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Wind power gears will be excessively worn due to lubrication failure during operation. Herein, the tribological properties of rubbing pairs are improved by filling solid lubricants into surface texture. In texture design, three types of topological textures (Circle (C), Hexagon (H) and Circle/Hexagon (CH)) were obtained by cell topology optimization, and then three cases with 20%, 30%, and 40% density were designed for each texture. Next, SnAgCu and TiC were deposited in texture of AISI 4140 steel (AS) to obtain 9 kinds of self-lubricating surfaces. Among them, AS with 30% CH density (AS-CH30) exhibits excellent mechanical and tribological properties. Compared with AS-C and AS-H, the maximum equivalent stress of AS-CH was decreased by 10.86% and 5.37%, respectively. Friction coefficient and wear rate of AS-CH30 were 79.68% and 78% lower than those of AS. The excellent tribological performances of AS-CH30 can be attributed to the synergistic effect of topological surface and solid lubricants. Topological surface can not only reduce fluctuation of equivalent stress, but also promote the stored lubricants to be easily transferred at the contact interface to form a 200 nm lubricating film containing solid lubricants (mainly), oxides and wear debris. [ABSTRACT FROM AUTHOR]

Inspired by the ability of biological structures to resist water pressure and flow resistance, this regulating mechanism was applied on the hydraulic cylinder. Bionic rhombic textures were combined with SnAgCu-Ti2C3Tx (ST) to improve the tribological properties of 42CrMo. After optimizing the texture parameters, the friction tests were performed on optimal experimental parameters-ST, predicted optimal structural parameters-ST and control experimental groups under dry/oil lubrication. Herein the optimized structural parameters were more conducive to the spreading of solid lubricants. The lubricating film was firmly bonded with substrate. The synergistic effect of optimized structural parameters, ST and oil lubrication can significantly improve the tribological properties of 42CrMo. [ABSTRACT FROM AUTHOR]

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]

In order to meet the stricter friction performance requirements of large machinery in the application field of slewing bearing, 42CrMo steel is taken as the research object. Through the preparation of smooth surface, groove textured surfaces with different densities and deposited Sn-Ag-Cu (SAC) solid lubricants, the tribological properties of samples with different surface treatments were, respectively, studied under the grease lubrication. The results show that the design of grooves can effectively alleviate the secondary damage of wear debris on the sample surfaces. Under the grease lubrication, the sample with SAC deposited on the surface has the smallest friction coefficient and deformation, which is mainly attributed to the synergistic effect among grooves, solid lubricants, and grease. [ABSTRACT FROM AUTHOR]

In order to further understand the role of MXene-Ti3C2 in oil–solid synergistic lubrication, three kinds of microporous channel composites, M50, M50-Sn-Ag-Cu and M50-Sn-Ag-Cu-Ti3C2, were designed and prepared in this study. Tribological behaviors under different environmental conditions of oil lubrication and dry friction were analyzed. The results show that M50-Sn-Ag-Cu-Ti3C2 exhibits excellent tribological properties under oil lubrication. Mxene-Ti3C2 enhances the strength of solid lubricant film, so that the oil film can give full play to the antifriction and wear resistance of solid lubricant film. The synergistic effect of lubricating oil, solid lubricants and bionic curved microchannel reduces the friction coefficient and wear rate. The vibration acceleration along the reciprocating direction is also reduced. [ABSTRACT FROM AUTHOR]

Herein, the analytic hierarchy process (AHP) and central composite experimental design in response surface methodology (CCD-RSM) are used to evaluate and optimize the tribological parameters of bionic textured AISI 4140-SnAgCu self-lubricating composite under the conditions of load (L: 20–40 N), velocity (V: 16–32 mm/s), and distance (D: 40–80 m). AISI 4140 biomimetic composites exhibit excellent tribological properties under the conditions of L27.15/V16.43/D40, L27.05/V17.08/D60, and L27.42/V17.85/D80, respectively. The sensitivities of influence factors on the tribological overall score are load, velocity, and distance, in order from high to low. The good antifriction properties of self-lubricating composites under conditions with the optimized tribological parameters benefit from the fact that the solid lubricants are uniformly spread at the contact interface. [ABSTRACT FROM AUTHOR]

Inspired by the surface texture of bivalve shell, bionic wavy grooves were designed and prepared on the bionic coating of TC4 using laser marking technology. A response surface method was used to optimize the parameters of bionic texture structure for improving the tribological behavior. The influence of coupling mechanisms of bionic coating and texture on the tribological performance of TC4 alloy was investigated. The results show that the bionic wavy grooves reduce the fluctuation of loading force. The coupling of bionic texture and coating breaks the continuity of coating interface, and the peeling wear debris is easily captured by the bionic wavy grooves. The repairing effect of solid lubricant is increased, so the complete lubrication film can be formed more easily on the worn surface during the sliding process. [ABSTRACT FROM AUTHOR]

In view of the uneven lubricating film of M50 aviation bearings under high load, it is of great significance to explore how to improve its friction performance through the synergistic lubrication of solid lubricant and lubricating oil. Inspired by the material transport of leaf veins, a bionic microchannel was designed for the contact interface. M50, M50-SnAgCu (MS) and M50-SnAgCu-Nb2C (MSN) biomimetic composites are prepared, respectively. The tribological properties of the material under dry friction and three grades of Mobil oil (DTE 24, DTE 25 and DTE 26) were investigated through ball-on-disk friction. The high-hardness Si3N4 ball is used as the counterpair. The results show that the average friction coefficient and wear rate of MSN are reduced by 29.63% and 28.36%, respectively. In addition, the furrows on the worn surface were significantly reduced. The synergistic lubrication of SnAgCu-Nb2C and the DTE 26 oil makes M50 have a excellent antifriction and wear resistance. The results can provide guidance for the research of synergetic lubrication behavior of materials. [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]

Improving the friction-induced noise suppression performance of TC4 has far-reaching significance for its wide application in the field of robots and semiconductors. The friction noises of TC4 with solid lubricant (Sn-Ag-Cu) filled into dimples (TCS) and TC4 were predicted by simulation analysis. The noise reduction performance of TCS during dry rotary sliding was discussed. TCS with dimple size of 0.6 mm (TCS-0.6) exhibited the prominent performance of noise reduction, which was attributed to the synergistic effect of dimples and solid lubricant. During the dry sliding process, the debris were contained by dimples, the stress distribution in matrix was modified by lubricant, and the defects were decreased. Hence, the roughness of worn surface was reduced, which was beneficial to obtaining the stable friction coefficient. Inhibiting the unstable vibration by controlling the friction coefficient of the system can effectively demote the friction-induced noise. [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]

Improving the tribological performance of TC4 has far-reaching significance for its wide application in the field of automobile and robot. The lubricating behaviors of TC4 with mixed solid lubricant (Sn-Ag-Cu with TiC) filled into surface dimples (TAC) during dry rotary sliding were systematically investigated. The results show that TAC has better tribological properties than TC4 and TC4-P. It attributes to the synergistic effect of surface dimples and mixed solid lubricant. The mixed solid lubricant in dimples is easier to be extruded to the frictional interface. The uniform and wear-resistant lubricating layer containing SAC and TiC is formed on the worn surface of TAC, reducing the direct impact of counterpart ball on substrate material. The fluidity of SAC endows TAC with the ability of self-repairing. [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]

The elastic and plastic deformations have significant effect on the tribological properties of the graphene-reinforced Ni3Al matrix self-lubricating composites. The primary purpose of this study is to investigate the tribological behavior and wear mechanisms of graphene-reinforced Ni3Al matrix self-lubricating composites by researching the effects of different loads and the corresponding friction heat on the elastic or plastic deformation. The dry sliding tribology tests of graphene-reinforced Ni3Al matrix self-lubricating composites are carried out at the loads of 7, 10, 13, and 16N, respectively. The elastic or plastic deformation is judged by comparing the yield stress with the contact stress analyzed by the numerical simulation method. It is found that graphene-reinforced Ni3Al matrix self-lubricating composites exhibit good tribological properties at 13 N due to the elastic deformation, leading to the formation of relatively stable wear resistant layer. Graphene-reinforced Ni3Al matrix self-lubricating composites show poor tribological performance at 16 N for the plastic deformation, resulting in the destruction of the wear resistant layer and the generation of surface cracks and material spalling. From the mechanical mechanism of wear, the plastic deformation and thermal stress are the important factors to lead to the material spalling. The results could be used to guide the selection of suitable working conditions for having good tribological performance of low wear and long service life. [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]

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]

A favorable hardness ratio (Hdisk/Hpin = Hd/Hp) could lead to a transition to mild wear during sliding contact. To determine a more appropriate Hd/Hp value for the sliding wear, the dry sliding pin-on-disk wear tests of Ni3Al matrix composites (NMCs) with multilayer graphene (MLG) are undertaken at Hd/Hp values of 0.99, 0.83, 0.42, and 0.35 at sliding speeds of 0.1, 0.3, 0.5, and 0.7 m/s. It is found that the tribological properties of NMCs are strongly affected by the various hardness ratios. At 0.1 m/s, the friction coefficient decreases with a decrease in Hd/Hp value. The low friction coefficient is 0.14 and the wear rate is 0.9 × 10-5 mm3 N-1m-1 under the ceramic counterpart with Hd/Hp of 0.35. At 0.7 m/s, the tribological properties show the opposite trend with a decrease in Hd/Hp. At an Hd/Hp of 0.35, the smooth compact layer on the worn surface could decrease the friction at 0.1 m/s, and the improved hardness in the subsurface by strain hardening would play an important role in the improvement of wear resistance. Under the metal counterpart with Hd/Hp of 0.99, plastic deformation only occurs on the contact surface and the MLG could suppress further shear deformation in the subsurface, leading to a low wear rate (2.4 × 10-5 mm3 N-1m-1) and friction coefficient (0.15) at 0.7 m/s. [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]

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]

Microstructure and functional mechanism of friction layer need to be further researched. In the present work, the friction coefficients and wear rates are analyzed through response surface methodology to obtain an empirical model for the best response. Fitting results show that the tribological performance of NiAl matrix composites (NMCs) with graphene nanoplatelets (GNPs) is better than that of NMCs without GNPs, especially at high sliding velocities and high loads. Further research suggests that the formation of integrated friction layer, which consists of a soft microfilm on a hard coating, is the major reason to cause the differences. Of which, the wear debris layer (WDL) with a low shear strength can reduce the shear force. The ultrafine layer (UL), which is much harder and finer, can effectively avoid fracture and improve the load support capacity. Moreover, the GNPs in WDL and UL can be easily sheared and help to withstand the loads, trending to be parallel to the direction of shear force. [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 wear fatigue of slewing bearings at the contact areas of raceways (AISI 4140 steel (AS)) and rollers (AISI 52100 steel) seriously reduces the service life of equipment. AS-SnAgCu-TiC composites (AS-SACT) were prepared by filling multi-solid lubricants into surface biomimetic textures of AS to improve the wear resistance. Tribological properties were tested using a block-on-ring tribometer. The materials of block and ring were AS and AISI 52100 steel, respectively. Compared with that of AS, coefficient of friction of AS-SACT was decreased by 67.93%, and wear height was reduced by 42.19%. Wear triggered the diffusion of SnAgCu from the bionic textures to worn surface. The hard phase of nano-TiC was wrapped by a cluster of multi-layer lubricants to form spherical particles, which not only converted sliding to rolling contact, but also repaired pits and furrows on worn surface. Hence, AS-SACT with self-repairing behavior had excellent properties of antifriction and wear resistance. [Display omitted] •Tribological properties of AISI 4140 steel were improved by texture and SnAgCu–TiC. •Average COF of AS-SnAgCu-TiC was 67.93% lower than that of AS (AISI 4140 steel). •Wear defects were filled with solid lubricants to produce self-repairing behavior. •Spherical particles transformed the frictional mode from sliding to rolling. •Nano-TiC particles wrapped by SnAgCu can promote wear defects to be filled. [ABSTRACT FROM AUTHOR]

Inspired by shell surface structure, the surface textures were extracted by curve fitting method and the corresponding bionic wavy textures filled with SnAgCu-WS 2 composite solid lubricants were prepared on the surface of TC4. The coupling effect of bionic wavy textures and SnAgCu-WS 2 and the effect of variable reciprocating friction frequency on the tribological properties of TC4 were explored. The results show that bionic textures improve the precipitation efficiency of SnAgCu-WS 2 , and the sliding effect of WS 2 promotes the spreading and repairing of composite solid lubricants in the wear track, thus improving the formation quality of the lubricating film and its adaptability to the change of reciprocating frequency. [Display omitted] • Bionic textures with lubricants were used to improve tribological performance of TC4. • Bionic wavy textures improve the precipitation efficiency of SnAgCu-WS 2. • Sliding effect of WS 2 promotes spreading and repairing of lubricants in wear track. • Coupling effects improve adaptability to the change of reciprocating frequency. • The average friction coefficient of TWs-SACW02 is reduced to 0.219 at 20 N and 1 Hz. [ABSTRACT FROM AUTHOR]

This research was carried out on the beneficial effect of graphene additive in self-lubricating composites for use at different loads of tribological application. The dry friction and wear behaviors of NiAl self-lubricating matrix composite with graphene (NSMG) were investigated at different loads at room temperature. Finite element method served as aided method to analyze the stress condition of contact pair, which would provide another perspective to comprehend the relationship between tribological behaviors and different degrees of load-induced deformation. In the load range of 2-16 N, the results indicated that NSMG showed excellent tribological performance at load of 16 N due to the formation of anti-friction tribo-film on the worn surface. Moreover, suitable load would lead to the contact situation transfer from multi-point contact to area contact, which could contribute to the beneficial effect on friction behavior of NSMG. [ABSTRACT FROM AUTHOR]

The tribological behaviors of the Ni3Al-WS2-Ti3SiC2composites and synergistic effect of composite solid lubricants are investigated from room temperature to 800°C. The results show that the Ni3Al matrix composites (NASC) exhibit excellent tribological properties throughout the test temperatures compared to Ni3Al-based alloy. The excellent tribological properties of NASC are attributed to the synergistic lubricating effect of WS2and Ti3SiC2. A lubricating film could be formed below 400°C, and an oxidation protection film is formed above 400°C on the worn surface of NASC during the sliding process, leading to low coefficients of friction (0.18–0.39) and wear rates (1.5–3.7 × 10−5mm3N−1m−1). [ABSTRACT FROM AUTHOR]

To better understand respective lubrication effects and mechanisms of graphite, multi-walled carbon nanotubes (MWNTs), and multilayer graphene (MLG), comparison of tribological properties of NiAl matrix composites (NAMC) containing graphite, MWNTs, or MLG is investigated. Tribological results clearly indicate that the incorporation of solid lubricant remarkably improves the tribological properties of NAMC. NAMC containing MWNTs have better tribological properties than that containing graphite. NAMC containing MLG have the best tribological properties. EPMA, AFM, and FESEM analyses of worn surfaces suggest that the discontinuous island-like solid lubricant-rich films with different compacting extent forms on the worn surfaces of NAMC containing solid lubricant. The worn surface of NAM shows the slighter delamination and comparatively more compact films than that of NAC; in contrast, the worn surface of NAG presents the slightest delamination and the most compact films. It is concluded that graphite, MWNTs, and MLG indeed possess different lubrication effects and mechanisms. [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]

Ni3Al-MoS2-TiC composites (NMTC) were fabricated using spark plasma sintering. The effect of TiC content on tribological properties and antiwear mechanisms of NMTC at high temperatures was investigated. The results showed that NMTC containing 10 wt% MoS2 and 6 wt% TiC exhibited the excellent tribological properties from 25 to 600°C. At 400°C, NMTC had the lowest friction coefficient of 0.28 and the considerable lower wear rate of 3.02 × 10−5 mm3 N−1 m−1. The excellent tribological properties of NMTC were attributed to the synergetic action of the lubricant-phase MoS2 and reinforcing-phase TiC. [ABSTRACT FROM AUTHOR]

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]

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]

The progress in aerospace field requires a new NiAl matrix composite that can stand against wear and decrease the energy dissipation through decreasing friction. In this study, the tribological behavior of NiAl–1.5 wt% graphene composite is investigated at room temperature under a constant load of 12 N and different sliding velocities. The results show that the friction coefficient and wear rate increase with increasing sliding velocity from 0.2 to 0.4 m/s due to the adhesion between the sliding bodies and tearing of the graphene layer. The friction coefficient and wear rate tend to decrease at a sliding velocity of 0.6 m/s as a result of severe plastic deformation and grain refinement of the worn surface. However, at 0.8 m/s the friction coefficient reaches a minimum value and the wear rate increases and changes the wear mechanism to fatigue wear. It can be concluded that various wear mechanisms lead to different tribological performance of NiAl–1.5 wt% graphene composite. [ABSTRACT FROM PUBLISHER]

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]

TiAl matrix self-lubricating composites (TMC) with various weight percentages of Ti3SiC2and MoS2lubricants were prepared by spark plasma sintering (SPS). The dry sliding tribological behaviors of TMC against an Si3N4ceramic ball at room temperature were investigated through the determination of friction coefficients and wear rates and the analysis of the morphologies and compositions of wear debris, worn surfaces of TMC, and the Si3N4ceramic ball. The results indicated that TMC with 10 wt% (Ti3SiC2-MoS2) lubricants had good tribological properties due to the unique stratification subsurface microstructure of the worn surface. The friction coefficient was about 0.57, and the wear rate was 4.22 × 10−4mm3(Nm)−1. The main wear mechanisms of TMC with 10 wt% (Ti3SiC2-MoS2) lubricants were abrasive wear, oxidation wear, and delamination of the friction layer. However, the main wear mechanisms of TMC without Ti3SiC2and MoS2lubricants were abrasive wear and oxidation wear. The continuous friction layer was not formed on the worn surfaces. The self-lubricating friction layer on the frictional surface, different phase compositions and hardness, as well as density of TMC contributed to the change in the friction coefficient and wear rate. [ABSTRACT FROM AUTHOR]

Highlights: [•] Tribological properties of NMSC from RT to 800°C were tested. [•] Tribological properties of NMSC strongly depended on the addition content of WAh. [•] WAh and TiC brought about an improvement in tribological properties of NMSC. [•] NE showed the excellent tribological properties from RT to 800°C. [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: 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]

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]

To improve the insufficient lubrication of slewing bearing, this study investigates the tribological properties of 42CrMo bionic textured composite surface (BTCS) with different densities under MXenes-Ti 3 C 2 lithium composite grease (MLCG). Inspired by the micro-texture characteristics of the clamshell, BTCS is composed of 42CrMo and Sn-Ag-Cu (SAC) alloy. The results indicate that the tribological performance of BTCS (ρ = 38%) is improved most significantly, the average friction coefficient (0.056) and wear rate (6.4 ×10−8 mm3N−1m−1) of the counterpart ball reach the minimum, and the worn surface is fine and smooth. This is mainly attributed to the synergistic self-repairing effect of MXenes-Ti 3 C 2 and SAC on the worn surface. Furthermore, SAC particles act as submicron rolling bearings, transforming the friction form into rolling-sliding. [Display omitted] • Bionic textured composite surface (BTCS) was designed and fabricated. • MXenes and SAC particles could achieve the synergistic self-repairing effect. • SAC particles could act as submicron rolling bearings on the worn surface. • BTCS can significantly improve the tribological properties under starvation. [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]