the process, especially in the first passes, the grip angle must be close in value to the coefficient of friction. With an increase in the coefficient of friction, the rolling of wire rod in the wire block becomes more stable. The results of the research show that in the case of external actions on the object, it is theoretically possible to find the limits of self-regulation for the rolling process in a wire block.Whenimplemented, thetechnique makes it possible to assess the limits of self-regulation not only by changes in the size of the workpiece, but by the amount of gauges wear in the rolls, in accordance with changes in friction conditions, temperature of the strip and other parameters.

Mathematical Modeling of Load Capacity and Durability of Metal-Polymeric Bearings with a Composite Bushing Based on Polyamides, Polytetrafluoroethylenes, Polyetheretherketones, or Polyethylene Terephthalates

Predictive assessments of the performance characteristics of metal-polymer (MP) plain bearings at the design stage are necessary and important for engineering practice. They include assessments of bearing capacity, linear wear of the bushing, and bearing life. However, no method for their calculation has been developed. The authors created a generalized analytical method for the mathematical modeling of MP sliding bearings as a classical science-based method to study the contact mechanics of conformal cylindrical bodies with consideration of polymer bushing wear. The contact problem of the theory of elasticity takes into account the significant difference in the elasticity characteristics of polymeric materials from those of steel: their Young’s modulus is 60–250 times smaller, and Poisson’s ratio is 1.27–1.37 times larger. The method was used to study MP bearings with bushings made from several common groups of tribopolymers: polyamides (PAs), polytetrafluoroethylenes (PTFEs), polyethylene terephthalates (PETs), and polyetheretherketones (PEEKs). The maximum contact pressures and durability of the dry friction bearings were calculated while taking into account the load; radial clearance; bushing thickness; the tribopolymers’ elasticity characteristics and wear resistance; the sliding friction coefficient; and the type of tribopolymer material. The Young’s modulus of a polymer material had a significant impact on the level of maximum contact pressures. Polymer fillers, depending on their type and the type of polymer, had very different effects on pressure changes (increase, no change, or decrease). An increase in pressure caused an increase in contact pressures. The durability of a mechanical bearing depended not only on the contact pressure but also on the polymer’s wear resistance, Young’s modulus, and friction coefficient. This study determined the quantitative and qualitative effects of these factors on the maximum contact pressures and bearing durability. The presented analytical method provides an effective and reasonable assessment of the specified service characteristics of sliding bearings with consideration of the multifactorial influence of the above factors.

Development of Objective Test Functions for Modeling and Sensitivity Analysis of the Mechanical Behaviour of Aluminum-Agro-Marine Waste Composites.

Abstract Aluminum-based composites reinforced with agro-marine waste materials present an eco-friendly, cost-effective solution for industries needing lightweight and durable materials. This study develops and evaluates the mechanical properties of aluminum (AA6061) composites reinforced with plantain stem ash, eucalyptus wood ash, and periwinkle shell powder for potential aerospace, automotive, and marine applications. Composite samples were prepared according to ASTM standards for tensile, compressive, flexural, wear, and fatigue tests. Objective Test Functions (OTFs) were derived using physical modeling and sensitivity analysis to filter impactful variables. Testing was conducted using universal testing machines, and wear/friction tests followed ASTM G99 guidelines. The physical models showed strong correlations (adjusted R²: 0.9033–1.0000). Measured properties included tensile strength (1907.46–2000.05 Pa), compressive strength (30.33–215.14 Pa), flexural strength (412.72–556.42 N-m²), wear rate (55.01–63.27 m³/m), coefficient of friction (0.102), and fatigue cycle (13.81–27.63 cycles). Except for the coefficient of friction, all results were consistent with the developed OTFs, confirming the material's structural integrity. The composites displayed favourable properties for use in aerospace, automotive, and marine industries, offering strength, lightweight characteristics, and corrosion resistance. The OTFs validated the material's performance, making it a viable alternative to conventional materials. Consequently, aluminum-agro-marine waste composites demonstrate excellent mechanical properties, with high potential for industrial applications.

Optimization analysis of carrier-track collision in braiding process

Abstract The relationship between the speed of the driver plate and the collision of the spindle and the track is studied in this work. It is theoretically analyzed that the spindle will collide with the track in different degrees in the process of motion, and the impact is more intense due to the vibration of the mechanism. First, the dynamic equation of the spindle-track model is established. Then, fireworks algorithm is used to optimize the speed of the driver plate, to reduce the collision and impact times of the spindle on the track, so as to reduce the severe collision times between the spindle and the track, resulting in the wear of mechanical parts and affecting the braiding effect. Finally, it is concluded that the number of collisions increases sharply with the increase in recovery coefficient when the random disturbance is not considered; second, the number of collisions decreases with the appropriate increase in friction coefficient when the random disturbance is not considered; and third, the number of collisions increases sharply with the increase in random disturbance.

Grain refinement and mechanical properties improvement of AlCuFeCoNi high-entropy alloy coatings fabricated by resonant ultrasonic assisted laser cladding

Laser cladding technology has gained significant popularity for the preparationof high-entropy alloy (HEA) coatings. This is primarily due to its notable benefits, such as a low dilution rate and a robust bonding capability. However, the laser cladding process’s rapid solidification effect and the high entropy impact led to the formation of defects in the coatings, such as non-uniform organization and elemental segregation. In this paper, the resonant ultrasonic vibration was used to regulate the organization and improve the microhardness and friction properties of the AlCuFeCoNi HEA coatings. The experimental findings demonstrate that ultrasonic vibration enhances both the width and depth of the coating’s molten state, while simultaneously reducing the height of the coating. Before and after the introduction of ultrasonic vibrations, the coating consists of two phases, body-centered cubic (BCC) and face-centered cubic (FCC). However, the magnitude of the FCC phase significantly increased with higher power. The internal grains of the coating were significantly refined by ultrasonic vibration, and the average grain size was refined from 68.34 μm to 35.28 μm, and the area occupied by equiaxial grains also increased with the increase of ultrasonic power, and the segregation of the FCC phase dominated by Cu elements was suppressed. When the ultrasonic power was 30 %, the microhardness of the coating was increased from 553.19 ± 5.15 HV0.2 to 600.47 ± 3.61 HV0.2. The addition of ultrasonic vibration increased the wear resistance of the coating and lowered the coefficient of friction from 0.558 to 0.409. Furthermore, the friction mechanism of the coatings before and after the addition of ultrasonic vibration did not change, and both were abrasive wear with slight oxidative wear.

Changing the Oral Tribology of Emulsions Through Crystallization of the Dispersed Triglyceride Phase.

Suspoemulsions are used for food, cosmetic and pharmaceutical products, including food such as dairy products and non-dairy alternatives. Product properties, such as flow behavior or sensory perception of non-dairy products differ from those of dairy products and are therefore perceived by consumers as products of inferior quality. One reason for this may be the crystallization behavior of the added triglycerides leading to differences in solid fat content in comparison to cow milk. This is discussed with the solidity of the dispersed phase as a parameter of suspoemulsions. The solidity was varied by using low and high melting triglycerides and measuring at different temperatures. The dispersed phase fraction is φ = 30%. The droplet size distribution showed a x50,3 of 1.2 and 3.66 μm, mimicking the droplet sizes of milk and dairy cream. Rheological frequency sweeps were carried out within a temperature range from 5°C to 50°C. The differences in solidity of the dispersed phase caused no changes in viscosity at each temperature. In contrast, oral tribology distinguished different solidities of the dispersed phase with changes in the friction coefficient. The friction coefficient was determined for increasing rotational speeds (0.01-100 mm/s), to compare the so called Stribeck curves with each other. In general, with increasing solidity of the dispersed phase, the friction coefficient increases. Comparing the Stribeck curves of pure butter fat suspoemulsion with those of plant-based fat suspoemulsions, different plant-based fats can be mixed, to mimic the friction profile of milk products in plant-based alternatives.

Tribo-oxidation mechanism of gradient nanostructured Inconel 625 alloy during high-temperature wear

The tribo-oxidation layer is typically formed at the contact interface of high temperature wear, which exhibits a significant effect on the friction behavior of gradient nanostructured (GNS) materials. This study systematically investigated the wear resistance, near-surface microstructure, and compositional changes of ultra-thick GNS Inconel 625 alloy subjected to surface mechanical rolling treatment (SMRT) under high-temperature sliding wear conditions. The experimental results indicated that as the temperature increased to 500 °C, a tribo-oxidation layer was formed on the surface of the GNS sample, thereby resulting in an abnormal increase in the coefficient of friction (COF) and a rapid decrease in the wear rate. The gradient nanostructures facilitated oxidation diffusion channels, promoting the formation of a protective Cr2O3 film and spinel oxides, reducing the wear rate. At lower temperatures, a rapidly formed Cr2O3 film shielded the matrix, forming a tribo-oxidation layer composed of Cr2O3 and nickel. At 800 °C, the tribo-oxidation layer exhibited complex structures, including glaze, spinel oxide, Cr2O3, and Cr2O3/Ni mixed layers. This complexity was attributable to the oxidation diffusion rate of the gradient nanostructures and tribo-oxide layers. The findings not only elucidated the tribo-oxidation mechanism of GNS nickel-based superalloys but also offered valuable insights for designing wear-resistant materials.

Controlled migration of oleic acid amide through adsorption on TS-1 zeolite for long-lasting anti-adhesive rubber composites

The adhesion of materials on the surface can affect the appearance, durability, and performance stability of rubber composites. Incorporating anti-adhesive additives into composites is an effective strategy to improve anti-adhesive properties, as these additives migrate to the surface to form an anti-adhesive layer. However, excessive migration rates can result in poor durability of the anti-adhesive layer and significant powder adhesion on the surface. This study prepared titanium silicate zeolite adsorbed with acid amide composite filler (OAA@TS-1) by adsorbing OAA onto the active sites of TS-1, which was then incorporated into natural rubber (NR). The adsorption effect reduces the migration rate of OAA within the rubber composite, allowing more OAA to remain in the matrix. Additionally, the adsorption is reversible, and the adsorbed OAA can overcome the adsorption through molecular thermal motion, which can migrate to the surface. After the anti-adhesive layer is worn, OAA can persistently migrate outward, effectively repairing the layer and enhancing the durability of the anti-adhesive properties. In comparison to rubber composites filled solely with OAA, the OAA@(TS-1) filled rubber composite exhibits a remarkable reduction of 55% in the amount of adherent powder on the composite surface and a 24% decrease in the coefficient of friction after three friction cycles. After slicing and leaving for 3 days, the contact angle increases by 18%. The long-lasting anti-adhesive rubber composite developed in this study demonstrates significant application potential in areas such as material conveyance and power transmission.

Effect of aged treatment on improving the performance of HVAF WC–Cr3C2–Ni coating on crystallization roller

The thermal shock resistance and high-temperature performance of WC–Cr3C2–Ni coatings on the surface of the crystallization roll after aged treatment were investigated in this study. The aging treatment at 320 ℃ for 2.5 h facilitated the diffusion of Cu element from the C17200 beryllium copper substrate toward the coating side of WC–Cr3C2–Ni coating, thereby enhancing the bonding between the coatings and substrates. After the aged treatment, the internal structure of the C17200 substrate changed from a dendritic structure to an equiaxed crystal structure, the hardness increased from 225.71 Hv0.5 to 406.52 Hv0.5 (80.4 % increased), and the wear resistance increased.Although the aging treatment reduced the hardness of the coating slightly (from 1257.58 Hv0.5 to 1155.16 Hv0.5, a decrease of 8.1%) and wear resistance (the coefficient of friction, from 0.335 to 0.312, a decrease of 6.9%). However, in the thermal shock test, the thermal shock resistance of the coating after aging treatment was increased from 19 times to 20 times (5.3% increased). However, the thermal shock failure cracks between the coatings and the substrates were transferred from the substrate part to the joint part of the two, which effectively avoided the waste of the crystallization roller substrate in the maintenance process. This research effectively reduces the purchase and maintenance costs of steel mills in actual production and provides theoretical support for cost reduction and efficiency increase in other HVAF (high-velocity air fuel) coating applications.

Study on the current-carrying friction and wear behaviors of a novel copper-impregnated carbon skateboard containing tungsten disulfide

To enhance the current-carrying friction behavior of carbon skateboards, this investigation focuses on developing a new copper-impregnated carbon skateboard containing tungsten disulfide. Its performance was evaluated by various current-carrying friction tests and tribological analysis techniques. As the current increased, the carbon skateboard gradually transformed from fatigue wear and abrasive wear to adhesive wear. The average contact resistance and average friction coefficient of the carbon skateboard containing tungsten disulfide were decreased by 25.11% and 11.43% at 40N, respectively, as compared to a commercial copper-impregnated carbon skateboard of the same type. Furthermore, the presence of tungsten disulfide reduced the formation and adverse effects of spalling pits, improving contact conditions and enhancing stability in the electrical contact resistance and coefficient of friction.

Experimental study of rotational friction damper for seismic response control: friction material comparison and configuration optimization

Rotational friction dampers (RFDs) can be incorporated into structures flexibly as energy-dissipation devices for seismic response control. However, the basic primary form of RFD has three main challenges and objectives in enhancing its performance: (1) avoiding strength fluctuation and jittering, namely, improving the stability of the performance, (2) enhancing the strength, and (3) relieving the basic assumption that the clamping pressure is uniformly distributed on the friction pads and ensuring the accuracy of the theoretical equation. To address these issues, this study proposes four potential approaches: (1) selecting a friction material with a stable performance, (2) increasing the friction coefficient, (3) increasing the clamping force, and (4) optimizing key configurations. Based on these concepts, two sets of experimental studies, including 27 friction pad material comparison tests and 17 lug plate and clamping bolt configuration optimization tests, were conducted. According to the test results, the fiber-reinforced resin-based composite (FRRC) material was found to be better than H62 brass and 7075 aluminum alloy in realizing a high friction coefficient and stable performance, as well as achieving uniformly distributed pressure. The four-bolt lug plate and six-bolt lug plate with stiffening ribs were found to be effective in realizing a high clamping force and, thus, a high RFD strength, as well as in achieving a uniformly distributed pressure. In contrast, the single-bolt lug plate could not realize a high clamping force because of the tightening torque limit. A six-bolt lug plate can cause pressure concentration and edge damage to the friction pad.

Featuring the aspects with temperature dependent viscosity of inclined MHD Williamson fluid along with heat source/sink, Soret and Dufour effects: A predictor-corrector approach

The boundary layer flow analysis of Williamson fluid moving on the stretched cylinder has applications in the polymer processing, drug delivery system, cooling systems, rheology of food products, dyeing, and finishing. The numerical solutions of governing Navier-Stokes equations at different scenarios of thermal and solutal aspects have lots of practical implications, including biomedical engineering, cooling and heating processes, chemical reactors, aerodynamics, environmental science, and thermal storage systems. From these practical applications, the authors were motivated to conduct a study in which the numerical behavior is examined by applying the Adams-Bashforth predictor and corrector approach of numerical analysis for the Williamson fluid model in the presence of varying viscosity, natural convection, and the inclined magnetic field. Furthermore, Joule heating, thermal radiation, and heat source/sink effects are included in the thermal aspects because these are the important concepts in thermal management and engineering and have applications in solar thermal energy systems, combustion engines, heat exchangers, nuclear reactors, thermal imaging, and safety. Apart from thermal aspects, the analysis of mass transfer focuses on the influence of chemical reactions and Soret-Dufour effects. The similarity transformations are adopted to convert partial differential equations into ordinary differential equations. Specifically, the well-known predictor and corrector numerical method named the Adams-Bashforth method in combination with the Runge-Kutta 4th order scheme is used to achieve the numerical solutions. The temperature, concentration, and velocity regions are displayed on the graphical and numerical conducts. A comparison is also made between the results obtained by the shooting method and the numerical findings of skin friction, Nusselt number, and Sherwood number determined by the Adams-Bashforth method. The determining results concluded that the restrictions in the flow of Williamson fluid are caused by variations in the inclination magnetic field, the surface curvature, and the Williamson parameter, whereas the motion of the fluid increases due to convection, which occurs due to thermal phenomena. The determined results indicate that the temperature distribution is enhanced due to the addition of thermal radiation, Eckert number, and magnetic field. The surface curvature, Soret number, and reaction coefficient marks the decrease impact on the concentration region. The temperature-dependent viscosity increases the drag force and friction coefficient. The Nusselt number is amplified by applying thermal radiation to the surface of the cylinder. The chemical reaction is the source of the increment in the Sherwood number.

High acetone soluble organosolv lignin extraction and its application towards green antifouling and wear-resistant coating

Marine fouling poses significant challenges to the efficiency and longevity of marine engineering equipment. To address this issue, developing effective marine antifouling coatings is critical to ensure the economic viability, environmental sustainability, and safety of offshore operations. In this study, we developed an innovative green antifouling and wear-resistant coating based on lignin, a renewable and sustainable resource. Lignin is considered environmentally friendly because it is abundant, biodegradable, and reduces reliance on petroleum-based materials. The coating was formulated with a controlled hydrophilic-to-hydrophobic ratio of 2:8, leveraging lignin's unique properties. Applying lignin increased the water contact angle by 14.5 %, improving surface hydrophobicity and contributing to the coating's antifouling efficacy. Moreover, the mechanical strength of the coating was enhanced by approximately 200 %, significantly boosting its durability in harsh marine environments. Additionally, the friction coefficient was reduced by about 85 %, further preventing organism adhesion. These results demonstrate that lignin-based coatings offer a greener alternative to traditional antifouling solutions. The results of this study not only help advance antifouling coating technology but are also consistent with the broader goal of promoting environmental responsibility in marine engineering practice.

Gelatin microcarriers as an effective adipose-derived stem cells delivery strategy in osteoarthritis treatment

Despite their clinical success, stem cells (SCs) in the treatment of osteoarthritis (OA) are limited by lower retention efficiency and restricted paracrine function. The development of effective SCs culture and delivery systems to maintain or promote SCs paracrine function is urgently needed. In this study, we focused on gelatin microcarriers with different sizes as SCs culture scaffold for OA therapy. The effect of culturing adipose-derived stem cells (ADSCs) on different size microcarriers (180 μm and 320 μm) to promote paracrine function was evaluated. The secretome of ADSCs cultured on microcarriers more effectively regulated macrophages and chondrocytes in a direction favorable to OA healing compared to culture plates. In particular, microcarriers with ADSCs effectively reduced the coefficient of friction at the cartilage interface. Injection low-dose ADSCs without and with different size microcarriers into the knee joints in rats' OA model was achieved. Even better OA therapeutic effects were achieved by using smaller size (higher curvature) microcarriers to deliver ADSCs at low doses. Microcarrier-based cell delivery strategies offer potential solution method for OA therapy.

Improve wear resistance of C/C composites as artificial bone using diamond-like carbon coatings

In this study, diamond-like carbon (DLC) coatings and silicon-doped diamond-like (Si-DLC) coatings were prepared on the surface of C/C composites by a combination of plasma-enhanced chemical vapor deposition (PECVD) and magnetron sputtering processes. The film composition, microstructure and atomic bond structure were characterized using X-ray photoelectron spectroscopy, field-emission scanning electron microscopy and Raman spectroscopy. The mechanical properties and friction behavior related to the Si element were investigated using nanoindentation and HT-1000 high temperature friction and wear tester. The biocompatibility of the materials was also evaluated by the MG-63 proliferation test. The results indicate that Si elements were successfully incorporated into the DLC films, bonding with C and O atoms, which altered the thermal stability and microstructure of the coatings, reduced the internal stress of the films, and increased disorder. Compared to C/C composites, all coated layers exhibited lower coefficients of friction, with the formation of transfer layers and graphitization induced by friction contributing to the excellent tribological performance. Both coatings showed no cytotoxicity and demonstrated good biocompatibility. Both coatings are effective in reducing wear and chip losses in C/C composites when used as artificial bones. This work suggests that diamond-like carbon coated C/C composites can be excellent structural materials for human body in biomedical science.

Synthesis and lubrication properties of hollow IF-MoS2 nanospheres

Hollow IF-MoS2 nanospheres were prepared by sulfidation reaction using MoO3 nanospheres as precursors in a reducing atmosphere. The composition and morphology of the obtained samples were characterized by x-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The formation mechanism was further studied. The results showed that smaller sized MoO3 nanospheres (synthesized from 0.05 mol of ammonium molybdate) could transform into hollow IF-MoS2 nanospheres under heat treatment conditions at 850 °C for 6 h. Furthermore, we evaluated the lubrication performance of hollow IF-MoS2 nanospheres. Comparative analysis with pure oil revealed that the mixed oil, with the addition of 2 wt. % IF-MoS2, exhibited a reduced friction coefficient ranging from 0.0194 to 0.0197.

Investigation of MoSe2 filled MAO Coating on TC6 alloy- tribological and corrosion characterization of multiple interface structure

To enhance the tribological properties and corrosion resistance of titanium alloys, this study proposes a novel tribological interface structure combining micro-arc oxidation ceramic coatings with MoSe2. Comprehensive analysis using X-ray diffractometry, profilometry, energy-dispersive spectroscopy, and scanning electron microscopy was conducted to evaluate the tribological characteristics of this structure under dry friction and liquid lubrication conditions. Electrochemical experiments assessed the corrosion resistance of the structure. The results indicated that under 3 N-2.5 cm/s, oil lubrication, the structure exhibited the best friction-reducing and lubricating performance, with the friction coefficient reduced by 75 %. The synergistic interaction between the low shear force MoSe2 particles and the TiO2-rich ceramic coating formed a lubricating layer on the surface, thereby achieving reduced friction and enhanced wear resistance. Additionally, this structure demonstrated excellent corrosion resistance. This study provides valuable insights for integrating micro-arc oxidation with new materials in engineering applications.

Ti3C2Tx and Mo2TiC2Tx MXenes as additives in synovial fluids - towards an enhanced biotribological performance of 3D-printed implants

Synovial joints, critical for limb biomechanics, rely on sophisticated lubrication systems to minimize wear. Disruptions, whether from injury or disease, often necessitate joint replacements. While additive manufacturing offers personalized implants, ensuring wear resistance remains a challenge. This study delves into the potential of Ti3C2Tx and Mo2TiC2Tx nanosheets in mitigating wear of additively manufactured cobalt-chromium tungsten alloy substrates when incorporated as additives into synovial fluid. The colloidal solutions demonstrate an excellent stability, a crucial factor for reproducible assays and potential clinical applicability. Analysis of contact angles and surface tensions reveals MXene-induced alterations in substrate wettability, while maintaining their general hydrophilic character. Viscosity analysis indicates that MXene addition reduces the dynamic viscosity, particularly at higher concentrations above 5 mg/mL, thus enhancing dispersion and lubrication properties. Friction and wear tests demonstrate a dependency on the MXene concentration, while Ti3C2Tx exhibits stable friction coefficients and up to 77 % wear reduction at 5 mg/mL, which was attributed to the formation of a wear-protecting tribo-film (amorphous carbon and MXene nano-sheets). Our findings suggest that Ti3C2Tx, when supplied in favorable concentrations, holds promise for reducing wear in biotribological applications, offering avenues for future research into optimizing MXene utilization in load-bearing joint replacements and other biomedical devices.

Effect of annealing parameters on the microstructure and tribological properties of FeCoCrNiMn laser cladding layers

The FeCoCrNiMn laser cladding layer exhibits low hardness and poor wear resistance, limiting its applications in the tribology field. The effect of annealing temperature (500 °C-900 °C) and holding time (2 h-14 h) on the properties of FeCoCrNiMn layers which fabricated on the 45# steel substrate were systematically studied. The results demonstrate that the layers' surface hardness and wear resistance initially increase and decrease with increasing annealing temperature and holding time. The FeCoCrNiMn layers subjected to annealing at 700°C for 8h exhibit optimal performance. Specifically, the micro-hardness and wear resistance of the 700°C-8h annealed layers (T700-8) increased by 15.8% and 41.4%, respectively, compared to the substrate. The friction coefficient of T700-8 is 0.635, which is 0.025 lower than that of the substrate. The primary wear mechanisms of the T700-8 are adhesive wear and oxidative wear. Microstructural analysis indicates that annealing at 700°C for 8h forms a Ni-Cr-Fe solid solution phase, strengthening the solid solution. Besides, the average grain size of the layers decreases from 178.7 μm to 115.2μm, indicating grain optimization induced by the annealing process. However, excessively long annealing time or excessively high annealing temperatures lead to the dissolvement of the Ni-Cr-Fe solid solution phase, thus decreasing the surface hardness and wear resistance. Therefore, appropriate annealing parameters can refine the crystal grain, and improve the wear resistance of FeCoCrNiMn layers.

Dependence of mechanical and surface properties on crystallographic orientation, twin boundaries, and temperature in CoCrFeMn0.3Ni high-entropy alloys

The CoCrFeMnNi high-entropy alloy (HEA) has been widely studied for its mechanical properties and thermal stability, yet its tribological behaviour remains under explored. In this article, we investigate the effects of temperature and twin boundary spacing on the surface nanotribological properties and subsurface damage of CoCrFeMn0.3Ni HEA through molecular dynamics simulations. Among the orientations, [001] exhibits the highest friction coefficient, indicating the greatest restriction to indenter movement. Higher temperatures reduce wear rates, showing good thermal stability, likely due to thermal softening that decreases high-stress regions and the driving force for dislocation nucleation. Monocrystalline HEA shows lower scratch resistance than twinned workpieces. The loading force correlates with twin boundary distance, with twins increasing strength but excessive twins causing softening. Material removal becomes easier in large twinned workpieces. In monocrystalline HEA, plastic deformation is dominated by partial dislocation slip. However, in twinned workpieces, there are not only partial dislocation slips but also dislocation slips parallel to the twin and twin migration. These findings have important implications for HEA design and their applications in extreme conditions.