Sliding Friction Tests Research Articles

The microstructure and tribological properties of M50 steel surface after titanium ion implantation

Titanium ions with different energies and doses were implanted into the M50 steel surface. In addition, titanium and nitrogen ion co-implantation was applied for comparison. The tribological properties and wear resistance of the implanted samples were characterized using a sliding friction tester, grazing incidence angle X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, surface profiler, Raman spectrometer, and nanoindentation tests. The results indicated that the compounds of the titanium ion–implanted samples mainly consisted of titanium and TiO2, CrN interstitial compounds formed after titanium and nitrogen ion co-implantation, thus generating an implantation layer that exhibited high nano-hardness and low wear rates. The linear contact sliding friction coefficient curves for the implantation samples were composed of an initial stage, ascent stage, and stable stage. The tribological properties effectively improved with increasing titanium ion implantation energies and doses. In addition, this beneficial effect became much more significant at a higher titanium ion dose. The titanium and nitrogen ion–co-implanted samples formed Fe2O3 and Fe3O4 tribo-oxide layers after the wear test, which were partially responsible for reducing the wear. The dominant wear mechanisms of the implanted samples were abrasive wear and oxidative wear.

Effects of Ultrasonic Surface Rolling Processing and Subsequent Recovery Treatment on the Wear Resistance of AZ91D Mg Alloy.

AZ91D Mg alloy was treated by ultrasonic surface rolling processing (USRP) and subsequent recovery treatment at different temperatures. The dry sliding friction test was performed to investigate the effects of USRP and subsequent recovery treatment on the wear resistance of AZ91D Mg alloy by a ball-on-plate tribometer. The microstructure, properties of plastic deformation layer and worn morphology were observed by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) analysis and microhardness tester. Results illustrate that the grains of AZ91D Mg alloy surface layer are refined to nanocrystallines. The maximum microhardness of the top surface of the USRP sample reaches 102.3 HV. When USRP samples are treated by recovery treatment at 150 °C, 200 °C and 250 °C, the microhardness of the top surface decreases to 90.68 HV, 79.29 HV and 75.06 HV, respectively. The friction coefficient (FC) and wear volume loss of the USRP-R-150 sample are the lowest among all the samples. The worn surface morphology of the USRP-R-150 sample is smoother than that of other samples, indicating that the wear resistance of AZ91D Mg alloy treated by USRP and recovery treatment at 150 °C is improved significantly.

Long-term low friction maintenance and wear reduction on the ventral scales in snakes

Snake skins evolved to withstand permanent friction and wear during sliding. Here, the microstructure of ventral scales of the snake Lampropeltis getula californiae was analyzed using scanning electron microscopy, and the long-term dynamic friction behavior was investigated by reciprocating sliding friction tests. A smooth epoxy resin with similar elasticity modulus and hardness was used for comparison purposes. Strong differences in frictional and wear mechanisms between the two materials were revealed in spite of similar mechanical properties. Snake skin showed a considerably lower frictional coefficient that kept stable over several thousands of sliding cycles. A reduction of the stick-slip behavior was also denoted by analyzing the variation of the friction coefficient in the forward and reverse motion influencing the wear mechanism. This frictional behavior can be explained by three different but complementary mechanisms: fibrous layered composite material of the skin with a gradient of material properties, surface microstructure, and the presence of ordered layers of lipid molecules at the skin surface.

Friction behavior of PTFE-coated Si3N4/TiC ceramics fabricated by spray technique under dry friction

PTFE coatings were deposited on the Si3N4/TiC ceramic substrate by using spray technology. The surface and cross-section micrographs, adhesive force of coatings with substrate, surface roughness and micro-hardness of the coated ceramics were examined. The friction and wear behaviors of ceramic samples with and without coatings were investigated through carrying out dry sliding friction tests against WC/Co ball. The test results indicated that the coated ceramics exhibited rougher surface and lower micro-hardness, and the PTFE coatings can significantly reduce the surface friction and adhesive wear of ceramics. The friction performance of PTFE-coated sample was affected by applied load due to the lower surface hardness and shear strength of coatings, and the main wear failure mechanisms were abrasion wear, coating delamination and flaking. It can be considered that deposition of PTFE coatings is a promising approach to improve the friction and wear behavior of ceramic substrate.

Wear of Quenched and Aged Cu–Be Alloy at Current Transfer

Sliding friction tests were carried out on quenched and aged unlubricated samples of C17200 beryllium bronze with and without the current flow through frictional contact. It is shown that the quenched samples are exposed to corrosion-mechanical wear by the oxidation of the friction surface, followed by the separation of wear particles as ultradispersed oxides. The wear of the aged sample is attended by the separation of big wear particles as a result of adhesive interaction. The application of electric current in sliding allows reducing the wear resistance of quenched bronze to 109.3 h/g as compared to the 143.9 h/g of the sample tested without current. The application of electricity results only in a negligible reduction in the wear resistance of the aged bronze samples from 86.6 to 77.8 h/g.

Evaluation of mechanical and metallurgical properties of cryo-treated tungsten carbide with 25% cobalt

In this study, the impact of cryo-treatment on mechanical and metallurgical properties of straight tungsten carbide (unalloyed) specimens manufactured with a binder content of 25% cobalt was evaluated. Wear rate of the untreated and cryo-treated specimens were compared in pin-on-disc dry sliding friction test and the mechanical properties like Vickers hardness and transverse rupture strength were studied. Metallurgical properties like saturation magnetization (Ms), coercivity (Hc), and microscopic evaluation to study the grain morphology, distribution, and presence of elements like η-carbides were evaluated to validate the outcomes of wear testing. The results show that cryo-treated specimens showed a significant reduction in wear rate. The coercivity and Vickers hardness showed an increase of around 9% and 2%, respectively in the cryo-treated specimens. From the metallurgical evaluation, the reduction in wear rate of cryo-treated specimens was credited to the martensitic phase transformation of the binder element. The microscopic evaluation confirmed that the morphology of tungsten carbide grains was unaffected.

Development and experimental research of a test bench for sliding friction and bending fatigue

In order to research the fatigue damage characteristics of components under the coupling of sliding friction and bending fatigue. A test bench of the coupling of sliding friction and bending fatigue was developed based on the analysis of the principle of bending fatigue and friction experiment. The test bench mainly includes drive module, load application module, data collection and processing module. The single sliding friction test, single bending fatigue test, coupling test of sliding friction and bending fatigue can be carried out by this test bench. The three functions of test bench were carried out by 45steel experiment. The rationality and validity of the test bench were well verified by experimental measurement. The results show that the variation of life curve of coupling of sliding friction and bending fatigue is consistent with that of standard rotary bending fatigue life curve. The fatigue life of specimens is reduced on account of the effect of sliding friction. Under the low bending load, the influence of sliding friction effect on fatigue life is more significant. The fracture has typical characteristics of fatigue striations and dimples morphology.

Effects of Porosity and SEBS Fraction on Dry Sliding Friction of EVA Foams for Sports Shoe Sole Applications

Ethylene vinyl acetate (EVA) foam is sometimes used in the outer soles of sport shoes. To improve the slip resistance of EVA foam, this study investigated the effects of porosity and the fraction of styrene–ethylene–butadiene–styrene (SEBS) on the dry sliding friction behavior of EVA foams. Sliding friction tests were performed against a pin specimen with a semicylindrical tip, which was covered with (rough surface) or without abrasive paper (smooth surface). The results revealed that the friction coefficient of the EVA foam increased with porosity when slid against a smooth surface, whereas its friction coefficient increased with porosity and SEBS fraction when slid against a rough surface. The results of this investigation provide insight into how to increase the dry sliding friction of resin foam against smooth and rough surfaces, which will also contribute to improving the slip resistance of shoe soles made from resin foam.

Study on low velocity cyclic impact wear of amorphous carbon films with different mechanical properties

The reproducible wear characterization methods were used to evaluate and analyze the cyclic dynamic loads damage and sliding wear process of the amorphous carbon films. The films with different properties (a-C, a-C:H and a-C: H/WC) on copper substrate (H62) were tested. The wear rates of the three different films have the same order of magnitude under sliding friction test. However, the films failure degrees were quite different in low velocity impact tests based on energy control. It is necessary to select the appropriate film for a given tribological application. The test results show: the a-C: H film has better impact wear resistance, while the damage of a-C:H/WC film is the worst due to the existence of WC interlayer. In the impact test, it was found that the fracture toughness of the a-C:H/WC film was inversely correlation to the H3/E2 and H/E ratio. Test results indicated that the film failure behavior includes fatigue cracking, chipping, and spalling. In addition, soft film is more durable than hard film under impact fatigue load.

Wear under Conditions of Dry Friction of a Composite Material Based on an Aluminum Alloy Reinforced with Nanocrystalline Graphite

Abstract—Structural-phase composition analysis and dry sliding friction tests are performed under loading of 1–15 N of a composite material based on an aluminum alloy reinforced with nanocrystalline. graphite The influence of loading on the friction coefficient and wear of the composite material–steel friction pair is assessed. Comparative analysis of the tribological properties of the composite material and initial aluminum alloy is carried out. The features of the surface morphology and chemical composition of the friction pair are studied.

Effects of Rosin Powder Application on the Frictional Behavior Between a Finger Pad and Baseball.

Rosin powder, which is composed of magnesium carbonate powder and pine resin, is often used as a grip-enhancing agent in baseball pitching. However, the effect of rosin powder on friction at the baseball–human finger interface remains unclear. This study aimed to investigate the effect of rosin powder on the friction coefficient between a baseball and a finger using sliding friction tests. Ten young adult males participated in this study who were asked to slide the index finger of their dominant hand over the leather skin of a baseball adhered to the force sensor, which was not a real baseball pitching situation. Our findings suggest that rosin powder application stabilizes friction under both dry and wet conditions; that is there was less dependence of the friction coefficient on the normal force and less variation in the friction coefficient among individuals. For most participants, the friction coefficient was not necessarily increased by the presence of rosin powder at the finger pad–leather sheet interface under dry conditions. However, under wet conditions, rosin powder application increased the friction coefficient compared with the non-powdered condition in the large normal force condition, indicating the efficacy of rosin powder as a grip-enhancing agent.

Fabrication and tribological behaviors of Ti3SiC2/Ti5Si3/TiC/Ni-based composite coatings by laser cladding for self-lubricating applications

In the work the in-situ synthesis of Ti3SiC2 (MAX) phase and silicide reinforced Ni-based composite self-lubricating coatings from Ti-Si-C system and NiCrBSi powders were carried and initiated by laser cladding with use of 5 kW fiber laser beam with 3 mm spot. The microstructures of the laser-clad in situ synthetic self-lubricating coatings were analyzed by a scanning electron microscope (SEM) equipped with an X-ray energy dispersive spectrometer (EDS). An X-ray diffraction (XRD) spectrometer and an electron back-scattered diffraction (EBSD) were used for determination of the reaction products in the composite coatings. The friction and abrasion behavior of the coatings were evaluated at room temperature by a dry sliding friction tester. The results indicate that in-situ chemical reactions took place between elements Ti, Si and C in the laser molten pool, and the reaction products included Ti3SiC2, Ti5Si3, and TiC ceramics as well as TiNix compound. Finally, three laser-clad Ti3SiC2/Ti5Si3/TiC/Ni-based composite coatings with the total thickness about 1 mm were fabricated on Ti6Al4V alloy. The average microhardness of the three coatings was 703.2 HV0.2, 751.9 HV0.2 and 850.6 HV0.2 respectively, which has been significantly improved, compared with the hardness of Ti6Al4V substrate (about 360 HV0.2). The average friction coefficient of the Ti3SiC2/Ti5Si3/TiC/Ni-based composite coating (50 wt% Ni25/50 wt% Ti-Si-C) reduced to 0.33 at room temperature, and it exhibited the wear rate of 13.5 × 10−5 mm3 N−1 m−1. The laser cladding Ti3SiC2/Ti5Si3/TiC/Ni-based composite coatings characterized by small amount of adhesive wear, plastic deformation and relatively smooth wear surface could be observed.

Effect of carbon nanotubes on structure and properties of the antifriction coatings produced by plasma cladding

Due to their high antifriction characteristics, the Sn-Sb-Cu alloys (referred to as babbits) are widely used to coat sliding bearings. However, some limitations of the present techniques for applying such coating materials cause a decrease in their fatigue strength because of the reinforcing phase particles growth. As a technique for restricting the increasing of the reinforcing particle sizes, this paper proposes plasma surface cladding with multiwall carbon nanotubes (MWNTs) as modifiers. The dry sliding friction tests performed according to the “pin-on-disk” scheme using as a counterface a steel 100Cr6 (DIN 17230) disk have shown that adding to the coating 0.25%wt of CNTs significantly improves the friction stability (the coefficient of friction process stability decreases twice with reducing the friction coefficient and wear resistance by 5% on the average). An attempt to reveal the mechanism for the MWNT influence on the structure and performance of the babbit-based coatings was undertaken. Studies of the coatings metal structure by soft X-ray absorption spectroscopy and also by the metallographic and fractographic analysis involving electron-microscopy have shown that MWNTs remain stable during plasma cladding process and save into the coating.

Preparation and tribological properties of MoS2-based multiple-layer structured films fabricated by electrohydrodynamic jet deposition

As a kind of solid lubricant, molybdenum disulfide (MoS2) plays a pivotal role in reducing wear and friction. How to prepare MoS2 films with excellent tribological properties has become a research hotspot. In this paper, four kinds of slurries were prepared to deposit pure MoS2 films, MoS2/Ti composite films and Ti-MoS2/Ti multiple-layer structured films on cemented carbide surfaces by electrohydrodynamic jet deposition. The composition and microstructure of the deposited films were investigated. The adhesive strength between the film and the substrate was evaluated by scratch tests. Furthermore, the friction and wear properties were investigated by reciprocating sliding friction tests. The results show that the Ti layer can improve the film-substrate adhesive strength, and the construction of multiple-layer structure can significantly reduce the friction coefficient and prolong the friction life of the MoS2 films.

Analysis of the Variation of Friction Coefficient of Sandstone Joint in Sliding

The friction coefficient of rock joints is closely related to the stability of the slope. However, it is difficult to predict the friction coefficient due to the influence of surface roughness and mechanical properties of rocks. In this study, we use a method that combines theoretical analysis with a sandstone sliding friction test and propose a model to predict the friction coefficient of Sandstone Joint. A sandstone sliding friction test was performed on a self‐made reciprocating sliding friction test device. Good agreement between the estimated values and test values verified the validity of the friction coefficient prediction model. Through an analysis of the friction coefficient in sandstone sliding, it was established that the larger the wear mass, the larger the friction coefficient in sliding, and the larger the wear area, the smaller the friction coefficient. With the cycles increasing of sandstone, the friction coefficient gradually decreased before finally reaching a stable value. Comparisons between the estimated value and test results showed that when the wear difference coefficient c = 2.0 and the meshing friction amplification coefficient K = 1.4, the minimum error was 2.89%. The results obtained are significant in the control of slope sliding.

A tough PVA/HA/COL composite hydrogel with simple process and excellent mechanical properties

Designing a hydrogel that matches natural cartilage in composition, structure, and properties has been challenging. In this study, polyvinyl alcohol (PVA), hyaluronic acid (HA) and collagen (COL) were used as raw materials to prepare composite hydrogels by the freezing-thawing method. The microcosmic characterization was characterized by scanning electron microscopy (SEM), Fourier transforms infrared (FTIR) and X ray diffractometer (XRD), respectively. A three-dimensional network structure similar to that of natural articular cartilage was observed in the composite hydrogels. The mechanical properties were investigated by tensile test and sliding friction test, illustrating that the 15%PVA-0.05%HA-1%COL hydrogel displays excellent tensile strength and elongation, reaching up to 1.62 MPa and 532%, respectively. Furthermore, the friction properties of the composite hydrogels are significantly better than that of the pure PVA hydrogel, and the average friction coefficient is less than 0.13. Thus, it is believed that this work provides a tough PVA/HA/COL composite hydrogel with simple process and excellent mechanical properties for cartilage tissue engineering as candidate materials.

Green oil additive g-C3N4: a feasible strategy to enhance the tribological properties of DLC film

The decrease of both friction and wear is very crucial for reducing oil consumption and the associated environmental pollution. Accordingly, the search continues for novel materials, coatings, lubricants, and systems constituted by the aforementioned ones that can potentially reduce friction and wear. In this paper, a solid–liquid composite lubrication system was constituted by combining g-C3N4 nanosheets as the lubricating oil additives with Ti-DLC film, to achieve a green lubricant providing extreme anti-wear and friction reduction functionality. Tribological properties of the composite lubrication system with different concentrations of g-C3N4 were evaluated using a ball-on-disc sliding friction tester at different normal loads. The results show that both the friction coefficient and wear rate first decreases and then increases with the increase of the g-C3N4 concentration. The lubricant with 1 wt% g-C3N4 exhibits the optimal lubricant property with the friction coefficient of 0.076, 0.078 and 0.082, reducing by nearly 24%, 20%, and 12% compared with base oil for the normal loads of 50 N, 100 N, and 200 N, respectively. However, further increase in the concentration of g-C3N4 results in significant increase in the friction and wear of the tracks. The wear rates show no marked variation with the increasing load, indicating that g-C3N4 nanosheets possess a wide load adaptation range in wear-resistance. As environmentally friendly oil additives, g-C3N4 nanosheets can effectively improve the tribological property of the composite lubrication system. Based on the characterizations of both the Ti-DLC film and wear scars by SEM, XPS, non-contact 3D surface profiler and EDS, the synergistic lubrication mechanism of the g-C3N4 nanosheets and Ti-DLC film is also proposed.

Measurement of Restitution and Friction Coefficients for Granular Particles and Discrete Element Simulation for the Tests of Glass Beads.

A slant plate flat throw test system for measuring the restitution coefficient of granular materials and a sliding friction test instrument for measuring the friction coefficient between discrete particles and continuum boundary surface materials are developed. The restitution coefficients of the glass bead particles, the glass beads relative to the glass plate, the composite of glass plate and the rubber membrane and the friction coefficients between the glass beads and the rubber film and the filter paper are measured by the designed methods. Based on the measured restitution coefficient and friction coefficient, the discrete element numerical simulation is carried out for triaxial test and plane strain test. Through comparing the experimental results and the discrete element numerical simulation results, the feasibility and rationality of the designed measurement methods and the discrete element numerical simulation are verified. The measuring methods developed in this paper can be further applied to the tests of other fine particles.

Electro-codeposition of CeO2 nanoparticles into cobalt matrix to improve the tribocorrosion performances of Co/nano CeO2 composite layers in biological solution for medical applications

Co/nano-CeO2 composite layers were developed by electro-codeposition method from a cobalt electrolyte containing dispersed CeO2 nanoparticles. The tribocorrosion performances of both Co/nano-CeO2 and pure Co layers were comparatively investigated by sliding friction tests under lubricated condition in biological Hank solution. The effect of embedded nano-CeO2 on the corrosion electrochemical response, friction coefficient and wear loss volume is analyzed. The results show that the codeposited of nano-CeO2 particles into cobalt matrix reduce the friction coefficient and wear weight loss as well as the shift of open circuit potential to active state, increasing the polarization resistance and reducing the corrosion damages.

Design and construction of a novel instrument for high-frequency micro-force electrical sliding friction testing.

Sliding electrical contact exists in various electrical equipment. However, its performance is significantly affected by the sliding condition such as the load, electricity, and the surface state of friction pairs. In this study, a novel instrument is designed and constructed for high-frequency microforce electrical sliding friction testing. The new instrument provides a unique experimental platform that enables high-frequency reciprocating friction and microforce loading, and it has an innovative data collection system that includes a cantilever beam structure to measure the microforce. In this instrument, parameters (positive force, friction, displacement, and voltage of frictional pair) are obtained and monitored in real time. The steel sheet and nickel-plated steel wire were used as materials to conduct an experiment, and the steel sheet morphology after the experiment was observed using a light microscope. Results show that the voltage and positive load significantly influence the friction coefficient and friction wear, which is crucial in understanding friction and wear behaviors.