bluuebunny/crossref_metadata_2025 huggingface dataset:
Wear Criteria of Cold Forging Tools
Authors: Dubar M. , Dubar L. , Dubois A. , Verleene A. , Oudin J.
Published: May 2005

In the cold forging industry, the tooling makes an important contribution to the cost price of the forged pieces. Predicting the degradation of the tools would constitute a significant advantage. A possible definition of tool life is when the roughness parameters of the formed pieces exceed fixed criteria, at which point the tool must be replaced or polished. In order to quantify the surface integrity of the tool, a new methodology of analysis has been developed by measuring the roughness of the formed piece. The upsetting sliding test is used to reproduce the contact conditions of the studied process in the laboratory. It allows quantification of the scatter in the friction coefficients caused by wear, and observations of the formed pieces and the wear of the tool surface. An industrial application using the AISI M2 tool steel is studied. It is shown that the tool wear can be predicted by measuring the roughness parameters of the workpiece. The application of the methodology allows the lifetime of the tool to be predicted before forming any workpiece.
A Comparative Study of Plasma Sprayed Coatings on Railway Brake Discs
Authors: Bartys H. , Guerin J.D. , Watremez M. , Bricout J.P.
Published: May 2005

In the railway context, increasing the number of trains in service relies in the development of new equipment. This objective requires increased peak speeds at the expense of stronger motorisations. The axle loads are thus heavier, especially for the new double-decker trains. These parameters have significant effects on the brake system in terms of size, non-suspended masses, and therefore energies to be dissipated. The constituent materials of the friction brakes of some railway equipment (full non-ventilated steel alloy discs for the TGV, for example) have thus reached their technological limits in terms of energy to be dissipated for fixed mass and size. It is therefore necessary to find more powerful braking devices using new materials. The Laboratoire d'Automatique et de Mécanique Industrielles et Humaines (LAMIH) has therefore decided to focus its research towards high energy full discs. This approach consists of coating the steel discs with low thermal diffusivity friction materials that have very strong and stable mechanical and tribological characteristics at high temperature. Using blown thermal plasma, the LAMIH has already tested reduced scale C38 discs coated with NiCr–Cr3 C2 cermet facing an Al2 TiO5 pad. Henceforth, studies relate to cobalt or nickel based superalloys obtained by the transferred plasma process with a view to making a reliable coating–substrate bond. Performance is evaluated in terms of friction factor, wear, contact temperature, and reliability.
Joint Second Prize Low Temperature Plasma Nitriding of 316 Stainless Steel – Nature of S Phase and Its Thermal Stability
Authors: Li X.Y.
Published: May 2005

Conventional plasma nitriding of stainless steels (at approximately 550°C) confers significant hardening of the treated case but at the expense of the corrosion resistance. Attempts have been made in the past decade to achieve combined improvements in wear and corrosion resistance of austenitic stainless steels (ASS) via low temperature thermochemical processes. However, varying degrees of success have been achieved in applications, which may be largely attributed to the lack of scientific understanding of the nature of the S phase and its thermal stability. The present work concerns two aspects of low temperature plasma nitriding of austenitic stainless steel: the study of the nature of the S phase and the thermal stability of the low temperature plasma nitrided layers on austenitic stainless steel. To achieve these tasks, systematic low temperature plasma nitriding of austenitic stainless steel has been carried out. The structure of the S phase was systematically investigated. The thermal stability of the low temperature plasma alloyed layers on stainless steel was studied employing both long term isothermal annealing and TEM in situ heating observations.
Micro-Impact Testing: A New Technique for Investigating Thin Film Toughness, Adhesion, Erosive Wear Resistance, and Dynamic Hardness
Authors: Beake B.D. , Goodes S.R. , Smith J.F.
Published: May 2005

A small scale probe testing method has been developed for investigating the behaviour of thin films under dynamic loading conditions. The primary objective of the development was to produce quantifiable techniques that closely simulate the conditions that thin films experience in service. Variations of the technique allow measurements related to: impact wear and adhesion failure, erosive wear resistance, fracture toughness, work hardening, and dynamic hardness. The common element in each variant is the acceleration of a test probe (usually diamond) towards the specimen surface and the monitoring its instantaneous position before and after collision. The impact energy can be controlled and either single impacts or multiple impacts can be produced. For single impacts, the energy delivered to the contact point can be quantified, allowing calculation of a dynamic hardness number.
Raman Studies on Surfaces of Artefacts
Authors: Coupry C. , Lautié A.
Published: May 2005

Raman microspectrometry is particularly suitable for the study of the surfaces of artefacts. This article outlines the advantages of this vibrational technique. Its capability for the identification of the compounds in the surface layers is illustrated by applications on wall paintings and dyed textiles, and the historical implications of the results are discussed.
Discoloration of Pigments Induced by Laser Irradiation
Authors: Zafiropulos V. , Stratoudaki T. , Manousaki A. , Melesanaki K. , Orial G.
Published: May 2005

Laser irradiation may alter the colour of certain pigments used in artwork. Owing to the increasing use of lasers in artwork conservation this problem becomes extremely crucial, especially in the case of a polychromy covered by environmental encrustation. X-ray diffraction analysis and optical microscopy were used to study the crystalline structure of selected irradiated pigments in order to identify the changes that take place upon laser irradiation. Two representative pigments were studied, cinnabar (HgS) and lead white (Pb(OH)2 .2PbCO3). The results revealed a change in the crystalline phase or chemical composition, respectively, which can be barely detected owing to its superficial character, which is of a nanometre scale.
Hybrid Sol–gel Clear Coatings for Decoration Brass Profiles
Authors: Dumont B. , Thiery R. ,   Welter J.-M.,   Duterne J.-P.
Published: May 2005

Frequently, it is desired that the original reddish to gold tones of copper, brass, and bronze surfaces are preserved when they are used in decorative areas, which are mainly interiors, but are also in architectural elements exposed to the environment. This can be achieved by applying a clear protective coating that not only creates a weather barrier, which prevents further deterioration of the surfaces, but also protects the surfaces against mechanical aggressions such as abrasion (dust), rubbing (during cleaning), or scratching. The objective of this work was to evaluate the relative performance of clear coatings: the acrylic varnish Incralac and a hybrid sol–gel coating, and some hard coatings (TiN and TiZrN) obtained by ionic deposition. The wear resistance of the three types of protective layers was investigated with linear scratch and abrasion tests. The results indicated great improvements in the wear resistance of brass by applying the hybrid sol–gel coating. The tested varnish, known for its high corrosion resistance, had very poor wear resistance. For hard coatings negative results observed for corrosion and abrasion resistance can be explained by the layer being too thin and porous. The hybrid sol–gel coating gives the best compromise in terms of tarnishing, corrosion (salt spray and atmospheric exposure), scratching, wear, application, aestheticism (coloration, brightness), and cost.
Electrolytic Deposits on Stainless Steel as High Temperature Coatings
Authors: El Hajjaji S. , Ben Bachir A. , Aries L.
Published: May 2005

Conversion coatings modified by deposits of alumina, with or without zirconium, calcium, or strontium additions, have been studied as a way of improving the thermal oxidation resistance of a 17Cr ferritic stainless steel. Conversion coatings, characterised by a particular morphology and strong interfacial adhesion with the substrate, facilitate the electrochemical deposition of ceramic layers and enhance their adhesion to the substrate. After heating, the coatings present a continuous composition gradient with refractory compounds at the surface. The influence of added elements (Zr, Ca, or Sr) on the behaviour of the alumina coating was investigated at 1000°C. Calcium improved the protective character of the alumina coating. The morphology and chemical composition of the different deposits were also analysed and results on the thermal stability of such coatings on Fe–17Cr ferritic stainless steel are presented.
Surface Modification Issues in Art
Authors: Espié L. , Aucouturier M.
Published: May 2005

Surface modification of art and patrimonial objects may be considered from very various viewpoints including archaeology, history of techniques, restoration, and conservation. The use of conventional or particular surface techniques has to be adapted to the specific object for possible non-destructive characterisation, non-invasive restoration, or prevention of future degradation. The present paper will first define the intervention field in the laboratory for such issues as surface assessment, techniques of restoration, and conservation recommendations. It will point out the status of patrimonial objects and the authorised range of each scientific investigation. A methodological analysis of various methods for surface characterisation and surface treatments will be proposed. The methods described will be illustrated by some examples: surface assessment of a prestigious museum bronze object, development of a programme for the restoration and conservation of silver museum artefacts, and research in progress on the understanding of the role of the surface in the quality of musical instruments.
Characterisation of Surface States on Patrimonial Works of Art
Authors: Elias M. , Menu M.
Published: May 2005

A gonio-spectrophotometer is used to analyse the backscattered light in the visible range from a 0·3 cm2 surface. The measurement is non-destructive, without contact and can be implemented in situ. For a metallic surface, the reflected intensity is measured as a function of the backscattered angle. The probability density of the normal to the surface is then deduced. The ratio roughness root mean square/correlation length is calculated. The method is applied to characterise the different techniques for applying gold backgrounds in primitive European paintings. For a non-metallic surface, the reflected intensity is measured as a function of the wavelength. The spectrum is compared with a database of mineral pigment spectra. The comparison allows the pigments to be identified and, moreover, to deduce the surface state of the painting layer. Examples of Egyptian and modern paintings will be presented.
Surface Modification Processes on European Union Bronze Reference Materials for Analytical Studies of Cultural Artefacts
Authors: Beldjoudi T. , Bardet F. , Lacoudre N. , Andrieu S. , Adriaens A. , Constantinides I. , Brunella P.
Published: May 2005

This paper presents research results obtained in the 4th Framework Programme (1994–1998) of the Standards, Measurements, and Testing Programme of the European Union, DG XII: ‘Improvement of means of measurements on archaeological copper alloys for characterisation and conservation’ (IMMACO) project. One of the aims of this project was to study copper alloy compositions of European objects dating from the Bronze Age to Roman times. This work has revealed that five types of alloy seem to be particularly representative of what was produced in Europe during this period. These alloy compositions will be certified as reference materials by the European Union. In the second part, artificial patinas have been made on the different bronze alloys using electrochemical polarisation as the surface modification technique. The characterisation of the corrosion surfaces and interfaces formed during the treatment with light microscopy and scanning electron microscopy (SEM-EDX, X-ray mapping) have shown that the artificial patinas seem to be very close to those from excavations. As a consequence the patinated specimens can be used as a substitute for genuine artefacts in the future to improve conservation techniques.
Characterisation and Location of Original Surface of Corroded Metallic Archaeological Objects
Authors: Bertholon R.
Published: May 2005

This paper aims to show different ways the original surface of archaeological metal artefacts can be preserved in the corrosion products. Depending on the corrosion mechanism, the original surface can be located owing to some features that can be used as clues. These feature include the remains of metallurgical structure fossilised in the corrosion products, the content of elements either coming from the soil or from the original alloy, and cleavage occurring at some corrosion interface. Moreover, some of the features of the corrosion layers can be compared with what happens at the very beginning of the corrosion process despite a relative gap in knowledge as regards the very long term corrosion mechanisms.
Investigation of Ti1-x Alx N Films as Diffusion Barrier Between Cu and Si
Authors:   Lii D.-F.,   Huang J.-L.,   Tsai W.-K.,   Lo W.-T.,   Yau B.-S.
Published: May 2005

Films of (Ti,Al)N have been grown onto Si(100) by direct current reactive magnetron sputtering from a Ti–Al alloy target (Ti/Al=90/10 at.-%) at different nitrogen flowrates and bias voltages. The effects of nitrogen flowrate and bias voltage on the electrical resistance of Ti1-x Alx N films were studied. The feasibility of using Ti1-x Alx N films as a diffusion barrier between Cu and Si was investigated. Results indicated that the atomic ratio of Ti/Al decreased, however nitrogen increased with an increase in the nitrogen flowrate. A higher critical nitrogen flowrate was required to obtain the stoichiometric composition for Ti1-x Alx N films deposited under lower bias voltages. The resistivity of Ti1-x Alx N films was substantially affected by the effects of stoichiometric structure and grain size. Results of sheet resistivity and Auger electron spectroscopy suggest the feasibility of using Ti1-x Alx N as a diffusion barrier material between Cu and Si up to 700°C.
Surface Modifications in Aerospace Applications
Authors: Kaysser W.
Published: May 2005

The long service life, often in harsh environmental conditions, and the stringent requirements of lightweight design make surface modification an essential part of materials technology for aerospace applications. Six contemporary developments are described, which are representative of advances in corrosion protection, fatigue life extension, metal matrix composite (MMC) based new design, and enhanced temperature capabilities by ceramic protective coatings. Coatings and corrosion inhibitors for aluminium skinned aircraft provide survivability, corrosion protection, and cosmetic appearance. Environmental concern on the presently used chromate have led to developments of self-priming topcoats, flexible primers, e.g. based on self-assembling silane molecules, temporary and multifunctional coatings. Fatigue life of titanium parts is shown to be enhanced by laser shock peening introducing compressive surface stresses. Preventing the onset of fatigue cracking from surfaces of titanium alloys and titanium aluminides is also the purpose of recently developed coatings, which hinder oxidation and oxygen penetration into titanium. Oxidation is also a major degradation problem of C/C and C/SiC composites. Classical protective coatings based on SiC are continuously complemented by multilayer coatings including, for example, yttrium silicates. The basis for future enhanced thermal barrier coatings may be provided by alternative ceramics such as lanthanum hexaluminates and an improved understanding of their damage mechanisms.
Preparation and Characterisation of Biocompatible Vitroceramic–Metal Systems for Applications in Medicine
Authors: Britchi M. , Olteanu M. , Jitianu G. , Branzei M. , Gheorghe D. , Nita P.
Published: May 2005

Vitroceramic coatings from the oxide system SiO2–CaO–Na2O–B2O3-TiO2 were obtained on metallic supports (titanium and austenitic steels with high Cr and Ni contents). The coating technology was classical enamelling. The metallic support is coated by either immersion or painting with a slurry layer resulting from a mixture of a frit (having the best oxide composition for each metallic support) with a liquid, fired at the enamelling temperature and then subjected to a thermal treatment for crystallisation. Good adherence between the two different materials is achieved when their thermal expansion coefficients are close to each other. The vitroceramic coating–metallic support system was characterised by optical microscopy, SEM, and X-ray diffraction. The adherence of the vitroceramic layer to the metallic supports was determined using microhardness tests carried out at the interface. Evidence of the processes occurring at the interface (gas bubbles, micropores, chemical binding, etc.) was also found. The coating layers are types of biocompatible and bioactive vitroceramic materials.
Comparative Study of Mechanical Properties and Residual Stress Distributions of Copper Coatings Obtained by Different Thermal Spray Processes
Authors: Gassot H. , Junquera T. , Ji V. , Jeandin M. , Guipont V. , Coddet C. , Verdy C. , Grandsire L.
Published: May 2005

In this work, the influence of the thermal spraying processes, atmospheric plasma spraying (APS), high velocity oxygen fuel (HVOF), and vacuum plasma spraying (VPS), on the microstructure and properties of copper coatings is discussed. The differences in microstructure, microhardness, and residual stress for each type of coating are shown. The X-ray diffraction (XRD) method is used to evaluate the mechanical anisotropical characteristics of the materials and the residual stress distribution. The particularity of this study is that the thickness of the coating is of the millimetre scale; the massive coating specimens without a substrate were obtained for XRD microelastic modulus measurements and for macrotensile measurement. Microhardness distributions have been obtained in coatings and in substrates that pass through the interface zones. It was observed that dense coatings could be obtained by industrial processes such as APS and HVOF, but they induce oxidation in the copper coating. The copper oxidation is limited in the VPS process. The elastic modulus values measured by the in situ XRD method show that the HVOF coating has more rigidity than the APS coating. HVOF and VPS copper coatings have higher microhardness values than the APS copper coating. The residual stress values are in traction in the APS, VPS, and HVOF coatings: the residual stress level in the HVOF and APS coatings is less important than that in the VPS coating. The microstructure observations show that the VPS copper coating has a recrystallised structure whereas the APS and HVOF copper coatings have a splat type structure. As a consequence, the VPS copper coating has a high Young's modulus, an important mechanical resistance, and a high elongation as compared with the other copper coatings.
Microstructure and Phase Composition of Microarc Oxidation Coatings Formed on Ti–6Al–4V Alloy in Aluminate Solution
Authors: Xue W. , deng Z. , Ma H. , Chen R. , Zhang T.
Published: May 2005

A dense ceramic oxide coating, about 50 µm thick, was prepared on a Ti–6Al–4V alloy by alternating current microarc oxidation in an aluminate solution. Its microstructure and phase composition were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The oxide coating contains two layers: an outer layer and a dense internal layer. The coating is mainly composed of TiO2 rutile and TiAl2O5 spinel phases. In the outer layer coating, the TiAl2O5 fraction is much higher than the rutile fraction. However, in the internal layer, rutile becomes the main phase while the TiAl2O5 fraction decreases significantly. During microarc oxidation, local melt–solidification processes take place in the coating, however, the microstructure of the Ti–6Al–4V substrate near the coating/metal interface is not changed. Aluminium from the solution is enriched in the outer layer coating, although it has also diffused into the interior of the coating.
Effect of Ni Interlayer on Corrosion Behaviour of Crn Pvd Coating Deposited onto Plastic Mould Steels
Authors: Steyer P. ,   Millet J.-P., Anderbouhr S. , Jacquot P.
Published: May 2005

The plastics industry commonly uses moulds made of steels containing MnS inclusions. These inclusions play the role of heterogeneities, which make manufacturing easier. Moreover, these types of alloy are thermal treatment free, cheap, and easily available. Unfortunately, their use in corrosive conditions is prevented owing to the poor corrosion behaviour of the MnS particles. In order to mask these highly sensitive inclusions and to enhance the surface mechanical properties, hard physical vapour deposition (PVD) CrN coatings, elaborated at two different temperatures, have been used. The coated specimens have been tested in saline corrosive solutions using electrochemical techniques. Corrosion results from dissolution of the anodic substrate through coating porosity, inherent to the PVD process, which leads to the deposit peeling off. The aim of the present study is to determine the corrosion resistance of an underlayer electroless nickel deposited coating on a 40CrMnMo8S substrate coated with PVD CrN.
Need for Environmentally Friendly Surface Modification Technology in the Japanese Automotive Industry
Authors: Okuno K. , Bessho T.
Published: May 2005

The environmental impact of the automotive industry needs to be addresses if it is to remain a viable mode of transport in the 21st century. There are a number of areas where the adverse environmental effects of car production and use can be reduced. These include reduction in waste from the production process, improving fuel efficiency, reducing CO2 emissions, and recycling car parts after use. This paper describes some of the environmental regulations being introduced and particularly focuses on the environmental factors regarding surface modification technologies in the automotive industry. The ways in which current surface finishing practices can be improved to reduce the environmental impact are described along with the ways in which surface technologies can be used to enhance the performance of lightweight materials for use in fuel efficient vehicles. The need to develop new surface technologies to find replacements for environmentally harmful materials is also highlighted.
Cleanliness Verification and Defining Acceptable Cleanliness Levels
Authors: Chawla M.K.
Published: May 2005

The key to surface finishing is a ‘properly’ prepared surface. Defining and maintaining the surface preparation at ‘proper’ levels is, at best, subjective. Often the failure of surface preparation processes is not discovered until problems, such as poor adhesion, occur downstream resulting in non-conformance owing to poor quality surface cleanliness. To assure consistent quality of surface cleanliness, it is important to define how clean the surface has to be. This paper discusses the types of contamination, the most common surface cleanliness measuring/verification techniques, factors affecting the choice of cleanliness measuring/verification techniques, and a structured approach to defining the ‘acceptable level of cleanliness’. In short, this paper discusses the ways to define how ‘clean’ is clean.
Cleanliness Standards and Defining Acceptable Cleanliness Levels: Analytical Techniques, Particulate Monitoring, and Successful Analytical Testing
Authors: Kanegsberg B.
Published: May 2005

A clean surface can be critical in surface engineering processes. Particles on the surface may interfere with the surface modification process causing defects and poor performance. Therefore, the level of cleanliness required in a particular application is defined by the final product performance and appearance. This paper describes a number of analytical techniques that are used to assess the cleanliness of a surface. Practical examples are also given of how these techniques have been used in industry to investigate problems associated with maintaining cleanliness levels and to identify sources of contamination.
Removal of Submicrometre Alumina Particles from Silicon Oxide Substrates
Authors: Moumen N. , Busnaina A.A.
Published: May 2005

In this paper, two techniques were used for the removal of submicrometre sized alumina particles used in post-CMP (chemical mechanical polishing) applications. Alumina particles were deposited onto a silicon oxide wafer by dipping the wafer in the CMP slurry and then spin drying them. Megasonic cleaning and brush cleaning techniques were used to remove the slurry residue. The removal efficiency of each technique (contact and non-contact) was evaluated as a function of the process parameters. The removal of particles was studied as a function of the cleaning parameters including temperature, cleaning time, and megasonic power in the case of megasonic cleaning, and brush pressure, rotational speed, and cleaning time in the case of brush cleaning. The results show that both cleaning techniques can be effective in removing slurry residue under certain conditions. Longer cleaning times and higher pressures had adverse effects on contact cleaning. Similarly, longer times and higher megasonic power had adverse effects on non-contact cleaning.
Surface Treatments and Coatings in the Steelmaking Industry – from Metallurgy to Processing
Authors: Nicolle R. , Guttmann M.
Published: May 2005

This review presents the main trends and achievements in the field of steel surface treatments, from metallurgy to processing. Development of new surface observation methods, by improvement of resolution and structure quantification, have led to a better insight into the metallurgy and physical chemistry of surfaces and to a detailed description of reactions. Reaction kinetics have been derived from numerous in situ kinetics experiments resulting in fine reaction and reactor modelling. Industrial operation of surface treatments has been characterised through direct measurements, residence time distribution (RTD), and cold models or hot pilots. They give important information for the validation of computation fluid dynamics (CFD) models. Such measurements of temperature, fluid composition, and velocity will confirm the local distribution of the process variables. All these results are being integrated into online process simulators for fully controlled surface treatments.
Role of Overlapping Passes on Fatigue Performance of Microalloyed 17MnCuNi7 Steel Treated by Continuous CO2 Laser Beam
Authors: Jeddi D. , Sidhom H. , Lieurade H.P. , Nizery F. , Fabbro R.
Published: May 2005

The widely used surface treatment by continuous CO2 laser beam requires superposition of several laser passes, which can lead to a softened zone and to the creation of tensile residual stresses in overlapping passes. In this study, the effect of overlapping passes, microhardness, and metallurgical transformations on the fatigue performance of 17MnCuNi7 steel has been investigated by three series of bending fatigue tests corresponding to three types of continuous CO2 laser beam treatments. It has been concluded that suitable selection of material and control of the laser treatment parameters provides for the elimination of tensile residual stresses in softened zones, and can lead to homogeneous hardening of the surface. The fatigue limit of 17MnCuNi7 steel depends mainly on the residual stress in the layers affected by laser treatment, despite any hardness loss caused by overlapping passes. The improvement made by this treatment varies from 10 to 20% compared with the fatigue limit in the tempered state.
Microstructure Formed in Body Centred Cubic Metals by Laser Shock Processing
Authors: Kaspar J. , Luft A.
Published: May 2005

This paper reports on a comparative study of the microstructural changes occurring within body centred cubic (bcc) metals (iron, molybdenum, and tantalum) by laser shock processing with different laser systems (titanium: sapphire laser and excimer laser). Using different complementary metallographic and electron microscopic investigation methods it is shown how the processing parameters (pulse duration and number of impacts) and the applied ablation mode (direct or confined ablation) influence the microstructure and hardness of these metals. The studies revealed that distinct as well as long range plastic deformation and hardening in iron, molybdenum, and tantalum can only be obtained by laser shock processing with nanosecond pulses in confined ablation mode using a thermo-protective coating. For all the metals investigated, slip and deformation twinning were observed to be active modes of deformation, though the microstructural changes and the degree of shock induced hardening depended on the material being treated. It is shown that the shock induced hardening increases with an increasing numbers of laser impacts. This strengthening is attributed to an increase in overall dislocation density.
Basic Study on Laser Ablation Surface Cleaning of Nuclear Facility
Authors: Zhou X. , Imasaki K. , Furukawa H. , Umino H. , Sakagishi K. , Nakai S. , Yamanaka C.
Published: May 2005

An ultra short pulsed Nd:YAG laser was employed to study the ablation effects and laser beam transport in optical fibres. Using 13 µm Zn coated carbon steel as a target, the relationship between ablation rate and laser fluence was investigated, and optimal processing conditions were determined. The laser induced products consisted of vapour and liquid particles. It was found that a smaller incident laser angle was more suitable for protecting the focusing lens from the pollution of the ablated products. The collection rate of the ablated products almost reached 100%. Additionally, a laser beam of over 5·6 W in power with a transportation rate of nearly 90% was output at the end of a 20 m long optical fibre. By this output power, a Zn coating of the same thickness could be completely ablated. A decontamination factor was introduced to estimate the cleaning effects of laser ablation, and satisfactory cleaning was obtained
Model of Structure of Al2O3 Layer Obtained Via Hard Anodising Method
Authors: Skoneczny W.
Published: May 2005

In the present paper, a model has been developed for the structure of an oxide layer obtained on aluminium as a result of the hard anodising process, which is widely used in industry. As a result of such processing, oxide layers with thicknesses within the range 30–100 µm (under certain conditions even up to 250 µm) can be obtained. It is worth noting that the oxide coatings obtained by this method on aluminium exhibit only a small level of porosity and have a high hardness. According to the method proposed, oxidation is carried out in a ternary water electrolyte called SAS, which contains sulphuric acid, adipic acid, and oxalic acid.
Joining of alumina ceramics to metals
Authors: Hafez K. M. , El-Sayed M. H. , Naka M.
Published: May 2005

The application of ultrasonic waves enhanced the wetting of alumina by Zn–Al filler alloy. Alumina ceramic was brazed to different metals such as Ti, Ni, Nb, Fe, and AISI 304 stainless steel using the Zn–5 mass-%Al brazing filler alloy. Different reaction products were formed at the alumina–metal interfaces, including solid solutions and intermetallic compounds. The alumina–Nb joint exhibited the highest bond strength value among the different couples, because Nb produces the lowest residual stress among the alumina–metal joints. The high mismatch in thermal expansion coefficient between the brazing filler and the AISI 304 stainless steel yielded the lowest bond strength among the joints.
Gas metal arc welding process with periodic control of shielding gas composition
Authors: Nakamura T. , Hiraoka K. , Takahashi M. , Sasaki T.
Published: May 2005

A shielding gas composition-controlled (SGC) welding process has been developed in which shielding gas composition changes periodically. This welding process has been successfully developed on the basis of computer simulation. A simulation model incorporating periodic change of shielding gas composition has been proposed and verified by welding experiments and observation of wire tip behaviour. In order to change shielding gas composition effectively, CO2 gas is locally and periodically introduced into Ar + 2%O2 shielding gas. As a result, CO2 and MIG arcs occur periodically during welding and the arc pole strongly oscillates over the groove wall. Oscillation control of the arc pole can be achieved by this shielding gas composition-controlled method. This newly developed welding system makes it possible to perform stable welding in narrow V-grooves and excellent welding joints are obtained with good fusion.
Study of grain size and microhardness of submerged arc welded joint of AISI 1060 steel
Authors: Pathak A. K. , Datta G. L.
Published: May 2005

Change in microstructure, grain growth, hardness and residual stress in a weldment are very much dependent on the temperature distribution, peak temperature and cooling rate. In the present work, three-dimensional transient finite element analysis has been used to predict the cooling rate and peak temperature at different points of the submerged arc welded joint. Grain size and microhardness of the submerged arc welded joint of AISI 1060 steel were experimentally measured and explained on the basis of estimated peak temperatures and cooling rates.
Laser welding of zinc coated steel in overlap configuration with zero gap
Authors: Pieters R. R. G. M. , Richardson I. M.
Published: May 2005

In the automotive industry, the use of zinc coated sheet steel is rapidly increasing as a result of consumer demand for improved corrosion resistance of automobile bodies. Laser welding of these zinc coated steels is currently under investigation with a strong emphasis on the overlap joint geometry. In the work presented in the present study, continuous wave laser welds have been performed on zinc coated steels in overlap configuration without a gap. It is shown that with suitable parameters, no detrimental effects occur as result of zinc vapour formation. Furthermore, a preliminary explanation is given indicating why stable welding is possible for certain power–speed combinations while in other cases it fails. From the results of this work, it can be concluded that stake welding of zinc coated steel is possible without the need for a gap or special beam manipulation techniques.
Effect of welding process and groove angle on type IV cracking behaviour of weld joints of a ferritic steel
Authors: Albert S. K. , Tabuchi M. , Hongo H. , Watanabe T. , Kubo K. , Matsui M.
Published: May 2005

Creep tests were carried out at 923 K and various stress levels on weld joints of 11CrMoWVNb (P122) steel prepared via gas tungsten arc, electron beam, and laser welding processes. All the weld joints exhibited typical type IV cracking. However, the rupture life of the weld joints was found to increase with decreases in the width of the heat affected zone (HAZ) and the groove angle. A comparison of the results with those for the simulated fine grained HAZ (FGHAZ) revealed that the creep damage and the type of fracture of the weld joint differ considerably from those of the simulated FGHAZ specimen. In the weld joints fracture was characterised by low ductility and formation of creep cavities, whereas the FGHAZ specimens exhibited good ductility and hardly any creep cavities were observed in them. These differences are attributed to the presence of a triaxial stress state in the weld joints, due to the existence of zones such as parent metal, weld metal, FGHAZ, and coarse grained HAZ, which differ considerably in their creep properties. Changes in the width of the HAZ or the groove angle of the joints alter the stress state in the weld joint, leading in turn to corresponding changes in the creep behaviour of the weld joints. Finite element analysis of the stress–strain distribution in the weld joint specimens during creep also confirmed these influences.
Continuous welding of Cu–Ni dissimilar couple using CO2 laser
Authors: Phanikumar G. , Dutta P. , Chattopadhyay K.
Published: May 2005

The evolution of microstructure during continuous laser welding of dissimilar metals has been studied for a binary Cu–Ni couple. The effects of laser beam scan speed and laser power on the shape and size of the melt pool, the weldment–substrate interface, the composition profiles, and microstructures of the weldments have been investigated. It is shown that the melt pools exhibit a characteristic asymmetry in shape. The observed microstructure is characterised by the existence of compositional and microstructural variations leading to a banded appearance suggesting localised mixing. Distinct differences exist in the evolution of the microstructure in the copper and nickel sides of the weld pool. An attempt is made to explain some of the experimental observations using thermodynamic and thermal transport arguments.
Microstructure and bend strength of WC–Co and steel joints
Authors: Wang H. , Yang D. , Zhao X. , Chen C. , Wang Q.
Published: May 2005

Tungsten inert gas arc welding of WC–30 wt-%Co cemented carbide and steel was carried out using a variety of filler alloys. Precipitation of Fe3W3C occurred at the joint interface and this reduced the bend strength and toughness of the welded joint. The problem could be alleviated by adjusting the carbon concentration of the filler metal.
Influence of post-weld solution treatment on mechanical properties and microstructure of fusion zone of cobalt free maraging steel weldment
Authors: Kumar D. Siva , Sinha P. P. , Prabhu N. , Prabhugaunkar G. V.
Published: May 2005

Post-weld solution treatment (PWST) was carried out on gas tungsten arc weldments of a cobalt free maraging steel. A substantial increase in fusion zone toughness was observed after PWST. It was established that the increase in fusion zone toughness was due to a reduction in austenite content of the fusion zone. The volume fraction of austenite decreased with increasing solution treatment temperature. The PWST led to a decrease in severity of microsegregation, which in turn caused a reduction in austenite content of the fusion zone. The activation energy for the process of homogenisation of austenite was found to be 265 kJ mol−1. The present work has clearly demonstrated that PWST before aging improves the fusion zone toughness in cobalt free maraging steel weldments.
Artificial neural networks – an aid to welding induced ship plate distortion?
Authors: Lightfoot M. P. , Bruce G. J. , Mcpherson N. A. , Woods K.
Published: May 2005

A preliminary study on the potential application of artificial neural networks in welded structures was expanded to metal inert gas welding of steel plates of grades D and DH 36. The main controllable variables were plate thickness, steel grade, plate cutting process, and heat input. A series of welded plates of each grade was manufactured, covering plate thicknesses of 6 and 8 mm. The topography of each welded plate was evaluated after tacking the plates together and after welding, allowing the actual distortion to be calculated. It was established that a multilayer perceptron network architecture configuration accurately represented the distortion for the 6 mm thickness plate, and for the 8 mm thickness plate after treatment of the data. The data generated were used to develop the PREDICTOR software package, which allows a distortion prediction to be produced, and to carry out a sensitivity analysis. Heat input was found to be the most sensitive factor related to distortion, with carbon content of the plates, yield/tensile strength ratio, carbon equivalent, and steel grade also having significant effects. Some test plates were modelled using finite element method software packages: the initially poor agreement was improved via the addition of significant detail, but the finite element model by its nature will normally predict symmetrical distortion from a symmetric weld, whereas the artificial neural network model developed was capable of predicting the asymmetric distortion observed in reality.
Arc power and efficiency in gas tungsten arc welding of aluminium
Authors: Cantin G. M. D. , Francis J. A.
Published: May 2005

A calorimetric study of gas tungsten arc welding of aluminium is described. The present study comprised experiments in which autogenous welding runs were each made on a block of electrical conductor grade aluminium. The blocks were all approximately cubic in shape which, when combined with the high thermal conductivity of aluminium, ensured that their temperature equalised soon after the completion of a run. Each sample was immersed in insulating material before welding so that heat losses to the surroundings were minimised. Thermocouples were attached to the block in each experiment and the bulk temperature rise was related to the energy input associated with the welding run. The effects of arc polarity, alternating current balance, shielding gas composition, arc length and welding current on the arc power and arc efficiency were investigated. The results obtained with alternating current are compared to those for direct current, and the differences are explained.
High power laser welding of Nb microalloyed steel plates
Authors: Harrison P. L.
Published: May 2005

Laser welding studies on 12 mm thick Nb microalloyed steels were done using a 25 kW CO2 laser at welding speeds of up to 3 m min−1 with the aim of identifying the influences of Nb and carbon on laser weldability and weld properties. Welds were examined for solidification flaws, penetration characteristics, microstructure and mechanical properties. Solidification cracking did not appear to be influenced by carbon or Nb in the ranges studied when welding at power levels between 22 and 25 kW. The area fraction of martensite was shown to increase with decreasing energy input and increasing carbon content. Weld metal toughness was improved by reducing carbon content in the range 0·08–0·05%C but was little influenced by Nb. Weld metal and heat affected zone hardness levels were reduced, as expected, by reducing carbon content. The results show that increasing Nb content leads to higher strength material without significant loss of toughness, while lowering carbon content can improve toughness without loss of strength. Thus low carbon Nb microalloyed steels with about 0·05%C can achieve a good combination of parent plate and laser weld properties and appear to be suitable for high power laser welding situations.
Fluxless laser beam joining of aluminium with zinc coated steel
Authors: Laukant H. , Wallmann C. , Müller M. , Korte M. , Stirn B. , Haldenwanger H.-G. , Glatzel U.
Published: May 2005

A laser welding–brazing (LWB) process to join zinc coated steel and aluminium sheets in two different flange geometries is reported. The deep drawing steel sheets are covered by a zinc layer of maximum thickness 10 μm, and a zinc based filler wire was used in the welding experiments with a Nd–YAG laser. Because of the differences in melting temperatures between iron (1808 K), aluminium (933 K), and zinc (693 K), it is possible to weld the aluminium alloy only. Owing to the zinc coating on the steel side, a Zn–Al alloy can be brazed onto the steel without any flux agent. The inevitable formation of a Fe–Al intermetallic phase at the bondline of the weld seam and the steel can be limited to a thickness of less than 5 μm and to a proportion of the contact area only. Mechanical as well as dynamic tests show results comparable to those obtained via other joining techniques. Salt chamber corrosion tests of varnished specimens display minor damage and no decline in tensile strength.
Diode laser brazing of aluminium alloy to steels with aluminium filler metal
Authors: Saida Kazuyoshi , Song Woohyun , Nishimoto Kazutoshi
Published: May 2005

Diode laser brazing of aluminium alloy (A5052) to interstitial free steel (IF steel) or type 304 stainless steel (SUS304) was conducted using aluminium filler metal (BA4047) with Nocolock flux. The processing parameters of laser power, wire feed rate and travel speed were varied. The strength of lap joints of A5052 on steels was evaluated by tensile shear test. The joint strength of A5052/steels was increased with increasing laser power and reached the maximum strength, more than approximately 80% of the A5052 base metal strength, at a laser power of 1300 W. Voids and incomplete penetration of filler metal were observed at the A5052/braze layer interface when the laser power was below 1100 W. The Fe–Al intermetallic compounds were formed at the steel/braze layer interfaces and grew drastically when the laser power exceeded 1300 W. Superior brazability of A5052/steels was found at brazing conditions corresponding to a temperature of filler metal droplet of 1050–1250 K.
Solidification cracking in low alloy steel welds
Authors: Shankar V. , Devletian J. H.
Published: May 2005

The high solidification cracking susceptibility of low C steel weld metals was investigated using pure Fe model alloys containing 0–0·23%C, 0–5%Ni and 0–0·0144%B. In addition, a few Fe–C–Ni ternary alloys were also tested. Solidification cracking susceptibility was tested using longitudinal varestraint and transvarestraint tests. Cracking was evaluated using crack length and brittleness temperature range criteria. The Fe–C alloys showed high cracking tendency in two regimes, the first in the ultralow carbon range of 0·03–0·05%C and the second in a narrow band close to 0·1%C. The cracking was much more than that attributable to solute segregation. In Fe–Ni and Fe–B alloys, cracking was a function of alloy content. Solidification cracking due to C and Ni was higher in the ferritic mode of solidification compared to the austenitic, unlike in stainless steels, where the ferritic mode provides high resistance to cracking. In Fe-C-Ni ternary alloys, cracking could be better related to composition in terms of a variable coefficient for C in the Ni equivalent. In the vicinity of 0·1%C, cracking was attributable to shrinkage due to solid state transformation from δ to γ in the brittle temperature range, and is similar to that occurring during continuous casting of steel. However, this factor did not appear to play a role in cracking in the ultralow C range of 0·03–0·05%C.
Voltage change in the GMAW process due to the influence of a droplet travelling in the arc
Authors: Zhu Peiyuan , Simpson S.
Published: May 2005

Experimental measurements have been made to investigate the meaning of the fluctuation or noise of electrical signals for the gas metal arc welding process through globular to spray transfer mode, with particular attention being paid to the so-called ‘drop spray’ transition mode. The results reveal that the welding arc voltage is significantly affected by the molten droplet travelling in the arc. A sharp drop in arc voltage appears just after the detachment of the droplet, reaching its minimum quickly and then recovering, according to the location of the droplet in the arc. Although the full explanation of the feature requires further study, we believe that an important influence is the geometrical effect. The existence of the droplet in the arc path significantly affects the geometrical shape of the arc and arc attachment at the anode, and hence the overall voltage of the arc.