bluuebunny/crossref_metadata_2025 huggingface dataset:
Fast method for measuring power density distribution of non-circular and irregular electron beams
Authors: Elmer J. W. , Teruya A. T.
Published: January 2014

A fast method for measuring the power density distribution of electron beams has been developed. The method employs a refractory metal disc containing regularly spaced radial slits and a Faraday cup to measure electron beam profiles as the beam is oscillated in a circular pattern over the disc. This beam profiling method can be used for real time focusing along a given beam sweep orientation by monitoring one of the beam profiles. When the focus setting is satisfactory, all of the beam profiles can then be stored for computed tomography (CT) reconstruction. The CT reconstruction renders an image of the powder density distribution and provides beam statistics as a permanent file for process control records. The process (taking ∼1 min to perform in its entirety using a conventional PC) was used to investigate the influence of focus setting on the power density distribution of 5 mA electron beams operating at accelerating voltages of 80 and 140 kv. Results of these tests show the effects of beam astigmatism on the power density distribution and the optimum focus conditions for these non-circular beams. In addition, these results show the ability of the 140 kV beam to focus more precisely and thus produce higher power densities than the 80 kV beam.
Algorithm based on non-linear programming method for optimum heat input control in arc welding
Authors: Kondoh K. , Ohji T.
Published: January 2014

A simple mathematical method for the estimation of the optimum heat inputs to make the temperature field coincide with a requirement during arc welding has been developed. The optimisation problem in the present work means the objective function which is defined as the difference between the calculated and required temperatures. An analytical solution of the heat flow equation is applied for the calculation of the temperature field in welding, and non-linear programming methods, i.e. the convex programming method and the steepest descent method, have been used to solve the objective function in the problem mathematically. It is concluded that both optimising methods are sufficient to determine the optimum heat input pattern in the case of gas tungsten arc (GTA) welding on thin plate and small sized pipe specimens. Furthermore, the applicability of the estimated optimum heat inputs is evaluated experimentally by bead on plate welding tests.
Modelling of heat transfer in short circuiting gas metal arc welding
Authors: Hermans M. J. M. , den Ouden G.
Published: January 2014

This paper deals with heat transfer during short circuiting gas metal arc welding of mild steel. Three major heat sources can be distinguished: arc heating of the anode, arc heating of the cathode, and Joule heating of the electrode extension. Based on these heat sources a model is presented which describes the heat transfe; both to the electrode and to the workpiece. The validity of the model was tested by comparing predicted values of the heat transfer with experimental data. It appears that good agreement exists between model and experiment.
Structural evolution of pulsed Nd-YAG laser welds of AISI 1006 steel
Authors: Frewin M. , Dunne D. , Scott A.
Published: January 2014

Although correlations of welding parameters with the metallurgical features of conventional fusion welds in low carbon steels are well established, information on process–structure–property relationships associated with pulsed laser welds is more limited. This paper presents results on the characterisation of weld metal and heat affected zone (HAZ) microstructures observed in laser welded AISI 1006 steel. Pulsed Nd-YAG laser welds in the bead on plate configuration were used for this purpose, both in overlapping and non-overlapping bead configurations. As very rapid heating and cooling cycles occur during laser welding, the microstructures observed in the weld metal are the result of rapid solidification producing thin columnar austenite grains extending from the fusion boundary, which transform to martensite and bainite during fast cooling to ambient temperature. The HAZ structure in the base plate can also be rationalised in terms of the rapid thermal cycling experienced. The HAZ is narrow with the intercritical reheated subzone being dominant. As microstructural development has a critical effect on the mechanical properties of welds, microstructural characterisation plays an integral role not only in the understanding of pulsed laser welding, but also in the selection of optimum welding conditions for the material of interest.
Progress in joining of advanced materials Part 2: Joining of metal matrix composites and joining of other advanced materials
Authors: Çam G. , Koçak M.
Published: January 2014

Advanced materials generally require novel joining techniques. Developments in new materials research should be conducted hand in hand with work on weldability and joining capacity aspects. Sound joint quality for any new material has always been considered a milestone in a research and development scheme for a new material, particularly in terms of widespread applications. Better understanding of the microstructure–mechanical properties relationships of the bonded or welded joints will feed back to the materials development activities both in conventional and new materials areas. The two joining processes diffusion bonding and laser welding are considered in this literature review, since these processes are capable of joining a wide range of materials of interest in the aerospace industry, as well as in many other industrial applications, and offer remarkable advantages over conventional fusion welding processes. Of particular interest is the ability to join the more difficult aerospace alloys with minimal component distortion and high reproducibility of joint quality. The purpose of the review is to outline progress made in this area and to make suggestions for future work. Part 1 (STWJ, 1998, 3, (3), 105–126) dealt with solid state joining, fusion joining, and joining of intermetallics, while Part 2 covers joining of metal matrix composites and joining of other advanced materials.
Residual stress measurement in ferritic steel tube welds using X-ray diffraction
Authors: Rai S. , Jayakumar T. , Rao C. Babu , Bhattacharya D. K. , Raj B.
Published: January 2014

The X-ray diffraction (XRD) technique has been used to measure the residual stresses before and after post-weld heat treatment in autogenous butt weld joints in 2·25Cr–1 Mo steel tubes. The tubes are used in the steam generator assemblies of fast breeder reactors. Measurement data show that the stress in the weld centre is ∼150 MPa maximum. The stress distribution around the weld centre is asymmetrical with larger amounts of compressive stress on the side of the tube sheet block. The stress becomes compressive beyond ∼5 mm from the weld centre reaching values of ∼200 MPa and more. Post-weld heat treatment (PWHT) at 923 K for 30 min removes most of the residual stresses and PWHT at 988 K for 2·5 h removes all the residual stresses in the weld regions.
Microstructure and properties of metal matrix compositel/stainless steel friction joints containing silver interlayers
Authors:   C. Maldonado, Zhai Y. , North T. H.
Published: January 2014

The influence of a silver interlayer and friction joining parameters on the microstructure and mechanical properties of friction joints between aluminium based metal matrix composite (MMC) and AISI 304 stainless steel substrates is investigated. The highest notch tensile strength properties were obtained in MMC/Ag/304 stainless steel and MMC/304 stainless steel joints produced using high friction pressure. The introduction of silver during MMC/304 stainless steel friction joining promoted the formation of a veined microstructure containing a mixture of silver, an intermetallic phase, and entrained Al203 (the intermixed region). A second microstructure, the plastic deformed region, consisted of a fine grained dynamically recrystallised MMC matrix including granular silver, Ag3Al, and reinforcing particles. The intermetallic Ag3Al formed as a result of mechanical mixing very early in the friction joining operation. The beneficial effect of using high friction pressure during friction joining was related to the formation and retention of microstructures containing Ag3Al.
Investigation of boundaries and structures in dissimilar metal welds
Authors: Nelson T. W. , Lippold J. C. , Mills M. J.
Published: January 2014

Cracking, or disbonding, along the fusion boundary in dissimilar metal welds has been a persistent problem, particularly in applications where austenitic alloys are clad on to structural steels for corrosion protection. Many failures in dissimilar metal welds occur as a result of cracking along a boundary that runs parallel to the fusion boundary in the adjacent weld metal. A preliminary investigation was undertaken to determine the nature and evolution of boundaries and structure in dissimilar metal welds using a simple ternary system composed of a pure iron substrate and a 70Ni–30Cu (Monel) filler metal. Changes in base metal dilution were found to alter the evolution of boundaries and structures near the fusion boundary dramatically. Optical metallography and electron microanalysis reveal that the resulting weld microstructures and boundaries are similar to those observed in engineering materials used for cladding and corrosion resistant overlay. Transmission electron diffraction analysis revealed orientation relationships between adjacent base metal and weld metal grains at the fusion boundary to be different from the cube on cube relationship normally observed in similar metal welds. A model is proposed describing the evolution of the boundary most susceptible to cracking in dissimilar welds.
Application of thermal modelling to laser beam welding of aluminium alloys
Authors: Norman A. F. , Ducharme R. , Mackwood A. , Kapadia P. , Prangnell P. B.
Published: January 2014

A thermal model has been developed for laser welding which describes the heat input in terms of point and line sources. The model was used to generate weld profiles which closely matched those found by experiment. Outputs of the model (the thermal gradient GL and the growth rate R) were used to describe the macroscopic grain structure found along the weld centreline. Columnar structures were predicted at low welding speeds (high GL/R ratio) and equiaxed structures at high welding speeds (low GL/R ratio). Using the thermal model, cooling rates of ∼1500 K s–1 were estimated for the lowest welding speed, which increased by an order of magnitude for the highest welding speed considered. There was excellent agreement between the dendrite secondary arm spacings measured by experiment and those predicted using the thermal model.
Laser welding with powder feed
Authors: Sun Z. , Kuo M.
Published: January 2014

Laser welding with a powder feed has been investigated using a 3·0 kW CO2 laser system. This type of welding is a modification of autogenous laser welding. In the present investigation, a straight thin tube nozzle was used to deliver powder to the welding area by a computerised powder feeder. The delivered powder is melted and mixed by interaction with the laser beam to form a weld with the base metal. This technique can extend the capabilities of autogenous laser welding while retaining many of its advantages. A series of welding parameters was used to produce butt joints with a satisfactory weld bead profile at various joint gap sizes. The main objective of the present study was to use a power feed to accommodate joint gaps which often present problems in autogenous laser welding. Promising results have been obtained. A joint gap of up to 1·0 mm has been welded successfully in 3·0 mm thickness steel: a great improvement compared with autogenous laser welding. In the present study, weld microstructure, composition, hardness, and tensile properties were investigated. The investigation indicated that the joints possess sufficient strength. The practical implication of the results is that tight fitup requirements for laser welding can be relaxed somewhat for many demanding industrial applications. Although further development is still required to optimise the technique, its potential has been demonstrated.
Current stepping programmes for maximising electrode campaign life when spot welding coated steels
Authors: Williams N. T. , Holliday R. J. , Parker J. D.
Published: January 2014

Improvements in electrode life are possible when resistance spot welding coated steels, through the application of current stepping techniques. The present investigation has evaluated a number of criteria for establishing optimum rates of current increase. The most significant improvements in welding performance were obtained when the current was increased as a function of electrode tip growth. It was found that electrode softening occurred at a faster rate when current stepping, compared to welding using standard conditions. This softening was caused by recrystallisation of the base electrode material and resulted in a fast tertiary stage of electrode tip growth. The practical implications of the work are discussed.
In process heat input control in arc welding
Authors: Kondoh K. , Ohji T.
Published: January 2014

An algorithm for in process optimum heat input control of arc welding is discussed, in which an analytical model of heat conduction is used to evaluate the temperature field during welding and the convex programming method is used in the optimisation of the heat input. The thermal response calculated using an analytical model corresponds well with that measured during welding and it is possible to identify the heat efficiency using the model. Furthermore, an in process optimising algorithm which includes the real time identification of heat efficiency is examined to estimate the optimum heat input for the required temperature field in gas tungsten arc welding under conditions where there is a change in the arc length. It is ascertained that the optimising algorithm is sufficient to determine the optimum heat input in real time during welding.
Microstructure and corrosion properties of AA2091-T3 in weld heat affected zone
Authors: Chen M.H. , Hwang R.Y. , Chou C.P.
Published: January 2014

The microstructure and corrosion behaviour of an AA2091-T3 alloy weld heat affected zone (HAZ) were investigated using differential scanning calorimetry and electrochemical measurements in 3·5% NaCl solution. The δ′ phase was precipitated during the welding cooling process. The amount of δ′ precipitates depends on the peak temperature of the weld thermal cycle. The quantity of Guinier–Preston (GP) zones was related to the duration of natural aging. Variation of pitting potential of the weld HAZ was due to the lithium content in the matrix. The increasing dissolution of GP zones and δ′ phase was accompanied by increasing lithium contents in the matrix and caused a negative shifting of pitting potential. The region containing the lowest quantity of GP zones and δ′ phase had the lowest pitting potential. The higher the peak tem perature of the weld thermal cycles the more precipitation of T2 phase on grain boundaries occurs. These T2 phases can cause severe intergranular exfoliation corrosion.
Effect of nitrogen on σ transformation in duplex stainless steel weld metal
Authors: Sato Y.S. , Kokawa H. , Kuwana T.
Published: January 2014

Duplex stainless steels were gas tungsten arc welded without filler material in various Ar–N2 mixed gas atmospheres. Weld metals having different nitrogen contents were annealed at 900–1300 K to examine the single effect of nitrogen on the σ transformation. Nitrogen content of the weld metal did not influence the nose temperature and the time for σ initiation in time–temperature–precipitation diagrams for σ, but did decrease the σ content after annealing for long times. These results were correlated with the nitrogen content and microstructure of the weld metals. The effect of σ on the fracture toughness of the weld metal was evaluated by the small punch (SP) test. A small amount of σ in the weld metal led to a marked decrease in the SP energy.
Effect of Nd–YAG laser pulse shape on welding characteristics of STS 310S stainless steel
Authors: Kim H.B. , Lee C.H.
Published: January 2014

This paper describes a study of the effects of pulse shaping on weld dimensions and weld discontinuities in continuous seam welds of STS 310S stainless steel using a Nd–YAG laser. Laser weldability tests for STS 310S and Inconel 600 were also carried out. Pulse shapes evaluated in this experiment were of the type generally applied in YAG laser materials processing, the ramped up type (three steps), and the ramped down type (three steps). The pulse energy was constant regardless of type of pulse shape. Penetration of laser welds increased as pulse width and peak power increased. The ramped up type pulse was the most effective for deep penetration. With regard to the weld discontinuities (porosity and hot cracking), the general type pulse gave poorest results and the ramped down type pulse gave the best.
Hot cracking in austenitic stainless steel weld metals
Authors: Radhakrishnan V.M.
Published: January 2014

Solidification cracking in austenitic stainless steel welds has been considered based on the solidification modes and the nickel and chromium equivalents in welding processes where the cooling rates are high. Taking a Creq/Nieq (Welding Research Council) ratio of 1.6 as a criterion for the final weld metal to avoid hot cracking, a methodology is proposed for the selection of filler or buffer material equivalents.
Trends in laser beam welding technology and fracture assessment of weld joints
Authors: Koçak M. , dos Santos J. , Riekehr S.
Published: January 2014

Recent advances in the industrial application of laser welding are reviewed, drawing on examples from the aerospace, automotive, shipbuilding, offshore, and white goods industries. Attempts are being made to introduce laser welding procedures into construction industry standards. The impact of the narrow, overmatched weld zone on joint properties and the difficulties this raises for quality assessment are briefly considered.
Effect of residual stress on fatigue strength of resistance spot weldment
Authors:   Yang Y.-S.,   Son K.-J.,   Cho S.-K.,   Hong S.-G.,   Kim S.-K.,   Mo K.-H.
Published: January 2014

The estimation of fatigue strength of spot welded joints is crucial to the strength design of spot welded steel sheet structures. In the present paper, the effect of residual stresses on the fatigue life of resistance spot weldments was studied. Residual stress fields in the weldments were calculated using thermoelastic–plastic finite element analysis and the equivalent fatigue stress considering the residual stress effect was obtained. This was followed by fatigue life predictions, which included the effect of the residual stresses and the actual loading stresses. The calculation and experimental results showed good agreement. Therefore, the proposed calculation model can be considered to be sufficiently powerful for the prediction of fatigue life
Improving Fatigue Strength of Aerospace Metal Fasteners by Surface Work Hardening
Authors: Turlach G
Published: January 2014

In the aerospace sector of manufacturing industry it is essential, in the design of lightweight vehicles, to optimize the static and dynamic properties of even such components as fasteners. This requirement is also increasingly being sought in the automobile industry. Thus, novel designs, optimized production procedures, and specialized materials have to be used. Roll forming is one technique which has been applied successfully for the improvement of resistance to fatigue, and fretting fatigue of metallic fasteners, by virtue of the work hardening and smoothing of the surface which takes place. High and ultrahigh strength materials, in particular nickel, titanium, and ferrous· based alloys, are the principal materials to benefit from this technique.
Morphology, Composition, and Residual Stresses of Compound Layers of Nitrocarburized Iron and Steels
Authors: Rozendaal H C F , Colijn F , Mittemeijer E J
Published: January 2014

Specimens of pure iron, an iron-carbon (1 wt-%C) alloy, and steels Ck 45 and En 40B (=24CrMo13) were salt bath nitrocarburized. M etallographic examination was performed after Murakami etching. This etchant provides a sensitive discrimination between pure nitrides and carbon containing nitrides (carbonitrides). Thus the two-phase (ε and γ’) constitution, as well as the carbon concentration profile within the compound layer, was revealed. Nitrogen, carbon, oxygen, and sulphur concentration profiles were quantitatively determined by electron microprobe analysis. Residual stress measurement and phase analysis were carried out by X-ray diffraction methods. Both macros trains (by analysis of line shift using the sin2 Ψ method) and microstrains (by analysis of line broadening using a Voigt single-line method) were determined. In view of a possible interaction between residual stresses in the compound layer and the diffusion zone, residual stresses were also determined in the diffusion zone beneath the compound layer. The results obtained provide a basis for a model to describe the constitution of the compound layer.
Plasma Carburiiing: Theory; Industrial Benefits and Practices
Authors: Jacobs M. H. , Law T. J. , Ribet F.
Published: January 2014

This paper describes the current status of the new technology of plasma carburizing, which has recently moved out of the development laboratory into industry. A description of the equipment is followed by a section on the kinetics and mechanism of this ion assisted surface treatment process. Emphasis is placed on the capability for rapid carburizing and then on the following processing benefits: better quality, excellent process control, good consistency, reduced distortion, good carburizing within holes, and excellent cleanliness of the treated parts. Practical aspects of masking and fixturing precede a section on industrial applications. It is concluded that plasma carburizing offers a superior alternative to other methods of carburizing when process control and quality of the end product are of paramount importance.
New Technique to Characterize Carbonaceous Contai1Inants on Metal Surfaces
Authors: Husby K. , Grinder O.
Published: January 2014

A new technique has been developed for the accurate determination of carbonaceous compounds on metal sUlfaces. The technique is based on oxidation of the samples in a furnace in flowing high purity oxygen as the furnace temperature is continuously raised. The carbon and hydrocarbons present on the metal surface oxidize selectively in specific temperature ranges. The reaction products are transformed in a separate oxidation furnace to CO2 and H2O. The concentrations of these compounds are continuously analysed using a high sensitivity infrared detector. The method gives an accurate quantitative value of the total surface carbon content and also semiquantitative information on the carbonaceous compounds present. The measurement technique is presented together with some experimental results from the surface analysis of carbonaceous impurities on low carbon steel sheets, copper tubes, and cemented carbide cutting tools.
Laser Transformation Hardining with a Toric Mirror
Authors: Melander M. , Chang Yao Shan
Published: January 2014

Mathematical models for the calculation of temperature, phase transformation, and stresses for progressive laser transforlnation hardening with a toric mirror are presented. The models have been used in calculations for cylinders with two different diameters in which the effects of travel speed, power input, and width of the laser beam were studied. Experiments have been carried out for two low alloy steels with 0.4 and 1.0% C, respectively. Hardness, residual stresses, and the amount of retained austenite have been measured. Further, an initially spheroidized structure seemed unsuitable for laser hardening. Finally, the size of the workpiece should be large enough to allow selfquenching and, thus, formation of martensite. This was found in both the experiments and the calculations.
Niflor – autocatalytic nickel–PTFE composite coating
Authors:   none
Published: January 2014

Autocatalytic nickel plating, more commonly known as electroless nickel, is a well established process, widely used in industry. The process is capable of providing a hard, wear and corrosion resistant coating to a wide range of components. Typical applications include building up of worn or overmachined parts; electroforming of gramophone masters, press tools, and moulds; facing of printing plates and the production of electrotypes for the printing industry
Laser Hardening of Ring Grooves in Medium Speed Dieselengine Pistons
Authors: Bransden A. S. , Gazzard S.T. , Inwood B. C. , Megaw J. H. P. C.
Published: January 2014

Internal combustion engine durability is enhanced if the side faces of the ring grooves in the pistons have a wear resistant surface. The present work concerns the development of a technique to achieve local hardening of medium speed steel crowned and cast iron pistons, based on the use of a 5 kW industrial laser. Specific aspects of the development which are discussed include: beam coupling and choice of absorbing coatings, choice of beam power density/interaction time, metallurgy, treatment of the edges of external corners, back tempering, and induced distortion and surface changes. The work has resulted in the treatment of prototype pistons for evaluation in engine trials.
Coating and Treatment Selection
Authors: Syan C. S. , Matthews A. , Swift K. G.
Published: January 2014

It is clear that the wider use of surface engineering principles in industry would bring considerable advantages. There is an urgent need to devise a recognized procedure which design engineers and others can use to select coatings and treatments and thereby extend the adoption of these principles. This paper reviews the attempts made to identify such a procedure, and sets out an approach to selection developed at Hull University which utilizes a computer expert system.
Properties of Crn and (Ti, Al)N Coatings Produced by High Rate Sputter Deposition
Authors: Münz W. D. , Göbel J.
Published: January 2014

CrNand (Ti, Al) N coatings have been deposited by high rate sputter deposition. CrN is one of the most uncritical coatings to produce, neither microhardness nor sputtering stability being influenced by sputtering conditions. Depending upon the nitrogen partial pressure during deposition and the aluminium content, (Ti, Al) N coatings with maximum microhardness values of 2200–3000 HV0.01 can be obtained. Such coatings have superior oxidation and wear resistance compared to normal sputtered TiN coatings.
Internal Stress and Microstructure of Titanium Nitride Coatings
Authors: Rickerby D. S. , Bellamy B. A. , Jones A. M.
Published: January 2014

Titanium nitride coatings were deposited on various substrates by sputter ion plating and the state of stress was determined by the sin2 Ψ method. The lattice distortions which occur in the nitride coatings have been resolved in terms of a macros train and microstrain, as determined from the breadth of the xray reflections, and the origins of each are discussed. The internal stress present in a coating is shown to consist of two components, one thermal in origin and the other structural, its sign and magnitude varying with substrate material and bias potential. During cooling from the deposition temperature partial relaxation of this internal stress (macrostrain) occurs via two mechanisms: plastic deformation of the substrate and yield of the film. The internal stress was completely relaxed on dissolution of the substrate, accompanied by a decrease in the lattice parameter of the film. By comparing the results from substrates biased and unbiased during deposition, and measurements made on adherent and free standing coatings, the microstrain measurements have been separated into two parts, one due to distortions at the grain boundaries and one due to the presence of defects in the crystallites. A model is proposed that accounts for all the experimental observations; this also provides an explanation for the distortions from cubic symmetry reported in titanium and hafnium nitride films.
New Technique for Monitoring Nitrogen Ion Implantation Dose
Authors: Gardner P. R. , Dearnaley G. , Rosenbaum S.
Published: January 2014

A new dosimetry technique for use in industrial nitrogen ion implantation is described. This relies on colour changes induced in anodized tantalum. Visual inspection of these dosimeters, by comparison with a set of calibrated standards, provides an accuracy of around ±20% over the range 1 × 1017-5 × 1017 nitrogen ions cm −2. Scope exists for more accurate use of the system by means of commercial colour analysis equipment. However, even as it stands, the material has been shown by field trials to be a useful accessory to commercial nitrogen ion implantation, i.e. for verifying applied dose, especially with complex workpiece geometries, and for evaluating implanter performance.
Comparison of Sliding Wear Resistance of Carburized and Nitrided Layers on 18Hgt Steel
Authors: Burakowski T. , Senatorski J. , Tacikowski J.
Published: January 2014

The sliding wear resistance of nitrided and carburized 18HGT low alloy steel cylindrical specimens was determined in ‘taper-three roll’ tests against 45 grade steel counter specimens. Specimens to be nitrided were hardened to 28 HRC before nitriding at 530°C for 6 h, whereas the carburizing treatment was at 930°C for 6 h followed by direct hardening and tempering. The wear characteristics were determined at the surfaces of the hardened specimens and after grinding to various depths within the diffusion layer. Hardness–depth profiles were also obtained and the layer microstructures were examined by SEM. In general, the two types of specimen showed similar wear resistance, although the nitrided steels performed better at low surface pressure (50 MPa). Seizure or accelerated wear was observed at pressures of 400 MPa and above. The surface zones showed higher wear resistances than the zones deeper in the hardened layer.
Laser Melting of Plasma Sprayed Nicocraly Coatings
Authors: Sivakumar R. , Mordike B. L.
Published: January 2014

MCrAlY coatings (M = Ni, Co, Fe alone or in combination) are currently used to protect gas turbine blades and vanes from oxidation and hot corrosion. The coatings are required to be fully dense and well bonded to the substrate. They are formed either by electron beam evaporation or by low pressure plasma spraying. Another possible route is to form them by normal atmospheric plasma spraying, followed by remelting with a laser to remove porosity and other defects. The feasibility of this approach has been investigated by melting plasma sprayed NiCoCr AIY coatings on a Nimonic 75 substrate. This work focuses mainly on the effect of various laser processing parameters on the structure of remelted layers. Preliminary data on the hot corrosion properties of the laser melted coatings are also presented.
Multilayer Submerged Arc Surfacing with High Chromium Iron Alloy
Authors: Mizoguchi S. , Tanigaki T. , Tokura M. , Koike H. , Nishimura H.
Published: January 2014

The wear resistance and durability of 40 mm thick· high chromium iron weld surfacing deposits have been investigated with reference to the low stress abrasion conditions experienced by the work roll of a coal crushing mill. It was found that an underlayer of austenitic stainless steel greatly reduced cracking and spalling of the deposit. The variations in welding conditions tested had relatively little effect. A modified ASTM G65 dry sand/rubber wheel abrasion test with a 3 kg load was shown to give results that correlated well with service experience. Extensive compositional testsindicated that carbon content was the lnajor factor controlling hardness and abrasion resistance, through its influence on chromium carbide volume fraction. The optinlum carbide content was found to be 55-65%, since above this range brittle fracture becomes excessive.
Ion Plated Black Nickel Coating for Photothermal Energy Conversion
Authors: Aboukhashaba A. , Sabbagh J. , Ei-Sherbiny M.
Published: January 2014

A nickel black solar selective coating, which is based on rich oxide-nickel metallic matrix deposited on nickel foil, was deposited by sputter ion plating in a reactive atmosphere. The optical properties of the nickel cermet are evaluated experimentally. A theoretical model of the proposed structure yields comparable but not identical results. The average value of the near normal hemispherical total solar absorptance as averaged over the air mass 2 solar spectrum is 0.95 ± 0.003. The near normal total thermal emittance, however, is 0.083 ± 0.005. The characteristics and stability of the coatings are also examined.
Formation of Diffusion Coatings on Iron and Steel: 3 Aluminium, Chromium, and Zinc Coatings
Authors: Sequeira C. A. C. , Pacheco A. M. G. , Nunes C. M. G. S.
Published: January 2014

The present paper is the last of a three part series dealing with metallic diffusion coatings for the protection of iron and steel. Special reference is made to application methods, composition and structure, physical properties, and corrosion and oxidation resistance of aluminium, chromium, and zinc diffusion coatings. Suggestions are made for future studies on the deposition and performance of diffusion coatings on iron and steel substrates.
Laser Cladding with Preplaced Powder: Analysis of Thermal Cycling and Dilution Effects
Authors: Powell J. , Henry P. S. , Steen W. M.
Published: January 2014

A theoretical model has been developed which analyses thermal cycling during the laser cladding process. The preplaced powder cladding method investigated involves scanning a defocused or rastered laser beam over a powder bed which is subsequently melted and welds to the underlying substrate. Previous practical work has shown that minimal dilution effects can be observed over a very large range of processing parameters. Theoretical modelling of the movement of the molten front has shown that after initial clad melt-substrate contact the melt recedes from the substrate and will only cross the cladding/substrate interface again under extreme conditions of input energy and laser-material interaction time.
Plasma Nitriding of Stainless Steel using Continuous and Pulsed RF Glow Discharge
Authors: Ei-Hossary F. , Mohammed F. , Hendry A. , Fabian D. J. , Szaszne-Csih Z.
Published: January 2014

A novel radio frequency (rf) plasma technique for nitriding engineering steels is described whichproduces a surface layer of exceptional hardness in extremely short nitriding times. The sample does not form part of the primary electrical circuit, as is the case, with de plasma methods, and the temperature at the metal surface is controlled by a variable pulsed mode operation of the inductively coupled nitrogen plasma. The rate of nitriding is compared to those obrained by conventional ammonia nitriding and by de plasma methods. The rapid rates of layer growth observed with the rf plasma are discussed in terms of an interstitial–vacancy coupled diffusion model. The results demonstrate the feasibility of a rapid and flexible process for nitriding all grades of engineering steels.
Application of Plasma Arc Injection Surface Alloying to Automobile Camshafts
Authors:   none
Published: January 2014

By adding alloying elements to the surface layer of the cam face of cast iron camshafts during melting and rapid cooling by plasma arc a chilled structure with high wear resistance has been successfully obtained. An injection system, introducing carbide powder into the plasma jet, was used to supply alloying elements to the molten matrix. The alloyed layer obtained, with a maximum thickness of 2 mm and an alloying element concentration of 200∼, had a homogeneous structure with very high hardness. Selection of a suitable concentration of alloying elements reduced the wear rate to 20% of normal levels in engine tests.
Influence of Ion Implantation in Extending Tool Life in Polymer Processing
Authors: Furze D. C. , Eyre T. S.
Published: January 2014

Polymer matrix composites are becoming more extensively used for a wide range of engineering applications. Wear of dies and tools has, however, become a significant problem, since the fillers and fibres used to achieve the design properties are often abrasive. Effective means of reducing wear in this type of equipment are therefore becoming increasingly important. Materials currently used for manufacture of tools, dies, screws and barrels, etc. include low alloy non-distortion through hardening steels and steels modified by hard chromium plating, hardfacing with Stellite, particularly for refurbishing worn components, and nitriding. In the present paper wear mechanisms occurring in the processing of polymers are reviewed. The advantages of the currently used processes for extending the life of tools and dies are discussed and this is extended to a discussion of the advantages of nitrogen ion implantation. A tribological test is described which processes a filled polymer through an extrusion system in which a slit die is used; this is made in two parts so that one half can be treated while the other half remains untreated to enable direct comparison. Surface topography and scanning electron microscopy are used to evaluate the extent of wear and the wear mechanism(s) involved. Ion implantation with nitrogen is shown to be effective in extending die life.
Surface Alloying of Steel Samples by Laser Aluminothermy
Authors: Ursu I. , Craciun V. , Mihailescu I. N. , Popa AI. , Alexandrescu R. , Morjan I.
Published: January 2014

New experimental results are reported that confirm the possibility of surface alloying steel samples with refractory metals by laser aluminothermy under the action of a low power continuous wave carbon dioxide source.
Formation, Microstructure, Surface Roughness, and Porosity of Electroless Nickel Coatings
Authors: Tomlinson W. J. , Mayor J. P.
Published: January 2014

The structure and properties of electroless nickel coatings containing 11% phosphorus have been studied in the as plated condition for various deposition times and after heat treatment. In addition to a general covering, in the early stages of deposition nodules of nickel form associated with the lay of the polished substrate, and as the thickness of the coating increases so do the surface roughness and the uniformity of the coating thickness. Porosity is associated with the surfaces of the vestigial nickel nodules. Porosity measured using the ferricyanide test is observed to decrease monotonically with the as plated thickness, and is a maximum after heat treatment at 400°C. Large non-metallic inclusions do not affect the porosity or coating uniformity. Information on the microhardness, crystal structures, and microstructure of the coatings is also presented.
Engineering Properties of Chromium Plating and Electroless and Electroplated Nickel
Authors: Gawne D. T. , Ma U.
Published: January 2014

The wear of chromium plating and electroless and electroplated nickel under dry sliding conditions is not directly related to hardness. The maximum wear resistance of electroless nickel does not occur at its peak hardness and chromium plating has the highest wear resistance even though it is not the hardest coating. As-deposited electroless nickel is susceptible to serious adhesive wear against plain carbon steel but this can be eliminated by a controlled heat treatment. The wear of electroplated and electroless coatings is strongly influenced by the nature of the counterface material. In particular, extremely high wear rates are encountered with stainless steel but the work shows that this can be avoided by chromium plating its electrocounterface. The results in general indicate that the wear of electroplated and electroless coatings is crucially dependent upon the wear mechanism: heat treatment of electroless nickel improves the adhesive wear resistance for metal/metal sliding but impairs the ductility for flexing, gouging, and heavy abrasive wear. The relative positions of electroplated, electro less, and composite coatings in the range of engineering coatings available are considered and the importance of wear diagnosis in materials selection and design is discussed.
Surface Characteristics of Continuously Annealed Steel Sheet in Heat Treated and Pickled Conditions
Authors: Leijon W. , Augustsson P. -E. , Olefjord I.
Published: January 2014

The aim of the present work was to simulate the chemical state of the surface of cold rolled steel sheet which results from some of the treatments used on a continuous annealing line (CAL, developed by Nippon Kokan). By using ESCA, GDOS, and SEM the surfaces of two different steels were characterised. One steel was a low alloyed, conventional deep drawing quality (DDQ) steel, the other a dual phase (DP) steel alloyed with manganese and silicon. The surface was studied after four different subprocesses: as received after cold rolling; after annealing and gas cooling; after water quenching; and after pickling. On annealing at high temperature in a protective atmosphere consisting of nitrogen and hydrogen the iron oxides are completely reduced. However, the elements manganese and silicon, which have high affinities to oxygen, will form oxides on the surface, distributed as discrete particles. The DP steel, which has a relatively high bulk concentration of manganese and silicon, exhibits a larger surface coverage of these oxides than the low alloyed DDQ steel. On water quenching the metallic part of the surface, consisting of iron, is reoxidised, forming a rather thick iron oxide film that almost covers the oxide islands. This thick film is unacceptable and must be removed by pickling. Simulation of the pickling process shows that the iron oxide formed during water quenching is completely removed. The surface after pickling consists of a thin iron oxide film formed during pickling and rinsing. The manganese and silicon oxide islands are not completely removed by pickling, as can be seen from the ESCA analyses and SEM. However, pickling reduces the difference in surface coverage of these oxides between the two types of steel.
Fabrication, Microstructure, and Cavitation Erosion Resistance of a Grey Iron Laser Surface Alloyed with 22%Cr
Authors: Tomlinson W. J. , Bransden A. S.
Published: January 2014

A flake graphite grey cast iron has been laser surface alloyed with 22%Cr, and the cavitation erosion of the coating in distilled and 3%NaCl waters has been investigated at 50°C using a 20 kHz vibratory apparatus with an amplitude of 15 μm. Except for a few pores, limited cracking, and an occasional undissolved particle of chromium, the coatings were relatively uniform in thickness (∼ 0.5 mm), composition, and microstructure, and had a high integrity ana continuity with the substrate. The microstructure consisted mainly of an austenite and ferrite mixture. The coating reduced the steady state erosion rate of cast iron in distilled and salt waters to 0·04 and 0·11 of the uncoated level respectively.
Optimisation of Deposition Parameters for Desired Mechanical and Frictional Properties of Reactively Sputtered TinX Films
Authors: Manory R. R.
Published: January 2014

A series of experiments for optimising titanium nitride films deposited on various substrates is described. The target to specimen distance was found to affect the deposition rate, the lattice parameter, and the microhardness of the films. The surface preparation was found to affect the form of the X-ray diffractograms obtained from the films. Optimisation of the films was based on maximum microhardness and not on maximum deposition rates. Microhardness values of (111) oriented films deposited on different substrates after such an optimisation exceeded 3300 HV(3g). The friction coefficient of these hard films against diamond was found to be in the range 0.06-0.14.
Contact Configuration Effects on the Dry and Lubricated Wear of Polymers
Authors: Hosseini S. M. , Stolarski T. A.
Published: January 2014

An investigation into the wear of polymers in tribologicql contact with steel is reported. Five polymers, polypropylene, poly(etrajiuoroethylene, high density polyethylene (HDPE), Nylon 6:6, and polyetheretherketone (PEEK), were tested in polymer pin on metal plate and metal pin on polymer plate configurations, with and without lubrication. The metal pin on polymer plate configuration gave significantly lower wear rates for all the polymers tested, suggesting that contact conditions are less severe than for the reverse configuration. Lubrication reduced the wear rate under both configurations, although with PEEK, which wears mainly by an abrasive mechanism, this reduction was negligible. Lubrication was also ineffective with HDPE in the metal pin on polymer plate configuration, film lubrication conditions not being attained. The results are discussed in terms of proposed friction and lubrication mechanisms.
Electrochemical Properties of Nitrided Ferrous Materials
Authors: Ibendorf K. , Schröter W.
Published: January 2014

Results of electrochemical and X-ray studies of pure iron and iron based alloys nitrided in an NH3-H2 atmosphere at 550°C are presented. Structural peculiarities of the nitrided layers are related to the solubility of some alloying elements, especially chromium, in iron nitrides. Current density-potential curves recorded on oblique sections at various ‘depths’ in 0.025M H2SO4 + 0.05M Na2SO4 aqueous solutions show, in principle, a distinct tendency to passivation of 8 compound layers. Significant changes in the electrochemical behaviour of iron-chromium alloys containing ∼6.5 and ∼13%Cr, as characterised by active anodic dissolution, were observed in the precipitation zone. A potential reversal on nitrided surfaces due to oxygen coverage and some effect of soluble alloying elements on the electrochemical behaviour of the 8 phase were also found.
Friction Hardening of Iron – Carbon Alloys
Authors: Kalner V. D.
Published: January 2014

Friction hardening is one of the new technologies utilising concentrated energy sources to surface harden iron based structural alloys. The process has the advantage of simplicity of the methods and devices used, and the high energy densities of frictional work attained in localised areas of a large workpiece can create surface structures having similar properties to those obtained by surface hardening with laser radiation, electron beams, or low temperature plasmas without any surface melting.
Non-Destructive Testing of Thin Layers by Holographic Sound Field Imaging
Authors: Crostack H. , Krüger A. , Pohl K. -J.
Published: January 2014

A technique that involves the holographic imaging of an ultrasound field induced on the surfaces of components and its application to flaw detection are described. Optimum test parameters deduced from tests with artificially produced flaws have been found to give good results when examining protective barrier coatings. The presence of flaws detected in plasma sprayed CoCrAIY and zirconia coatings has been confirmed by metallographic analyses. Good resolution of location, size, and (in the case of cracks) depth has been achieved. The technique should be of use for complex components such as turbine blades since the imaging process is not affected by shape.