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The effect of boride content on the microstructure, electrical conductivity, and mechanical properties of TiB2-MB2/Cu composites (M = Cr, Mo, and Zr) was systematically investigated. The composites were prepared via spark plasma sintering. The results indicated that the double borides were uniformly distributed in the Cu matrix without visible agglomeration, and excellent interfacial bonding was achieved between the borides and the Cu matrix. The electrical conductivity of the Cu composite with 5 wt% TiB2 and 15 wt% ZrB2 increased by 503 % compared to the Cu-20 wt% TiB2 composite. However, the hardness of the Cu composite with 5 wt% TiB2 and 15 wt% ZrB2 decreased by only 22 %. The wear resistance of the composites was significantly enhanced due to the synergistic effect of the dual-phase boride particles. The wear resistance of the Cu composite with 5 wt% TiB2 and 15 wt% ZrB2 was 4.12 times higher than that of the Cu-20 wt% TiB2 composite standard sample when tested under an applied load of 10 N. The worn surface of the composites exhibited minimal roughness. Therefore, the Cu matrix composites with dual-phase borides achieved desirable comprehensive performance in terms of electrical, mechanical, and tribological properties.

Grinding process monitoring is key to assessing the intelligence of grinding processing and ensuring manufacturing quality of the intended product. The grinding force in the grinding process is an important characteristic, and the grinding force signal has a close relationship with the degree of wheel wear, grinding heat, grinding wheel and workpiece contact state, and other entities. Therefore, the analysis of the grinding force signal using the time domain and frequency domain analysis methods can effectively reveal the grinding characteristics and wheel wear evolution mechanism in the gear grinding process. In this study, the microcrystalline corundum grinding wheel was used to conduct the profile grinding test on 20CrMnTi steel gears installed in vertical machining centers. A high-performance general-purpose dynamometer was used to collect the discrete time series data of the grinding force in real time; a confocal laser microscope and scanning electron microscope were used to observe the wear characteristics of the microcrystalline wheel surface; finally, a micrometer was used to measure the thickness of the wheel’s end-top surface to assess the degree of wheel wear in a quick and simple way. To improve the precision, automation, and intelligence level of the gear grinding process considering the microcrystalline corundum grinding wheel, online monitoring of the grinding process and wear mechanism of the grinding wheel was performed. The intrinsic correlation between the time-frequency domain signals of the grinding force, the contact status of the grinding wheel and workpiece, and the wear degree of the grinding wheel was established. Thus, in this study, a new online monitoring method for monitoring the grinding process of the grinding wheel was proposed based on real-time force signals. Meanwhile, the wear mechanism underlying the morphology of microcrystalline corundum grinding wheels was characterized and analyzed using laser confocal microscopy and scanning electron microscopy. The results showed that the distribution pattern of waveform characteristic indicators such as kurtosis, waveform index, peak index, and pulse index in the time domain spectrum of the grinding force showed a distinct trend of varying cutting depth grinding state ≥ steady-state grinding state of a significantly worn grinding wheel ≥ steady-state grinding state of a lightly worn grinding wheel > noncontact state. However, the variation of the two waveform characteristic values of the grinding force, amplitude spectrum and pulse indicator under different grinding states is completely opposite to that of the time domain signals. After assessing the three-dimensional roughness of the working surface of the grinding wheel, it is observed that there is a slight decrease and a subsequent rapid increase in the roughness of the working surface of the wheel with the evolution of wheel wear. The polycrystalline structure of the microcrystalline corundum abrasive particles gives them the ability to update and sharpen along the microcrystalline interface, showing layer-by-layer cleavage peeling.

In this research, the structural features, tribological performance, and corrosion resistance of an Al/Cu/MoS2/WC hybrid composite fabricated by the accumulative roll bonding (ARB) method were analyzed. Microstructural observations indicated that a uniform dispersion of Cu, MoS2, and WC particles is achieved after seven ARB passes. No phase transition occurred during ARB process. Moreover, hardness tests revealed that the microhardness of both Al and Cu layers increased with increasing ARB passes, reaching 84 HV and 157 HV, respectively, after seven passes. It was further revealed that the ARB process significantly improves wear resistance of the hybrid composite, demonstrated by a decrease in wear rate from 1.38 to 0.35 mm³/Nm after seven ARB passes. Adhesive, abrasive, and delamination mechanisms were observed in all samples, with delamination dominating at higher ARB passes. Furthermore, the corrosion resistance of the composite improved with increasing ARB passes, where the corrosion current density of the composite fabricated by seven ARB passes was 165 times (from 7.10 × 10⁻⁶ A/cm2 to 4.2 × 10⁻⁷ A/cm2) lower than that of the composite obtained after the first ARB pass.

As a typical age-strengthened alloy, Cu–Cr–Zr alloys have high strength, good electrical conductivity, and excellent wear resistance. In this work, the Cu–Cr–Zr–Nb alloys were in different aging states after the aging process. After aging at 460 °C for 4 h, the alloy was peak-aging. The common effect of the existence of the FCC Cr particle, which was coherent with the Cu matrix, and the increase in hardness improved the wear property of the alloy. The results of the wear test showed that the optimal wear parameter was a speed of 300 rpm and a load of 5 N. Under these wear parameters, the alloy had the lowest mean coefficient of friction (COF) value and the least mass loss, having the best wear resistance. Furthermore, the wear mechanism of the alloy was mainly adhesive wear and abrasive wear.

The AISI M2 coatings were prepared on H13 die steel substrates by laser cladding technology. The effects of MoS2 addition on the microstructure and wear resistance of the coatings were investigated. The results showed that adding MoS2 can reduce the wear rate of M2 coating, enhance the hardness of the coating, and affect the wear mechanism of the coating. The wear rate of the M2 coating is 3.33 × 10−5 mm3/N·m, mainly consisting of oxidative wear and abrasive wear. When the MoS2 addition reached 7 wt%, the wear rate is only 1.88 × 10−5 mm3/N·m, and the wear mechanism is mainly oxidative wear. The microstructure of the coatings was analyzed using X-ray diffraction techniques and scanning electron microscopy techniques, and its mechanism was thoroughly studied. MoS2 can refine grains and promote fine grain hardening. The average grain size of the M2 coating is 3.42 μm, but the average grain size of the coating containing 7 wt% MoS2 decreases to 1.40 μm.

As one of the main problems in the processing of carbon fiber reinforced polymer (CFRP), tool wear affects the quality and efficiency of hole making. As a new CFRP hole making process, the suction-type internal chip removal method can effectively slow down the tool wear rate. In order to further clarify the reasons for this method to slow down the tool wear, this study investigates the wear mechanism of the internal chip removal tool. The main contents include: first, the experimental parameters such as drilling axial force, drilling temperature, and tool wear are obtained through the experimental method, and the drawing of the drilling temperature change curve of internal chip drilling is completed; second, the polar analysis method is used to study the influence of the drill parameters on the drilling axial force and the tool wear, and the basis for the selection of the structure of the internal chip drill is given; finally, the method of comparative experiments of the internal chip drilling process and the non-internal chip drilling process is used to conclude that the use of the internal chip drilling process can effectively slow down the tool wear rate. Finally, the method of comparing the internal chip removal and non-internal chip removal processes is used to conclude that the use of internal chip removal processing method can effectively reduce the axial force, drilling temperature, and slow down the tool wear.

The gear friction pairs in RV reducer always withstand a broad range of temperature, sliding velocity and heavy load. In the research, three types of heat treatment methods (carburizing + quenching, nitrocarburizing and high concentration nitrocarburizing) are applied on the 20CrMo (cycloidal gear material) disc to study the tribological behavior and wear mechanism. The friction coefficient, wear depth and wear rate of the three types of friction pairs under various temperature (−20 °C, 25 °C, 50 °C, 100 °C) are measured and the microstructure characteristics are analyzed by SEM and EDS. The results reveal that high temperature can dramatically decrease the wear scar dimensions and wear rate due to the more active lubricant. Although the lubricant lost its activity at −20 °C, the friction coefficient and maximum wear depth for GCr15/20CrMo (carburizing + quenching) and GCr15/20CrMo (high concentration nitrocarburizing) are relatively less than 0.1 and 4 μm. The wear rate of GCr15/20CrMo (carburizing + quenching) and GCr15/20CrMo (high concentration nitrocarburizing) are 14.49 μm3/N·m and 17.20 μm3/N·m, which are only 28.7% and 34.1% of GCr15/20CrMo (nitrocarburizing). With the temperature increases to 25 °C, tribofilm is more likely to form on the 20CrMo specimen after nitrocarburizing, leading to better wear resistance. At high temperature (50 °C and 100 °C), GCr15/20CrMo (high concentration nitrocarburizing) system presents excellent tribological behavior by the combination of good lubricant activity, formation of tribofilm and refined nitrides. The wear rate even reaches 0.45 μm3/N·m and 0.43 μm3/N·m at the sliding velocity of 300 mm/s and 562 mm/s under 100 °C. Overall, specimen with high concentration nitrocarburizing process exhibits exceptional wear performance under full operating conditions of RV reducer.

The friction properties and heat resistances of the iron-copper based powder metallurgy friction materials were tested by MM3000 friction and wear testing machine under 7 continuous braking conditions. The wear mechanism of the friction materials at two different rotate speeds (line speed in equivalent radius) was studied by scanning electron microscopy and energy disperse spectroscope analysis. The results show that when the line speed is 19.40 m·s−1, the dynamic friction coefficient of the friction materials decreases slightly with the increase of surface pressure, which is 0.267~0.312 at 0.44 MPa and 0.258~0.308 at 0.80 MPa. Under the continuous braking condition as the line speed of 19.40 m·s−1, the surface pressure of 0.44 MPa, and the braking energy in unit area of 268 J·cm−2, the dynamic friction coefficient fluctuates greatly, while under the other conditions, the dynamic friction coefficient fluctuates little. With the increase of braking energy, the average dynamic friction coefficient under 7 kinds of continuous braking conditions changes between 0.300~0.334, and the dynamic friction coefficient is above 0.250, without the obvious decline phenomenon, indicating that the iron-copper based powder metallurgy friction materials have the good heat resistance. Under the line speed of 19.40 m·s−1, the friction and wear mechanism of the iron-copper based friction materials is mainly abrasive wear and oxidation wear. Under the line speed of 30.00 m·s−1, the friction and wear mechanism of the iron-copper based friction materials is mainly fatigue wear and oxidation wear.

Impact wear (repetitive impact-induced wear) has been identified as a significant issue in various engineering components, such as valves, electrical contacts, and pumps. This study investigates the impact wear behavior of martensitic stainless steel, a commonly used material for valves. Understanding the wear behavior is crucial for minimizing losses and enhancing component performance. Repetitive impact tests were conducted using a custom-built testing machine with a well-defined impact position. Four impact loads were applied (10 N, 20 N, 30 N, and 40 N) at 30,000 impact cycles. It was observed that plastic deformation precedes the transition to fatigue wear after multiple impact cycles under loads 20 N and over. However, under 10 N, plastic deformation was not observed clearly, and the initial damage mode primarily involved pitting, followed by delamination wear. Wear rates were found to correlate well with the contact pressure, and the equation for predicting the wear rate was derived from such a relation. A valuable guideline for minimizing wear and designing operating contact pressure in martensitic stainless-steel components is achieved via the upper and lower bound curves.

The effect of shot peening treatment on dry sliding wear behavior of medium manganese steel in as-hot rolled and solution-aging states were studied. The results show that before shot peening, the wear resistance of the solution-aging sample was better than that of hot-rolled steel. The excellent wear resistance was due to the synergistic effect of Ti (C, N) particle precipitation strengthening and grain refinement in the matrix, resulting in high strain hardening ability. After shot peening, different microscopic evolution mechanisms caused great contrast in properties. The as-hot rolled sample released internal stress by generating deformation twins (DTs) during shot peening. With the increased shot peening time, the DTs thickened and interacted with dislocations, effectively reducing the free dislocation path, releasing residual stress, and significantly improving wear resistance. However, solution-aging steel generated many dislocations, resulting in residual stress concentration at Ti (C, N) particles, promoting crack initiation and propagation, and deteriorated wear resistance.

Zr-Y modified silicide coating was deposited on TC4 alloy by the pack cementation process. The microstructure， friction and wear performance， and wear mechanisms of the coating were investigated. The results show that the Zr-Y modified silicide coating has a multi-layer structure， an outer layer consists of TiSi2 and a small amount of ZrSi2， a thin middle layer is TiSi， and an inner layer is a mixture of Ti5Si4 and Ti5Si3. The micro-hardness of the coating is much higher than that of the TC4 substrate and exhibits an obvious decrease tendency from the surface to the interior. The Zr-Y modified silicide coating possesses good anti-wear performance when wearing against GCr15 and Al2O3 balls at a high-temperature of 600 ℃. When wearing against GCr15， the wear rate of the coating is about 3.59×10-5 mm3/（N·m）， which is about 36.6% of that of the TC4 substrate， and the main wear mechanisms are characterized by the adhesive of GCr15 on the coating surface and oxidation wear. When wearing against the Al2O3 ball， the wear rate of the coating is about 9.75×10-5 mm3/（N·m）， which is about 18.9% of that of the TC4 substrate， and the wear mechanisms are fatigue wear， oxidation wear， and adhesion wear.

As machines become more sophisticated and manufacturing processes more complex in the manufacturing industry, there is a need to build simple systems that enable condition monitoring without specialized knowledge. Therefore, AI-based condition monitoring is attracting attention. To improve the accuracy and interpretation of sliding surface condition monitoring, this study aims to elucidate the relationship between wear mechanisms and data obtained from each sensor such as friction coefficient, acoustic emission, vibration acceleration, and contact electrical resistance. In this paper, we investigated a method to reduce the opacity of anomaly detection using machine learning and explored sensor data useful for condition monitoring of the sliding surface. The usefulness of SHAP (SHapley Additive exPlanations), one of the explanatory methods of machine learning, was verified by using it on the analysis results of anomaly detection. As a result, it was found that SHAP is useful as a method to give interpretation to the analysis results of machine learning for monitoring the condition of sliding surfaces, because the condition of sliding surfaces over time, which cannot be understood by unsupervised learning, can be understood in more detail than before based on the contribution of each sensor data. In addition, a comparison of the contribution of each sensor data to the wear behavior for each sliding distance and the predictions by SHAP revealed the possibility that the data from the vibration acceleration sensor mounted perpendicularly to the sliding direction might effectively detect signs of seizure.

Significance Impregnated diamond bits (IDBs) have been widely used in various hard rock drilling activities, especially deep drilling. Drilling process with IDBs relies on diamond edge wrapped by metal matrices to break the rock formation, which means the wear pattern of the diamond bit reflects the interaction between bits and rock, as well as the existence form of broken particles, which directly determine the drilling efficiency and service life of the drilling tools. But up to now there have not been so much in-depth study on its wear mechanism and analysing method in geological drilling. Progress and Analysis Therefore, this paper reviews the research literature on IDBs wear in the field of geological drilling, summarizes the abnormal bit wear problem according to engineering project experineces and industrial standards. Firstly, based on the experiences of geological drilling activities and industry standards, different types of abnormal bit wear of drill bits were summarized. Then, the evaluation methods of drill bit wear were introduced from the aspects of wear images and drilling signals. The wear mechanism and influencing factors of the drill bit in the drilling process were sorted out from three aspects: The overall drill bit, diamond, and metal matrix. In addition, mainstream methods of controlling drill bit wear performance were listed, and the research progress of wear analysis equations was introduced, besides, how machine learning methods can assist in the study of drill bit wear was discussed. Conclusion and Prospect Thus, IDBs have great potentials in deep hard rock drilling, and their wear performance is the key influnencing the whole drilling activity. To this end, research directions such as artificial intelligence assisting data analysis, microscale computational simulation, additive manufacturing, and material processing modification were analyzed and discussed, aiming to explore advanced methods for monitoring, analyzing, and regulating the wear of diamond drill bits, so as to meet the needs of remote monitoring and controlling in drilling activities such as geological deep drilling and extraterrestrial drilling.

Water-lubricating bearings made of polymer-matrix composites have provided a new approach to prolong the service lifetime of key component in marine propulsion system. However, it was still crucial to find a convenient and effective material to manufacture the water-lubricating bearing with ultralow friction. Herein, a new kind of polyetheretherketone (PEEK) composite with ultralow coefficient of friction (COF), high mechanical strength and thermal stability has been developed. An 80.7% decrease in the COF of PEEK was achieved by incorporating the fillers. A possible mechanism between the heterogeneous nucleation and mobility hindrance of PEEK chain segment caused by different fillers was proposed. The ultralow COF endowed the water-lubricating bearing with low running noise and reduced energy consumption. The high mechanical strength and thermal stability caused the superior carrying capacity and reliability. Therefore, the prepared PEEK composites can be a possibility to realize the water-lubricating bearing with high durability and long service lifetime.

The high-temperature mechanical properties and tribological behavior of the Al0.5CoCrFeNb0.5Ni high-entropy alloy (HEA) were investigated. The results show that Al0.5CoCrFeNb0.5Ni HEA consists of FCC, BCC and (Cr–Co–Fe)2Nb-type Laves phases. The hardness is about 572 HV at room temperature and decreases slightly at high temperatures, still maintaining a high value (>350 HV) at 900 °C. The yield strength is nearly 2000 MPa at room temperature and tends to decrease with rising temperature (800–1200 °C). The observation of the microstructure after the hot compression tests and the evaluation of the true stress-strain curves illustrate that the softening mechanism is primarily dynamic recrystallization, which occurs mainly in the FCC and BCC phases. The degree of wear increases and then decreases from 200 °C to 800 °C. The best wear resistance was observed at 800 °C, showing the maximum friction coefficient and the minimum wear rate, which was attributed to the increased oxidation that formed oxide layers mainly consisting of Cr2O3 to protect the wear surfaces. The wear mechanism of alloys is affected by temperature. Below 400 °C the wear is mainly abrasive and adhesive wear, at temperatures above 600 °C, the wear transitions from abrasive to oxidative wear, and at 800 °C the wear changes to oxidative wear.

Three kinds of circular spline materials are studied for harmonic reducers, stainless steel 2Cr13, medium carbon alloy steel 40Cr, carbon 45 steel. Through the analysis of microstructure, hardness, three-dimensional and two-dimensional morphology in microwear and friction coefficient, the differences in wear resistance of different materials are attained. The results show that the microstructures of 2Cr13 and 40Cr are tempered sorbite, and the microstructure of 45 steel is ferrite and pearlite. The hardness of the 2Cr13 and 40Cr is similar and much larger than that of the 45 steel. The morphology of 2Cr13 is adhesion and spalling, and the wear mechanism is adhesion wear. The morphology of 40Cr and 45 steel is furrow and spalling, furrow and adhesion, and the wear mechanisms are abrasive wear. The friction coefficients' differences of the three materials are negligible, and the area of wear of 2Cr13, 40Cr and 45 steel are 5 008 μm2, 1 645 μm2 and 6 535 μm2. 40Cr exhibits better wear resistance than 2Cr13 with similar hardness. The hardness difference between 45 steel and the friction pair material is the largest, and the wear resistance of the 45 steel is the worst.

A FeCrMoNiCuBSiC metallic glass coating was designed and then deposited by the high-velocity oxygen fuel (HVOF) spraying technique. X-ray diffraction, a scanning electron microscope, and a microhardness tester were applied to characterize the phase, microstructure, and mechanical properties of the coating. The amorphous phase was the main phase in the coating, and crystal phases were almost undetectable in the XRD results. The coating had a dense structure (the porosity was 1.47 ± 0.32%) and high Vickers microhardness (848 ± 22 HV0.3). The wear behavior of the coatings sliding against WC-Co was studied with a pin-on-disc wear test system and was compared with that of 316L stainless steel. The coating improved the wear resistance of the steel by around 7–9 times at different sliding speeds. As the sliding speed was increased, the wear loss rate of the steel obviously increased, yet the loss rate of the coating decreased first and then increased. This happened because the contact flash temperature induced by friction increases with the sliding speed, which results in oxidative behavior and crystallization events in the coating. The dominating wear mechanism of the coating is fatigue wear combined with oxidative wear.

High entropy alloy (HEA) has high hardness, strength and excellent friction and wear properties, which also has broad application prospects in wear-resistant and high temperature coating, aerospace and military fields. However, one third of the world's total energy is consumed by various forms of friction or wear and tear, causing untold economic losses each year. The important way to reduce the wear is to increase the hardness of materials. The surface modification of high entropy alloy is an effective way to improve the friction and wear properties. In this paper, the research progress of high entropy alloys at home and abroad in recent years is reviewed, especially the surface treatment technology which can improve the friction and wear properties of high entropy alloys is introduced, and the influence of surface strengthening treatment on the friction and wear properties and mechanism of high entropy alloys is discussed. Surface treatment mainly includes surface mechanical strengthening, surface heat treatment strengthening, chemical heat treatment strengthening, surface laser cladding treatment, surface plasma treatment, surface electron beam treatment, vapor deposition technology. The purpose of this work is to provide a reference for the research on the friction and wear property of high entropy alloy, to provide corresponding ideas for the possible industrial demand in the future, and to provide the key research direction for future application.

The effect of microstructure and mechanical properties of submicro grained commercial pure titanium (CP–Ti) on the wear mechanism is still unclear. In the present work, CP-Ti samples were subjected to multi-axial forging (MAF) and low-temperature annealing treatment to prepare ultrafine-grained (UFG) material. The mechanical properties, microstructure, and tribological characterization between coarse-grained (CG) sample and UFG samples were comparatively studied. The results showed that the MAF sample could reach a grain size of 165 nm, while its grains coarsened slightly after low-temperature annealing. The MAF sample had the highest strength and hardness and the lowest coefficient of friction, but only a 7.3 % decrease in wear rate compared to the CG sample. The 400 °C annealed MAF sample possessed a good combination of tensile strength (814 MPa) and elongation (18.6 %), resulting in the lowest wear rate of 16.8 × 10−5mm3/(N∙m). The dominated wear mechanisms of the CG sample, MAF sample and 500 °C annealed MAF sample were abrasive wear, adhesive wear and delamination wear, while the primary mechanism of the 400 °C annealed MAF sample was abrasive wear and adhesive wear. It was found that the wear mechanism transforming, higher hardness and sufficient work hardening could be responsible for lower wear rate of the 400 °C annealed MAF sample. The 400 °C annealed MAF sample showed a thinner and more homogeneous deformation layer near the worn surface, and its thickness of deformation layer was about 8 μm.

Semisolid injection molding is a novel and ideal process for manufacturing particle reinforced magnesium composites. The main purpose of this article is to reveal the wear mechanism of SiC/AZ91D composite prepared by this method. AZ91D Mg alloy and its composites reinforced with 1 % and 2.5 % SiC particles were manufactured by the semisolid injection molding method and their microstructure and wear behavior were investigated. The composites are composed of a Mg matrix, consisting of unmelted AZ91D particles distributed in a resolidified Mg base, and uniformly-dispersed SiC particles. The dry wear tests showed that adding SiC reinforcement increases the friction coefficient, enhances the wear resistance at the low loads of 5 N and 10 N, but reduces the wear resistance at the high load of 20 N. The dominant wear mechanism is abrasive wear, accompanied by small contributions from adhesive and oxidative wear.

This study examined the effects of milling parameters on the development of Ni/Al2O3 nanocomposites and the refinement of NiO and Al powders. Ball milling of certain mixtures was followed by sintering at 800 and 1100 °C for 2 h. The X-ray diffraction results of the dry-milled powders indicated that increasing the ball-to-powder weight ratio from 20:1 to 42:1 resulted in finer particles, which enabled the synthesis of Ni/Al2O3 nanocomposites by milling at 200 rpm for 1.5 h. Extending the milling duration at lower rotational speeds yielded powders with nanoscale particle sizes. However, as shown by scanning electron microscopy and energy dispersion spectroscopy, a nanocomposite with metallic matrix was formed by the mechanochemical reaction, and the crystallite size was estimated using the Williamson–Hall plot. Furthermore, we used differential scanning calorimetry diagrams to analyze the effects of milling on the temperatures of phase transformation and/or reduction reactions. The tribological performance of the developed nickel metal matrix composite was investigated using a ball-on-disc tribometer under various loading conditions. Indeed, the friction coefficient increases with the applied forces and decreases with milling. Comprehensive examinations of the worn surfaces were carried out using a scanning electron microscope and a 3D optical profiler.

A380-Yb (Ytterbium) alloy was prepared by the ultrasonic melting casting method, and effects of hot extrusion on the microstructure and wear properties of the alloy were studied. The results indicate that the addition of rare earth Yb can refine the microstructure of the matrix alloy. After hot extrusion (extrusion ratio of 22.56) of the as-cast A380-Yb alloy, the secondary phase in its microstructure was further refined and the distribution became more uniform. EBSD (electron backscatter diffraction) organizational analysis shows that the average GND (geometrically necessary dislocation) density of extruded rare earth aluminum alloy is significantly increased, by 16.5 times that of the cast matrix alloy. In addition, there are a large number of grains parallel to the orientation and orientation in the extrusion direction. The alloy undergoes dynamic recrystallization during hot extrusion, and the proportion of small-angle grain boundaries is significantly reduced. Under the same friction and wear conditions, the wear rate and average friction and wear coefficient of the extruded rare earth aluminum alloy are relatively small, reduced by 53.8% and 42.6%, respectively, compared to the cast matrix alloy. Its wear mechanism is mainly abrasive wear and slight plastic deformation. In addition, the study also found that under fixed other wear conditions, as the friction speed increases, the wear rate of the extruded rare earth aluminum alloy shows a trend of first decreasing and then increasing. However, with the increase in load, its wear rate gradually increases, and the change in wear morphology is consistent with the trend of wear rate. When the wear rate is high, the wear mechanism of the extruded aluminum alloy is mainly delamination wear and adhesive wear, and is sometimes accompanied by severe plastic deformation. When the wear rate is low, its wear mechanism is mainly abrasive wear.

The 7A04 Al alloy is a commonly used lightweight metal material; however, its low wear resistance limits its application. In this study, the wear resistance of this alloy was improved by preparing micro-arc oxidation (MAO) coatings, MAO/MoS2 composite coatings, and hard-anodized (HA) coatings on its surface. The friction and wear behaviors of these three coatings with diamond-like coated (DLC) rings under oil lubrication conditions were investigated using a ring–block friction tester. The wear rates of the coatings on the block surfaces were determined using laser confocal microscopy, and the wear trajectories of the coatings were examined using scanning electron microscopy. The results indicated that, among the three coatings, the MAO/MoS2 coating had the lowest coefficient of friction of 0.059, whereas the HA coating had the lowest wear rate of 1.47 × 10−6 mm/Nm. The MAO/MoS2 coatings exhibited excellent antifriction properties compared to the other coatings, whereas the HA coatings exhibited excellent anti-wear properties. The porous structure of the MAO coatings stored lubricant and replenished the lubrication film under oil lubrication. Meanwhile, the introduced MoS2 enhanced the densification of the coating and functioned as a solid lubricant. The HA coating exhibited good wear resistance owing to the dense structure of the amorphous-phase aluminum oxide. The mechanisms of abrasive and adhesive wear of the coatings under oil lubrication conditions and the optimization of the tribological properties by the solid–liquid synergistic lubrication effect were investigated. This study provides an effective method for the surface modification of Al alloys with potential applications in the aerospace and automotive industries.

In this study, the effects of applied pressure (0, 90, 120, and 150 MPa) during solidification on the microstructure, mechanical properties, and impact–abrasive wear resistance of Cr-Mn-Mo steel prepared by squeeze casting were systematically investigated. The results demonstrated that the materials produced under pressure showed smaller grains compared to those of the samples fabricated without pressure. Compared to the unpressurized sample, the grain diameter of the sample prepared at 120 MPa decreased by 37.7%, the length of the primary arm shortened by 40.7%, and the spacing of the secondary arm contracted by 14.1%. Furthermore, the impact toughness results indicated that the samples prepared without pressure exhibited brittle fracture characteristics, whereas quasi-destructive fractures predominated in the samples prepared at 120 MPa. Simultaneously, three-point bending strength exhibited a gradual increase with increasing pressure, reaching a maximum value of 855.5 MPa when prepared under 150 MPa. Additionally, the impact–abrasive wear resistance of Cr-Mn-Mo alloyed steel produced by squeeze casting was significantly enhanced compared to the samples produced without pressure. The samples without external pressure exhibited a combination of abrasive and adhesive wear, whereas the wear characteristics of the samples prepared under pressure includes grooves, cutting marks, flaking pits, and accumulating ridges.

Impregnated graphite is a common material for friction pairs in aeroengine seals, especially at high temperatures. For the convenience of the application of graphite materials in aeroengines, an SRV-4 tribometer and a synchronous thermal analyzer are employed to study the tribological properties and thermal stability of pure, resin-impregnated, metal-impregnated, and phosphate-impregnated graphite against stainless steel from room temperature to 500 °C. The results indicate that impregnations can improve the wear resistance and thermal stability of graphite at high temperatures. Compared with other impregnated graphite materials, the resin-impregnated graphite shows a good friction coefficient and poor wear rate and thermal stability over 300 °C, due to the degradation and oxidation of the resin-and-graphite matrix. The metal- and phosphate-impregnated graphite materials exhibit excellent wear resistance and thermal stability under 500 °C as a result of the protection of the impregnations, while the average friction coefficient of the metal-impregnated graphite is much greater than the phosphate-impregnated graphite, and even reaches 2.14-fold at 300 °C. The wear rates for the graphite impregnated with resin, metal, and phosphate are 235 × 10−7, 7 × 10−7, and 16 × 10−7 mm3N−1m−1 at 500 °C, respectively. Considering all aspects, the phosphate-impregnated graphite exhibits excellent tribological properties and thermal stability.

In fields such as industrial engineering and healthcare, additive manufacturing technology is a focal point for researchers. Wear represents a significant challenge for additive manufacturing technology, increasingly emerging as a research hotspot in recent years. This review categorizes and summarizes wear issues in additive manufacturing technology, providing a comprehensive overview of wear mechanisms, materials, and the effects of additive manufacturing processes on wear. Research indicates that different wear mechanisms result in varying wear characteristics. The inherent properties of the materials significantly influence wear during the manufacturing process. Modifying material compositions and optimizing microstructures can enhance the wear properties of additive manufacturing products. Additionally, the study of additive manufacturing technology in repair and maintenance is a current and anticipated research hotspot for the coming decades. In the research of additive manufacturing processes, the effective regulation of process parameters and their post-processing play a positive role in enhancing the wear characteristics of products produced via additive manufacturing. Lastly, the challenges and recent advancements concerning wear issues in the field of additive manufacturing technology research are summarized.

Aiming at the problems of low processing efficiency, low groove shape accuracy and poor surface quality caused by grinding wheel wear in the grinding process of Cf/SiC composite grooves. In this paper, based on the motion mode of grinding wheel grinding, the wear volume formula of grinding wheels was analyzed, and the grinding wheel wear comparison experiment of different bond diamond grinding wheels grinding Cf/SiC composite grooves was carried out, and the more suitable kind of diamond grinding wheel for grinding Cf/SiC composite grooves was selected. From the experimental results, compared with the ceramic-bonded diamond wheel and resin-bonded diamond wheel, the grinding times of electroplated diamond wheel grinding Cf/SiC composites were increased by 20 and 104, respectively, and the surface roughness of the groove was most stable and the processing damage was smallest. Therefore, the best quality of grinding Cf/SiC composites groove was obtained by the electroplated diamond grinding wheel, and its life in grinding Cf/SiC composites was the longest. At the same time, the wear mechanism of the electroplated grinding wheel was explored, the wear on the bottom surface of the electroplated grinding wheel was more serious than that on the circumferential surface. The wear on the bottom surface was mainly wear and tear, and it gradually diffused along the inner diameter of the grinding wheel with the increasing grinding times.

The ceramic-steel-pentaerythritol ester system has a broad application prospect under high temperature conditions, which are respectively in the fields of aviation, aerospace and advanced equipment manufacturing. However, a comprehensive understanding of the friction and wear mechanisms of this system across a broad temperature range remains elusive. The tribological properties of the system at 25–475 °C were studied. With the increase of temperature, the evolution of the tribofilm follows the sequence: discontinuous tribofilm → uniform tribofilm → tribofilm removal. At 200–300 °C, an approximately 100 nm thick amorphous PxOy compound tribofilm is formed, and its nanohardness and modulus are reduced by 81.33 % and 54.02 %, respectively, compared with base steel. The tribofilm effectively reduces shear resistance by blocking friction pair contact. When the temperature exceeds 300 °C, it will lead to high-temperature coking, which adversely affects the lubrication performance. It is worth noting that the system can endure short-term service at a maximum temperature of 475 °C. Therefore, this research can help achieve continuous, stable operation of high-temperature resistant systems, as well as short-term use under extreme conditions encountered by complex equipment.

For M50 bearing steel, which is widely used in aerospace engine main bearings, fretting wear is an important but neglected category of wear failure during engine cold startup. High temperature tempering is crucial in heat treatment to enhance its microstructure and wear resistance. In order to investigate the influence of different tempering conditions on fretting wear performance of M50 steel, it is essential to conduct a comprehensive study. This research explores how heat treatment processes affect the fretting wear properties of M50 steel by varying the tempering temperature (450 °C, 500 °C, 550 °C, 600 °C, and 650 °C). We analyzed the microstructure evolution and fretting wear behavior under different conditions using SEM, EDS, XRD and other characterization methods. The results show that the tempering temperature influences fretting wear through martensite, retained austenite, and carbide transformations. In the 450 °C–600 °C range, wear volume and wear rate decrease with hardness. At 550 °C tempering, M50 achieves the highest hardness (59.71 HRC) and a lower wear rate (9.661 × 10−8 mm3/(N·mm)). M50 steel exhibits optimal fretting wear performance at 550 °C tempering. Overall, wear behavior occurs in the mixed slip regime, shifting towards partial slip with higher tempering temperatures. When the tempering temperature is low, the fretting wear mechanism is predominantly dominated by fatigue wear and abrasive wear, while at higher tempering temperatures, the fretting wear mechanism is primarily governed by oxidative wear and adhesive wear.

Plasma Mo–Si–Ti coating including the (Ti, Mo)5Si3, MoSi2 and TiSi was prepared on γ-TiAl surface to improve the wear resistance. The coating had 12-μm deposition layer and 5-μm diffusion layer, as well as gradual decrease of grain size from substrate to coating, providing gradient structure and high fracture toughness. Hardness (H), elasticity modulus (E), H/E and H3/E2 values of substrate and coating were 8.4 and 19.6 GPa, 167.2 and 251.8 GPa, 0.050 and 0.078, and 0.021 and 0.119 GPa, indicating that coating had high hardness, resistance to plastic deformation and load bearing capacity. During friction, both the substrate and coating showed abrasive and oxidative wear. The substrate flaked off in the form of large wear debris, causing the high wear rate. However, oxide film and compacted layer of fine debris made the wear rates of substrate to decrease as the load increased. The coating released most of external stress in the form of elastic work, showing high load-bearing capacity. High fracture toughness inhibited the generation of cracks and reduced the spallation of coating. Moreover, fine grains promoted the generation of oxide film on coating surface and improved the adhesion between oxide film and coating. Meanwhile, the presence of oxide film resulted in a reduction of wear rate as the load increased. The excellent nanomechanical properties and fracture toughness reduced the fracture of coating and reduced the specific wear rate of γ-TiAl by about 98%, which could effectively improve the wear resistance of γ-TiAl at room temperature.

In this study, Al–7Si–Cu alloys with different contents of Cu were prepared by ultrasonic agitation casting method. The microstructures were characterized by scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). Dry sliding friction and wear properties with different Cu contents and loads were investigated. The results indicated that the alloy with 3.0 wt% Cu content revealed the optimal microstructure, comprehensive mechanical properties, and tribological properties. The hardness, tensile strength, and yield strength were enhanced by 83%, 57%, and 59%, respectively. The friction coefficient and wear rate reduced by 33% and 24% at 40 N load, respectively. The wear mechanism of Al–7Si–Cu alloy was mainly abrasive wear and delamination wear accompanied by oxidation wear. The improvement of the tribological properties of the alloy was attributed to the combined improvement of the microstructure and mechanical properties.

Depositing two martensitic stainless steel filler metals with chemically different composition, crane wheels were restored to study the development of mechanical properties and wear resistance. For this purpose, a two-layer clad was deposited using each filler metal through submerged arc welding process. Microstructural evolution shows that solidification modes are different in the hardfaced clads due to the discrepancy in the ratio of chromium equivalent to nickel equivalent (Creq/Nieq). A reduction in Creq/Nieq leads to the enrichment of liquid metal in austenite-promoter elements, resulting in the presence of austenite phase in the matrix, as identified by XRD pattern. Following a post-weld heat treatment in the constant temperature of 500 °C for an hour, apart from the tempered martensite, fresh martensite as a consequence of transforming austenite phase is formed in the matrix. This transformation significantly increases the mean value of microhardness from 360 to 462 HV0.3. Also, uniaxial tensile test shows that the formation of fresh martensite approximately limits the elongation of the clad. The fractography studies show that the fracture mode in both clad is the same and ductile, with embedded carbides in dimples. Tribological behavior of the clads shows that the formation of fresh martensite in the clad results in higher wear resistance, with specific wear rate of 1.8 × 10−5 mm3/Nm at the maximum load. In addition, oxidative wear mechanism is dominant at lower load of 10 N, while the wear mechanism changes at higher load of 60 N to severe plastic deformation.

This study explores MAX-phase materials for self-lubricating performance in high-speed turbomachinery, especially for aircraft engines and diverse industries. Ti2AlC was effectively synthesized and sintered using spark plasma sintering (SPS) under vacuum conditions at 30 MPa and 1000 °C, followed by rigorous cyclic oxidation at 1200 °C. The microstructure, element distribution, and phase analysis of the sintered and worn surfaces were examined using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Mechanical properties were evaluated through Vickers hardness and nanoindentation tests, while tribological properties were examined using wear tests. The results indicated that TiO2 and Al2O3 had a self-lubricating or anti-wear effect, significantly decreasing the wear rate. Furthermore, a transition was observed in the wear rate, going from high to low. This change was attributed to the formation of TiC particles, which can deform plastically and further reduce the overall wear rate.

In this study, high-temperature nitriding was used to improve the surface hardness and wear resistance of Co–27Cr–22Fe alloy in a thermogravimetric analyzer. The high-temperature nitriding treatments were performed at 1200 °C for 3 and 10 h. Subsequently, at room temperature, the dry sliding wear test was carried out, and the possible effects of load on friction performance and microstructure of different specimens were investigated. The results show that the microstructure of as-received specimens is composed of γ-Co and MC carbides, while the microstructure of the nitrided specimens contains γ-Co, MC carbides, acicular AlN, and granular (Ti, Nb)N. The thickness of the nitriding layer is 375 μm and 708 μm for nitriding 3 h and nitriding 10 h, respectively. An improvement in microhardness (∼425 HV) was attained for nitrided specimens. For the as-received specimens, the wear rate decreases with increasing load. The as-received specimen exhibits better wear resistance than the nitrided specimen under a high load (∼30 N). The wear mechanism under different loads was mainly abrasive wear, accompanied by adhesive wear. For the nitrided specimens, the specimens show different wear mechanisms under varying loads. Under low load (∼5 N and ∼15 N), the high-temperature nitriding improves the wear resistance, and it exhibits abrasive wear and oxidative wear. Under high load (∼30 N), the wear resistance of the nitrided specimen was significantly reduced, and the wear mechanism is mainly abrasive wear, fatigue wear, and oxidative wear.

Abstract Introduction: The thermal spraying method with the aim of increasing the working life of steel parts is one of the most important solutions in surface engineering to solve the problem of wear. Methods In this research, NiCrBSi and NiCrBSi-MoS2 coatings were applied on 304 stainless steel by thermal spraying, and then the wear behavior was evaluated at ambient temperature and 500 degrees. Phase investigations were done by X-ray diffraction test. The chemical composition of the coatings was checked with the help of energy dispersive spectrometer analysis. Porosity was investigated with the help of optical microscope and scanning electron microscope images. The hardness of the samples was measured using a microhardness test. In order to check the adhesion and tribological behavior of the coatings, VDI3198 and ASTM-G99 pin-on-disk tests were used, respectively, and finally, the wear mechanism was evaluated using SEM images and EDS analysis of the wear surfaces of the samples. Findings: Phase analysis (XRD) and chemical composition (EDS) showed that the coating has an amorphous and crystalline phase and the most important phases of the coating are nickel-gamma, carbide and boride. Porosity measurement results with the help of image analysis software showed higher porosity of NiCrBSi-MoS2 coating. The results of hardness measurement from the cross-section of the samples indicated an increase in the hardness of the substrate in the presence of coatings, and the addition of MoS2 particles decreased the hardness of the NiCrBSi coating. The coating with MoS2 has better adhesive behavior due to its crystalline structure and better plastic deformation ability. The tribological results indicated the superiority of the NiCrBSi-MoS2 coating due to the appropriate ability of plastic deformation as well as the intrinsic lubrication property (based on the crystal structure) in this test. It was found that at ambient temperature, the samples mainly had lamellar wear mechanism, and at high temperature, oxidation wear as a secondary mechanism helped to destroy the surface. Conclusion: The addition of MoS2 to NiCrBSi coating caused more porosity, more roughness, less hardness and better wear behavior of the coating. The addition of MoS2 to the coating improved the wear resistance of the coating at high temperature.

The intensive quenching process compared to traditional methods results in a lower quenching cracking tendency. The comprehensive mechanical properties of an intensive quenching workpiece has good advantages. In order to improve the performance and product quality of a 45 steel workpiece, the hardening–tempering treatment used in the traditional quenching process is replaced by an intensive quenching process. This study investigates the tribological properties of 45 steel and their differences and connection under the intensive quenching and high-temperature tempering process in comparison to when under the traditional hardening–tempering process. Both intensive quenching and tempering and hardening–tempering workpieces are composed of carburized particles and ferrite. Compared with hardening–tempering workpieces, intensive quenching and high-temperature tempering workpieces have a finer and more uniform microstructure and higher hardness, impact toughness, and yield strength. Wear tests show that intensive quenchingand tempered specimens have better wear resistance. At the same frequency, the coefficient of friction and relative wear rate of the intensive quenching and tempering specimens were lower than those of the hardening–tempering treatment, and the wear surface was flatter. The wear morphology shows that the main wear mechanisms of the intensive quenching and tempering workpieces and those of hardening–tempering are abrasive and adhesive wear, and that the main wear mechanism changes from adhesive wear to abrasive wear as the frequency increases.

Poly Ether Ether Ketone (PEEK) is a kind of special engineering plastic with excellent properties such as high-temperature resistance, self-lubrication, wear resistance, and high mechanical strength. However, its blending or composite modification applications still face numerous challenges. The primary objective of this research was to evaluate the friction and wear performance of a three-layer self-lubricating bearing bush, which was made from a modified material containing short carbon fiber and Poly Ether Ether Ketone (SCF/PEEK). The bearing bush is used as a surface contact layer on the pistons of a hydraulic motor in the interface with the cam roller. The bearing bush was processed using a 15% SCF-modified PEEK material, and the friction and wear test was conducted using a self-built friction test machine. This study aimed to assess the frictional and wear characteristics of the SCF/PEEK-modified material in the bearing bush. The results show that as the experimental pressure rises from 15 MPa to 25 MPa, the friction coefficient of the SCF-modified bearing bush experiences a significant decrease from 0.420 to 0.296. Furthermore, the stability of the frictional morphology of carbon fibers indicates its effective adaptability to low speed and high load conditions.

High-entropy carbide ceramics have attracted extensive attentions for potential applications as high temperature structural materials, the mechanical and tribological performance of (TiNbTaWMo)C high-entropy carbides over wide temperature range combined with the oxidation behavior were investigated in the present study. (TiNbTaWMo)C high-entropy carbides were successfully prepared from five kinds of carbide powders by spark plasma sintering at 2000 °C. The mechanical properties of (TiNbTaWMo)C and the tribological performance at room temperature –800 °C were studied. The Vickers hardness, bending strength and fracture toughness of the sintered (TiNbTaWMo)C high-entropy carbides are 21.31 ± 0.43 GPa, 477.15 ± 34.17 MPa, and 6.41 ± 0.85 MPa m1/2, respectively. At room temperature, the friction coefficient is stable at 0.35, and the wear rate is as low as 3.39 × 10−7 mm3/Nm. With temperature increasing, friction coefficient increases firstly and decreases above 600 °C, which is contributed by the formation of oxide films at high temperatures. The wear mechanisms of (TiNbTaWMo)C high-entropy ceramics at different temperatures were discussed in detail by microstructures and phase analysis of the worn surfaces together with the oxidation behaviors of (TiNbTaWMo)C at 600 °C and 800 °C.

Ni–Mo–SrSO4 composites with different Mo amount were prepared by hot pressing in a vacuum. The oxygen-deficient environment derived from the degradation of SrSO4 during fabrication process led to the formation of SrMoO4, Sr2NiMoO6, and SrO in the sintered composites. With the increment in the contents of Mo, excessive dissolved Mo atoms accelerated the oxidation of Ni in the oxygen-deficient environment, which eradicated SrMoO4 phase. As compared to sintered material containing Sr2NiMoO6 and SrO, the appearance of SrMoO4 led to a distinct decrease in the density and microhardness. To reveal the effect of SrMoO4 on the wear mechanism, the tribological properties of the sintered composites against Al2O3 ball were investigated at different temperatures. The result indicated that the in-situ composite consisting of 80.75 wt.% Ni, 14.25 wt.% Mo, and 5 wt.% SrSO4 exhibited good friction and wear properties at room temperature (RT) and 800 °C, which was attributed to the development of the intact tribofilm with grooves consisting of SrMoO4, Sr2NiMoO6, NiO, and h-MoO3 at RT and the synergistic lubricating effect of SrMoO4, Sr2NiMoO6, and oxides (NiO, α-MoO3, SrMoO4, α-NiMoO4, and β-NiMoO4) at 800 °C.

The tribological properties of the self-lubricating polymer were improved by strengthening the properties of the transfer film. The graphene oxide (GO) reinforced polytetrafluoroethylene (PTFE)/poly-p-phenylene terephthamide (PPTA) composites (GPPs) were prepared by dual-size synthesis. The tribological properties of GPPs were studied on a ball-on-disk tribometer. GPPs have low friction coefficient (minimum = 0.061) and hydrophobicity (maximum = 137.1385°). The structure–property relationships and the practical effect of transfer film enhancement induced by GO were revealed. We attempt to provide guidance for the GO reinforced self - lubricating polymers design. Finally, in light of the excellent properties of GPPs, this study provides guidance for the GO reinforced self - lubricating polymers design.

Abstract The polyetheretherketone (PEEK)-highly cross-linked polyethylene (XLPE), all-polymer knee prosthesis has excellent prospects for replacing the traditional metal/ceramic-polyethylene joint prosthesis, improving the service life of the joint prosthesis and the quality of patients’ life. The long-term wear mechanism of PEEK-XLPE knee joint prosthesis is comprehensively evaluated from wear amount, wear morphology, and wear debris compared to that of CoCrMo-XLPE joint prosthesis. After 5 million cycles of in vitro wear, the wear loss of XLPE in PEEK-XLPE (30.9±3.2 mg) is lower than that of XLPE in CoCrMo-XLPE (32.1±3.1 mg). Compared to the XLPE in CoCrMo-XLPE, the plastic deformation of XLPE in PEEK-XLPE is more severe in the early stage, and the adhesive peeling and adhesion are lighter in the later stage. The size distribution of XLPE wear debris in PEEK-XLPE is relatively dispersed, which in CoCrMo-XLPE is relatively concentrated. Wear debris is mainly flake and block debris, and the wear mechanism of XLPE was abrasive wear. The wear volume per unit area of PEEK femoral condyle (10.45×105 µm3/mm2) is higher than that of CoCrMo (8.32×105 µm3/mm2). The PEEK surface is mainly furrows and adhesions, while the CoCrMo surface is mainly furrows and corrosion spots. The PEEK wear debris is mainly in flakes and blocks, and the CoCrMo wear debris is mainly in the shape of rods and blocks. The wear mechanism of PEEK is abrasive wear and adhesion, and that of CoCrMo is abrasive wear and corrosion.

Abstract Epoxy resin (EP) composites with satisfactory thermal and tribological performance are highly required for engineering moving components. However, the simple addition of fillers leaded to the serious filler agglomeration and limited promotion in tribological properties. In this work, we constructed a new kind of three-dimensional (3D) reduced graphene oxide (RGO)/Si3N4 hybrid aerogel for EP composites, which was prepared by a facile hydrothermal self-assembly method followed by freeze-drying technique. As a result, the dispersibility of Si3N4 whiskers was greatly improved through wrapping of polydopamine—polyethyleneimine copolymer (PDA—PEI) copolymer and physical spacing of 3D skeleton. Furthermore, benefiting from the synergistic effect of RGO and Si3N4@PDA—PEI in the thermal network, the thermal conductivity of RGO/Si3N4 hybrid aerogel (GSiA)—EP increased by 45.4% compared to that of the neat EP. In addition, the friction coefficient and wear rate of GSiA—EP decreased by 83.7% and 35.8%, respectively. This work is significant for opening a tribological performance enhancement strategy though constructing 3D hybrid architecture.

Abstract The fretting wear among the steel wires aggravates the wire rope’s fatigue damage, affects the service performance of the wire ropes, and threatens mine hoisting safety. In this paper, the practical friction behavior and wear mechanism among the wires in the wire rope are investigated. A series of tests were carried out on multiple steel wires in helical contact and tension-torsion coupling under different fretting parameters, twisting parameters, and lubrication conditions by self-made friction and wear testing machine. The results show that the coefficient of friction (COF) among the steel wires decreases slightly with increasing lateral loads and tension, and the effect of twist angle on the COF has opposite results under different lubrication conditions. Lateral loads, tension of the steel wires, twist angle, and lubrication condition all affect the fretting morphology among the steel wires. Fretting wear with larger twist angle structure leads to more energy loss. The energy loss of fretting is directly related to the fretting morphology among the contact surfaces, and the dissipated energy is lower in the two forms of complete slip and sticking. The wear depth and width increase with the increase of lateral loads, steel wire tension, and twist angle. And the wear width and depth under dry friction conditions are higher than those under oil lubrication conditions. In addition, the wear mechanism under dry friction conditions is mainly abrasive wear, adhesive wear, and fatigue wear. And the wear mechanism under oil lubrication conditions is mainly abrasive wear and fatigue wear.

NiMo alloy and NiMo–5SrSO4 composite were fabricated to reveal the effect mechanism of Sr2NiMoO6 and SrO derived from the decomposition characteristics of SrSO4 in vacuum on the microstructure, density, microhardness, and tribological properties against Al2O3 ball at different temperatures. The formation of Sr2NiMoO6 and SrO led to a negligible increase in the density and microhardness of the sintered composite. Below 400 °C, compared to NiMo alloy, the poor tribological properties were observed in NiMo–5SrSO4 composite, which was responsible for the appearance of Sr2NiMoO6 and SrO on the worn surface. However, with the further increase in the temperature, the friction coefficient and wear rate of NiMo–5SrSO4 composite reached as low around 0.26 and 1.32 × 10−5 mm3/Nm at 800 °C respectively, which was attributed to the synergistic lubricating effect of SrMoO4 generated from the tribochemical reaction between SrO and MoO3, Sr2NiMoO6, and oxides (MoO3, NiO, and NiMoO4) on the rubbing surface.

ABSTRACTDue to the processing of alumina ceramic cutting tools with complex shapes using traditional methods is difficult and time-consuming, vat-photopolymerization-based 3D printing was adopted to fabricate Al2O3 ceramic cutting tools with grooves for the first time. Subsequently, cutting performance evaluation and wear mechanism analysis were conducted. The relative density, Vickers hardness, and bending strength of the alumina cutting tools were determined. The effects of the cutting speed, feed rate, and cutting depth on the cutting performance and wear mechanism of the cutting tools were systematically investigated. In addition, two commercial cutting tools, namely cemented carbide and ceramic tools without grooves, were used for comparison. The cutting speed has the highest influence on the cutting performance, whereas the cutting depth has the least influence. The cutting performance of the prepared alumina cutting inserts with chip breaker grooves superior to that those without chip-breaking grooves and that of the cemented carbide tools. The wear mechanisms of the prepared alumina cutting tools and commercial tools were determined to be abrasive and adhesive wear, and those of the cemented carbide tools were adhesive wear and breakage. This work opens a new avenue for the future preparation of high-performance and complex-shaped ceramic cutting tools.

In order to explore the wear mechanism of Cr4Mo4V bearing steel under the condition of instantaneous dry friction， the silicon nitride ball and Cr4Mo4V steel disc friction pair were used to explore the influence of load changes on the friction characteristics of Cr4Mo4V bearing steel under the conditions of an ambient temperature of 300 ℃， a speed of 0.3 m/s and a sliding dry friction. Results showed that when the load increased in the range of 1.2～2.4 GPa，the friction coefficient of Cr4Mo4V bearing steel decreased from 0.89 to 0.42，while the wear rate increased from 2.05×10-6 mm3/(N·m) to 2.68×10-6 mm3/(N·m). Oxidation reaction occurred on the worn surface， and the types of oxides produced under different load conditions were different. Besides， the main wear mechanisms of Cr4Mo4V were oxidation wear and adhesion wear.

45 steel has the problems of low wear resistance and poor corrosion resistance. CoCrFeMnNiMox (x=0.00, 0.25, 0.50, 0.75, 1.00) high-entropy alloy coating was prepared on 45 steel by laser cladding. The influence of Mo on the microstructure and properties of coating were explored in detail. The results show that the CoCrFeMnNiMox high-entropy alloy coating is composed of a single face-centered cubic (FCC)solid-solution phase. The microstructure of the Mo-containing coating is a typical dendritic and interdendritic structure, which is caused by the heterogeneous nucleation of the molten pool during the solidification process. The microhardness of the coating increases with the increase of x, and the maximum microhardness of the Mo1.00 coating is 2.391 GPa. Quantitative calculations show that solution strengthening is the main reason for the increase of microhardness. With the increase of Mo mass fraction, the wear mechanism evolves from adhesive wear to abrasive wear and oxidative wear. The Mo1.00 coating has the lowest volume wear rate (0.68×10-4 mm3/(N·m)). The influence of the passivation process on the corrosion resistance of coating was analyzed based on the point defect model theory. The addition of the Mo element increases the dehydration rate of the passivation behavior of coating, which makes the oxide layer thicker, and thereby improving the corrosion resistance of coating. The corrosion mechanism of coatings is intergranular corrosion. Mo0.75 coating has the smallest self-corrosion current density and the most positive self-corrosion potential, which are 3.69×10-6 A/cm2 and -0.432 V, respectively.

This article investigates the sliding wear behavior of ZTA (zirconia toughened alumina) particle (ZTAp)- and NbC (niobium carbide) particle (NbCp)-reinforced Fe60 matrix composites (ZTAp–NbCp/Fe60). ZTAp–NbCp/Fe60 was produced through vacuum sintering and tested on an M-2000 wear-testing machine. As revealed by the results, the wear loss increased with the increase in rotation speed and load. Abrasive wear occurred in the mild wear region; adhesive wear and serious abrasive occurred in the moderate wear region; and fatigue wear and ZTAp broken occurred in the severe wear region. According to the aforementioned conclusions, a more clean and intuitive wear mechanism diagram was established. In the process of wear, ZTAp was well combined with the matrix, and there was no crack at the interface. Meanwhile, in the wear process, ZTAp could block furrow, weaken the wear of the micro-convex ring, and improve the sliding wear performance of the composite material.

The effect of the microstructure of siliconized graphite on tribological properties is investigated by using a high-temperature and high-pressure water-lubricated tribometer on a self-mated ring-on-ring configuration under an applied load of 500–1500 N with a spindle speed of 100–5000 rpm in both 90 °C (5 MPa) and 25 °C (1 MPa) water environments, respectively. The Stribeck curves measurement and continuous wear tests are performed and analyzed in both water environments. The wear behaviors of the graphite, SiC, and free-silicon phases in siliconized graphite are demonstrated to explore the wear mechanism. The larger wear depths of a low-worn surface roughness on the three phases contribute to the boundary lubrication. The shallower wear depths are observed on the SiC and Si phases under the mixed lubrication, corresponding to partial contact wear of surface asperities. The wavy surface of the SiC phase and uniform flow-oriented striae of the Si phase are attributed to hydrodynamic lubrication, caused by full water film scouring the worn surface. Finally, an integrated evaluation method of G duty parameters is successfully used to identify the lubrication regimes of siliconized graphite from the boundary, mixed, to hydrodynamic lubrications for a water-lubricated thrust bearing application in the main coolant pump of a nuclear power plant.

Abstract Background Wear is a destructive phenomenon and one of the principal causes of material failure in moving components during surface interaction while in service. AlCoCrCuFeNi high-entropy alloy with its many properties is a potential material for aero-engine applications attributed to its outstanding relatively lightweight, high strength, good thermal, oxidation, and corrosion resistance properties. Hence, the investigation into the tribological behaviour of AlCoCrCuFeNi high-entropy alloys is essential to reduce maintenance costs and prolong the service life of this advanced material for aerospace applications. Most AlCoCrCuFeNi high-entropy alloy compositions were fabricated via arc melting, which has been reported to have defects attributed to slow solidification, consequently reducing the mechanical properties of the alloy with limited reports on other fabrication methods. Therefore, there is a need for the use of advanced manufacturing techniques for fabricating these alloys to improve the tribological properties. In this study, AlCoCrCuFeNi high-entropy alloy was fabricated via laser metal deposition. The influence of the laser processing parameters, rapid solidification, and the applied load on the tribological properties of the as-built alloys under dry conditions has been studied for aerospace applications. The counter ball rolling friction analysis was also investigated using COMSOL Multiphysics. Results The results showed that at a high laser power of 1600 W and a scan speed of 12 mm/s, the lowest wear rates and highest hardness values were observed. The average coefficient of friction at room temperature was 0.1 and 0.3 at a speed of 21 m/s. The dominant wear mechanism at room temperature was abrasive wear as the wear rate increased linearly with an increase in load from 10 to 20 N. The scan speed had the most significant influence on the wear behaviour of the as-built high-entropy alloy attributed to the rapid rate of solidification which occurs at higher scan speeds. Conclusions The study examines the wear characteristics of high-entropy alloys fabricated via laser deposition technique in comparison with those fabricated via conventional routes. Although there were similarities in the phase structures of both techniques, the results showed that the wear resistance of the laser-deposited high-entropy alloy was comparatively higher than the same alloy prepared via conventional methods. Laser additive manufacturing was concluded to be a more successful method in fabricating high-entropy alloys.