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Inspired by rhombic textures on shark skin surface, this paper designs bionic micro-textures filled by solid lubricants SnAgCu and Ti3C2TX to improve the tribological properties of 42CrMo steel. Compared with 42CrMo steel, the average friction coefficient and wear depth of 42CrMo-SnAgCu-Ti3C2TX with bionic micro-textures at 25 N were separately decreased by 41.52 and 79.07%, and decreased by 50.77 and 80% at 35 N, respectively. Two-dimensional material Ti3C2TX can be well combined with SnAgCu to promote the formation of a smooth and continuous lubricating film on the worn surface, which plays an excellent antifriction and wear resistance role under the specific working conditions. [ABSTRACT FROM AUTHOR]

To improve the tribological performance of CSS-42L bearing steel, smooth surfaces (SSs), groove-textured surfaces (GSs), GSs with Sn-Ag-Cu (GSs-SAC), and GSs with Sn-Ag-Cu-Ti3C2 (GSs-SACT) were prepared on CSS-42L. In addition, experimental studies were conducted on tribological properties. The obtained results indicated that GSs-SACT exhibited the best anti-friction and noise reduction performances. These remarkable tribological performances were attributed to the synergistic effects of grooves, Sn-Ag-Cu, and MXene-Ti3C2. The inconsistent rules of frictional forces were improved by the grooves and SACT, which inhibit the friction-induced noise. The micro-nano size-effects of MXene-Ti3C2 enhanced the repairing effect and anti-friction property of composite lubricants, which improved the profile characteristics of GSs-SACT. [ABSTRACT FROM AUTHOR]

The superior tribological properties of bearings with low friction appear to be actualized by not a single lubrication, but the adaptive multi-mode co-lubrication in which the interface can adjust according to the friction conditions. This study attempts to reveal the friction adaptive mechanism of textures under grease lubrication. The single-stage linear groove surfaces (SLGSs) and the multi-stage bionic texture surfaces (MBTSs) were respectively designed, and MXenes lithium composite grease (MLCG) with MXenes as an additive was prepared. Compared with the non-textured surface, the friction coefficient of MBTS-1.5 is reduced by 67.6%, and the wear rate is reduced by 45.4%. The friction contact area presents an adaptive multi-mode lubrication trend from oil to grease-solid synergistic lubrication. [Display omitted] • MBTSs can help to improve the flow characteristics of grease. • MXenes and thickener could achieve the synergistic self-repairing effect. • MXenes can form a beneficial friction layer at the friction interface. • Multi-mode lubrication system has excellent adaptability and reliability. [ABSTRACT FROM AUTHOR]

To expand the applications of MXene-Ti3C2 in the field of oil lubrication, rounded groove surfaces filled with Sn-Ag-Cu-Ti3C2 on CSS-42L bearing steel (RGSs-SACT-600) were prepared. Block-on-ring friction and vibration tests under oil lubrication were carried out. The results showed that the synergistic effects of Sn-Ag-Cu-Ti3C2 and grooves improved the variation characteristics of friction forces and reduced friction and vibration on the surfaces. Sn-Ag-Cu-Ti3C2 with excellent adsorption to lubricating oil suppressed the oil film rupture and improved the heat dissipation at the friction interface. The tribochemical reactions were induced by Sn-Ag-Cu and Sn-Ag-Cu-Ti3C2, improving the tribological properties on the worn surfaces. Under low speed and high load, RGSs-SACT-600 with uniform profiles had excellent bearing capacity and antifriction performance. [ABSTRACT FROM AUTHOR]

Improving the tribological properties and reducing the friction noise of Inconel 625 is of great significance for the extended application of Inconel 625 in mechanical parts and other fields. In this paper, composite anti-wear surfaces (CASs) with micro-texture filled by Sn-Ag-Cu (SAC) were prepared. The tribological and frictional noise properties of CASs and smooth surface (SS) with different texture spacing during dry sliding friction process were studied through a series of experiments, tests and analyses. The results show that CASs can improve tribological properties and noise suppression performance significantly. With the texture density of 25 % (CASs-1200), the friction coefficient is 0.464 under a load of 20 N, the wear rate is about 2.65×10−5 mm3/(N·m), and the friction noise is 88-89.5 dB. Due to the synergistic effect of surface microgrooves and solid lubricants, the excellent tribological performance of CASs was realized. Microgrooves make the lubricant mixture be easier precipitated onto the worn surface. An intact lubrication film with high shear fitness was formed on the worn surface, reducing the direct contact between the grinding ball and the substrate. Meanwhile, it reduces the radiated energy generated by the collision between the counterpart ball and matrix and the transition of counterpart ball on the uneven small platform, so as to achieve the effect of noise suppression. Especially, suppression effect of high-frequency noise in 2400-3000 Hz is close to 100 % in CASs-1200, inhibiting the high-frequency scream effectively. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the friction noise properties of M50 matrix curved microporous channel composites filled with solid lubricant Sn-Ag-Cu (MS). Design/methodology/approach: Pure M50 (MA) and MS are prepared by selective laser melting and vacuum-pressure infiltration technology. The tribological and friction noise properties of MA and MS are tested through dry sliding friction and then the influential mechanism of surface wear sate on friction noise is investigated by analyzing the variation law of noise signals and the worn surface characteristics of MS. Findings: Experimental results show that the friction noise sound pressure level of MS is only 75.6 dB, and it mainly consists of low-frequency noise. The Sn-Ag-Cu improves the surface wear state, which reduces self-excited vibration of the interface caused by fluctuation of friction force, leading to the decrease of friction noise. Originality/value: This investigation is meaningful to improve the tribological property and suppress the friction noise of M50 bearing steel. [ABSTRACT FROM AUTHOR]

Based on the microporous structure lubrication method, Ti6Al4V(TC4)-based self-lubricating composites (TC4-SAC) with microporous channels filled by lubricant Sn-Ag-Cu are prepared. The effects of microporous channel parameters on stress and deformation of TC4-SAC are analyzed by finite element method. In addition, the friction and wear behaviors of TC4-SAC with different microporous channel parameters are compared, and the self-lubricating mechanisms of TC4-SAC are also analyzed. The results show that microporous channel parameters have a significant influence on the mechanical and tribological performance of TC4-SAC. Moreover, when the vertical depth of microporous channel = 3.5 mm, the micropore pitch = 3 mm, and the micropore diameter = 0.8 mm, TC4-SAC can obtain the best mechanical property and self-lubricating characteristic. [ABSTRACT FROM AUTHOR]

To overcome the poor tribological performance of M50 and widen its working range under high temperature, M50-Sn-Ag-Cu composites with curved microchannels (MCCs) and straight microchannels (MCSs) were prepared by Laser Additive Manufacturing Technology, respectively. Tribological properties of M50-based composites were studied. The results showed that MCCs had the better tribological performance. At 25 °C-15 N-0.2 m/s, compared with MCSs, the average friction coefficient of MCCs at the stable friction stage was reduced by 10.7%. In contrast to MCSs, MCCs had a wider operating temperature range than MCSs, and the average friction coefficient of MCCs was decreased by 23.4 at.% 350-450 °C. According to the simulation results, the lubricant expansion of MCCs was 1.56 times that of MCSs at 400 °C. The curved microchannels design makes the storage and formation capacities of the lubricating film be enhanced without weakening the bearing capacity of MCCs. The two-way opening design of the curved microchannels could reduce the stress concentration between lubricant and friction interface, hence ensuring the efficient precipitation of lubricant. The research work could have a guiding role for widening the temperature range of M50 composites and improving the reliability of high-end equipment bearing. [ABSTRACT FROM AUTHOR]

Friction noise will not only affect the life of equipment, but also endanger human health. It is imperative to reduce the friction noise of mechanical system. Tribological properties and friction noise of Ti6Al4V alloy (TC4) and Ti6Al4V-4.6 wt.% MoS2-3.7 wt.% TiC (TMT) self-lubricating composites under 5, 10 and 15 N at 0.2 m/s are investigated using a self-built friction noise experimental apparatus. The results show that MoS2 and TiC have the good synergistic effects on tribological and friction noise performance. A lubricating film enriched with MoS2 is formed on the worn surface to reduce the stick–slip and surface roughness, and the energy of transition on the worn surface is reduced; hence, the friction noise is decreased. TiC can improve the hardness and wear resistance of TMT, and it supports the lubricating film to hinder the development of plowing grooves and peeling pits to a deeper level. The worn surface and friction noise performance of TMT are best at 10 N. This study has the far-reaching implications for improving the tribological properties and inhibiting friction noise of TC4 alloys. [ABSTRACT FROM AUTHOR]

Ti6Al4V alloy has broad application prospects in the aircraft industry. However, when it is served as frictional motion components, the poor friction and wear properties may greatly influence the reliability and working life of the entire mechanical system. Therefore, this paper mainly investigates the tribological performance and self-repairing functionality of Ti6Al4V-multilayer graphene (MLG)-Ag composites (TMAC) from 25 to 600 °C. The results show that TMAC obtains better tribological behavior in comparison with Ti6Al4V alloy (TC4), Ti6Al4V-MLG composites (TMC) and Ti6Al4V-Ag composites (TAC). It should be ascribed to the synergistic action of the reinforcement MLG and lubricant Ag, which are crushed and spread out by mechanical and thermal stress in the friction process, leading to the formation of a lubricating film on the wear scar. Along with the spreading of lubricating film, Ag and MLG can precipitate onto the microdefective areas, thus playing an important role in repairing the wear scar of TMAC. [ABSTRACT FROM AUTHOR]

Abstract As the main steel used in aircraft bearings, tribological properties of M50 directly affect the performance of aero-engines. In this paper, the anti-friction and wear properties of friction surface of M50-10 wt%(50Sn40Ag10Cu) composites (MSACC-2) sliding against Si 3 N 4 ball from 25 to 450 °C were investigated. XRD, XPS, EPMA, FESEM, and EDS mapping were conducted to understand the major mechanism leading to the improvement in the sliding behavior of MSACC-2. Results show that the surface of MSACC-2 exhibits excellent anti-friction and wear performances from 25 to 450 °C. At 350 °C, MSACC-2 shows the best tribological performance (0.18–0.27, 1.5–2.2 × 10−6mm3N−1m−1). It is attributed to the formed lubricating structure on the friction surface which is composed of the upper surface lubricating layer and underneath load-bearing layer. The surface lubricating layer mainly contains massive added Sn-Ag-Cu, intermetallic compounds of Cu 6 Sn 5 and Ag 3 Sn produced during the preparation process, and FeSn, FeSn 2 and oxides formed in friction process. The load-bearing layer can support the surface lubricating layer to play an outstanding anti-friction and wear effect. Moreover, the martensitic phase transformation on surfaces caused by Sn-Ag-Cu and the action of cyclic stress of Si 3 N 4 balls makes MSACC-2 have more excellent wear resistance performance. Graphical abstract Image 1 Highlights • The surface of MSACC-2 exhibits excellent anti-friction and wear properties. • 50Sn40Ag10Cu is an ideal solid lubricant for M50 over a wide temperature range. • Lubricating structure on surface consists of lubricating layer and load-bearing layer. • Lubricating layer contains added Sn-Ag-Cu and Ag 3 Sn, FeSn 2 produced during friction. • Phase transformation on surface makes MSACC-2 exhibit the best wear resistance. [ABSTRACT FROM AUTHOR]

The sliding friction and wear behaviors of TiAl-multilayer graphene (MLG)-silver composites (TMSCs) sliding against Si 3 N 4 balls from 0.10 to 0.30  m/s were studied in this paper. The tribological test results showed that friction coefficient and wear rate of TMSCs decreased with the increasing of sliding speed from 0.10 to 0.30  m/s. TMSCs exhibited the lower fiction coefficient and the less wear rate at 0.30  m/s, which was attributed to the formation of intact tribo-film containing MLG and Ag on the worn surface. In the formed tribo-film, Ag worked as the solid lubricant to provide good lubricating effect, while MLG with high strength played the active role in enhancing the anti-rupture ability of tribo-film. It indicated that TMSCs obtained the excellent tribological performance due to the remarkable synergistic effect of MLG and Ag. Moreover, the friction heat increased with the increase of sliding speed, which made contributions to the formation of tribo-film. [ABSTRACT FROM AUTHOR]

M50 steel is widely applied to manufacture aircraft bearings where service lives are mainly determined by the friction and wear behaviors. The main purpose of this study is to investigate the tribological behaviors and wear mechanisms of M50-1.5 wt.% graphene composites (MGC) prepared by laser additive manufacturing (LAM) (MGC-LAM) sliding against Si3N4 ball from 25 to 550 °C at 18 N-0.2 m/s. XRD, EPMA, FESEM, and EDS mapping were conducted to understand the major mechanisms leading to the improvement in the sliding behavior of MGC-LAM. The results indicated that MGC-LAM showed the excellent friction and wear performance at 25-550 °C for the lower friction coefficient of 0.16-0.52 and less wear rate of 6.1-9.5 × 10−7 mm3 N−1 m−1. Especially at 350 °C, MGC-LAM obtained the best tribological performance (0.16, 6.1 × 10−7mm3 N−1 m−1). It was attributed to the dense coral-like microstructure, as well as the formed surface lubricating structure which is composed of the upper uniform lubricating film with massive graphene and the underneath compacted layer. [ABSTRACT FROM AUTHOR]

The contact stresses of materials in moving mechanical assemblies are rather important for minimizing friction and decreasing machinery energy dissipation. In this study, the effect of contact stresses on the friction and wear behaviors of TiAl-10 wt.%Ag was studied at 0-240 min using the united methods of experiment research, numerical simulation and theoretical analysis. The results showed that the high contact stresses led to the plastic deformation of TiAl-10 wt.%Ag at 0-50 min. The friction coefficients and wear rates decreased rapidly with the lowering of contact stresses from 1034.28 to 710.52 MPa. At elastic deformation stage (50-240 min), the forming of lubricating film was beneficial to the decrease in friction coefficients and wear rates at 50-150 min, whereas the lower contact stresses caused the increasing of friction coefficients and wear rates. The competition between film lubrication and contact stresses caused the lowering of friction coefficients and wear rates at 50-150 min. At 150-240 min, the lubricating film maintained the equivalent lubricating behaviors, whereas the lowering of contact stresses led to the slight improving of friction coefficients and wear rates. This study was meaningful for optimizing applied loads to realize the excellent contact stress state and tribological behavior of mechanical parts. [ABSTRACT FROM AUTHOR]

The objective of searching the optimum applied load was to minimize friction and decrease wear in mechanical moving components. The friction and wear behaviors of TiAl-10wt.%VO nanowires (TiAl-10wt.%VO) were evaluated sliding against the fixed AlO balls with the Vickers hardness of 18.07 GPa at the applied loads of 6-24 N. The testing results showed that the smaller friction coefficient and wear rate of TiAl-10wt.%VO were obtained at 18 N, if compared to those at 6, 12 and 24 N. The smaller friction coefficient and wear rate were mainly attributed to the forming of cambiform structure of large crystalline grain, the higher totals of oxide interionic potential and the higher thickness of friction layer at 18 N, if compared to those at the other applied loads. It was obvious that the applied load of 18 N was reasonable for obtaining the lower sliding friction coefficient and the less wear rate of TiAl-10wt.%VO. [ABSTRACT FROM AUTHOR]

In this study, the friction and wear behaviors of TiAl matrix composites with MTC (TMSCT) and TiAl matrix composites with MoO powder (TMSCP) are investigated. The results reveal that TMSCT show the excellent tribologcial performance, if compared to TMSCP. The direct contact layers of TMSCP against different counterface balls obtain huge cracks overall, whereas only fine crack is generated in TMSCT against AlO ball, where MTCs are distributed around the crack evenly. The finite element simulations show that only the stress of TMSCT against AlO ball exceeds the yield strength of TMSCT. It reveals that MTCs in TMSCT can reduce the stress for the weak binding force of multilayer structure and make the direct contact layers be more stable by preventing the propagation of crack after the crack being produced, resulting in the excellent antifriction and antiwear properties of TMSCT against different counterface balls. [ABSTRACT FROM AUTHOR]

The friction and wear behaviors of TiAl matrix self-lubricating composites (TMSC) with MoO tabular crystal (MTC) against GCr15 steel ball are tested using a constant load of 10 N and a constant speed of 0.2 m/s from room temperature to 600 °C. The result shows that, during the sliding friction and wear process, the MTC which has the microstructure of multiple layers could reduce the shear stress, leading to the reduction of friction coefficient. Meanwhile, TMSC with MTC exhibits the excellent tribological performance over a wide temperature range, if compared to TiAl based alloy. Moreover, MTC can improve the tribological properties of TMSC obviously below 400 °C. [ABSTRACT FROM AUTHOR]

The textured surface is one of the hotspots in the field of tribology research on reducing friction and wear. By calculating and optimizing the micro-texture structure, researchers designed and prepared textures with excellent tribological properties on the mechanical part surfaces. In this work, the tribological performance of 42CrMo matrix composite textured surfaces (CTSs) with different textured densities under grease lubrication was studied. The CTS was composed of 42CrMo alloys and SnAgCu-MXenes-Ti 3 C 2 (SACM). The results showed that when the textured density ρ of CTS was 36%, the friction coefficient (0.090) and wear rate (5.4 × 10−9 mm3N−1m−1) of counterpart ball could be respectively reduced by 75.7% and 38.6% compared with those of counterpart ball against the untextured sample. CTS could enhance the stability of friction system. Mxenes-Ti 3 C 2 wrapped by SnAgCu could form the lubricating layer containing sub-micron rollers on the worn surface, effectively reducing the friction and wear of samples under grease conditions. [Display omitted] • The composite textured surfaces (CTSs) were designed and prepared. • MXenes wrapped by SnAgCu could form sub-micrometer rollers in wear scar. • CTS exerted tribological enhancement function under starvation. • CTS could produce excellent synergistic effect with grease. [ABSTRACT FROM AUTHOR]

Studies have been carried out to explore the friction and wear behaviors of NiAl matrix self-lubricating composites containing graphene nanoplatelets (NG) against an Si3N4 ball from 100 to 600°C with a normal load of 10 N and a constant speed of 0.2 m/s. The results show that NG exhibits excellent tribological performance from 100 to 400°C compared to NiAl-based alloys. A possible explanation for this is that graphene nanoplatelets (GNPs) contribute to the formation of a friction layer, which could be beneficial to the low friction coefficient and lower wear rate of NG. As the temperature increases up to 500°C, the beneficial effect of GNPs on the tribological performance of NG becomes invalid due to the oxidation of GNPs, resulting in severe adhesive wear and degradation of the friction layer on the worn surface of NG. GNPs could hold great potential applications as an effective solid lubricant to promote the formation of a friction layer and prevent severe sliding wear below 400°C. [ABSTRACT FROM AUTHOR]

The friction layer structure has been proved to be formed during severe plastic deformation and markedly improves the tribological properties of material. The dry friction and wear performance of graphene-reinforced TiAl matrix self-lubricating composites (GTMSC) at different sliding velocities are systematically researched. GTMSC show the best tribological properties and special friction layer structure containing a wear-induced layer and a grain refinement layer with a nanocrystalline (NC) structure under surface after sliding at a sliding speed of 1.1 m/s. Nanoindentation results show that the grain refinement layer has a higher hardness and elastic modulus than the wear-induced layer. This special microstructure of friction layers beneath the surface after sliding leads to a low coefficient of friction and high wear resistance of GTMSC. Moreover, it is deduced that the appearance of an NC structure results in hardening of the material. The formation mechanisms of friction layers are researched in detail. It can be concluded that the formation of a wear-induced layer results from frictional heat and fracture of the counterpart. The formation of a grain refinement layer is due to severe plastic deformation and dynamic recrystallization. Severe plastic deformation results in the formation of an NC structure and dynamic recrystallization leads to grain refinement. [ABSTRACT FROM PUBLISHER]

The tribological properties of Ti3SiC2/TiAl composite (TTC) slid against a GCr15 steel counterface were investigated at sliding speeds in the range of 0.2–0.8 ms−1and loads that ranged from 2 to 8 N. The results showed that the tribological properties of TTC strongly depended on the covering percentage of tribofilm on the TTC worn surface, which varied with changes in sliding speed and load. The tribofilm mainly consisted of Al-Ti-Si oxides, which provided a self-antifriction action that resulted in a reduction in the friction coefficient and an increase in the wear rate. [ABSTRACT FROM AUTHOR]

A research is conducted on the possible beneficial synergistic effects of multiple additives in self-lubricating composites for use in high temperature friction and wear-related mechanical assemblies. Dry sliding tribological tests of NiAl matrix self-lubricating composites (NMSCs) on a HT-1000 ball-on-disk high-temperature tribometer are undertaken against SiN at 25-800 °C. The results show that the subsurface microstructures beneath wear scar of NMSCs change with addition of different lubricants, which have great effects on tribological mechanisms and tribological performances. NMSC with addition of MoS and TiSiC exhibits distinct subsurface microstructure beneath wear scar and excellent tribological performance among all samples. [ABSTRACT FROM AUTHOR]

TiB was chosen to further improve the tribological properties of TiAl matrix self-lubricating composites containing Ag. The possible synergetic action of a combination of TiB and Ag was investigated using a pin-on-disk high temperature tribometer from room temperature to 600 °C. The tribological test results indicated that the addition of TiB obviously enhanced the wear resistance of the composites over a wide temperature range. Moreover, the composites containing TiB had a low friction coefficient at 600 °C. The subsurface analysis of cross sections of worn surfaces showed that TiB played the role in wear-resistant skeleton and restricted the plastic flow of Ag during dry friction process. The investigation showed that TiB and Ag could exhibit good synergistic effect on improving the tribological properties of composites. [ABSTRACT FROM AUTHOR]

The main objective of this work has been the characterization of wear behavior of the graphene nanoplates (GNPs) in Ni3Al matrix composites (NMC). The friction and wear behaviors of NMC with the addition of 1 wt.% GNPs against Si3N4 ball are tested under different loads using a constant speed of 0.2 m/s. Tribological test results have revealed that small amounts of GNPs are able to drastically improve the antifriction and antiwear properties of NMC. A possible explanation for these results is that, the GNPs not only provide an enhanced effect for NMC to produce better wear resistance, but also form a local protective layer on the contact surfaces to reduce the friction. The investigation shows that GNPs hold great potential applications as an effective solid lubricant for Ni3Al matrix composites and possibly other alloys. [ABSTRACT FROM AUTHOR]

In recent years, reducing friction and wear-related adverse impacts on efficiency and durability in moving mechanical systems has gained increased attention. Herein, the search continues for novel materials and lubricants that can potentially reduce friction and wear. As one of the emerging self-lubricating materials, the tribological potential of graphene has been researched deeply. This article was dedicated to explore the combined lubrication of multilayer graphene (MLG) and WS. The as-prepared sample of NiAl-1.5 wt% MLG-5 wt% WS (NB) exhibited excellent tribological properties. During the sliding process, a continuous lubricating film was formed to provide the low-strength junctions at the interface, reducing the friction coefficient and wear rate. Moreover, the MLG played the role of reinforcement particles and improved loading carrying ability. [ABSTRACT FROM AUTHOR]

More durable, low-friction bearing materials over a wide temperature range are needed for turbine components and other high-temperature bearing applications. The current study reported the tribological properties of TiAl matrix self-lubricating composites (TMC) containing MoS2 (a low-temperature lubricant, below 500°C), hBN (a medium-temperature lubricant, below 600°C), and Ti3SiC2 (a high-temperature lubricant, above 600°C) designated as MhT against an Si3N4 counterface at temperatures ranging from 25 to 800°C in air. The load was 10 N and the sliding speed was 0.2 m/s for all tests. Tribological studies indicated that TMC containing MhT showed a lower friction coefficient and wear rate in comparison to TiAl-based alloy at all test temperatures, which was attributed to the excellent synergetic lubricating effect of MoS2, hBN, and Ti3SiC2. TMC containing 5 wt% MhT exhibited the best tribological properties over a wide temperature range. [ABSTRACT FROM AUTHOR]

Research on the friction layer is needed to minimize friction- and wear-related mechanical failures in moving mechanical assemblies. Dry sliding tribological tests of NiAl matrix composites (NMCs) with 1.5 wt% graphene nanoplatelets (GNPs) sliding against different counterface balls are undertaken at the condition of 10 N-0.234 m s in this study. When sliding against GCr15 steel, a uniform and thick friction layer is formed, resulting in a lower friction coefficient (0.29-0.31) and wear rate (2.0-3.1 × 10mmNm). While sliding against AlO and SiN, the formation and stability of the friction layers are restricted in the severe wear regime, and the NMCs exhibit higher friction coefficients and wear rates. Therefore, various counterface balls have a great effect on the stability and thickness of the friction layer, thus affecting the tribology performance of NMCs. The result also shows that GNPs exhibit enrichment and self-organized microstructures in the friction layer. In addition, the friction layer is also found to be divided into two layers, protecting the subsurface from further damage and reducing shear. [ABSTRACT FROM AUTHOR]

Abstract: Investigations in graphene of controlling friction and wear of Ni3Al matrix self-lubricating composites (NMSC) are needed for moving mechanical assemblies. The friction and wear behaviors of NMSC with graphene nanoplatelets (GNPs) against Si3N4 ball are tested using a constant load of 10N and a constant speed of 0.2m/s from room temperature (RT) to 600°C. Tribological test results have revealed that small amounts of GNPs in the NMSC are able to drastically reduce the friction coefficients and wear rates over the effective operating range (RT-400°C). A possible explanation for these results is that the refinement of grains accompanying the slippage of laminated sheets between GNPs could provide a source of the stress dissipation and form the GNP protective layer during sliding process, leading to the reduction of wear rates as well as the friction coefficients. It is concluded that GNPs hold great potential applications as an effective solid lubricant for moderate loads and stress, and can be easily used for the preparation of the self-lubricating composites in the future. [Copyright &y& Elsevier]

Abstract: The effect of sliding speed and load on the friction and wear behavior of NiAl–10wt%Ti3SiC2 composites (NAT) at room temperature was investigated through determination of friction coefficients and wear rates in different conditions and analysis of morphologies and compositions of wear debris and worn surfaces of both NAT and Si3N4 ball. The results showed that the friction coefficients decreased and wear rates increased with increase in load, whereas they both decreased with increase in sliding speed. The transition in the wear mode from mild to severe wear was strongly influenced by the sliding speed and load. [Copyright &y& Elsevier]

Abstract: The dry sliding friction and wear behavior of Ti3SiC2/(WC–10Co) composites (TWCs) against GCr15 steel pair at room temperature was investigated through the determination of friction coefficient and wear rate under different conditions and the analysis of the morphologies and compositions of wear debris, worn surfaces of TWC and GCr15 steel. The friction coefficients of TWC with 3wt.% WC–10Co were in the range of 0.40–0.48, and the wear rate varied from 0.6×10−4 mm3 (Nm)−1 to 1×10−4 mm3 (Nm)−1. At the load of 10N and sliding speed of 0.353m/s, the glazes were formed on the worn surfaces of TWC. The wear mechanisms were complicated, including micro-cutting and abrasive wear of TWC, oxidation wear of GCr15 steel, as well as adhesive wear caused by the glaze flaking. [Copyright &y& Elsevier]

Taking GCr15 steel as the research object, the groove-textured surfaces (GTSs) and the composite antifriction surfaces (CASs) with the grooves and Sn–Ag–Cu were prepared. Experimental researches on the tribological performance, friction-induced vibration and noise of SS (smooth surface), GTSs and CASs were conducted. The results showed that SS exhibited the obviously abrasive wear characteristics, thus the uneven surface was obtained, leading to the high-frequency scream. The fluctuation of friction force caused by the grooves on GTSs could suppress the high-frequency scream but cause the low-frequency chatter. The cooperate effect of grooves and Sn–Ag–Cu increased the fluctuation amplitude of friction force, hence CASs profile with obvious wrinkles was formed, suppressing the friction-induced vibration and noise. Image 1 • The noise is suppressed by the cooperate effect of grooves and Sn–Ag–Cu. • The grooves could suppress the scream and cause the low-frequency chatter. • The amplitude of frictional force fluctuation is increased by Sn–Ag–Cu. • CASs profile with obvious wrinkles could suppress the vibration and noise. [ABSTRACT FROM AUTHOR]

To overcome the poor tribological performance of titanium alloys and broaden their applications in the rapidly developing aerospace industry, this paper studies the friction and wear behaviors of TC4 alloy with surface microporous channels filled by Sn-Ag-Cu (SAC) and Al 2 O 3 nanoparticles using the dry sliding tests. Moreover, the synergistic lubricating mechanism of SAC4 and Al 2 O 3 nanoparticles is also investigated in detail. The results show that TC4 alloy with surface microporous channels filled by SAC4 (50Sn-45Ag-5Cu) and 6 wt% Al 2 O 3 nanoparticles (TC4-SACA3) presents excellent antifriction property and wear resistance over a wide range of temperatures and applied loads. Especially at 400 °C-10 N, TC4-SACA3 can obtain the smallest friction coefficients of 0.185 and the minimal wear rate of 3.6 × 10−5 mm3N−1 m−1, which is attributed to the synergistic effect of SAC4 and Al 2 O 3 nanoparticles. During the sliding process, SAC4 can precipitate from the microporous channels under the heat-force driving and then gradually form a smooth lubricating film on the friction surface. Meanwhile, some Al 2 O 3 nanoparticles wrapped by lubricant SAC4 can improve the load carrying capacity of lubricating film, and the other exposed Al 2 O 3 nanoparticles on the friction surface play a role of "micro-bearings" between the friction pairs. Unlabelled Image • TC4 alloy with surface microporous channels is prepared by LAM technology. • SAC4 has good wettability with TC4, preventing lubricating film peeling prematurely. • Pores with SAC and Al 2 O 3 nanoparticles present anti-friction and anti-wear abilities. • TC4-SACA3 maintains excellent self-lubricating property in tough friction condition. [ABSTRACT FROM AUTHOR]

To overcome the failure of liquid lubricants in the fields of energy equipment and aerospace industry, the synergistic effect of surface micro-textures and solid lubricants is a promising approach to solve the problem. This paper sought to improve the tribological performance by designing the surface composite structure on a Ni 3 Al metal matrix, in which surface micro-textures were filled by solid lubricants 96.5Sn-3.0Ag-0.5Cu alloys (SAC305). Dry reciprocating sliding tests were conducted as a basic assessment for synergistic lubricating analysis of surface composite structure. Results showed that the composite structure with the surface texture density of 28% and deposited SAC305 alloys had the lowest friction coefficient (0.39) and mean wear volume (0.37mm3) in comparison with other prepared samples. The reasons of the surface composite structure reducing the friction and wear of Ni 3 Al alloys mainly are that SAC305 alloys deposited into surface micro-grooves can improve the capacities of load-carrying and resistance to plastic deformation of the contact surface, and a SAC305 lubricating film formed on contact interface can reduce the direct contact between the counterpart ball and Ni 3 Al matrix. The Ni 3 Sn 2 phase generated at the interface under the roles of friction behavior, which acts as a transiting layer to connect Ni 3 Al matrix and SAC305 alloys, promotes the formation of the self-adaptive friction structure. Moreover, the interconnection between the dynamic change of the friction coefficient and a lubricating film formed on contact interface was established, which could be used to evaluate the wear characteristics applied in the engineering field under harsh conditions. Unlabelled Image • Composite structure of surface grooves and solid lubricant was prepared successfully. • The surface texture density of 28% and deposited SAC305 alloys showed the excellent tribological performance. • A SAC305 lubricating film formed on contact interface can reduce the direct contact of friction pair. • Dynamic change of the friction coefficient can evaluate the wear characteristics. [ABSTRACT FROM AUTHOR]