Friction Coefficient Of Samples Research Articles

Wear Behavior of DLC Coated HSS with Hydraulic Fluids

The worldwide rotary pump market was estimated at around $5000 million in 2020 and the market is supposed to increase by 20% toward the end of 2026, seeing a compounded annual growth rate of 3% over a period from 2022-2026. The scrapping of an engineered component made from non-renewable resources at an early stage in life due to wear goes against the ethics of the conservation of natural resources as the frictional processes lead to dissipation of a part of input energy. In this context many research works focused on analyzing wear behavior using various formulated and vegetable oils but no works investigated on using hydraulic oils as lubricant for wear preventative nature. The objective of the work was to obtain diamond-like carbon coating on high-speed steel samples and test them for better wear preventative behavior with different hydraulic fluids. The HSS ball sample of 12.7 mm diameter were used as a substrate on which the dlc coating was to be developed using then RF-PECVD technique. The developed DLC coating was characterized by conducting X-Ray diffraction which suggested the coating to be of amorphous structure, Raman spectroscopy which determined the content of graphite (sp2 ) to be 47% and that of diamond (sp3 ) to be 53%.Further nanoindentation was conducted to compare the hardness of the high-speed steel sample before and after coating which was 12.22GPa and 35.56GPa respectively. The four ball test was performed to investigate the anti-wear properties of lubricating oil at specific conditions such as higher load, controlled temperature and constant rotating speed of the ball as per the ASTM D4172. The four ball results show that the coefficient of friction for samples reduces by around 36% when test oil 3 is used in uncoated samples and 48% in coated samples. Also, the wear rate for the test oil 3 for coated samples was found to be 0.7381x10-6 mm/Nm, which is the lowest wear rate among the other test oils. The outcome of the project is the reduction of coefficient of friction by 84% with respect to dry condition when test oil 3 is used. Therefore, it can be deduced that test oil 3 stands out as the most effective lubricant among the trio of test oils.In this direction , further work can be carried out by carrying out four ball tests with lubricant oils in combination with additives to it so as to enhance the base oil property and suppress undesirable base oil properties. Fabrication and manufacturing of the vane model can be done to validate the result with the help of experimental work. Key Word: DLC; HSS; Raman Spectrograph; AFM; 4-Ball Test, Hydraulic Oil.

The Effects of Reinforcement with TaC on the Microstructure and Wear Properties of Lamellar Graphite Cast Irons

Lamellar graphite cast irons are prevalently used in several industrial applications, especially the automotive industry, due to their high compressive strength, high thermal conductivity, high castability, vibration damping ability, good mechanical strength, friction and wear resistance, better machinability than other cast irons, and good mold filling. In this study, changes in the wear volumes, wear rates, wear track profiles, and friction coefficients of lamellar graphite cast irons in which Tantalum Carbide (TaC) was added at different reinforcement ratios (A (0.025 wt.%), B (0.155 wt.%), C (0.285 wt.%), and K (unreinforced, 0 wt.%)) were investigated. Additionally, by examining the wear surfaces of the samples using a scanning electron microscope (SEM), their wear mechanisms were determined. As a result of the analyses, it was determined that different reinforcement ratios did not have a noticeable effect on wear track profiles under a load of 1 N. On the other hand, different reinforcement ratios showed an effect on wear track profiles under loads of 3 N and 5 N. The most perceptible wear track profile was formed in Sample C under 5 N. It was observed that increased load values resulted in increased wear volumes, but the increases in the wear rates of the samples were not significant, and the numerical values were close to each other. The highest wear volumes were determined in the reinforced C sample and the unreinforced K sample under 5 N load. As the magnitude of the load that was applied increased, the friction coefficients of Samples B and C decreased, but the friction coefficients of Samples K and A increased.

Tribological properties of flexible composite surfaces through direct ink writing for durable wearing devices

Polydimethylsiloxane (PDMS), as a polymer material with excellent mechanical properties and flexibility, is widely used in flexible wearable devices, soft robots and other fields. Commonly, the Mold-flipping is used to produce PDMS based samples, while it is time-consuming and impractical for the large-scale fabrication. With the additive manufacturing, printing pastes can be freely configured thanks to direct ink writing (DIW) technology, enabling rapid and high precision manufacturing. Herein, we have improved the rheology of Sylgard-184 by adding crosslinkers and silica nanoparticles to make it printable. By adjusting the printing path, flexible surfaces with textures were created. Ball-on-disc dry friction experiments were carried out on the specimens. Results show that the texture produced by the print path can effectively reduce the coefficient of friction (COF) compared to samples produced by the conventional molding. When the print path is at 60° to the sliding direction, COFs for samples are reduced by 23.2% to 32.9%. Our findings provide a new strategy for preparing flexible and wearable devices through significantly enhancing the wear resistance of substantiable usage and prolonging the lifespan.

Increase in properties of copper electrical contacts in formation of composite coatings based on Ni–C–Ag–N system

The article is concerned with analyzing the structure and properties of the Ni–C–Ag–N coating formed on copper by the complex method combining the electroexplosive spraying of coating, its irradiation by a pulsed electron beam and a subsequent nitriding in plasma of a gas discharge of low pressure. The structural constituents of coating's surface after the electroexplosive spraying as well as after the electron-beam processing and nitriding are studied. It is shown that a coating's thickness amounts to ≈90 μm. The wear resistance of a copper sample with the deposited coating exceeds that of the copper without the coating by ≈ 1.6 times. The friction coefficient of samples with the coating (μ = 0.5) is less than that of the copper without the coating (μ = 0.679) by ≈ 1.35 times. It is established that the hardness of the coating increases as the substrate is approached and reaches the maximum value of ≈1780 MPa (the hardness of substrate is 1300 MPa). By means of micro-X-ray-spectral analysis it is detected that the main chemical element of the coating is silver, but copper, nickel, carbon and nitrogen are present in a considerably smaller quantity. It is established by the methods of diffraction electron microscopy that the main phases of the coating are solid solutions.

Structure and properties of composite coatings of the SnO2–In2O3–Ag–N system intended for strengthening the copper contacts of powerful electric network switches

The goal of the research is to analyze the structure and properties of the coating SnO2–In2O2–Ag–N formed on copper by a complex method. The method of coating formation combined the electroerosion spraying, irradiation by pulsed electron beam and subsequent nitriding in plasma of a gas discharge of a low pressure. It is shown that the thickness of the coating amounts to ≈100 μm. The wear resistance of a copper sample with the deposited coating is ≈ 2.8 times higher than that of copper without the coating. The friction coefficient of samples with the coating (μ = 0.479) is ≈ 1.4 times less than that of copper without the coating (μ = 0.679). It is established that the coating hardness increases as the substrate is approached and reaches its maximum value of ≈1400 MPa (substrate hardness is 1270 MPa). By means of micro-X-ray- spectral analysis it is detected that the main chemical element of the coating is silver, with copper, tin, indium, oxygen and nitrogen being present in a much smaller quantity. By the methods of X-ray phase analysis it is revealed that the main phases of the coating are copper-and silver base solid solutions. Tests for the electroerosion resistance showed that the coatings meet the requirements of standards for electromagnet starters with the category of application AC-3 of direct action.

THE STRUCTURE AND COEFFICIENT OF FRICTION OF WELDED NICKEL ALLOYS INCONEL 625 AND INCONEL 718

In this study, the coefficients of friction for three series of welded nickel alloy joints, subjected to different heat treatments (lack of heat treatment, solution heat treatment, precipitation hardening), were determined. Heat treatment of the prepared samples was aimed at eliminating the structural and stress gradient, because the electron beam welding technique is dedicated for constructions with very high quality and strength requirements. Given the nature of the electron beam process, the authors are aware that the obtained weld’s structures are characterized by different properties from parent materials, and also from structures melted under equilibrium conditions. The scientific aim of the presented work is to determine the influence of heat treatment on the microstructure, mechanical properties, and performance of dissimilar joints of nickel alloys Inconel 625 and Inconel 718. In order to determine the coefficient of friction for samples, the scratch test method was used. As a result of the research, it was proved that subjecting the welds to the precipitation hardening has a significant effect on abrasion resistance.

TRIBOLOGICAL PROPERTIES OF HIGH CARBON STEELS IN AN AS-CAST STATE AND AFTER PLASTIC DEFORMATION

The aim of the study was to conduct dry sliding tests on the designed hypereutectoid steels with the controlled contents increase of carbon, chromium, and manganese. Chromium and manganese were used to balance the changes related to the higher secondary carbides’ precipitation in the chemical composition of the matrix. Samples were investigated by the use of the block on disk friction method under the load of 100 N. The duration of each test was 2000 s with the wear track length approx. 500 m. The samples were investigated in the as-cast state and after hot plastic deformation. Two sets of four samples were prepared from the ingots and plastically deformed material. The heat treated (quenched and tempered) 100Cr6 steel was used as the counter-sample, with a new counter-sample used for each test. The obtained results show a decrease of the average friction coefficient for samples after plastic deformation. The phenomena that influenced this effect the most, observed in the alloy with the higher concentration of alloying elements, were grain boundary net defragmentation of secondary carbides and the elimination of Widmannstaten needles. The main wear mechanisms occurring during the tribological tests were sliding wear and material spalling.

Tribological properties of B4C–TiB2–TiC–Ni cermet coating produced by HVOF

Abstract In this study, B4C–TiB2–TiC–Ni coating was sprayed on the surface of 4130 steel by high velocity oxy-fuel torch. The tribological behavior of samples was studied by ball on disk wear testing. Structural evolution of the coating was analyzed by X-ray diffractometry. The microstructure of the coating, wear track and Al2O3 ball was investigated by scanning electron microscopy, field emission scanning electron microscopy and optical microscopy. Elemental analysis of the wear track was done by energy dispersive X-ray spectroscopy. It was found that a cermet coating containing B4C, TiB2, TiC and Ni phases with good bonding to the 4130 steel substrate with no sign of any cracking or pores was formed. The wear mechanism of the composite coating was delamination. The friction coefficient of samples was decreased with increasing load because of higher frictional heat and creation of more oxide islands.

Tribology Properties of IGZO Films by the Sliding Contacts of Reciprocating Motion

In the present study, sliding tribo tests with reciprocating motion were carried out to simulate the thumb-driven wear arising in indium gallium zinc oxide (IGZO) specimens prepared at five inclination angles during film deposition. Frictional and normal forces, Fx and Fy, and vibrations were used to analyze energy dissipation (ΔW) and composite mean force fluctuation intensities (IFSS). Friction coefficient is lowered by decreasing the mean surface roughness (Ra); its increase can raise ΔW. The friction coefficients of samples prepared with a nonzero inclination angle were lower than that of the IGZO_0° specimen.

Friction properties of groove texture on Cr12MoV surface

To analyze the influence of surface texture on friction properties of Cr12MoV’, ordinary grinder and spinning technology were adopted to obtain the grooved surface morphology of samples, and then the impact of spindle speed and feed in z-direction on surface morphology in the process of spinning was studied. In addition, the corresponding friction coefficient of sample was obtained through friction and wear tests. The results show that the peak clipping and the valley filling were conducted on the grinding surface, which could improve the surface roughness effectively and make the grinding trench-type wear scar more uniform. Both the area ratio of groove and groove spacing increased initially and then decreased with the increase of the spindle speed or the feed in z-direction. As a kind of micro-process, the groove could influence the friction coefficient of sample surface, whose distribution was beneficial to the reduction of friction coefficient. Compared with the surface obtained through ordinary grinding, grooved surface morphology through spinning technology was more conductive to reduce the friction coefficient, which could be reduced by 25%. When the friction coefficient of sample was reduced to the minimum, the texture of groove corresponded had an optimal area ratio and an optimal groove spacing, 37.5% and 27.5 μm, respectively.

Understanding the effects of inter-particle contact friction on the elastic moduli of granular materials

Understanding the mechanical stiffness of closely packed, dense granular systems is of interest in many fields, such as soil mechanics, material science and physics. The main difficulty arises due to discreteness and disorder in granular materials at the microscopic scale which requires a multi-scale approach. The Discrete Element Method (DEM) is a powerful tool to inspect the influence of the microscopic contact properties of its individual constituents on the bulk behavior of granular assemblies. In this study, the isotropic deformation mode of polydisperse packings of frictionless and frictional spheres are modeled by using DEM, to investigate the effective stiffness of the granular assembly. At various volume fractions, for every sample, we determine the stress and fabric incremental response that result from the application of strain-probes. As we are interested first in the reversible, elastic response, the amplitude of the applied perturbations has to be small enough to avoid opening and closing of too many contacts, which would lead to irreversible rearrangements in the sample. Counterintuitively, with increasing inter-particle contact friction, the bulk modulus decreases systematically with the coefficient of friction for samples with the same volume fraction. We explain this by the difference in microstructure (isotropic fabric) the samples get when compressed to the same density.

Dry friction and wear characteristics of impregnated graphite in a corrosive environment

Tribological properties of impregnated graphite are greatly influenced by preparation technology and working conditions and it’s highly susceptible to corrosion environmental impacts, but the experimental research about it are few. In this paper, three kinds of impregnated graphite samples are prepared with different degree of graphitization, the tribological properties of these samples in the dry friction environment and in a corrosive environment are analyzed and contrasted. The tribo-test results show that the friction coefficient of samples is reduced and the amount of wear of samples increase when the graphitization degree of samples increases in dry friction condition. While in a corrosive environment (samples are soaked N2O4), the friction coefficient and amount of wear are changed little if the graphitization degree of samples are low. If the degree of graphitization increase, the friction coefficient and amount of wear of samples increase too, the amount of wear is 2 to 3 times as the samples tested in the non-corrosive environment under pv value of 30 MPa · m/s. The impregnated graphite, which friction coefficient is stable and graphitization degree is in mid level, such #2, is more appropriate to have a work in the corrosion conditions. In this paper, preparation and tribological properties especially in corrosive environment of the impregnated graphite is studied, the research conclusion can provide an experimental and theoretical basis for the selection and process improvement of graphite materials, and also provide some important design parameters for contact seal works in a corrosive environment.

Tribological Properties of Nano-MMT/In Lubricant Additive on 45<sup>#</sup>Steel Tribo-Pair

1:1 MMT/In composite nanopowders were prepared by nanoMMT and nanoIn modified with coupling agent KH550, and the nano-MMT/In lubricating oil dispersion system was prepared by 150N base opl containing 3 mass fraction of nano-MMT/In composite powders, and then took the dispersion effect by laser particle size analyzer ,TEM and IR. The anti-wear and friction-reducing behaviors of that lubricating oil dispersion system were observed on the MMU-10G abrasive-wear tester with 45#steel tribo-pair, the morphology and the element of the worn surfaces were analyzed by SEM and EDX. The results showed that the grain size of the modified nano-MMT/In was smaller than the one without modification, and the modified nano-MMT/In had the good dispersion in the system; compare with the one in base oil system, the average friction coefficient of sample of 45#steel tribo-pair in nano-MMT/In additive lubricating oil system had declined by 27.5%, and the total wear mass loss had declined by 63%; The surface of sample after friction had created the self-repairing film that contain the characteristic element of MMT and In, that phenomenon was caused by the interaction of nano-MMT and nano-In.

Tribological behavior of Ti-6Al-4V and Ti-6Al-7Nb Alloys for Total Hip Prosthesis

The aim of the study is to evaluate the friction and wear behavior of high-strength alloys Ti-6Al-7Nb used in femoral stem and compare it with a Ti-6Al-4V alloy cylindrical bar corresponding to ISO 5832-3 part 3/01-07-199 standard. The tribological behavior was investigated by wear tests, using ball-on-disc and pin-on-disc tribometers. These tests consisted of measuring the weight loss and the friction coefficient of samples. The oscillating friction and wear tests have been carried out in ambient with oscillating tribotester in accordance with standards ISO 7148, ASTM G99-95a, and ASTM G133-95 under different conditions of normal loads (3, 6, and 10 N) and sliding speeds (1, 15, and 25 mm·s−1). As counter pairs, a 100Cr6 steel ball with 10 mm in diameter was used. Results show that the two alloys had similar friction and wear performance, although their grain structures and compositions are different. Occurrence of large frictional occurred, is probably caused by formation and periodic, localized fracture of a transfer layer. Higher friction with larger fluctuation and higher wear rate was observed at the higher siding speed. The Ti-6Al-4V wear mechanism transforms from ploughing and peeling off wear at low sliding speed to plastic deformation and adhesive wear.

Research on the Performance Influence of Second Adhesive to Friction Materials

The friction materials have many species and they are being used widely, but people have higher requests to friction materials along with the development of technology. the friction material of this expermental optimization formula have the advantages of suitable and stable friction coefficient under high temperature, low wear rate, good restoration characteristics and so on. It can effcetively reduce heat fade of friction and wear under high temperature barking. fricton and wear performance of friction material with second adhesive is better than common preparation friction material , it has higher friction coefficient and lower wear rate, It was determined by physical chemical properities of tin and sulfer. while heating or wearing, the temperature of friction material reach melting temperature of tin, it will become molten state, and sulfer has strong oxidation, on the one hand, tin and sulfer occurred chemical reaction, generating sulfide, stannous (one sulfide tin),on the other hand, while the sulfer is being molten state, it will absorb some abrasive dust, at the same time of generating sulfide, abrasive dust will be adsorb and solidify to pits of friction surface, forming abrasive dust membrane, let the friction coefficient of sample become stable rapidly, reducing the wear rate of friction material.

Effect of Ag Content in Palygorskite/Ag Blending Nanocomposite on Friction and Wear Properties of 45 Mild Steel Tribopair

The in situ mechanochemical auto-restoration technology of tribosurfaces has become a subject of great interest in recent years. This paper reports a study of the effect of Ag content in palygorskite (P)/Ag nanocomposites on friction-reducing and anti-wear properties of 45 mild steel tribopair. The electron microprobe has been used in its surfaces topography and elemental analysis. The study shows the auto-restoration layers formed on the tribopairs can decrease the wear mass loss and friction coefficient of these samples remarkably; when the Ag content in P/Ag was properly increased, it can help to decrease the friction coefficient of the tribopair samples.

A New Idea for Improving Heat Fade Performance of Organic Based Friction Materials

A new idea for improving heat fade performance of organic based friction materials was invented; the method is to dope high specific heat material to the matrix for increasing the specific heat capacity of matrix. In this paper, selecting mullite as additive, organic based friction samples doping mullite were prepared by thermoforming methods, the specific heat of samples were analyzed by TG-DSC, and its friction and wear were tested by GB/T 5764-1998 in China. The results show that doping mullite to matrix can dramatically improve the heat fade performance of organic based friction materials, the friction coefficient of samples can keep steady among 0.3-0.4 when the test temperature is from room temperature to 350°C,while the friction coefficient of the reference samples without mullite decline from 0.38 to 0.19.

Fretting Wear Resistance of ATW Cr<sub>3</sub>C<sub>2</sub>/Ni<sub>3</sub>Al Composite Hardfacing on IC6SX

The fretting wear performance of surface wear-resistant Cr3C2/Ni3Al composite deposited onto IC6SX alloy by manual argon tungsten-arc welding was investigated in this study. The results showed that the welded substrate exhibits a very good performance in comparison to the unwelded substrate at 500°C and 800°C, with 51.5% and 57.8% decrease of the fretting sectional area respectively. However, the fretting sectional area of the welded substrate is larger than that of the unwelded substrate at RT indicating poor fretting resistance as the reinforce phases of the welding layer is harder and more harmful to the sample surface. Examination of the fretting surfaces indicated that both the welded and unwelded samples undergo gross slip at RT and 500°C, and partial slip at 800°C. Coefficient of friction (COF) results were given by the SRV-4 tester which shows that as the temperature goes up, the COF of samples became lower and more stable. The results showed that the COF of welded substrate is lower than that of the unwelded substrate most of the time.

Effect of Braking Speeds on the Tribological Properties of Carbon/Carbon Composites

This paper describes the tribological properties of carbon/carbon composites used as braking materials under various braking speeds, in which the materials with three kinds of microstructures were used: rough lamina (sample A), smooth lamina (sample B), and the mixture of rough lamina and smooth lamina (sample C), respectively. Friction tests were carried out through a laboratory dynamometer. Polarized optical microscopy (OM) and scanning electron microscopy (SEM) were used to characterize the microstructure and worn surface. Results indicated that the friction coefficient of sample A reached a peak value at braking speed lower than that in both sample B and sample C. However, when the friction coefficients reached to the peak values the temperature inside the worn surface was observed to be approximately 250°C for all of the samples. The weight losses in all of the samples were observed to increase with increasing braking speed; however, the oxidation losses at speed of 28 m·s−1 are higher than that of 30 m·s−1 for all of the samples.

Mesoscopic objects, porous layers and nanocomposites—Possibilities of sol–gel chemistry

The goal of this study was to prepare mesoscopic objects, thin porous films and nanocomposite coatings with the use of sol–gel technique. Silica nanotubes, titania nanoparticles, porous titania and zirconia coatings as well as titania nanocomposites were successfully synthesized by changing the type of sol–gel precursor, sol composition and applying dip-coating deposition procedure in order to obtain thin films or coatings. All materials were visualized and characterized by the Atomic Force Microcscopy (AFM) technique. Moreover, characterization of titania nanocomposites was extended to the tribological tests performed by means of microtribometer operating in normal loads range of 30–100 mN. The AFM analysis of mesoscopic objects and nanoparticles showed that the diameter of synthesized silica nanotubes was 60–70 nm and the size of titania nanoparticles was 43 nm. In case of porous layers the pore size in titania and zirconia coatings oscillated between 100 and 240 nm, however their shape and distribution were irregular. Microtribological studies of nanocomposites revealed the moderate decrease of the coefficient of friction for samples containing 5, 15 and 5 wt.% of zirconia nanoparticles in titania coatings annealed at 100, 500 and 1000 °C respectively. An enhancement of antiwear properties was already observed for 1 wt.% of nanophase content, except the sample annealed at 500 °C. It was also found that the annealing at high temperatures is a primary factor which affects the reduction of friction and wear of titania coatings while the presence of nanoparticles has secondary effect. Investigations in this study carried out with the use of the AFM technique highlighted the potential and flexibility of sol–gel approach in designing of various types of advanced materials in a form of mesoscopic objects, porous coatings and composite layers. Results collected in this study clearly demonstrated that sol–gel technique can be applied effectively in preparation of broad range of modern materials.