摘要:

AbstractAn overview of ion–surface interactions is presented, pertaining to their importance in modern thin film processing. The fundamentals of the physics of energetic ion–surface collisions are reviewed briefly, with particular emphasis on low energy ions (i.e. ion energies below 1 keV). Recent examples of ion assisted processes are discussed from the areas of sputtering, ion beam etching, and reactive ion etching. These examples demonstrate that by using low energy ions, advantage can often be taken of the beneficial effects of ion–surface bombardment in controlling film removal while minimising the adverse effects of ion induced damage to the film.MST/1690

ISSN:0267-0836    

DOI:10.1179/mst.1992.8.7.565

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractDiamond and diamondlike carbon films possess several unique characteristics that govern their tribological properties, in particular their high hardness and lubricity nature. In this paper, the influence of the deposition methods on the adhesion of the films and on their wear resistance and frictional properties is summarised. It is observed that the deposition technique contributes greatly to the variation in microstructure of the diamond or diamondlike carbon film. The multitude of tribotesters (pin-on-disc, reciprocating ball-on-plate, ball-on-three flat, etc.) used to evaluate these films also complicate the interpretation of the tribological performance and confuse direct comparisons of the deposition techniques. Also, the effect of non-diamond carbons and hydrogen in the film is elucidated in relation to the friction coefficient. The application of these films to rolling and sliding components in various industries is highlighted, together with their limitations. The hard brittle nature of the film makes it an excellent candidate in abrasive and erosive applications, but less desirable in rolling contact. Choice of substrate material is critical in order to support the film under high contact stresses.MST/1692

ISSN:0267-0836    

DOI:10.1179/mst.1992.8.7.574

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractLubricated sliding wear tests were carried out on various surface coatings that were deposited on AISI 52100 and M50 steel substrates. The coatings include titanium nitride (TiN) deposited via an ion plating process, an electroplated chromium termed thin dense chrome (TDC), and a vanadium carbide (VC) deposited via the Toyota diffusion (TD) process. The tests were carried out using a synthetic turbine oil at one sliding speed and stepwise loading until catastrophic failure of the coating occurred. Friction coefficients were measured throughout the test interval, which showed that the vanadium carbide coating produced the lowest values (less than 0·055). Furthermore, this coating process had the greatest load carrying capacity, followed by the ion plated TiN on the M 50 substrate. Optical and scanning electron microscopy revealed that each coating process exhibited a different wear mode. In the TiN and VC coatings, polishing occurred along with the formation of cracks perpendicular to the sliding direction. Portions of the TiN coating spalled off the substrate via a delamination process. The TDC coating exhibited only a polishing wear mode.MST/1691

ISSN:0267-0836    

DOI:10.1179/mst.1992.8.7.582

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractTi–6Al–4V titanium alloy, AISI 316L stainless steel, and UHMW (ultrahigh molecular weight) polyethylene are commonly used as friction materials in orthopaedic joint prostheses. The most interesting property of the titanium alloy is its high corrosion fatigue resistance. However, its friction and wear behaviour is unsatisfactory, even when rubbing against a soft material such as polyethylene; it cannot be used without a surface treatment. The 316L stainless steel has superior friction and wear characteristics, but its mechanical properties are inferior and crevice corrosion is often associated with wear. The UHMW polyethylene wears and flows. Wear is related to the surface properties, whereas creep is linked to the bulk mechanical properties. Ion implantation is a surface treatment mainly used in industry for increasing the wear resistance of metals, such as in cutting tools, and for changing the electrical or optical properties of ceramics and polymers. In the present work, the technique is applied to orthopaedic materials, to improve their surface properties and to increase the lifetime of the prostheses. The treatment does not deteriorate the bulk characteristics of the materials. As far as metals are concerned, structural modifications are produced in a thin layer of<1μm thickness. They depend on the implantation parameters, namely, nature of the ions, energy, dose, and temperature, and are analysed using glow discharge spectrometry and grazing incidence X-ray diffraction. For polymers, ion implantation leads to two different effects: a modification of the first atomic layers, which induces an increase in wettability, and a variation of the structure at greater depths, which influences the mechanical properties. These effects are analysed using specific methods such as electron spectroscopy for chemical analysis, electron spin resonance, and attenuated total reflectance infrared spectroscopy.MST/1689

ISSN:0267-0836    

DOI:10.1179/mst.1992.8.7.589

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractFrom the hot hardness test, information can be obtained concerning the time dependent flow, or creep, of the material beneath the indenter. Analysis of these data for selfsimilar indentation (i.e. indentation using a pyramid or cone) leads to equations from which the power law creep exponent and activation energy for creep can be derived, within limits imposed by the approximations of the method. The technique is used to analyse hot hardness data for metals and ceramics, drawn from a number of sources.MST/1484

ISSN:0267-0836    

DOI:10.1179/mst.1992.8.7.594

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractA theoretical analysis of the annealing behaviour of irradiation damage in the form of mixed distributions of dislocation loops, voids, and bubbles is presented. Two limiting cases are considered. The first is where no external vacancy sources and sinks exist, such that vacancies are conserved during the annealing process and the second is where such sources and sinks do exist. Numerical examples are given and comparisons are made with the annealing behaviour of an irradiated reactor component. The influence of an applied stress on the annealing behaviour is evaluated.MST/1592

ISSN:0267-0836    

DOI:10.1179/mst.1992.8.7.602

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractSuperplastic forming of AA 7475 aluminium alloy sheets of grain size ~15μm has been studied by imposing hydrostatic back pressures of between 0·1 and 2·86 MPa. Qualitative and quantitative studies of the effect of hydrostatic pressure on the cavitation of the alloy were carried out on formed domes. On the diametral section of a dome, cavities were mainly found in the centre of sheet thickness, where the grains were coarser than those near the surface. Dome height at failure was significantly increased by imposing hydrostatic back pressures during superplastic forming. For domes that were formed into top hat shapes, a maximum height/base radius ratio of 2:1 was obtained under a hydrostatic pressure of 2·86 MPa. Flat tensile testpieces were machined from top hats to evaluate the room temperature mechanical properties. It was found that the postformed ductility deteriorated with superplastic strain more rapidly than did the ultimate tensile strength. The effect of surface grooves, which were observed in formed domes and top hats, on postformed properties was also examined.MST/1576

ISSN:0267-0836    

DOI:10.1179/mst.1992.8.7.611

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractThe microstructural evolution of a 12 wt-%Cr steel (3CR12) during cooling from a solution heat treatment at 1380°C has been investigated. Emphasis has been placed on determining the microstructural factors responsible for the persistent occurrence of grain anisotropy in this steel. Energy dispersive X-ray spectroscopy was used to determine the composition of the phases resulting from the solid stateδferrite to austenite transformation. It is shown that the high temperatureδferrite phase partially decomposes to austenite via a Widmanstätten growth mechanism and consequently a banded two phase structure is produced after hot rolling. The element partitioning, which arises during the solid stateδferrite decomposition, leads to irreversible compositional banding. An empirical model is proposed for the events leading to the generation of the banded phase structure and the formation of an elongated ferritic microstructure in 3CR12 after subcritical annealing.MST/1500

ISSN:0267-0836    

DOI:10.1179/mst.1992.8.7.621

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractStress relaxation tests were carried out over the temperature range 800–1000°C to study the precipitation of Nb(C,N) in a family of high strength low alloy steels. The effects of addition of boron (~0·003 wt-%), amount of deformation (0, 5, and 25%), and holding time on the kinetics, nature, and size distribution of the strain induced Nb(C,N) precipitates were investigated. Specimens were quenched at various stages of the stress relaxation process and then examined using transmission electron microscopy and electron energy loss spectroscopy (EELS). The evolution of the size distribution indicated that the presence of boron accelerates the kinetics of precipitation and leads to a finer and more dense distribution. The presence of boron in the large undissolved TiN particles was not detected using EELS; by contrast, a boron peak was observed in the strain induced Nb(C,N) precipitates. The latter were of cuboid shape and were heterogeneously distributed. The particle size measurements are consistent with a parabolic law for the growth of the precipitates. The diffusion coefficient of niobium, in the presence and absence of boron, was estimated in this manner and it is concluded that boron does not significantly affect the growth and coarsening of the precipitates. Instead, boron intervenes in the nucleation stage and increases the rate of nucleation.MST/1279

ISSN:0267-0836    

DOI:10.1179/mst.1992.8.7.628

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractThe laser surface alloying process was used to introduce two different alloying materials, tungsten carbide (WC/Co) and carbon, into the molten surface of a case hardening steel (16MnCrS5), to improve its hardness and wear resistance. The chemical composition and the resulting microstructure in the alloyed layers were of particular interest in this investigation, because the strengthening mechanism was strongly dependent upon the type and amount of the alloy material. For laser alloying with carbon the increase in hardness and wear resistance was based on the martensitic transformation in the composition range concerned. For alloying with tungsten carbide it was necessary to consider two different strengthening mechanisms, namely, martensitic transformation and precipitation of carbides. In both cases the grain refinement in the laser affected zone had an additional effect. Resistance to dry abrasive sliding wear was measured using a conventional pin-on-disc wear testing machine. For both alloy materials the wear rate was substantially lower than that of a substrate that had been laser remelted without alloying additions.MST/1556

ISSN:0267-0836    

DOI:10.1179/mst.1992.8.7.637

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor