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This paper describes a preliminary study of the mechanisms of the removal of surface coatings in hydrodynamic flows. The bulk cohesive and interfacial properties of model deposits were measured and experiments under liquid flows were also performed to investigate the effects of hydrodynamic stresses on the deposits. Comparisons were made between the erosion characteristics of deposits under hydrodynamic...
The friction and wear behaviour of ZrO 2 -Y 2 O 3 ,ZrO 2 -Y 2 O 3 -CeO 2 and ZrO 2 -Al 2 O 3 composite ceramics against hardened steel AISI-52100 were investigated using a pin on plate configuration under reciprocating motion. The reproducibility of the results was examined in this configuration. Wear characteristics were...
This paper attempts to identify the mechanisms of wear and friction for G-3500 grey cast iron, their interdependency and evolution with time. A model for wear and friction is proposed and compared with some of the current theories. The model describes the mechanisms of particle formation, detachment and entrapment, and shows the correlation between the noise observed in friction data obtained in prolonged...
The tribological behavior of specimens coated by two layers, titanium nitride film as the top layer and titanium film as the underlayer, is studied. The coating layers of the bottom specimens were deposited using the cathodic arc ion plating process technique. Experiments were carried out on a wear test machine using a thrust-washer adapter to simulate the surface contacts between the steel ring (the...
In part II of this study, comparisons of some tribological parameters are made for specimens coated with titanium nitride as the top layer, but using different materials as the underlayer. For the specimens coated by the cathodic arc plasma deposition method, electroless nickel films of various thicknesses were deposited as the underlayer. For the specimens coated by the cathodic arc ion plating method,...
In this paper the phase structure and the distribution of elements in Mo-Ag and Mo-Ni multilayer films deposited by ion-beam mixing (IBM) were investigated using transmission electron microscopy (TEM) and Auger electron spectroscopy (AES). The microhardness and tribological properties of the multilayer films were also investigated. The rubbing surfaces were examined using scanning electron microscopy...
We have studied the influence of a dynamic ion mixing (DIM) treatment performed at 750°C on different mechanical properties of SiC coatings deposited on TA6V substrates. The deposition method is based on the sputtering of an SiC target with an ion beam (1.2 keV Ar + ) delivered by a Kaufman type ion source. The growing films of SiC are continuously bombarded during deposition with 160 keV...
PTFE friction at initial stages and upon transferred layer formation is conditioned, to a great extent, by molecular and kinetic processes in the surface layers. Antifrictional properties of transfer layers are largely dependent on temperature in the contact zone. It is shown that the typical PTFE friction force dependence on temperature could provide an explanation of its self-lubricity and high...
Fretting test were carried out with a sphere-on-flat geometry to investigate the wear mechanisms of electrodeposited Cu/Ni multilayer films. The effect of the layer spacing of multilayer films on the fretting wear and friction coefficient of the specimens has also been studied in the fretting conditions. Scanning electron microscopy (SEM) and electron probe microanalyser (EPMA) were used to observe...
Dry sliding wear behaviour of bamboo (Phyllostachys pubescens) against a grey iron (HT200) was examined on a block-on-ring machine. The wear volume of bamboo was a function of the normal load, the sliding velocity and the relative orientation of bamboo fibres with respect to the rubbing surface. The wear volume increased with the normal load and sliding velocity. The normal-oriented specimens (N-type)...
The present tendencies in miniaturizing the equipment and the machine tools, decreasing the aircraft weight, avoiding the complicated oil cooling and lubricating systems, running the ball or roller bearings in contaminated media or in the presence of the electric fields, determined a higher use of the lubricating greases in technical applications which is estimated at about 80% of the bearings assemblies...
A theory is firstly developed of the noncontact friction forces between the sliding nanoasperity and substrate. The linear force-velocity dependence is substantiated. We differ two principally distinct types of the friction forces: the static force, independent of the tip velocity V, being of adhesive nature, and the dynamical one, proportional to V. Several mechanisms have shown to contribute the...
The starting process, i.e., transition from static to kinetic friction in polymer-polymer microbearings, was studied. Load, sliding speed and time of contact before starting were varied during the experiments. AFM studies of rubbing surfaces were performed and the real surfaces were brought into contact in computer simulations to evaluate the adhesive and frictional interactions. Correlation between...
In the present paper, a simplified approach to the adhesive theory of friction, which encompasses both the concept of work of adhesion and the growth of the real area of contact, is presented. The starting point is to consider the average shear strength of the asperity junctions as dependent on the effective work of adhesion, which is influenced by the thermodynamic work of adhesion and irreversible...
Adhesion is an important component in the wear of tools and components. Among the methods to quantify adhesion, reciprocating fretting is a possible test method. This paper describes results from reciprocating fretting tests involving cutting tool materials and work materials. Powder metallurgical high speed steel (HSS) tool inserts with and without TiN coating were evaluated for adhesive affinity...
An investigation has been carried out to study the effect of high substrate bias voltages on the morphological, mechanical, adhesive and tribological properties of diamond-like carbon (DLC) films. The morphological study shows that the film has a tendency to be rougher, when it is prepared with increased substrate bias voltages. Relatively lower hardness and poor wear resistance (the coefficient of...
The sliding wear properties of transformation-toughened CMC and MMC coupled with high-speed steel have been studied at speeds in the range 0.9–9.4m/s for MMC and 0.2–11.1m/s for CMC and at a pressure of 5MPa. It was shown that at low sliding speeds (0.2–4m/s), both friction coefficient and wear rate of the yttria-doped tetragonal zirconia polycrystal ceramics (Y-TZP) increased with sliding speed and...
Interaction between a soft rubber asperity and its hard counterpart is traced with the help of a finite element computation. The analysis is aimed to estimate the influence of adhesion between rubber and rigid surfaces and the energy losses arising from the deformation of rubber bulk to the sliding resistance. At the contact zone, interfacial bonds are formed due to adhesion and their resistance to...
The purpose of this study is to demonstrate the friction control between wheel and rail can solve wheel/rail contact problems, such as wheel-slipping, rail corrugation, squeak noises, wheel/rail wear and so on. Firstly, fundamental tests with two-roller-rigs were carried out to evaluate the friction performances of several types of friction modifiers. Then, for the purpose of realizing the friction...
The adhesion test under the conditions of different wheel/rail contacts, such as various speeds, axle-loads, contamination situation, was carried out. In order to simulate track irregularities, the rollers of the test rig were excited with hydraulic system in the test. The test results showed that the adhesion coefficient of wheel/rail decreased with increasing in the axle-load and running speed under...
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