Friction Track Research Articles

Using Thin Ultra-High-Molecular-Weight Polyethylene Coatings to Reduce Friction in Frost-Resistant Rubbers.

Frost-resistant rubbers retain their highly elastic properties over a wide temperature range. They are used in various friction units (e.g., seals), but their high friction coefficient and low wear resistance lead to the need for frequent replacement. In this paper, we propose applying thin (several hundred microns) UHMWPE coatings to formed rubber rings. The application technology depends on the required coating thickness. Friction tests of the coatings and pure UHMWPE were performed using the ball-on-disk (unidirectional sliding) scheme for various loads and velocities. In the experiments, the friction coefficients and temperatures near the contact area were determined. Friction tracks were studied using microscopy methods. The sliding contact of the ball and the two-layer material was modeled to obtain the dependences of the deformation component of friction on the sliding velocity for coatings of different thicknesses. UHMWPE is sensitive to frictional heating, so the thermal problem of determining the temperature in the contact area was also solved. It is shown that the minimum friction coefficient occurs for coatings with a thickness of 600 μm. At the same time, in the case of the 300 μm coating, the surface of the friction track is practically no different from the initial one. Thus, the studied combination of polymers provides antifrictional properties and wear resistance to the surface layer while maintaining the damping properties of rubber.

Surface Layer Performance of Low-Cost 3D-Printed Sliding Components in Metal-Polymer Friction

Abstract The paper presents the results of contact strength and tribological property tests of spare parts made of a popular resin using a 3D DLP printing technology. Two printer models by the same manufacturer were used in the study. The post-processing technique, which shapes the final functional properties, was diversified. Surface performance properties were compared, i.e. Shore hardness, indentation hardness, Martens hardness, elastic modulus, and parameters related to surface creep and relaxation. Tribo-logical durability in rotary motion and tribological wear in reciprocating linear motion were also evaluated using micro- and nanotribometers. This was followed by surface analyses of the friction track of the analysed materials using microscopic methods: a scanning electron microscope, a WLI interferometric microscope, and an optical microscope. The results were statistically processed and the relationship between the parameters determined in the indentation test was determined.

Features of Increasing the Wear Resistance of 90CrSi Tool Steel Surface under Various Electrophysical Parameters of Plasma Electrolytic Treatment

The paper investigates the feasibility of plasma electrolytic treatment (PET) of 90CrSi tool steel to enhance hardness and wear resistance. The influence of electrophysical parameters of PET (polarity of the active electrode, chemical-thermal treatment, and polishing modes) on the composition, structure, morphology, and tribological properties of the surface was studied. Tribological tests were carried out under dry friction conditions according to the shaft-bushing scheme with fixation of the friction coefficient and temperature in the friction contact zone, measurements of surface microgeometry parameters, morphological analysis of friction tracks, and weight wear. The formation of a surface hardened to 1110–1120 HV due to the formation of quenched martensite is shown. Features of nitrogen diffusion during anodic PET and cathodic PET were revealed, and diffusion coefficients were calculated. The wear resistance of the surface of 90CrSi steel increased by 5–9 times after anodic PET followed by polishing, by 16 times after cathodic PET, and up to 32 times after subsequent polishing. It is shown that in all cases, the violation of frictional bonds occurs through the plastic displacement of the material, and the wear mechanism is fatigue wear during dry friction and plastic contact.

Pre-Compensation Strategy for Tracking Error and Contour Error by Using Friction and Cross-Coupled Control

This paper focuses on improving the tracking accuracy for servo systems and increasing the contouring performance of precision machining. The dynamic friction during precision machining is analyzed using the LuGre model. The dynamic and static parameters in the friction model are efficiently and accurately identified using the improved Drosophila swarm algorithm based on cross-mutation. The friction tracking error can be deduced from the friction state space and an expression is derived. To compensate for the tracking error caused by friction, a feedforward compensation control is designed to avoid signal lag in traditional friction controllers. Furthermore, the factors of multi-axis parameter mismatching that impact the machining profile accuracy are analyzed for multi-axis control. An adaptive cross-coupled control-based pre-compensation strategy of contour error is designed to reduce both the tracking error and the contour error. The effectiveness of the proposed method is validated through several experiments, which demonstrate a remarkable improvement in tracking performance and contour accuracy.

Initial and grow-up stages of material transfer on Arc-DLC coating in aluminum forming processes at high temperatures

The mechanisms of material transfer in aluminum forming processes at high temperatures have remained a contentious tribological issue. This study aims to investigate the transfer mechanisms in the initial and grow-up stages of 6082-T6 aluminum alloy against commercial Arc-DLC coating under lubricant-free forming conditions. The warm and hot upsetting sliding test (WHUST) was used as the tribological test. It was conducted with two sliding configurations: the full sliding test to study the evolution of aluminum transfer and the short sliding test with a 2-mm sliding distance to observe the initiation of aluminum transfer. Furthermore, the effect of different sliding speeds, 0.5 and 5.0 mm/s, and initial temperatures of the specimen, 300 °C–500 °C, on the phenomenon of aluminum transfer was examined. Experimental results found that the aluminum transfer on the Arc-DLC coating in the initial stage of all cases was mainly caused by mechanical plowing. However, in the grow-up stage, the aluminum transfer could be dominated by mechanical plowing and/or adhesive bonding, depending on contact conditions. The different transfer mechanisms caused variations in the coefficient of friction and surface characteristics on the friction track. It led to the skewness Ssk could be an indicator to differentiate the transfer mechanisms.

In-situ SEM microrobotics for versatile force/deformation characterization: application to third-body MoS2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$MoS_2$$\\end{document} wear particles

This article explores the challenges and solutions in the physical characterization of materials at the microscale using robotized systems, with a specific focus on manipulating and characterizing micrometer-sized particles with different and complex 3D shapes and internal sub-micrometer structures. In this paper, the studied particles are Molybdenum diSulfide (MoS2) based materials generated within the contact interface during friction. These particles are being studied because they offer a particularly promising solution for reducing mechanical friction and the associated high energy losses. However, they are distributed randomly within the contact area and possess intricate sub-micrometer structures. Characterization demands precise manipulation techniques in an in-situ Scanning Electron Microscope(SEM) environment. To address these challenges, existing commercial micro and nanomanipulation tools are integrated within a vacuum SEM chamber, and robotics strategies are investigated to enable the whole process from particle preparation, and manipulation setup definition, to effective MoS2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} particle characterization all in-situ SEM. A set of several complementary experimental investigations are done and involve force measurement and deformation estimation studies, leading to the first qualitative results on MoS2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} based particles directly from the friction track. The work contributes to advancements in both microscale manipulation and characterization. It also has implications for lubrication research.

Enhanced Friction and Disturbance Compensation-Based Trajectory Tracking Control for Flexible Manipulator System

Enhanced Friction and Disturbance Compensation-Based Trajectory Tracking Control for Flexible Manipulator System

Effect of the Tool Path on Hardness Uniformity in an Annular Zone of X20Cr13 Steel Surface-Hardened by Friction Stir Processing

This paper presents the numerical and experimental results of hardening of an annular zone on the flat surface of an X20Cr13 steel specimen by friction stir processing (FSP) with a WC-Co hard alloy tool moving along circular and fan-shaped paths. A finite element model of the process is proposed for predicting the temperature distribution through the width and depth of the annular zone for the considered tool paths and for detecting the reverse tempering regions. The influence of the paths of a cylindrical friction stir tool with a flat end on microhardness distribution in the surface layer of the hardened zone was studied experimentally. It was shown that FSP along the fan-shaped path provides uniform hardening of the annular zone, while processing along the circular trajectory leads to softening of the material in the regions where the friction tracks overlap. The uniformity of surface hardness in the friction stir processed annular zone of X20Cr13 steel was evaluated by calculating the “covering uniformity” (CU) index proposed by Campana. The hardening behavior is in full agreement with the results of finite element simulation of the FSP process. Hardness measurements and microstructural studies showed that the fan-shaped tool path provides surface layer hardening to a depth of 400 μm with the CU index ranging from 0.78 to 1.00. In the case of the circular path, the CU index ranges from 0.48 to 0.72 at the same depth. The proposed research methods can be applied to evaluate the FSP efficiency when using other workpiece and tool materials.

Study on tool wear mechanism and chip morphology during turning of Inconel 713C by textured inserts

The present study aims to analyze the tool wear mechanism and chip morphology during dry (D) and graphene solid-lubricant (S), turning of Inconel 713C with a new novel textured (honeycomb (T2) and rectangular(T3)) and further compare with the textured dimple tool (T1). In addition, the performances were compared with the untextured tool (T0). The machining tests for all conditions were carried out at different levels of cutting speeds (75 m/min and 150 m/min), feed rate (0.1 mm/rev and 0.2 mm/rev), and a constant level of depth of cut (0.5 mm). Honeycomb-textured cutting tools performed better. Improvements of 33.3 % (T1D), 50 % (T3D), and 75 % (T2D) without graphene and 66.6 %(T1S), 75 % (T3S), and 100 %(T2S) with graphene are observed compared to T0. The primary mechanism for the better performance of T2S was the reduced tool chip contact length (8–50 %), chip width (30.4 %), friction coefficient (57.4 %), chip thickness (17.8 %), and higher shear angle (14.2 %) compared to dry textured and untextured tools at the end of tool life. Additionally, the T2S (solid lubricant-impregnated honeycomb) demonstrates a decrease in equivalent chip thickness (19.8 %) and an increase in shrinkage factor (17.2 %) at worn-out tool life conditions at high cutting speed and feed rate. Under the same conditions, T2S has 27.3 % lower cutting force and 36.2 % lower surface roughness of machined workpieces compared to the untextured tool at the end of tool life. The chip micrograph reveals the chips are shorter, and the chip radius is lower for T2S tools with smooth friction tracks and fine deformed lamella on the free surface of the chip. Under SEM, flank wear, adhesion materials, abrasion, micro-chipping coating peeling, and BUE were dominant wear mechanisms. However, T2S tools effectively reduce Ni elements' diffusion and suppress the built-up edge's adhesion by improving friction characteristics at the tool-chip interface region. Lastly, the outcomes of experimental results suggest that the honeycomb texture for dry machining of Inconel 713C.

Tribological Properties of Carbon Tool Steel after Plasma Electrolytic Nitrocarburizing

The effect of plasma electrolytic nitrocarburizing on the wear resistance of carbon tool steel in friction couples with hardened steel and lead-tin bronze is considered in order to study the mechanism and type of wear, as well as the influence of structural and morphological characteristics of the surface on them. The microgeometry of friction tracks and its change with an increasing duration of friction tests are analyzed. The equilibrium roughness is determined, which is optimal for the friction couple and ensures minimal wear. The optimal values of the plasma electrolytic nitrocarburizing parameters, which provide the lowest values of the friction coefficient and wear rate, have been determined. The phase and elemental composition of the surface layer was studied using X-ray diffraction analysis and EDX analysis. The relationship of the microstructure of the nitrocarburized layer of tool steel with the friction coefficient and weight wear is established.

The regeneration of the tools to cellulose cutting using electric arc surfacing method

The regeneration of the tools to cellulose cutting using electric arc surfacing method. The paper presents the laboratory results of the regeneration of the tools to cellulose cutting, using electric arc surfacing method. Three types of regenerating material was used in the rod electrodes form. Additionally, each material was applied with additional non-magnetic powder in the coating. Finally, the layer with the highest microhardness was covered with a ZrN coating in the Arc PVD process. The relative wear coefficient, the friction moment, the friction coefficient, the width of friction track and the microhardness were measured. The SEM observations and EDS investigations were applied for the studies of the microstructure of investigated materials. The best results were obtained for the regeneration using regenerating material, marked as “T-590 + powder”, with ZrN coating.

Sonochemical Synthesis of CuO Nanoplatelets and Their Tribological Properties as an Additive in Synthetic Oil Using Reciprocating Tribometer

This Research aimed to improve the tribological properties of commercially available lubricating oil (5W-40) by incorporating CuO nanoplatelets (NPs) synthesized using a simple and cost-effective sonochemical method. To evaluate the performance of the nanolubricant, a reciprocating tribometer was indigenously designed and developed to measure the coefficient of friction (COF) and wear tracks between two AISI 1045 steel surfaces. The CuO NPs were characterized using XRD to confirm their purity and phase, while SEM and FE-TEM were utilized to study their morphology and composition. Raman spectroscopy was used to reveal three distinct Raman active peaks of CuO at 283, 330, and 616 cm−1. Zeta potential measurements demonstrated good dispersion quality, with a value of 92.0 mV for 0.1% concentration. SEM and FE-TEM analysis of the nanolubricant showed the formation of a tribo-film over the CuO NPs and adding 0.1% CuO NPs reduced COF by 32%. These findings suggest that incorporating synthesized CuO NPs in commercially available lubricating oil can enhance its tribological properties, leading to improved machine efficiency and lifespan, as well as reduced energy demand. Overall, the study demonstrates the potential benefits of using CuO nanoplatelets as an additive in lubricating oil, which could have significant implications for the development of more efficient nanolubricants.

Relationships between third body flows, load-bearing mechanisms and particle emissions in automotive braking

During automotive braking, the third body generated by friction forms a tribological circuit that feeds the contact between the disc and the pad and provides the energy dissipation capacities of the disc brakes. This results in emissions of airborne matter particles, composed of fine and ultrafine particles, are mostly carcinogenic metal oxides. In order to reduce these particle emissions, it is important to investigate the factors involved in their formation, and in particular the link between the particle emissions dynamics, the tribological circuit and the thermomechanical load in the contact.This study focuses on a martensite stainless steel as an alternative to a lamellar graphite cast iron usually used for automotive brake discs. Thus, 2 disclining friction pairs are studied in the objective to evaluate the effect of disc material and braking conditions on the production and the emission of particulate matter during braking by friction. This paper presents the results obtained with a sintered metal matrix composite lining, the steel discsintered metal lining couple being used for motorcycle applications. Tests were carried out on a laboratory tribometer dedicated to braking simulation. Two situations of automotive braking, typical of urban and suburban traffic, were modeled and studied. Using a visible high speed camera, the evolution of the disc friction track in terms of morphology was observed. In addition, an infrared thermal camera was used to visualize the thermal dissipation localization. Particle emissions were studied in operando thanks to a sampling chamber under controlled air flow and two particle matter analyzers providing a particle rate by size in the range [6 nm; 10 μm]. Furthermore, an impactor was used to collect emitted particles for post-mortem chemical composition analyses. Pad and disc friction surfaces were analyzed using scanning electron microscopy and energy dispersive spectroscopy.During these tests, an evolution of the size and density profile of the particles collected by the analyzers was observed, and was correlated to a thermomechanical localization in the form of hot bands or hot spots according to the cases studied. The analyses of rubbed surfaces, crossed with these localizations, allowed us to develop scenarios favoring the feeding of the rate of coarse, fine or ultrafine particles.

The effect of nanofluids reinforced with different surfactants on the machining and friction-wear properties of Waspaloy

In present investigation, a number of experiments were done to determine the impact of surfactants on Waspaloy machining characteristics and the friction-wear behavior on the ball-on-disc tester. The experiments were carried out in dry, base fluid (sunflower oil), Cuo, and ZnO nanofluid conditions with/without surfactant. Four distinct surfactants, including Gum Arabic (GA), Sodium Dodecyl Sulfate (SDS), CeTyltrimethylAmmonium Bromide (CTAB), and PolyVinyl Pyrrolidone (PVP), were employed to prepare the nanofluids with surfactant. In addition, viscosity, pH, and thermal conductivity measurements were made to determine the prepared nanofluid's thermo-physical properties. Tool wear and its mechanisms, surface roughness and cutting temperature in machining experiments, coefficient of friction (CoF), microhardness, and wear track width in ball-on-disk tests were choosen as evaluation criterias. From both the machining and ball-on-disk test results, it was determined that the ZnO + PVP nanofluid condition outperformed the other conditions. The ZnO + PVP nanofluid condition provided 53.9 %, 36.52 %, and 44 % improvement in tool wear, surface roughness, and cutting temperature, respectively, compared to the dry cutting condition. Also, considering the results of the ball-on-disk test, it was found that the CoF and width track width values for the ZnO+PVP nanofluid condition were both 76.02 % and 56.11 % lower than the dry condition.

EFFECT OF THE TOOL PATH ON HARDNESS UNIFORMITY IN AN ANNULAR ZONE OF X20CR13 STEEL SURFACE-HARDENED BY FRICTION STIR PROCESSING

This paper presents the numerical and experimental results of hardening an annular zone on the flat surface of a X20Cr13 steel sample by friction stir processing (FSP) with a WC-Co hard alloy tool moving along circular and fan-shaped paths. A finite element model of the process is proposed for predicting the temperature distribution through the width and depth of the annular zone for the considered tool paths and for detecting the reverse tempering regions. The influence of the paths of a cylindrical friction stir tool with a flat end on microhardness distribution in the surface layer of the hardened zone was studied experimentally. It was shown that FSP along a fan-shaped path provides uniform hardening of the annular zone, while processing along a circular trajectory leads to softening of the material in the regions where the friction tracks overlap. The uniformity of surface hardness in the FSP-hardened annular zone of X20Cr13 steel was evaluated by calculating the CU index proposed by Campana. The hardening behavior is in full agreement with the results of finite element simulation of the FSP process. Hardness measurements and microstructural studies showed that the fan-shaped tool path provides surface layer hardening to a depth of up to 400 μm with a CU index ranging from 0.78 to 1.00. In the case of a circular path, the CU index ranges from 0.48 to 0.72 at the same depth. XRD analysis of the hardened layer revealed pronounced peaks corresponding to the (110)α, (200)α and (211)α lines, indicating the formation of martensite with different tetragonality at the given depth. The proposed research methods can be applied to evaluate the FSP efficiency when using other workpiece and tool materials.

Secondary Structures on the Friction Surface of Diamond-like Coating

Peculiarities of the formation of secondary structures on the surface of a diamond-like coating are studied on the example of a friction contact between a steel ball and a diamond-like coating. The friction surface was examined in various areas; the zone of wear products (the boundary of the friction track) and the original surface outside the friction area. It is shown that secondary structures with a high content of iron, nickel, manganese, chromium, and oxygen are characteristic of areas with the highest wear resistance. Such secondary structures are formed because of the intense interaction of the diamond-like coating with the steel of the ball during dry friction.

Alkylated Polyphenyl Ethers as High-Performance Synthetic Lubricants

Lubricants exhibiting both thermal and chemical stability that consequently generate less hydrogen during friction are required to avoid the hydrogen embrittlement of moving mechanical components. The present work studied the effects of the length and number of alkyl chains on the tribological properties of polyphenyl ethers (PPEs), which feature good thermal and radiation resistance. PPEs were found to have much lower friction coefficients compared with a poly-alpha-olefin and alkyldiphenyl ether, and the effect of the running-in process on friction appeared to be negligible. The formation of polymers on the friction track evidently decreased the friction coefficients of the lubricants and the wear rates were almost zero for all the PPEs, indicating excellent anti-wear properties. Analyses with a quadrupole mass spectrometer connected to a friction tester under vacuum indicated negligible hydrogen generation from 4P2E, which had no alkyl chains, after the running-in. R1-4P2E, having a C16H33 chain, showed hydrogen desorption similar to that of the alkyldiphenyl ether, which had a C18H37 alkyl chain. R2-4P2E, with two C16H33 chains, produced significant hydrogen, but with a long induction period; thus, it provided good wear protection. Although alkyl chains increased the risk of hydrogen generation, PPEs with such chains may have applications as standard lubricants.

Robust Composite Finite-Time Convergent Speed Control of Induction Machine Based on Multiple Sources Disturbance Estimation Technology Generalized Proportional Integral Observer

To improve the robustness of the conventional finite-time convergent speed controller (FTCSC) against unpredictable disturbances, a finite-time generalized proportional integral observer (FT-GPIO) is proposed based on the state observer to achieve finite-time convergence of the closed-loop control system. First, an FTCSC is devised to improve the speed convergence performance of the induction machine (IM) control system. However, the system will inevitably be affected by multiple sources disturbances, such as friction, load disturbance, parameter mismatch, and torque current tracking error, resulting in performance degradation. To improve the disturbance rejection ability of the IM control system, an FT-GPIO based on multiple sources disturbance estimation technology is designed. Finally, a 1.1-kW IM is used as a case study, and the experimental results are provided to verify the effectiveness of the proposed robust composite finite-time convergent speed controller.

Features of the Formation of Surface Structures under Dry Friction of Al-30Sn Composite against Steel

Features of the frictional interaction of a sintered Al-30Sn composite, which is used as a coating of bearing inserts, with steel counterbody in the absence of liquid lubricant were studied. The tribological tests were carried out according to the pin-on-disk scheme at room temperature. The friction coefficient μ of the friction pair is increased up to approximately 0.6 during the running-in process. Its growth stops when the stage of steady state friction begins, and then μ fluctuates around some relatively high and constant value. The study of the friction surfaces of the friction pair showed that the aforementioned increase in μ is due to the formation of a discrete transferred layer on the friction track surface and strain hardening of the subsurface layer of the Al-30Sn sample under the action of hard particles of the transferred layer. It was established that tin is transferred on the friction track surface mainly in a composition of wear particles, despite the high content of the solid lubricant in the investigated samples. The wear intensity of the samples subjected to processing by equal channel angular pressing with route A is much lower than that of the sintered (unprocessed) ones. The main wear mechanism of Al-30Sn composites under dry friction against steel is a delamination of the highly deformed subsurface aluminum grains along their interphase boundaries.

Tribotechnical properties of experimental hard alloys with modified cobalt binder

Introduction. This paper discusses tribomechanical characteristics of experimental hard alloys with a modified cobalt binder under friction without lubrication on hard-to-cut materials – stainless steel and titanium alloy. The research objective is to evaluate the process of friction interaction for each friction pair according to a number of parameters, and to determine the optimal combinations of “experimental hard alloy – structural material” on the basis of the established tribological indicators.Materials and Methods. Tribological tests of hard alloys were carried out using a cylinder-to-disc friction scheme for different sliding speeds and temperatures under constant load without the use of lubricants. Comparison of the friction interaction process was carried out by the frictional force, volumetric wear and roughness of the friction tracks on the counterbody. Stainless steel 12H18N9Т and titanium alloy ВТ3-1 were used as counterbody materials. The resistance of experimental compositions to the abrasive type of wear was determined through measuring the surface dynamic microhardness on a scanning nanohardness tester by analyzing the thickness of the scratches caused by the indenter.Results. According to the results of surface microindentation, the experimental alloys 2.22 (binder 5.65% Co + l.8% Mo + 0.6% Ti) and 2.23 (binder 5.1% Co + 2.7% Mo + 0.61 % Ti) are characterized by the highest microhardness. For these materials, the average scratch width at various forces was minimal. During tribological tests, the best frictional characteristics were recorded for stainless steel in combination with experimental alloy 2.22, and for the friction pair “titanium alloy VT3-1 — hard alloy 2.23”. The friction of this combination of materials was characterized by low friction coefficients with a low level of fluctuations, minimal wear of samples, and changes in the initial microrelief of their surfaces.Discussion and Conclusions. As a result of the research, the optimal friction pairs from the point of view of tribological interaction were established, specifically “titanium alloy VT3-1 — hard alloy 2.23” and “stainless steel 12X18N9T – hard alloy 2.22”. The frictional interaction for these combinations of materials is characterized by minimal volumetric wear, which will contribute to increasing the wear resistance of the tool in the areas of elastic contact on the front and rear surfaces.