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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]

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]

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]

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]

Purpose This paper aims to predict and evaluate the wear rate of TiAl-2 Wt.% MoO3 tabular crystals (TMCs) using the Newton interpolation methods.Design/methodology/approach The friction and wear behaviors of TMC were examined using pin-on-disc apparatus at different times, namely, 1,200, 2,400, 3,600, 4,800 and 6,000 s. The wear rates of five different times as interpolation nodes were measured and calculated by electron probe microanalysis (EMPA) and field emission electron microscope (FESEM). Then, the prediction formula of wear rate was constructed using the Newton interpolation method. The accuracy of the prediction formula and the relationship with friction layer and worn surface are verified for evaluating the reliability of the prediction formula.Findings The prediction formula shows a similar variation trend of TMC as the experimental results, indicating that the prediction formula can forecast the wear rate and working condition of TMC. Moreover, the microstructures of friction layer and worn surface also have a strong impact on the prediction formulas.Originality/value The prediction formulas of the Newton interpolation polynomial can be adopted to predict working longevity in the mechanical components, which can guide the practical engineering application in industrial fields. [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 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 friction and wear behavior of NiAl alloy containing graphene nanoplatelets (NG) under different sliding velocities were investigated. NG shows the better tribological performance, if compared to NiAl-based alloy without graphene nanoplatelets (NA). In the range of sliding velocities varying from 0.2 to 1.2 m/s, the formation of glaze layer in NG could be easily distinguished. The beneficial effect of graphene nanoplatelets (GNPs) for the formation of glaze layer of NG is obvious, if compared to NA, resulting in the reduction of friction and improvement of wear resistance of NG. Moreover, a suitable higher sliding velocity will be better for the formation of glaze layer, but the wear rate will gradually increase with the increase of sliding velocity. It can be concluded that GNPs hold great application prospect as an effective solid lubricant to improve the tribological performance of NiAl alloys. [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 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 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]

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]

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]

More durable, low-friction self-lubricating materials in modern industry are greatly needed for tribological systems. The current paper presents the tribological performance of TiAl matrix self-lubricating composites (TSC) containing MoS, hexagonal BN and TiSiC designated as MhT against GCr15 steel counterface under several sliding speeds from 0.2 to 0.8 m s and applied loads from 6 to 12 N. The results suggested that MhT played an important role in decreasing friction coefficients and wear rates. The covering percentage of transfer layers on worn surfaces varied with the changing of sliding speeds and applied loads, hence resulting in the distinct friction and wear characteristics of TSC. TSC containing 10 wt% MhT exhibited the best excellent tribological performance at 10 N-0.8 m s, which could be due to the formation of the best compaction and largest coverage of transfer layer on the worn surfaces. [ABSTRACT FROM AUTHOR]

Inspired by microstructures on tree frog surface, this article designs bionic micro-texture combined with solid lubrication SnAgCu to improve the tribological properties of AISI 4140 steel. The optimized bionic texture parameters are obtained by RSM. Tribological tests were carried out on Optimal Test (OT), Optimal Prediction (OP) and Control Group (CG). Compared with OT, the discontinuous layer phenomenon on wear track of OP is significantly reduced, lubricant content is increased, and numbers of pits near the textures are reduced. A uniform thickness of 2.4 µm lubricating film was formed on worn surface of OP, and the film was well bonded with substrate. Consequently, optimizing the micro-texture by RSM can significantly improve the tribological properties of AISI 4140 steel. [Display omitted] • Optimizing the bionic texture can significantly improve the tribological properties. • The optimized bionic texture parameters are obtained by RSM. • The bionic hexagon structure on the surface of AISI 4140 steel is designed. • The OP has better lubricating effect and anti-friction and wear resistance. [ABSTRACT FROM AUTHOR]

To expand the applications of MXene-Ti 3 C 2 in solid-liquid lubrication system, CSS-42L smooth surfaces (SSs), groove surfaces (GSs), groove with Sn-Ag-Cu composite surfaces (GSs-SAC) and groove with Sn-Ag-Cu-Ti 3 C 2 composite surfaces (GSs-SACT) are prepared. The tribological behaviors of samples under dry friction and oil lubrication are studied. The results show that Sn-Ag-Cu-Ti 3 C 2 has the excellent oil film adsorption capacity. The micro-hydrodynamic effects of oil in the grooves are produced under oil lubrication. The synergistic effects of oil, Sn-Ag-Cu-Ti 3 C 2 and grooves reduce the fluctuation amplitudes of friction force and load, improving bearing capacity of oil film and profile characteristics on the surfaces. GSs-SACT with uniform and smooth profiles shows the tribochemical wear and obtains the excellent antifriction and wear resistance properties. [Display omitted] • The change rules of friction forces and load are improved on GSs-SACT. • Sn-Ag-Cu-Ti 3 C 2 with excellent wettability promotes the oil-film adsorption on GSs-SACT. • The synergistic effects of Sn-Ag-Cu-Ti 3 C 2 , groove and oil show excellent antifriction. • GSs-SACT with uniform and smooth profiles has excellent wear resistance. [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]

To expand the applications of MXene-Ti 3 C 2 in the field of high temperature tribology (450 °C), CSS-42L smooth surfaces (CSs), textured surfaces (TSs), textured surfaces with Sn-Ag-Cu (TSs-SAC) and textured surfaces with Sn-Ag-Cu-Ti 3 C 2 (TSs-SACT) were prepared. The tribological behaviors under high temperature were investigated, and TSs-SACT showed excellent tribological properties at high temperatures. The amplitudes of friction force and coefficient could be reduced on TSs-SACT with the best antifriction performance. At high temperatures, the crystallinity, microhardness, residual strain and grain size on TSs-SACT are improved, which promotes the formation of enamel layers. The tribochemical reactions improve the wear resistance of enamel layers. TSs-SACT with uniform profiles has strong resistance to plastic deformations, prolonging the life of enamel layers. [Display omitted] • Synergistic effects of Sn-Ag-Cu-Ti 3 C 2 and groove show excellent antifriction. • Tribological enhancements of Sn-Ag-Cu-Ti 3 C 2 prolong the life of enamel layer. • Tribochemical reactions improve the wear resistance of enamel layer. • TSs-SACT with uniform and smooth profiles has excellent wear resistance. [ABSTRACT FROM AUTHOR]