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Inspired by the fan-shaped scale and mechanism of mucus secretion of crucian carp surface, the bionic scale textures were designed and combined with Sn-Ag-Cu-Nb2C to fabricate TC4-based self-lubricating composites (TTSACN). The optimal textured parameters (radius = 710 μm, width = 300 μm, depth = 390 μm) were obtained by response surface methodology (RSM). The friction and wear behaviors of TTSACN under dry friction conditions were studied. The experimental results showed that the optimal bionic texture could capture wear debris and promote the restoration and migration of lubricants on the worn surface, improving the formation quality of lubricating film. Compared with TC4, the friction coefficient and wear loss of TTSACN with optimal bionic texture were reduced by 23.03% and 96%, respectively. [ABSTRACT FROM AUTHOR]

The bionic rhombic textures with SnAgCu and Nb2C were used to improve tribological properties of M50. Compared with M50, friction coefficient and wear depth of M50-SnAgCu-Nb2C with 45° textures at 15 N were separately decreased by 42.67 and 70.37%, and those of M50-SnAgCu-Nb2C with 60° textures at 25 N were, respectively, decreased by 42.04 and 65.03%. Nb2C can promote the combination and spread of composite lubricants in bionic textures, and a uniform and dense lubrication layer was formed at the interface. The synergistic effect of SnAgCu-Nb2C and bionic textures can play an excellent antifriction and wear resistance role under specific working conditions. [ABSTRACT FROM AUTHOR]

High wear is the primary failure mechanism of Inconel 625 in mechanical parts. The surface modification is workable method to improve tribological performance of Inconel 625. In this paper, the groove-textured surfaces with different widths and pitches were prepared on the surfaces of Inconel 625 by electrical discharge machining technology. The Sn-Ag-Cu solid lubricant was deposited on the grooves. The synergistic effects of Sn-Ag-Cu solid lubricant and groove-textured surface on the tribological performance of Inconel 625 were studied. Results show that the groove-textured surface of Inconel 625 filled with Sn-Ag-Cu solid lubricant shows the lowest friction. Compared with the untextured sample, the friction coefficients of groove-textured sample with the groove density of 20% and the groove-textured sample with the groove density of 25% filled by Sn-Ag-Cu are reduced 35% and 48%, respectively. The textures can trap wear debris under the dry sliding condition. In addition, Sn-Ag-Cu alloys filled in the grooves supply the sufficient lubricant at the contact interface during the sliding process. The lubricating film on the contact surface is formed gradually, which is mainly due to the shear adaptability and low melting point of Sn-Ag-Cu alloy. It shows that deposition of Sn-Ag-Cu solid lubricant coating on the groove-textured surface is an effective way for improving the friction and wear performance of Inconel 625. [ABSTRACT FROM AUTHOR]

In order to meet more rigorous tribological requirements for aerospace and automobile applications, there is a need to improve the wear and frictional performance of Ni 3 Al-based metal matrix composites. This investigation sought to improve performance by designing gradient-type Ni 3 Al metal matrix, self-lubricating composites (GNMMCs), in which each layer contained a different content of graphene nanoplatelets (GNPs). Dry sliding tests of a novel material are conducted as a basic assessment for the reference of the specific applications. Rotating sliding tests of GNMMCs against Si 3 N 4 balls were performed under different loading conditions to compare with Ni 3 Al metal matrix without graphene nanoplatelets (NA) and with homogeneous graphene nanoplatelets (NMCs). The results show that the friction coefficients and wear loss of GNMMCs under different loading conditions are lower than those of NA and NMCs. It is attributed to the facts that together, GNPs and oxides on the worn surface can form a tribo-layer with excellent anti-friction and wear performance, and GNPs accumulations in the worn subsurface can further enhance the strength of the tribo-layer to resist deformation. Additionally, the deposited layers with a gradient GNP content of GNMMCs present a grain gradient structure transiting from the fine grains to coarse grains, which is characteristic of a gradient hardness change. When GNMMCs with high strain accommodating ability are compressed under heavy loading, plastic deformation propagates from coarse grains to fine grains progressively to accommodate the stresses, and that process effectively maintains the wear resistance of tribo-layer. Image 1 • The gradient Ni 3 Al self-lubricating composites (GNMMCs) is designed. • The microstructure and mechanical properties of GNMMCs are investigated. • Wear tests of GNMMCs are performed under different loading conditions. • Wear resistance and strengthening mechanism of GNMMCs are discussed. [ABSTRACT FROM AUTHOR]

Dry tribological tests of M50 matrix composites containing 0, 2.5, 5.0, and 7.5 wt% Ag are undertaken at 0.2 m/second 15 N from 25°C to 450°C against Si3N4 ceramic balls. The results indicate that the tribological performance is strongly dependent on the content of solid lubricant Ag. M50 matrix composites containing 5.0 wt% Ag exhibits the great tribological performance with the low friction coefficients of 0.23 to 0.43 and less wear rates of 1.89 to 3.52 × 10−6 mm3 N−1 m−1 from 25°C to 450°C, which is attributed to the formation of thick lubricating film on the worn surface. Furthermore, the migration model of solid lubricant Ag in M50 matrix composites is established to predict the thickness of formed lubricating film. [ABSTRACT FROM AUTHOR]

As the main steel used in the aero-engine main shaft bearings, the tribological properties of M50 can directly affect the performance of aero-engine. The purpose of this study is to design the reasonable composition of Sn-Ag-Cu alloy and investigate the wear mechanisms of M50-10 wt.%(Sn-Ag-Cu) composites (MSACC) prepared by SPS sliding against Si3N4 ball from 25 to 550 °C at 12 N-0.25 m/s. XRD, EPMA, FESEM and EDS mappings are conducted to understand the major mechanisms leading to the improvement in the sliding behavior of MSACC. The results indicate that MSACC with different specifications of Sn-Ag-Cu alloy shows excellent friction and wear properties from 25 to 550 °C compared to M50. M50-10 wt.%(50Sn40Ag10Cu) (MSACC-2) shows the distinguished tribological performance for the lower friction coefficients of 0.22-0.61 and less wear rates of 1.7-4.1 × 10−6 mm3 N−1 m−1, which is attributed to the formed excellent lubricating structure consisting of the lubricating film with massive Sn-Ag-Cu alloy and intermetallic compounds formed during the friction process, as well as the underneath mixed layer who can well support the lubricating film due to the good intersolubility between the designed Sn-Ag-Cu alloy and M50 (Fe). [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 used in aero-engine bearings and other high-temperature bearings. However, the poor wear of M50 steel resistance restrains its further applications. In this paper, the sliding tribological behaviors of M50 steel, M50-Ag composites (MAC) and M50-Ag-TiC composites (MATC) against Si3N4 ball were investigated from 150 to 600 °C at 15 N-0.2 m/s. MATC showed better tribological properties in comparison with M50 and MAC. Especially at 450 °C, MATC obtained the lowest friction coefficient of 0.15 and smallest wear rate of 1.3 × 10−5 mm3 N−1 m−1. The excellent tribological performance of MATC during the friction test was attributed to the continuous lubricating film containing lubricant Ag and reinforcement TiC, as well as the subsurface compacted layer that could well support the lubricating film to prevent it from being destroyed. At 600 °C, because of the tribo-chemical reaction between Ag and Mo oxide during sliding process, the newly formed Ag2MoO4 lubricating film was well spread out on the friction surface, which could continuously improve the tribological behavior of MATC. This investigation was meaningful to improve the anti-friction and wear resistance of M50 matrix bearing over a wide temperature range. [ABSTRACT FROM AUTHOR]

In order to analyze the effects of frictional heat on the tribological performance of Ni3Al matrix self-lubricating composite containing 6.2 vol.% graphene nanoplatelets (NB), the dry sliding friction tests of Ni3Al-based alloy and NB against GCr15 steel ball are undertaken under different loads from 3 to 18 N. The effects of different amount of frictional heat on the friction and wear mechanism of NB are also studied. The results show that tribological performance of NB is better than that of Ni3Al-based alloy under same working conditions. The addition of graphene nanoplatelets promotes the formation of stable glaze layer on worn surface. In addition, graphene nanoplatelets enhance the thermal conductivity of NB, which makes the surface temperature of wear scar of NB in a proper range (about 413 ℃) at 13 N and avoids the serious friction and wear caused by the accumulation of frictional heat. At 13 N, NB shows the lower friction coefficient (0.32) and wear rate (3.6 × 10−5 mm3·N−1·m−1). It is attributed to the appropriate local temperature (about 413 ℃) of worn surface, resulting in the formation of stable glaze layer with good friction reducing and wear resistance on worn surface. This study was meaningful for optimizing applied loads to realize the appropriate frictional heat and good tribological behavior of NB. [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]

In order to improve tribological performance of NiAl-based alloy, NiAl matrix composites containing 1.5 wt.% multilayer graphene (MLG) are prepared through additive manufacturing (AM) and spark plasma sintering (SPS), which are denoted as NMAM and NMSPS, respectively. Tribological behaviors of NMAM and NMSPS against SiN balls are researched under constant speed (0.2 m/s) and varied loads (from 4 to 16 N) for evaluating the tribological properties of NMAM and NMSPS. The results present that NMAM exhibits the excellent tribological properties [low friction coefficients (0.26-0.40) and considerable wear resistance (2.8-4.6 × 10 mm N m)] as compared to NMSPS, which attributes to the uniform enrichment of MLG with properties of high tensile strength and being easily sheared off on the worn surfaces. Owing to the use of spherical prealloyed powder containing multilayer graphene and the characteristics of layer by layer depositing in the AM process, NMAM has a more compact and uniform substrate, which persistently provides a source of the formation of continuous and stable frictional layer. Due to the characteristics of AM rapid solidification, NMAM has the small grain size and well-compacted microstructure, which can effectively reduce the probability of spalling wear and lead to the increase in wear resistance of materials. The research can offer the reference for self-lubricating materials prepared by AM technology. [ABSTRACT FROM AUTHOR]

This article was dedicated to explore the combined lubrication of silver, MoS and carbon nanotubes (CNTs) based on the changes in applied loads and sliding speeds. The results showed that the formed lubricating films played the major role in undertaking the equivalent stress, as well as effectively reduced friction resistance and material loss. It led to small friction coefficient and less wear rate at 1.2 m/s. At 1.2 m/s-16 N, an integrated lubricating film containing Ag, CNTs and MoS was continuously formed, which well provided the excellent lubricating property, resulting in lower friction coefficient (0.19) and less wear rate (1.56 × 10 mm/N m). The formation of Ag and CNTs enriched islands acted as the bearing areas and played the major role in resisting friction resistance. Meanwhile, solid lubricant MoS was enriched in the lubricating film and effectively protected lubricating film from being destroyed, resulting in small friction coefficient and less wear rate at 1.2 m/s-16 N. [ABSTRACT FROM AUTHOR]

The application of NiAl-based alloy (NA) in the field of aerospace was limited by its poor tribological properties. For improving the tribological performance of NA, multilayer graphene (MLG) and TiSiC were added in NiAl matrix composites. Tribological behavior of NiAl matrix composites containing 1.5 wt.% MLG and 10 wt.% TiSiC (NMT) against SiN ball at 12 N-0.2 m/s from 25 to 750 °C was investigated. The results showed that NMT exhibited the excellent tribological behavior [lower friction coefficients (0.26-0.57) and less wear resistance (3.1-6.5 × 10 mm N m)] due to synergetic effect of MLG and TiSiC over a wide temperature range from 25 to 750 °C. At 25-350 °C, part of MLG enriched on worn surface could play a role in reducing friction and improving wear resistance. At 350-550 °C, although MLG gradually lost the lubricating properties, the partial decomposition of TiSiC could continually improve the tribological properties of NMT. At 550-750 °C, TiSiC on worn surface was oxidized to form lubricating film, while TiSiC in the subsurface played an important role in supporting the film, resulting in the excellent high-temperature tribological performance. The research had good guiding significance for the preparation of wide temperature range self-lubricating material and the study of synergetic effect of complex solid lubricants. [ABSTRACT FROM AUTHOR]

In this study, the effect of friction layer thickness and subsurface nano-hardness of wear track on tribological behavior of γ-TiAl matrix composites is investigated. The results of dry sliding tribolocial tests of γ-TiAl matrix composites with 0-2.25 wt.% multilayer graphene (MLG) (0.25 wt.% in tolerance) under different applied loads are reported. The testing results show that the optimized addition amount of MLG is 1.75 wt.% at 12 N (friction layer thickness 3.23 µm, subsurface nano-hardness of wear track 9.03 GPa). It can be found that a continuous and thick friction layer is formed in γ-TiAl-1.75 wt.% MLG at 12 N, resulting in a lower friction coefficient of 0.31 and wear rate of 2.09 × 10 mm N m. During dry sliding process, the high subsurface nano-hardness of wear track leads to the increase in resisting plastic deformation capacity and reduces the material loss. Meanwhile, the thick friction layer contains MLG with high tensile strength which is easily sheared off. Hence, γ-TiAl matrix composites show excellent tribological performance of a friction-reducing and an increase in wear resistance. The investigation shows that γ-TiAl-1.75 wt.% MLG, due to its excellent tribological behavior at 12 N, can be chosen as a promising structural material for minimizing friction- and wear-related mechanical failures in sliding mechanical components. [ABSTRACT FROM AUTHOR]

In order to analyze the effects of friction layer thickness on the tribological performance of NiAl matrix self-lubricating composites containing Ag and MoO tabular crystals (NiAl-Ag-MoO), the dry sliding tribological tests of NiAl-Ag-MoO against SiN ball are undertaken under 4-16 N and 20-800 °C at 0.2 m/s. The results show that the friction layer thickness of NiAl-Ag-MoO is obviously affected by the applied loads and ambient temperatures. At 12 N-400 °C-0.2 m/s, NiAl-Ag-MoO exhibits excellent tribological performance, and the friction layer thickness obtained the maximum value of about 5 µm. Moreover, the simulation results, which based on the building of finite element models with different thickness of the friction layer, indicate that the decreased degree of the maximum equivalent stress in the substrate of NiAl-Ag-MoO with maximum thickness of friction layer is the larger one (about 39%), if compared to other thickness. It could avoid the generation of cracks and the spalling of subsurface materials during the dry sliding process, resulting in the excellent tribological performance. The results could be used to guide the selection of suitable working conditions and study the self-lubricating mechanisms of NiAl-Ag-MoO for having stable friction layer structure and excellent antifriction and antiwear performance. [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]

In order to improve the efficiency and durability of the kinematic pair systems, the research continues for novel materials and lubricants that can potentially reduce friction and wear. This article was dedicated to explore the combined lubrication of graphene nanoplatelets (GNPs) and MoS nanospheres (NSs) at different testing temperatures. Furthermore, the glaze layer with grain refinement could have a strong bearing capacity and resist the damage caused by high stress. At 450 °C, a integrated lubricating film containing GNPs and MoS NSs was continuously formed to provide the low-strength junctions at the interface, resulting in a lower friction coefficient of 0.15 and a smaller wear rate of 1.56 × 10 mm N m. Meanwhile, the GNPs played the role of reinforcement particles and improved loading carrying ability, while MoS NSs demonstrated the effect of repairing with being pressed into the microfurrows of the worn surface. [ABSTRACT FROM AUTHOR]

The sliding wear of Ni3Al matrix composites with addition of 1.5 wt.% graphene nanoplates was studied through pin-on-disc wear testing. The spontaneous formation of a tribo-layer produced during sliding wear was found to result in a deviation from Archard scaling and an unexpected high wear resistance that was not based on hardness alone. The tribo-layer exhibited specific microstructural evolution with significant severe deformation and grain refinement after wear. In the grain refinement area, the accumulation of dislocations and an increase in misorientations were found to lead to strain hardening. For the plastic deformed area, reduction in the dislocation density inside the elongated ultrafine grains reduced strain hardening compared with the grain refinement area. It can be concluded that the deviation from Archard scaling occurred primarily as a result of the microstructural evolution of the tribo-layer, resulting in the specific performance of mechanical and tribological properties of Ni3Al matrix composites under cyclic sliding wear process. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In order to improve the tribological properties of NiAl self-lubricating composites, VO nanowires with average width of 39 nm were synthesized by hydrothermal method. Furthermore, NiAl self-lubricating composites containing VO nanowires (NAV) were successfully fabricated using spark plasma sintering technique. The tribological characteristics and wear mechanisms of NAV were evaluated at different sliding speeds, counterface ball materials and elevated temperatures. The results revealed that the frictional properties of NAV improved slightly with adding VO nanowires at room temperature if compared to NiAl self-lubricating composites without solid lubricant as investigated in previous studies, while the wear mechanisms of NAV change widely with the change of the counterface ball materials and sliding velocities. VO nanowires showed a beneficial effect on tribological performance of NAV at high temperatures owing to the formation of the VO-enriched glaze film at temperatures above 700 °C, which acts as the lubricous and protective mask against the severe wear. [ABSTRACT FROM AUTHOR]

Many studies have shown that the excellent tribological properties of materials are primarily attributed to the formation of expected frictional layer on the worn surface. This article is dedicated to explore the possible formation and acting mechanism of frictional layer of TiAl-12Ag-5TiB composite. At normal load of 12 N, a frictional layer that consists of wear-induced layer and plastic deformation layer is observed. The soft wear-induced layer supported by the harder plastic deformation layer leads to the low friction coefficient and high wear resistance. The harder plastic deformation layer is induced by repetitive tribo-contact and considerable plastic deformation. Its high hardness improves the wear resistance of composite, and fine-grained structure promotes the diffusion of lubricating phase during dry friction process. The soft wear-induced layer can be divided into tribofilm and mechanically mixed layer. The mechanically mixed layer that consists of Ag and Ti-Al Oxides can continuously be provided to the worn surface to form a tribofilm with low shearing stress junctions, lowering the friction coefficient. [ABSTRACT FROM AUTHOR]

The wear and friction behavior of materials depends on the structure of the surface layers that can develop during sliding contact. The evolving dynamic recrystallization process of the friction layer of Ni 3 Al matrix composites (NMCs) at different contact loads was characterized. A pin-on-disk contact geometry was used. Silicon nitride ceramic was chosen as the pin material because of its inertness. A wear-induced tribo-layer composed of a grain growth layer and a nanocrystalline (NC) structured layer was formed. The soft wear-induced (0.6 GPa) layer, supported by the harder NC structure layer (7.4 GPa), is proposed to be beneficial both to achieving a low friction coefficient and a high wear resistance for the NMCs. [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]

The tribological behaviors of NiAl-Ti3SiC2composites (NMC) against Si3N4at elevated temperatures were investigated by carrying out dry sliding wear tests at the condition of 10 N–0.2 m/s. The results showed that NMC without Ti3SiC2had a high friction coefficient and wear rate at elevated temperatures, and the addition of Ti3SiC2could improve the high-temperature tribological properties. Both the friction coefficient and wear rate of NMC obviously decreased at 600 and 800°C with the addition of Ti3SiC2. The excellent tribological behaviors of NMC with 5 wt% Ti3SiC2at elevated temperatures implied that 5 wt% Ti3SiC2could be the optimal content. [ABSTRACT FROM AUTHOR]

More durable, low-friction bearing materials are needed for turbine components and other high-temperature bearing applications. The current study presents the sliding friction and wear behavior of a TiSiC/TiAl composite (TTC) against a SiN counterface at temperatures ranging from 25 to 800 °C in air. The load was 10N, and the sliding speed was 0.2 m/s for all tests. The friction coefficient of both the TiAl and the TTC composite increased with rising temperature up to 400 °C, but beyond that, the friction coefficient of the TTC decreased, making it more lubricative than TiAl at the higher temperatures. It is proposed that at high-temperatures, TiSiC-formed oxides that were incorporated into a well-consolidated tribo-film drastically reducing the friction coefficients and wear rates of the TTC material. [ABSTRACT FROM AUTHOR]

Abstract: An investigation was conducted on the possible beneficial synergistic effects of multiple additives in self-lubricating composites for use in high temperature friction and wear applications. The sliding friction and wear rates of NiAl based self-lubricating composites with different solid lubricant additions (PbO, Ti3SiC2–MoS2, Ti3SiC2–WS2) were obtained from room temperature to 800°C with a pin-on-disc configuration. Dry sliding wear tests against Si3N4 balls (the pin specimens) were run using a constant load of 10N and a constant speed of 0.2m/s. The results showed that the composites with Ti3SiC2–MoS2 exhibited excellent self-lubricating and anti-wear properties over a wide temperature range. MoS2 lubricated better at low temperatures, while Ti3SiC2 lubricated better at high temperatures. The Ti3SiC2–MoS2 binary lubricant presented the best synergetic lubricating effect of the three candidate compositions. [Copyright &y& Elsevier]

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]

Dry sliding tribological tests of Ni3Al matrix self-lubricating composites (NMSC) with addition of 15wt% Ti3SiC2 are undertaken against Si3N4, Al2O3, WC-6Co at 25–800°C. The results show that the tribological properties are strongly dependent on the counterface materials. NMSC against Si3N4 shows the lower friction coefficients (0.31–0.48) and wear rates (0.34–2.1×10−5 mm3 N−1 m−1) from 25 to 800°C, while there is no clear difference in tribological performance of NMSC against Al2O3 or WC-6Co. NMSC against Si3N4 may be the optimal design for the excellently tribological performance. [ABSTRACT FROM AUTHOR]

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]

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]

[Display omitted] • An ordered patterning composite (OPC) structures are bio-inspired by shells. • The surface texture density promotes the formation of lubricating film. • The excellent tribological properties of OPC structures depends on the materials properties, components, and surface texture density. • The self-compensating lubrication behaviors are explained by theoretical models and experiments. Composite surface structures inspired by biological characteristics have the potential to strengthen the synergistic effects of surface micro-textures and solid lubricants by improving their tribological properties. This investigation sought to discuss the lubrication mechanisms by designing bio-inspired shell-like Ni 3 Al matrix composite surface structure, in which an ordered patterning composite (OPC) structures contained Ni 3 Al matrix and solid lubricants Sn-3.0Ag-0.5Cu(SAC305) alloys. Reciprocating dry sliding tests of OPC structures with different surface texture densities against high-carbon steel balls were performed, and the results were compared to those for orderly pattern (OP) structures without the SAC305 alloy. The results showed that the appropriate volume fraction of the SAC305 alloy should further promote decreases in the friction coefficients and wear losses. This could be attributed to the self-compensating lubrication behaviors of the SAC305 alloy. It formed a lubricating film with a certain area and thickness, which should be controlled by the material properties and components of the bio-composite surface structures, as well as the surface texture density. Additionally, methods based on a combination of theoretical models and experimental measurements further confirmed that the soft and hard materials of the OPC structure played different roles. The soft material (SAC305 alloy), which had a high surface energy and low hardness, had a better material transfer tendency than the hard material (Ni 3 Al matrix), which had a low surface energy and high hardness. This resulted in the formation of a transfer film and the occurrence of self-compensating lubrication behaviors. [ABSTRACT FROM AUTHOR]