Antifriction Performance Research Articles

Fabrication of AlCrN coatings on WC-Co substrates with diamond films interlayer

Physical vapour deposition (PVD) AlCrN coatings were deposited on the microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) coated WC-Co substrates. The structure, morphologies and frictional characterization of as-fabricated composite coatings were investigated. The surface roughness of MCD coated specimen covering with the AlCrN coating dramatically decreased to ~239 nm. The AlCrN/diamond coatings could provide excellent antifriction properties compared to the monolayer AlCrN coating, especially the value of coefficient of friction for AlCrN/NCD coated specimen decreased to ~0.23, it was much lower than that of the AlCrN coated specimen with ~0.50. The results showed that adopting this method, smooth surfaces for MCD coated samples and high antifriction performance for AlCrN coated samples were obtained simultaneously, which provided a beneficial technology for broadening the application field of AlCrN and diamond coatings.

Impact of Boron Nitride Nanoparticles on the Wear Property of Lithium Base Grease

In order to satisfy the requirement of lubrication under extreme working conditions (e.g., heavy load, high speed, and high temperature), a lubricating grease containing boron nitride (BN) nanoparticles was prepared by ultrasonic dispersion. And the effect of different content of nanoboron nitride on the tribological properties of lubricating grease was studied by means of a four-ball friction tester. The results showed that the grease containing 0.60 wt.% BN nanoparticles had the best anti-friction performance, as well as the smallest friction coefficient and wear scar radius. Additionally, a Raman spectrometer, scanning electron microscope, and three-dimensional profilometer were used to analyze the chemical composition, characterize the morphology of the wear scar in the steel balls after the friction tests, and the analysis results show that BN nanoparticles can not only produce lubricating film to protect friction pairs, but also its layered structure is easy to cause sliding of the friction pairs under the action of friction. Therefore, under the synergism of lubricating film and layered structure, the friction coefficient is obviously reduced and the friction reduction performance of grease is improved.

Microstructure, mechanical properties and wear resistance of an Al–Mg–Si alloy produced by equal channel angular pressing

Microstructure, mechanical properties and wear resistance in an ultrafine-grained Al–Mg–Si alloy fabricated utilizing a combination of equal channel angular pressing (ECAP) and dynamic aging were investigated in this paper. The results indicated that the grain size of the ECAP alloy was significantly refined, i.e., to ~239 nm after three ECAP passes. Meanwhile, the yield and tensile strength of the ECAPed material reached 340 MPa and 445 MPa, respectively, while maintaining a significant uniform elongation of 14%. Wear resistance results demonstrated that the wear rate, wear depth and width of the ECAPed material decreased in comparison with the solution-treated (SST) and peak-aged (T6) conditions under a load range of 5–25 N. The adhesive wear that occurs in the undeformed specimens at 10 N does not appear in the ECAPed specimen at the same load, indicating that the ECAPed specimen delay the appearance of more serious wear mechanisms under certain loads. The cooperative interaction of high density nano-scale β" precipitates and dislocations resulted in a combination of super-high strength and good work hardening ability which suppressed the extension of cracks between the friction layer and the plastic deformation zone. As a consequence, the combination of ECAP and dynamic aging brings a significant improvement for antifriction performance of the 6061 aluminum alloy.

Experimental Analysis of Milling Aluminum Alloy with Oil-Less Lubrication of Nano-Fluid

The nano-fluid added with nano-particles in the easily degradable vegetable oil base ensures that the contact angle of the aluminum alloy 7075 under the vegetable oil base is slightly improved, and the lubrication performance is further strengthened, the cutting force is reduced, the surface quality is improved, and the roughness is reduced. When milling the aluminum alloy 7075, the lubrication performance effect of the nano-fluid is evaluated. Taking aviation aluminum 7075 as workpiece. The contact angle, cutting force, surface roughness and SEM appearance of the workpiece were evaluated under four lubrication conditions: dry processing, emulsion pouring, micro lubrication of cottonseed oil and cottonseed oil-based + 0.5% Al2O3 nano-particles. The experimental results show that the contact angle of nano-fluid to aluminum alloy 7075 is slightly larger than that of vegetable oil, but with the addition of nano-particles, the chips roll from sliding, making the surface morphology of the machined surface good, the cutting force minimum, the roughness minimum, indicating that the nano-fluid lubrication and antifriction performance is good.

Tribological behaviors of polyimide composite coatings containing carbon nanotubes and fluorinated graphene with hybrid phase or blend phase

In this work, hybrid phase and blend phase composed of carbon nanotube (CNT) and fluorinated graphene (FG) were doped into pure polyimide via a solution doping method to improve the tribological properties of polyimide. The effect of the hybrid phase and blend phase on mechanical and tribological properties of polyimide (PI) composite coatings were systematically investigated. The results showed that there was a much stronger interfacial interaction to enhance the mechanical properties of PI composite coating modified by the blend phase. The tensile strength increased by 46 %, hardness increased by 43 %, and storage modulus increased by 96 % at room temperature. The significantly enhanced mechanical properties can provide plenty of energy to resist wear for PI composite coating, and thus resulting in a 61 % reduction in wear rate. In addition, due to the lubricating properties imparted by the hybrid phase, the coefficient of friction (COF) of PI composite coating modified by hybrid phase was reduced by 13 %, showing the best anti-friction performance.

Preparation and tribological properties of solid-liquid synergetic self-lubricating PTFE/SiO2/PAO6 composites

Herein, 25 kinds of polytetrafluoroethylene (PTFE) composites with solid-liquid synergetic self-lubricating property were prepared by filling PTFE matrix with hollow SiO2 particles and lubricating oil (PAO6). Hollow SiO2 particles containing PAO6 acting as lubricating fillers were applied to enhance the tribological performances of PTFE matrix. The generated PTFE composites displayed solid-liquid synergetic self-lubricating property and could achieve ultralow friction. Factors such as the cold-pressed pressure and the SiO2 content that affect the tribological performance of the composites were investigated in detail. The compactness of the composites was enhanced when the cold-pressed pressure increased. The porosity of the composite with 25 wt% SiO2 decreased from 38.2% to 14.3% when the cold-pressed pressure was increased from 10 MPa to 50 MPa. As the cold-pressed pressure was increased, the antiwear performance of the composites was enhanced but their antifriction performance become worse. The composites containing PAO6 achieved lower coefficient of friction (COF) and smaller wear rates than composites without PAO6. The COF value decreased from 0.143 (pure PTFE) to an ultralow value of 0.037 (composite 5%-10 MPa-oil). The enhanced antifriction performance of the composite was associated with the synergistic lubricating effect of the liquid lubricant of PAO6 and the lubrication of the PTFE matrix. All the prepared PTFE/SiO2/PAO6 composites exhibited excellent antifriction performance and improved antiwear property and thus can be used to fabricate a new kind of self-lubricating materials.

Nano-crystallization-Driven High Temperature Self-lubricating Properties of Magnetron-Sputtered WS2 Coatings

In consideration of high temperature conditions, this paper focuses on the self-lubricating properties of WS2 coatings at high temperature. A low coefficient of friction (CoF) about 0.07–0.2 for WS2 coatings can be attained at temperatures of 100–400 °C. The chemical stability, mechanical and tribological properties were investigated by energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), nano-indentation tester and ball-on-disk tribometer, respectively. According to XRD and XPS spectra, the as-sputtered WS2 coatings existed as 2 h-WS2 structure. The crystal transition of WS2 coatings from amorphous to (002) basal plane-oriented lubricating film, which was obtained by the synergistic effect of load and friction, and provided anti-friction performance at 100–400 °C. At 500 °C, the WO3 formed by oxidation of WS2 on the sample surface with lower hardness reduces the CoF and improves wear resistance. The wear resistance and anti-friction performance are discussed in terms of morphology of the wear scars, anti-oxidation capability of the coating and tribochemical reaction product of the friction pair.

Microstructure and tribological property of Ni–MoS2 composite coatings prepared by ultrasonic and mechanical stirring electrodeposition

To optimize the deteriorated mechanical properties of the loose MoS2 coatings, ultrasonic oscillation was employed to change the deposition mode of MoS2 particles, hence their structure and mechanical properties. The electrodeposition of Ni–MoS2 self-lubricating composite coating was assisted by magnetic stirring (Mag-NM) or ultrasonic oscillation (US-NM), respectively. A comparison of coating structure, depositing mechanism, and friction performance was investigated by means of XRD and SEM. Moreover, the influence of MoS2 concentration on the coating morphology and the friction performance was explored. The results demonstrated that the Ni–MoS2 composite coatings have superior antifriction performance compared to pure Ni coating. Comparing to the porous structure of Mag-NM coatings, the US-NM coatings obtained compact structures with well-dispersive MoS2 particles. There is 80.4% hardness reduction occurred on the Mag-NM coatings, but only 8.8% reduction of the US-NM coatings. With the increase of MoS2 concentration, a clear and continuous wear trace was formed on the Mag-NM coatings. The protrusion grinding indicates the excellent wear resistance of the US-NM coatings.

Study on plowing performance of EDEM low-resistance animal bionic device based on red soil

The anti-drag and anti-friction performance of low-resistance animal in soil have always been the focus of study on soil-plowing devices. In this paper, a new soil plowing device is designed by imitation of the low-resistance bear claws. Taking the angle, rotating speed, forward speed and plowing depth as factors, the power and specific energy consumption as response indicators, the single-factor experiment in the red soil condition is carried out to analyze the influence of various factors on the indicators. The EDEM simulation model of the bear-claw bionic ditcher based on the properties of red soil is designed to verify the accuracy of the model and obtain the motion characteristics of the bear-claw bionic ditcher. The double-multiple regression model based on the red soil ditching parameters is obtained by the optimization of the rotating surface. The experimental results show that: angle, forward speed, rotating speed, interaction angle and forward speed, interaction rotating speed and forward speed have significant influence on power and specific energy consumption. The best parameters in the red soil condition are angle of 11.5°, rotating speed of 260 r/min, forward speed of 0.24 m/s, plowing depth of 13 cm, power of 0.5994 kW, specific energy consumption of 221.85 kJ/m3, maximum resultant force of 336 N, maximum lateral force of 85 N, maximum horizontal force of 197 N, and maximum vertical force of 174.7 N. The power and specific energy consumption of the bionic ditcher are smaller than the traditional ditching blade, and the biotic ditcher designed has low resistance.

Preparation and Tribological Properties of Carbon-Coated WS2 Nanosheets.

WS2-C is produced from a hydrothermal reaction, in which WS2 nano-sheets are coated with carbon, using glucose as the carbon source. In order to investigate the tribological properties of WS2-C as a lubricant additive, WS2-C was modified by surfactant Span80, and friction tests were carried out on an MRS-10A four-ball friction and wear tester. The results show that Span80 can promote the dispersibility of WS2-C effectively in base oil. Adding an appropriate concentration of WS2-C can improve the anti-wear and anti-friction performance of the base oil. The friction coefficient reached its lowest point upon adding 0.1 wt % WS2-C, reduced by 16.7% compared to the base oil. Meanwhile, the wear scar diameter reached its minimum with 0.15 wt % WS2, decreasing by 26.45%. Moreover, at this concentration, the depth and width of the groove and the surface roughness on the wear scar achieved their minimum. It is concluded that WS2-C dispersed in oil could enter friction pairs to avoid their direct contact, thereby effectively reducing friction and wear. At the same time, WS2-C reacts with the friction matrix material to form a protective film, composed of C, Fe2O3, FeSO4, WO3, and WS2, repairing the worn surface.

Friction-reducing effect and damage mechanism of laser micro-texture on diamond films during friction

Diamond films are often applied in places where there is intense friction. The use of lasers to fabricate textured arrays on diamond films can effectively reduce the friction coefficient. In this paper, we use a UV nanosecond laser to produce periodic linear and pit micro-textures over the areas of [Formula: see text]. Laser irradiation was below the single-pulse ablation threshold corresponding to the conditions of surface graphitization during the multi-pulse irradiation. Irradiated graphitization can be detected by Raman spectroscopy, and at the same time, lattice distortion and crack initiation that accompany graphitization can be obtained by XRD and SEM, respectively. The shape of the texture also has a great influence on the residual stress. Grooved texture released the residual stress, but pit texture gave rise to uneven stress, as shown in the test result. SEM was used for observing morphological change at the edge of texture and the mechanism of internal stress changes is analyzed. Detection of texture antifriction performance by reciprocating friction and wear tester. After rubbing, the layered shedding marks of the edge of the texture were observed, and the influence of the superposition of residual stress and external stress on the texture damage was proved based on this.

Experimental Study on Tribological Property of MoS2 Nanoparticle in Castor Oil

In this paper, the antiwear and antifriction performance of MoS2 nanoparticle in castor oil was studied. The ball-on-disc tests were performed for different concentrations of MoS2 nanoparticle. Coefficient of friction, wear loss, and worn surface morphology were investigated. The results show that MoS2 nanoparticle could reduce the possibility of asperities direct contact, resulting in the reduction of the coefficient of friction and adhesive wear. However, MoS2 nanoparticle in excessive concentration could agglomerate into large particles, playing the role of an abrasive particle, which reduces the beneficial effects of MoS2 nanoparticle.

Wear and Corrosion Resistance of Cold-Sprayed Cu-Based Composite Coatings on Magnesium Substrate

The applications of magnesium-based alloys are often limited by their poor corrosion and wear resistance performance. The aim of this study is to improve the performance of magnesium alloys by using metal–ceramic coatings. Cu-Ni/Al2O3 and Cu-Zn/Al2O3 coatings were deposited by cold spray. Their microstructure, microhardness, tribological, and corrosion behavior were compared with those of Cu-Al2O3 coatings. The results showed that the Cu-Al2O3 coatings exhibited higher microhardness, lower wear rate, and better corrosion resistance than the Mg alloy substrate, but their antifriction performance was not ideal. Adding Ni or Zn to the Cu-Al2O3 coating resulted in a denser coating with lower porosity. Ni increased the microhardness of the Cu-Al2O3 coating but did not improve its antifriction performance or wear resistance, while Zn increased the microhardness, antifriction performance, and wear resistance of the Cu-Al2O3 coating. The corrosion resistance of the Cu-Al2O3 coating was enhanced by adding Ni, which improved the compactness of the coating, in contrast to the addition of Zn, as the rapid corrosion of Zn resulted in formation of loose corrosion products without protective effect. Thus, such modification of Cu-Al2O3 coatings should be based on application requirements.

A top-down exfoliation for MoS2 nanosheets based on Li+/Na+-intercalated and shearing synergistic process

Bulk MoS2 was exfoliated in few layers by combining hydrothermal exfoliation in mixed LiOH/NaOH solution and shearing exfoliation. The as-exfoliated MoS2 nanosheets were verified by a series of characterizations. The results indicated that the thickness of the as-exfoliated MoS2 nanosheets was about 5 layers. Furthermore, the as-exfoliated MoS2 nanosheets exhibited the better antifriction performances in base oil.

Fabricating the Superhydrophobic Nickel and Improving Its Antifriction Performance by the Laser Surface Texturing.

The superhydrophobic surface can change the friction property of the material, reduce the adhesion of the friction interface, and produce a certain slip, thereby reducing the friction coefficient. The laser has high energy, high density, and is especially suitable for the surface treatment of materials. The laser surface texturing is a good way to construct superhydrophobic surfaces. The experiment uses a nanosecond pulse laser to construct the groove texture on the nickel surface. The contact area between the air and the droplets retained on the rough surface is increased, effectively preventing the water droplets from entering the gully of the surface microstructure, reducing the water droplets and the solid surface. The contact area ultimately makes the surface exhibit excellent superhydrophobicity. A superhydrophobic nickel surface having an apparent contact angle of water (ACAW) of 160° and a sliding angle (SA) of less than 10° was prepared. The MM-W1B vertical universal friction and wear tester was used to test the groove texture samples with different depths. The surface texture can capture the wear debris generated by the wear and store the lubricant, which is beneficial to the formation of fluid dynamic pressure lubrication and improve the load. The friction coefficient is reduced from 0.65 of the unprocessed surfaces to 0.25 after the texturing, and the friction performance is greatly improved.

Bio-tribocorrosion behavior of a nanocrystalline TiZrN coating on biomedical titanium alloy

A nanocrystalline TiZrN graded coating was deposited on biomedical titanium alloy by DC reactive magnetron sputtering process. The microstructure and compositions of the coating were characterized by XRD, TEM and EPMA. The electrochemical corrosion and bio-tribocorrosion behavior of the coated titanium alloy under open circuit potential (OCP) and applied potentials (−0.15 V ~ +0.25 V) were investigated in Hank's solution with and without 25% calf serum. Compared with TiN coating, the hardness of TiZrN coating is greatly increased due to the Zr solid solution strengthening and nanocrystalline strengthening. Under the conditions of OCP and applied anodic potentials, the TiZrN coated Ti alloy exhibits significantly improved anti-tribocorrosion and anti-friction performances, which are attributed to that the stable Ti and Zr oxide or oxynitride passive film on coating near surface and the increased mechanical properties of the coating decrease the synergistic effect of corrosion and wear. 25% calf serum in Hank's solution enhances the chemical stability of the TiZrN coating through adsorption and bio-lubrication mechanism, and therefore further improves the tribocorrosion performance of the coated Ti alloy.

Effects of thread groove width in cylinder liner surface on performances of diesel engine

The performance of diesel cylinder liner-piston ring (CLPR) friction pairs with different surface textures are very important and affect the service life, reliability, and economy of diesel engines. The aim of this study was to gain insights into interactions between thread groove surface texture (TGT) and the friction and wear behavior of a marine diesel CLPR. Four kinds of TGT with different widths, including 1, 2, 3, and 4 mm, were designed and machined on cylinder liners and then tested using a four-stroke CLPR friction and wear tester. The cylinder liner pressure, contact resistance between cylinder liner-piston ring, and worn surface morphologies of cylinder liners were obtained to examine cylinder liner performance with different width TGT. Compared with untextured cylinder liners, the experimental results showed that TGT significantly affected tribological behavior and consequently affected sealing performance of CLPR systems. Specifically, 3 mm TGT had the clearest effect on CLPR system performance, as the CLPR antifriction performance showed an average friction reduction of 30.9%, oil film lubrication performance, reflected by contact resistance, increased by 33.3%, and sealing performance improved by 14.4%. These results aided in the understanding of specific applications of surface texture on wear performance in CLPR friction pairs which could be applied in slower sliding long stroke marine engines.

Facile Synthesis of Uniform Calcite Microcubes and Their Enhanced Tribological Performance in Lithium-Based Commercial Grease

This study describes a facile synthesis of calcium carbonate (CaCO3) monodispersed fine particles from an abundant indigenous and economical source (quicklime) and its enhanced tribological performance as a green additive in commercial lithium grease (CLG). The effects of various experimental parameters on particle morphology were thoroughly examined, and the conditions were optimized. The synthesized uniform particles were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometry, and thermogravimetric (TG) /differential thermal analysis (DTA), and their results confirmed the calcite structure of the synthesized particles. The friction and wear studies were carried out under the applied load of 0.863 N at an ambient temperature for 5 min. The tribological performance of various amounts (1–7%) of cubic-CaCO3 (CCC) particles in CLG showed that 5 wt. % of CCC was the optimum concentration as additive in the present case. For comparison purposes, a commercial CaCO3 powder was used and a decrease in the friction coefficient of CLG was observed to be 33.4% and 16.4% for 5 wt. % CCC and commercial CaCO3 additives, respectively. The significantly enhanced antiwear and antifriction performance of the optimum CCC-CLG in comparison with the blank and commercial CaCO3-additized CLG was quite encouraging, and extensive studies in a real machine-operating environment are in progress for evaluation of the CCC-CLG blend to be used as an economical, green, and high-performance lubricant in mechanical components.

The Influence of Nanocomposite Carbon additive on Tribological Behavior of Cylinder Liner/Piston Ring

Nanocomposite Carbon additive were dispersed at varying concentrations (1, 3, 5wt%) in SN/GF-5 lubricants for automotive engines. Raman spectroscopy is used to characterize the morphology of carbon.The effect of Nanocomposite Carbon additive on the friction and wear properties of the piston ring friction pair is investigated by using UMT friction tester. The tribological mechanism of Nanocomposite Carbon additive is further investigated by scanning electron microscopy, energy dispersive spectrometer and three-dimensional shape spectrometer. The results show that Nanocomposite Carbon additive exhibits excellent antifriction performance at high load and friction coefficient at low load. The effect of the nanocomposite carbon additive is the best when the mass fraction is 3%; however, the nanocomposite carbon additive concentrations is too high, which will lead to increased wear under high load. The nanocomposite carbon particles can smooth the micro-convex of the friction pair surface and reduce the surface roughness. The contact area of the friction pair is significantly increased, and the pressure is significantly reduced. The nano-composite carbon avoids the breakage of the bearing oil film when the metal surface peaks contact each other, ensuring the integrity of the oil film and uniformly carrying a large load.The nanocomposite carbon lubricant additive shown in this study can reduce energy consumption and extend engine life, resulting in significant cost savings.

Wear and Corrosion Behavior of Graphene-Nanoplate-Reinforced Copper Matrix Composites Prepared Through Electrostatic Self-Assembly

Synthesis of graphene nanoplates (GNPs)/copper (Cu) composites is one of the key challenges in the uniform dispersion of GNPs in the Cu matrix because of their density difference. In this work, GNPs/Cu composites are synthesized through electrostatic self-assembly and spark plasma sintering. The GNPs are uniformly dispersed in the Cu matrix. The graphene protective films are formed in the composites to protect the Cu matrix. The antifriction performance of the GNPs/Cu composites is investigated using a ball-on-disk apparatus. The corrosion resistance of the GNPs/Cu composites is estimated using potentiodynamic polarization curves. Wear and corrosion mechanisms are analyzed through scanning electron microscopy with energy-dispersive spectroscopy. The antifriction performance and corrosion resistance of the composites can be significantly improved by adding GNPs.