bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tribological and Mössbauer Studies of Ion-Implanted Iron
Authors: Williamson D.L. , Qu Yi , Wei Ronghua , Sampath W.S. , Wilbur P.J. 
Published: March 2011

AbstractA modified pin-on-disc wear test technique and conversion electron M6ssbauer spectroscopy (CEMS) have been used to characterize the tribological and microstructural properties, respectively, of pure Fe implanted with N and Ar ions at high current densities. CEMS measurements were made before and after wear testing. For the lubricated, mild adhesive wear conditions used here, no evidence was found for iron-nitride dissolution or N atom migration. Disordering of γ'-Fe4N did occur as a result of the wear process. All Nimplanted surfaces were tribologically superior to the Ar-implanted surface and an extremely wear-resistant surface layer about 30-50 nm thick was produced with a dose of 8x1016 N atoms/cm2, at a dose rate of 100 μA/cm2. However, once this layer was worn away the wear rate returned sharply to that of unimplanted pure Fe. A high retained N dose has been observed even for a dose rate of 750 μA/cm2 during which the sample reached 280°C.
Friction Characteristics of B+- and N2+-Implanted Fe-Cr Alloys.
Authors: Sasaki Jun , Iwaki Masaya 
Published: March 2011

AbstractA study has been made on friction and hardness of boron and nitrogen ion implanted Fe-Cr alloys. Ion implantation has been carried out with doses ranging from 5 wt% up to 20 wt% at energies of 50, 100 and 150 keV at room temperature. Reciprocal traces for friction coefficient measurements were performed by using a Bowden-Leben tester at a low speed without lubricant. Hardness was measured by using a micro-Vickers tester at a load of 2gf. Hardness of the specimen increases after the implantation with either of ion species. Friction measurements with reciprocal sliding show that a life-time of decreased friction coefficient depends on implanted ion species, Cr concentrations and acceleration energies. For B+- implantation, the lower the chromium contents are, the longer a decreased friction coefficient lasts. Meanwhile, the friction reduced by nitrogen implantation lasts longer for higher chromium content substrates. Dependence of friction coefficient on an acceleration energy is discussed for B+-implantation.
Unlubricated Sliding Properties of Ion Beam and Excimer Laser Mixed Fe-Ti-C Multilayered Films
Authors: Hirvonen J-P. , Nastasi M. , Jervis T.R. , Tesmer J.R. , Zocco T.G. 
Published: March 2011

AbstractMultilayered Fe-Ti-C films consisting of eleven sublayers were vacuum deposited onto an AISI 304 stainless steel substrate and subsequently mixed using either 400 keV Xe ions or an excimer laser operating at a wavelength of 308 nm. Ion mixing was accomplished in a two step process: the multilayers were first irradiated with 1xl017 Xe/cm2 at 520 °C, after which half of the sample was irradiated with 5x1015 Xe/cm2 at 0 °C. Laser mixing was carried out at both 1.1 and 1.7 J/cm17 with the number of pulses varied between 1 and 10. Pin-on-disc studies revealed only slight differences between the two kinds of ion beam mixed samples, whereas the dry sliding properties of laser mixed samples were strongly dependent on the total fluence used. In the optimum conditions, similar friction coefficients were obtained on both kinds of samples.
Surface Mechanical Properties of Ti Alloys Produced by Excimer Laser Mixing of Ti on AiSi 304 Stainless Steel
Authors: Jervis T. R. , Hirvonen J-P. , Nastasi M. , Zocco T. G. , Martin J. A. , Pharr G. M. , Oliver W. C. 
Published: March 2011

AbstractWe have investigated the properties of surface alloys of Ti formed by excimer laser melting and mixing of Ti overlayers on AISI 304 stainless steel substrates.The thickness of the initial Ti surface layers and the fluence and number of pulses used to mix the surface were varied toinvestigate a broad range of processing conditions. Samples were uniformly translated at different speeds under repetitive pulses of homogenized laser radiation at 308 nm to vary the number of pulses incident on the sample. We investigated the surface structure and composition, the wear and friction behavior, and the surface hardness of the resulting alloys.The extent of mixing is observed by Rutherford backscattering spectroscopy to be proportional to the number of pulses incident on the sample. Amorphous surface layers are formed at some mixing levels with a composition which indicates that Ti substitutes for Fe in the stainless steel on a one to one basis. Incorporation of C from surface and interface contamination is observed but at a level much below that found in comparable ion implanted materials.Friction coefficient measurements indicate that there exists an optimum level of mixing for each layer thickness. Excessive mixing degrades both the coefficient of friction and the wear performance in dry sliding tests.As with the tribological measurements, the surface hardness showed a dependence on amount of mixing. The surface hardness of the as deposited samples was higher than that of the laser mixed samples, initially decreased with mixing, and finally increased with further mixing.
Solid Lubricating Films for Extreme Environments
Authors: Singer Irwin L. 
Published: March 2011

AbstractAdvances in solid lubricating films for vacuum and high temperature applications are reviewed. Traditional lubricants (e.g. graphite and dichalcogenides) are being improved and new lubricating materials (e.g. amorphous carbons) are being discovered with the aid of recent developments in deposition processes and surface analytical methods. Ion bombardmenttreatments have increased film adhesion, lowered friction coefficients and enhanced the wearlife of MoS2films, as well as created new forms of lubricating carbons (amorphous, polymeric and diamond-like). Composite films and multilayer coating treatments are providing extra protection for surface and films against environmental degradation. Ultralow friction coefficients (<0.01) have been achieved with MoS 2 as well as diamond-like carbon films. Material selection, in some cases (e.g. thin metal films), can nowbe made basedon scientific principles, although many tribomaterials are still being developed by trialand error methods.
Modifications of Molybdenum-Disulphide Films by Ion-Bombardment Techniques
Authors: Mikkelsen Niels JØrgen , SØrensen Gunnar 
Published: March 2011

AbstractThe present paper reports on the structural and tribological studies of MoSx films in the thickness range of 3-4000 Å bombarded with inert-gas ions in the hundred-keV energy range. It has been shown that it is possible to amorphize MoS1.8 crystalline films with 400-keV Ar ions at a dose of lxl016 ions/cm2 Contrary to previous studies, there is evidence for both a lowfriction coefficient and an increased sliding life of sputtered MoSx films when amorphized by the ion-bombardment technique. The paper will discuss the influence of ion dose and tribological differences between bombarded and nonbombarded MoSx films. With the availability ofhigh-intensity ion beams in the mA range, the possibility of a direct ion synthesis of a molybdenum surface with high-intensity sulphur-ion beams will be discussed, and friction measurements of these systems will be presented.
Tribological Applications for Advanced Ceramics
Authors: Jahanmir S. 
Published: March 2011

AbstractAdvanced structural ceramics offer unique capabilities as tribomaterials. They are being used today in diverse applications such as tips for ball-point pens, precision instrumentbearings, and cutting tool inserts. Tribological applications of ceramics can be divided into several categories based on the properties of the ceramics. These include: resistance to abrasion and erosion; resistance to corrosive wear; wear resistance at elevated temperatures; low density; and electrical, thermal and magnetic properties. Examples of present utilization of ceramics in each category are described and a few examples of potentialfuture applications are given. Many scientific and technical barriers must be overcome before the full potential of ceramics in tribological applications is realized. These barriers are discussed in terms of the limited knowledge regarding tribological performance, problems with reliability, and lack of design knowledge and experience. It is clear that the wide-spread use of advanced ceramics requires further research and development. However, it must be realized that the solutions to the scientific and technical problems will be slow.
The Effect of Surface Finishing on the Tribological Behavior of a 94% Alumina Ceramic Material
Authors: Spodnik Jeffrey L. , Wert James J. 
Published: March 2011

AbstractThe effect of surface finish on the unlubricated sliding wear behavior of a 94% A12O3 ceramic material has been investigated using a reciprocatingright cylinder-on-flat tribometer. The surface finishes evaluated were produced using a combinationof SiC and diamond abrasive particles.Profilometry was employed to characterize surface topography and x-ray diffraction was used to determine the residual stress associated with each finishing process.The coefficients of friction and controlling wear mechanisms varied dramatically as the maximum asperity height was altered by different finishing techniques. Below a peak profile of 0.25 μm, the coefficient of friction varied between 0.60 and 0.75 due to preferential shearing of the siliceous binder phase which segregated at surfacial pores and grain boundaries. Binder adhesion in the sliding contact produced stick-slip frictional behavior. Surfaces with asperity heights in excess of 10 μin exhibited intergranularfracture or grain “pluck-out”. These surfaces contained minimal real areas of contact and yielded friction coefficients of 0.30 - 0.35. Removed alumina grains actedas hard abrasives in the contact zone and enhanced transgranular fracture by a lateral cracking mechanism. Evidence of crack propagation as a result of Mode II and Mode III shearloading was discovered at subsurface pore sites. The influences of microindentation hardness and fracture toughness are discussed in terms of their relative importances on the observed wear behavior.
The Tribooxidative Behavior of Rutile-Forming Substrates
Authors: Gardos Michael N. 
Published: March 2011

AbstractAn assessment of the literature indicates that in high temperature air not only titanium,but also titanium carbide (TiC) and titanium nitride (TiN) react to form rutile, the mostthermodynamically stable polymorph of titanium dioxide. It has been recently hypothesizedthat slightly oxygen-deficient rutile (TiO2-x) behaves as a low shear strength, lubricious oxide.Although the oxidation kinetics-driven reaction of the less stable TiC results in thickeroxide layers than on TiN, the most prevalent film morphology and oxide structure on both TiC and TiN are the same as those generated on the much softer Ti and its alloys. In mostcases of static oxidation and tribooxidation at high temperatures, the oxide layers grow in extremely thin (1 to 5 μm) sheets, which periodically delaminate from the substrate. The kinetics of delamination are highly dependent on substrate properties. These sheets form an array of loosely cohering (under static conditions) or tightly cohering (under triboconditions) scales, similar to the morphology of multilayered pastry dough. The most thermodynamically stable [(110)] cleavage planes of rutile tend to align preferentially in the plane of the peeling flakes, but without any azimuthal order. It is suggested that rutile can be rendered lubricious (a) by this unique structure, (b) by keeping its shear strength minimal by intrinsic (i.e., environment-independent) control of the number of oxygen vacancies within the oxide layers, and (c) by tailoring the load-carrying substrate used to form the rutile films in-situ. Accordingly, the removal rate ofrutile and the friction coefficient provided by the oxide/substrate tribosystem may be further controlled by taking advantage of (a) the high, but still significantly different hardnesses and ideal habit plane orientation of the TiC and TiN mother matrix underlays, and (b) the differences in the reaction kinetics of layered oxide growth on these highly oriented, hard metal coating matrices at elevated temperatures, in air.
Tribochemical Lubricious Oxides on Silicon Nitride
Authors: Fischer T. E. , Liang H. , Mullins W. M. 
Published: March 2011

AbstractThe concept of lubrication by a tribochemically generated oxide layer on the surface of silicon nitride is further investigated. Previous work has shown that low friction coefficients (μ≈0.1) are obtained in a range of sliding velocities and loads when otherwise unlubricated silicon nitride slides in humid air at temperatures between 150 and 650ºC. In order to verify the hypothesis that this behavior results from a competition between the growth of an oxide layer (with growth kinetics accelerated by friction) and its removal by wear, we have performed model experiments at room temperature, wherethe oxide layer is grown statically (i.e. without friction) and the friction coefficient and its evolution in time are subsequently measured. In order to avoid high friction by plowing, ultraflat surfaces were first prepared by sliding in water. The experiments showed that the oxide layer growing in humid air on silicon nitride produces a friction coefficient as low as μ≈0.05 that survives about 30 Newton meter of sliding, which corresponds to several hundred passes of the counterface. When sliding in water, the surface acquires a high friction coefficient (μ≈0.7) very rapidly. The difference in the lubricating properties of tribochemical surface layers on aluminum oxide and silicon nitride can be understood on the basis of the differing surface chemistries of these materials. We offer a tentative lubrication mechanism based on low adhesion between the oxide surface and the silicon nitride counterface and the structure of oxides grown inhumid ambients.
Fundamentals of Tribology at the Atomic Level
Authors: Ferrante John , Pepper Stephen V. 
Published: March 2011

AbstractTribology, the science and engineering of solid surfaces in moving contact, is a field that encompasses many disciplines: solid state physics, chemistry, materials science, and mechanical engineering. In spite of the practical importance and maturity of the field, the fundamental understanding of basic phenomena has only recently been attacked. In this paper we will attempt to define some of these problems and indicate some profitable directions for future research. We make three broad classifications: (1) fluid properties--compression, rheology, additives and particulates; (2) material properties of the solids--deformation, defect formation and energy loss mechanisms; and (3) interfacial properties--adhesion, friction chemical reactions, and boundary films. Research in the categories has traditionally been approached by considering macroscopic material properties. Recent activity has shown that some issues can be approached at the atomic level: that is, the atoms in the materials can be manipulated both experimentally and theoretically, and can produce results related to macroscopic phenomena. This experimental and theoretical activity is reviewed and related to the traditional research areas.
Surface Analysis of Fretting Damage in Electrical Connectors
Authors: Braunović M. 
Published: March 2011

AbstractA number of bolted-type tin-plated copper connectors commonly used for distribution transformers were examined using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDX). The connectors studied had been removed from service because of unsatisfactory performance under normal operating conditions as manifested either by overheating or instability.Detailed examination revealed the presence of extensive fretting damage in thecontacting surfaces. The fretting debris was composed mainly of tin oxide and oxidized base-metal particles. Localized melting and wear of the tin plating were also observed.
Monte Carlo Simulation of Adsorption of Di-Block Copolymers
Authors: Shih Wan Y. , Shill Wei-Heng , Aksay Ilhan A. 
Published: March 2011

AbstractIn this paper we are concerned with the morphology of the polymers adsorbedon surfaces, in particular di-block copolymers. Our work is motivated by the experimental findings of Fladziioannou et al. [1] on the steric forces between two adsorbed layers of di-block poly(vinyl-2-pyridine)\ polystyrene (PV2P\ PS) copolymer on mica surfaces. The PV2P block binds strongly on the mica surfaces and the PS block extends into thesolvent toluene (good solvent for PS). Hadziiouannou et al. found that the repulsive forces between the two surfaces start at a distance 1) larger than 10 times the radius of gyration RG of a free P' in toluene. Furthermore, the starting distance D increases with increasing degree of polymerization N of PS in a fashion I) ~ Na with a close to I. We,tudy the adsorption of di-block copolymer with Monte Carlo simulations. The Monte Carlo simulations are especially powerful in dealing with kinetics which is important in systems where hysteresis is observed II1 and cannot be appropriately taken into account by analytical (or numerical) calculations based onequilibrium assumptions.
Development of the Computer Controlled Seizure Testing Methodology
Authors: Dubrovsky R. , Shih I-Tsung 
Published: March 2011

AbstractIn this paper the computer controlled methodology and the testing apparatus were developed and designed to study seizure as a destructive wear. The seizure testing methodology is based on obtaining the power losses information in testing zone during any time of testing period. These losses are dueto the different friction coefficient in the area of load and sliding zone.They can be automatically recorded and recomputed into the friction force and\or friction coefficient. The friction force and\or friction coefficient - sliding distance relationship can be plotted and the starting point of mass transfer which results in increasing the friction coefficient can be detected. The test results are presented using developed methodology as well as traditional optical microscope and surfanalyzer.
Sliding Wear of Metallic Materials at 25 and 550 ºC.
Authors: Fischer A. 
Published: March 2011

AbstractA new wear tester for temperatures up to 1100ºC is introduced. Firstresults of sliding wear tests are shown and discussed. Due to enhanced tribooxidation at 550ºC the wear rates of one-phase materials are lower compared to those measured at 25ºC. The wear rates of hard phase containing alloys increase with temperature, because the metal matrices loose their capability of supporting the hard phases bringing about additional abrasion.
The Adhesion and Deformation Properties of CVD TiC Coated Bearing Balls Under Heavy Loads
Authors: Hanson Robert A. 
Published: March 2011

AbstractCVD TiC coatings on steel bearing balls have been demonstrated to improve conventionally lubricated instrument bearing performance and life, particularly where wear mechanisms predominate. Lightly loaded, approximately 1,400 (200 ksi) MPa maximum Hertz stress, coated bearing balls have run billions of load cycles without coating integrity failure. Data is presented to characterize the behavior of TiC coated steel balls under heavy loads, to approximately 4,200 MPa (605 ksi) maximum Hertz stress, for 175,000 load cycles. As in the lightly loaded tests, there was no indication of coating integrity failure, ie. cracks or delamination. At loads of 2,500 MPa (364 ksi) and above, somewhat below the elastic limit of the 440C substrate, there was evidence of plastic deformation of the coated surface.
Improvement of the Wear Resistance of Magnetic and Vitreous Substrates Coated with Thin Diamond Like Carbon Layers
Authors: Meunier P.L. , Texier F. Le , Coutellier J.M. , Mackowski J.M. 
Published: March 2011

AbstractResults of wear tests on VTR carried out on magnetic and nonmagnetic dummies coated with a thin (20-30 nm) diamond-like carbon are reported.The diamond-like carbon thin films have been obtained by two techniques : RF Plasma Deposition by decomposition of hydrocarbon and Dual Ion Beam Sputtering (DIBS). The first one is more suitable for vitreous materials such as S1O 2, Fotoceram, and magnetic material Sendust (FeSiAI) though DIBS technique turned out to be the proper candidate for polycrystallines Ferrite Substrates.A multilayer : diamond-like Carbon\Sendust\A120 3TiC dummy (25nm\3 itm\Substrate) tested on VTR tapes at 5 ms-1 exhibited a 3000 h life time without significant wear.
Utilization of Ultrasonic Measurements to Quantify Aging-Induced Material Microstructure and Property Changes
Authors: Doctor Steven R. , Bruemmer Stephen M. , Good Morris S. , Charlot Larry A. , Taylor T. Thomas , Boyd Donald M. , Deffenbaugh John D. , Reid Larry D. 
Published: March 2011

AbstractMany structural components are exposed to thermal environments that promote aging-induced changes in material microstructure and properties. The extent of these changes may lead to a reduction in the design safety factors and, as a worst case, premature failure of the component. In order to illustrate how nondestructive measurements can be used to indicate these changes, ultrasonic measurements were conducted on stainless steel. Specimens from a high-carbon, Type 304 stainless steel were subjected to various thermal treatments to introduce differing precipitation morphologies. Specimens were examined using transmission electron microscopy to quantify the size, density, and distribution of the precipitates formed. Ultrasonic measurements were performed to assess sensitivity to the change in precipitation levels. Shear-wave birefringence provided the most consistent measurements for tracking precipitate morphology changes. Birefringence velocity differences increased as precipitate size and density increased on grain boundaries and as additional precipitates formed in the matrix. The ability to nondestructively monitor the precipitation process is important since susceptibility to environmentally assisted cracking and low-temperature embrittlement correlated with this microstructural change.
A Study of Microdeformation and Creep-Fatigue Damage using Acoustic Emission Technique
Authors: Liu Yunxu , Li Xingren 
Published: March 2011

AbstractThis paper deals with the relationship between the plastic deformation damage and microstructure by means of Acoustic Emmission. The plastic deformation behavior of AISI 4340 steel of various microstructures was investigated in both the tensile and creep-fatigue testings with a view to providing new insights into properties of high performance steel. Based on Theory of Damage Mechanics, a creep-fatigue law was derived and formulated. The reason of early failure and the service life prophecy of high strength steels was studied.The damage micromechanism of four stages was studied by the optical microscope, scanning electron microscope, and microhardness tester. It seems that the nucleation and the growth of the voids at the martensiteferrite interface is the dominant mechanism of damage. The monitoring of Acoustic Emmission indicated that the plastic deformation did not appear in the circulating hardening stage. But in the circulating softening stage, the accumulation of the plastic deformation and the creep-fatigue damage become more and more severe. The total energy of Acoustic Emmission was successfully applied to measure the degree of the damage caused by the plastic deformation.