Showing papers on "Tribology published in 1995"
TL;DR: In this paper, an understanding of the molecular mechanisms of tribology in thin films and at surfaces has been presented, which is of fundamental importance in many pure and applied sciences, such as computer simulations.
Abstract: Friction, wear and lubrication between materials in contact are of fundamental importance in many pure and applied sciences. Owing to the development of experimental and computer-simulation techniques for studying these phenomena at the atomic scale, an understanding is beginning to emerge of the molecular mechanisms of tribology in thin films and at surfaces.
1,393 citations
TL;DR: In this article, a general framework identifying groups of interactive parameters and assessing wear material performance through investigating these groups of parameter is presented, which is suggested that material loss can be rationalized from the understanding and description of the three wear precursors which delineate the groups of parameters, being surface, subsurface and third body behavior.
344 citations
TL;DR: In this paper, an overview of the friction and wear properties of high temperature resistant polymers, in particular polyetheretherketone (PEEK), under various testing conditions against smooth steel counterparts is given.
338 citations
TL;DR: In this paper, penetration rate equations have been developed to quantify the wear and corrosion processes and wear-corrosion synergism in a standard format, so that these data can be utilized to develop practical engineering criteria for any tribosystem.
235 citations
TL;DR: In this article, the frictional behavior of mica surfaces with silicon nitride tips has been investigated systematically with the AFM as a function of load, tip geometry, mica lattice orientation and humidity.
170 citations
TL;DR: In this paper, a study of the tribological properties of two locally developed polymeric composite materials for bearing applications is presented, based on a scanning electron microscope examination, which revealed that the reinforcement volume fraction as well as orientation have considerable effect on the friction and wear of polyester composites.
154 citations
TL;DR: In this article, the wear and friction characteristics of diamond-like carbon (DLC) films and composite surface layers were studied by conducting pin-on-disc experiments on M 50 steel and Ti-6A1-4V alloy.
Abstract: An innovative approach to improving tribological behavior of surfaces and meeting long-term durability requirements of engineering devices is to design and develop novel systems incorporating multilayers and/or duplex diffusion/plasma coating treatments. In the present work, the wear and friction characteristics of diamond-like carbon (DLC) films and composite surface layers were studied by conducting pin-on-disc experiments. M 50 steel and Ti-6A1-4V alloy were used as substrate materials. The composite layers consisted of a N-diffusion zone obtained by ion nitriding, followed by a 500 A vapor-deposited Si bond layer and a 0.4 µm DLC film. The purpose of the bond layer was to enhance adhesion between the substrate and the DLC films. An ion-beam method was used for the deposition of the DLC films. The pin-on-disc results showed that for both materials the DLC coating produced a reduction in the coefficient of friction of about one order of magnitude. The reduction in the coefficient of friction was found to be consistent with the formation of a carbon-rich transfer film on the contact surfaces. Wear scar profiling and weight loss calculations showed that the wear resistance of the DLC-coated materials was dramatically improved. Comparisons between duplex N-diffusion layer/DLC coating and single DLC coating on Ti-6A1-4V alloy substrates showed that the duplex treatments possessed a significantly higher wear resistance. Nitriding was found to cause substrate hardening that reduces subsurface deformation, thus improving coating support and extending considerably DLC film lifetime.
145 citations
TL;DR: The role of dopants in the mechanisms governing friction and wear of sputtered MoS2 films is not well understood as discussed by the authors, however, the role of the dopants is well known.
Abstract: The fact. that dopants improve the friction and wear properties of sputtered MoS2 films is well known. However, the role of dopants in the mechanisms governing friction and wear are not well understood. The purpose of this work is to gain a fundamental understanding of their role by co-depositing a number of materials, i.e., Ni, Fe, Au, and. Sb2O3, with MoS2 and evaluating their effects on film chemistry, crystallinity, microstructure, and tribology. Friction and wear measurements were collected, using ball-on-flat and dual-rub shoe tribom-eters. Other physical and chemical properties were obtained using SEM, XPS, XRD) and Raman spectroscopy. Crystalline MoS2 was seen in all of the films. In Sb2O3-doped films, an amorphous phase was also observed. The presence of dopants caused film densification and affected crystallite size. They had little effect on the overall crystallite orientation. In addition, dopants caused a reduction in the mean and. variance of the friction coefficient and an increase in wear ...
134 citations
TL;DR: In this article, a mathematical model, based on experimental observations that the transition is caused by the development of wear protective layers on the rubbing surfaces, is proposed, which are developed mainly from accumulated wear debris particles retained within the wear tracks; these can have various characteristics, depending on the experimental conditions and the properties of the metal.
131 citations
TL;DR: In this paper, the effect of oxide debris present in the vibrating contact on the velocity accommodation and, consequently, on the coefficient of friction has been investigated in an unlubricated contacts.
123 citations
TL;DR: Particle effects on friction and wear of 6061 aluminium (6061 Al) reinforced with silicon carbide (SiC) and alumina (Al2O3) particles were investigated by means of Vickers microhardness measurements and scratch tests as mentioned in this paper.
Abstract: Particle effects on friction and wear of 6061 aluminium (6061 Al) reinforced with silicon carbide (SiC) and alumina (Al2O3) particles were investigated by means of Vickers microhardness measurements and scratch tests. Unreinforced 6061 Al matrix alloy was also studied for comparison. To explore the effect of heat treatment, materials subjected to three different heat treatment conditions, i.e. under-aged, over-aged and T6, were used. Multiplescratch tests using a diamond and a steel indentor were also carried out to simulate real abrasive wear processes. Vickers microhardness measurements indicated that T6 heattreated composites had the highest hardness. Single-scratch tests showed that the variation of friction coefficient was similar to that of Vickers hardness and the peak-aged composites exhibited the best wear resistance. The wear rate of fine particle-reinforced composites was mainly affected by hardness. However, the wear rate of large particle-reinforced composites was influenced by both the hardness and fracture of the particles.
TL;DR: In this paper, a sliding experiment on PEEK composites filled with CuS and PTFE powders while rubbing against tool steel surfaces was performed under ambient conditions in a pin-on-disk configuration.
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15 Dec 1995
TL;DR: In this article, the authors present a tribology and design reference for component failures, maintenance, and repair of component failures and their repair in the automotive domain, including bearing drives and seals.
Abstract: CONTENTS INCLUDE: Bearings Drives and seals Lubricants Lubrication and working conditions Component failures, maintenance and repair Basic tribology and design reference.
TL;DR: In this paper, two magnesium/silicon aluminium alloys each reinforced with 20 vol.% SiC particulates have been worn against three makes of automobile friction linings (brake pads) and wear processes at the interfaces of the specific rotor-pad combinations have been characterised through the analysis of friction traces and the use of electron microscopy.
TL;DR: Friction and wear of 13 different materials with silicon nitride (Si3N4) matrix were investigated under unlubricated conditions by means of the pin-on-disc configuration with self-mated couples as discussed by the authors.
TL;DR: In this article, the lateral forces are measured as a function of normal load, controlled by an external ramp generator, and the local friction coefficient can be extracted by means of the two-dimensional histogram technique.
TL;DR: In this article, a materials triangle approach is used to determine which type of PVD coating should be used for which application, based on a case study of different industrial case studies.
Abstract: Since the beginning of the 1980s ceramic PVD coatings have been used in industry for many applications. At present four types of PVD coatings are frequently used: TiN, Ti(C,N), (Ti,Al)N and CrN. Based on a materials triangle approach, it is shown which coating should be used for which application. Different industrial case studies will demonstrate the effectiveness of PVD coating. Some recent developments, of which various aspects are still mainly in the research phase, like diamond(like) coatings, duplex treatments, self lubricating coatings, Ti2N coatings and PVD coatings deposited at low temperatures (<250 °C), are also described.
TL;DR: In this paper, the authors studied the friction and adhesive forces acting on the tip of a friction force microscope in contact with a flat surface as a function of humidity and found that the adhesive forces decrease substantially with increasing humidity during sliding of the tip across both sample surfaces, implying that the surfaces are lubricated by adsorbed water.
Abstract: To simulate the nanotribological effects of adsorbed water molecules and the capillary condensation of water around contacting asperities, we have studied the friction and adhesive forces acting on the tip of a friction force microscope in contact with a flat surface as function of humidity. On the hydrophilic surface of silicon oxide strong capillary formation occurs around the tip. In contrast, on the hydrophobic surface of silicon oxide covered with a perfluoropolyether lubricant, the water capillary formation around the tip is greatly suppressed. Friction and adhesive forces decrease substantially with increasing humidity during sliding of the tip across both sample surfaces, implying that the surfaces are lubricated by adsorbed water.
TL;DR: In this paper, the friction behavior of pulsed laser-deposited tungsten disulfide films was described using a ball-on-flat apparatus, in which a 440C stainless steel ball was held on a rotating disk coated with WS2 film, was used as the lest configuration.
Abstract: This research describes the friction behavior of pulsed laser-deposited tungsten disulfide films. A ball-on-flat apparatus, in which a 440C stainless steel ball was held on a rotating disk coated with a WS2 film, was used as the lest configuration. Friction measurements were made in dry nitrogen and in laboratory air. Wear surfaces were characterized by scanning electron microscopy and Raman spectroscopy. The friction coefficient of the film in dry nitrogen was 0.04, and in laboratory air it rose to between 0.10 and 0.15. In the dry nitrogen case, friction induced some degree of crystallinity into the otherwise amorphous film, while rubbing in air mostly resulted in oxidation of the film. Transfer films formed in a dry environment were smooth, tenacious and firmly adherent to the steel counterface. By contrast, the films formed in air were patchy and powdery in nature. Presented at the 49th Annual Meeting in Pittsburgh, Pennsylvania May 1–5, 1994
TL;DR: In this paper, an unlubricated ball-on-flat wear test was conducted on sintered silicon carbide in self-mated sliding in air, where the contact load was varied from 3.2 to 98.0 N and a temperature range of 23°C to 1000°C.
TL;DR: A rheological model for thin film lubrication has been developed in this paper, which can be applied to thin-film lubrication, and the model contains three material property parameters, i.e., the conventional viscosity, the thickness of the surface layer, and a surface-layer viscosity.
Abstract: A rheological model has been developed which can be applied to thin film lubrication. It is known that great differences are seen between behavior in thin (molecular scale) films and in bulk (macroscopic) rheological measurements. There appear to be layers near the surface in which viscosity is increased by many orders of magnitude. The model contains three material property parameters, i.e., the conventional viscosity, the thickness of the surface layer, and a surface layer viscosity. A modified Reynolds equation is developed. Behavior of correction factors to Reynolds' equation and to the shear stress are shown. Results are computed for a one-dimensional converging wedge contact. The effect of increasing the layer thickness parameter is to increase the load and reduce the friction coefficient. Increasing the surface layer vicosity also tends to increase the load and reduce the friction coefficient. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conferen...
TL;DR: In this article, the tribological properties of physically vapour deposited coatings of TiN, TiAlN,TiCN, and CrN have been studied using different pin-on-disc test procedures.
Abstract: Tribological properties of physically vapour deposited coatings of TiN, TiAlN, TiCN, and CrN deposited on discs made of two different tool steels have been studied using different pin-on-disc test procedures. Seizing and adhesive wear were studied by a step-load test using a steel bali, friction properties by using a flat steel pin under low load, and the wear resistance was studied by using an Al 2 O 3 ball, simulating a more abrasive wear situation. In all tests, coating improved the performance of the samples, reducing seizing and wear considerably. TiAlN exhibited the most stable friction and wear mode, which is attributed to a stable aluminium oxide surface layer. The wear tests against Al 2 O 3 showed that the Ti-based coatings reduced the severe wear of the uncoated hardened steel by approximately 4 times, while the softer, but more ductile, CrN reduced the wear by a factor of 2. The results have been related to nanoindentation hardness measurements and compared with results from field tests of coated tools. In particular, the test results for TiAlN seem to be in very good accordance with practical results from field tests. Thus, pin-on-disc tests can make up a relevant and convenient test method for evaluation of fundamental tribological properties of physically vapour deposited coatings. However, proper test conditions must be carefully chosen in order to evaluate the relevant applications.
TL;DR: In this article, a pressure-shear plate impact experiment is introduced to study time-resolved friction at interfaces subjected to high sliding speeds under relatively high normal pressures, where the conditions of slip at the interface are varied by changing the surface roughness of the impacting plates and by varying the applied normal to shear stress ratio.
Abstract: A pressure-shear plate impact experiment is introduced to study time-resolved friction at interfaces subjected to high sliding speeds under relatively high normal pressures. The conditions of slip at the interface are varied by changing the surface roughness of the impacting plates and by varying the applied normal to shear stress ratio. The configuration offers the simplicity of allowing the interpretation of the experimental data by using the frame-work of one-dimensional plane wave analysis. The interfacial material pairs investigated in the present study are comprised of a wear-resistant grade of tungsten carbide and either an AISI 4340 steel or a Ti-6AI-4V alloy. The experimental results indicate that the coefficient of friction increases with the increase in surface roughness of the tungsten-carbide plates and with cumulative slip at the interface.
TL;DR: All current artificial joints at best are lubricated by mixed lubrication and hence wear is taking place throughout the life of the prosthesis.
TL;DR: In this paper, a pin-on-disk tribometer was used to measure the friction coefficient and wear rate of diamond-like carbon (DLC) films on silicon wafers and silicon nitride balls by RF plasma-assisted chemical vapor deposition at a pressure of 700 mTorr and a substrate temperature of 360 K.
Abstract: Diamond-like carbon (DLC) films were deposited on (100) silicon wafers and silicon nitride balls by RF plasma-assisted chemical vapor deposition at a pressure of 700 mTorr and a substrate temperature of 360 K. The friction coefficient and the wear rates were measured using a pin-on-disk tribometer in 40% humid and dry air. Friction coefficients are near 0.05 in all cases measured. In dry air, the wear of silicon nitride and steel against DLC is below measurement capability because of a protecting DLC transfer layer, and wear of DLC is 2.5 ± 10−8 mm3/Nm against silicon nitride and 6.5 ± 10−9 mm3/Nm against steel. In humid air, the DLC transfer layer does not adhere to the solids, and wear of both bodies is larger. Unmeasurable wear is obtained when DLC slides against itself in humid air; the wear rate is 5 ± 10−9 mm3/Nm in dry air. These results are interpreted in terms of the properties of a friction-induced transformation of the surface layer of DLC.
TL;DR: In this paper, the effect of graphite phase on the wear performance of spheroidal cast irons was investigated under both two-body (pin-on-disc) and three-body impact conditions.
TL;DR: In this paper, ball-on-disk experiments are carried out to investigate metal-diamond-like carbon (DLC) coatings in conditions of sliding wear against steel and WC balls.
Abstract: The design of anti-friction coatings able to perform well in different wear conditions without lubricants requires a combination of adequate hardness and toughness, good adhesion, a low friction coefficient and a low wear rate. Recently introduced metal-diamond-like carbon (DLC) coatings can be a major step towards the achievement of such combination. These coatings consist of an amorphous a.CH matrix with the possible incorporation of metal, metal carbide and/or graphite grains. Previous studies of Tix%-DLC coatings deposited on Ti-TiN-TiCN-TiC supporting interlayers showed their good protective properties against abrasive, impact and single scratch wear. Here, ball-on-disk experiments are carried out to investigate these coatings in conditions of sliding wear against steel and WC balls. A comparison of the results for Tix%-DLC and ceramic. TiN, TiCN and CrN coatings shows particularly low friction coefficients (below 0.2) and low normalized wear rates for the Tix%-DLC coatings. The results reveal a corr...
TL;DR: In this paper, the authors reported that the coefficient of sliding friction for the materials tested under boundary or unlubricated conditions should more properly be reported as a range of values rather than one single nominal value.
TL;DR: In this article, the authors investigated the mechanics of roll formation between sliding bodies at elevated temperatures and humid conditions using tribological rolls, which are used as the model material for reciprocating linear sliding tests.
Abstract: The present study investigates the mechanics of roll formation between sliding bodies at elevated temperatures and humid conditions. Silicon is used as the model material for reciprocating linear sliding tests. The evolution of tribological rolls initially involves the rapid oxidation of silicon wear debris by water, the deformation of SiO2 particles into platelets, and then the compaction of these particles into a film deposited on the wear surface. The formation of compacted silica film requires minimum adsorption of water which enhances the adhesion between silica platelets. The stress cycle imposed on the film leads to the delamination of platelets near the sliding surface. The delaminated debris cluster into multiple aggregates that are subsequently rolled into dense cylindrical particles so as to relieve the interfacial shear stress. When the film and rolls are formed, the friction and wear rate is maintained at low steady state values.
TL;DR: In this article, the effect of the operational variables and of the humidity on friction and wear varied for the different materials under investigation, while the coefficient of wear showed great variations and depended strongly on the humidity of the surrounding air.
Abstract: The tribological behaviour of different ceramics in contact with steel was studied for the case of oscillating sliding motion with a ball-on-disc apparatus. The influence of several test condition parameters was investigated by a systematic variation of the stroke, frequency, and normal load at room temperature in laboratory air at different levels of relative humidity. Each of the four parameters was varied in three stages. While the coefficient of friction was only mildly influenced by the operational variables, the coefficient of wear showed great variations and depended strongly on the humidity of the surrounding air. The effect of the operational variables and of the humidity on friction and wear varied for the different materials under investigation.