bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffusion bonding of Ti–25Al–10Nb alloy
Authors: Wu Y. T. , Wei W. S. , Koo C. H.
Published: January 2014

Titanium aluminide is a potential material for high temperature structural application. Recent research on Ti–25Al–10Nb indicates that the alloy possesses excellent superplasticity at high temperature and is suitable for diffusion bonding. In this study, the bonding process parameters, such as surface roughness, bonding temperature, bonding time, bonding pressure, and post-bond heat treatment (PBHT), affecting the properties of bonded joints were investigated. The American Welding Society constrained single lap shear test was applied to assess the quality of the joints. Experimental results showed that a smooth surface roughness is beneficial for the diffusion bonding of Ti–25Al–10Nb. Shear strength of joints increased with the bonding temperature, bonding pressure, and bonding time. However, in the bonding temperature range 850–950°C, shear strengths of joints were all less than 80% of that of the base metal in the single lap shear test. After PBHT at 1050°C for 120 min, the quality of joints could be improved significantly. As rolled Ti–25Al–10Nb can also be diffusion bonded and the bond interface and micro voids eliminated during annealing through recrystallisation and grain growth. Interlayer diffusion bonding using 18 μm thick aluminium foil as an inter layer could lower the bonding temperature to 700°C, but line defects caused by solidification were still present at the centre of the inter layer. Even if the alloy joint was homogenised at 1050°C for 24 h, voids remained in the bonded region. Solid state diffusion bonding of Ti–25Al–10Nb using a TiAl3 interlayer of approximate thickness 50 μm, coated on one side of the joining alloy surfaces, was also investigated. No microvoids were observed in the joint of the solid state diffusion bonded alloy after PBHT at 1050°C for 12 h.
Investigation into properties of laser welded similar and dissimilar steel joints
Authors: Çam G. , Yeni Ç. , Erim S. , Ventzke V. , Koçak M.
Published: January 2014

Laser beam welding is currently used in the welding of steels, aluminium alloys, thin sheets, and dissimilar materials. This high power density welding process has unique advantages of cost effectiveness, deep penetration, narrow bead and heat affected zone (HAZ) widths, and low distortion compared to other conventional welding processes. However, the metallurgical and mechanical properties of laser welds and the response of conventional materials to this new process are not yet fully established. The welding process may lead to drastic changes in the microstructure with accompanying effects on the mechanical properties and, hence, on the performance of the joint. The thermal cycles associated with laser beam welding are generally much faster than those involved in the conventional arc welding processes. This leads to the formation of a rather small weld zone that exhibits locally a high hardness in the case of C–Mn structural steels owing to the formation of martensite. It is currently difficult to determine the tensile properties (full stress–strain curves) of the laser welded joint area owing to the small size(∼V 2·3 mm) of the fusion zone. Complete information on the tensile and fracture toughness properties of the fusion zone is essential for prequalification and complete understanding of the joint performance in service, as well as for conducting a defect assessment procedure on such welded joints. Therefore, an experimental investigation into the mechanical properties of laser welded joints was carried out to establish a testing procedure using fiat micro tensile specimens (0·5 mm in thickness, 2 mm in width) for determination of the tensile properties of the weld metal and H AZ of the laser beam welds. Three similar joints, namely St 37–St 37, St 52–St 52, and austenitic–austenitic, and two dissimilar ferritic–austenitic joints were produced by CO2 laser, using 6 mm thickness plates. The mechanical properties have been examined by microhardness survey and testing of conventional transverse tensile, round tensile, and fiat microtensile specimens. The results for the micro tensile specimens were compared with those for standard round tensile specimens and this clearly showed the suitability of the microtensile specimen technique for such joints.
Laser welding of high hardness armour steel
Authors: Bassett J.
Published: January 2014

A feasibility study of laser welding of high hardness steel (HHS) armours has been carried out at SMC DERA. The main issues investigated were weldability using different fillers and various combinations of beam power and travel speed; heat affected zone (HAZ) size and hardness; Charpy toughness; and ballistic behaviour. The best results in terms of a combination of cracking resistance and toughness were obtained in the autogenous weld, the filler wires tested clearly not being ideally suited to laser welding. A relationship emerged between the weld hardness profiles, in respect of both weld metal hardness and variable HAZ width and softening with beam travel speed, and their ballistic performance.
Effect of nature of grain boundaries on intergranular liquation during weld thermal cycling of nickel base alloy
Authors: Guo H. , Chaturvedi M. C. , Richards N. L.
Published: January 2014

An Inconel 718 based alloy containing only trace amounts of C, S, and P was subjected to thermal cycling in a Gleeble 1500 system to induce microstructural features which are produced in the heat affected zone (HAZ) during welding. In the thermally cycled material many grain boundaries were observed to liquate; however, the liquation was heterogeneously distributed, that is, only some grain boundaries, and often only a few segments of the same grain boundary, liquated. Orientation imaging microscopy and electron backscatter diffraction analysis in a scanning electron microscope revealed that the liquated grain boundaries or segments of a grain boundary that liquated were always non-special geometry (or random) boundaries, whereas low reciprocal volume density Σ coincident site lattice and twin boundaries did not liquate. Therefore, it is concluded that the extent of B segregation, to which liquation of grain boundaries in the H AZ during welding has been attributed, is greater on random boundaries owing to their ability to accommodate a large number of B atoms in comparison with the low Σ boundaries leading to their liquation during Gleeble simulation.
Correlation between weld formation and processing parameters in CO2 laser welding of steels
Authors: Kuo M. , Sun Z. , Pan D.
Published: January 2014

Laser welding, which has undergone rapid development in the past few decades, is one of the most important applications in laser materials processing. Although some general data are available, precise welding parameters are equipment specific. In the present study, a series of autogenous laser welds on mild and stainless steels has been investigated, using a Trumpf 3·0 kW CO2 laser system, to establish welding parameter windows. The correlation between laser power, welding speed, and weld bead profile for bead on plate welding has been obtained. For a constant laser power, penetration depth reaches a stable value as welding speed exceeds 11 000–13 000 mm min-1. This value is defined as the penetration threshold. Lower welding speed produces deeper penetration. However, under such conditions, the unstable keyhole and weld pool could result in undercut and porosity. The maximum penetration achievable for sound welds on both mild steel and stainless steel was investigated. The correlation between penetration threshold and power level was also established. The parameter windows established for autogenous welds can be adopted effectively on butt jointsif welding speed is reduced by 25%.
Derivation of carbon equivalent to assess hardenability of steel
Authors: Kasuya T. , Ichikawa K. , Fuji M.
Published: January 2014

A method to derive carbon equivalent to assess hardenability is demonstrated. The assumptions used in the present method are the additivity rule and the empirical calculation of the incubation time in the time–temperature–transformation diagram. In the present study, the empirical equation for the incubation time before ferrite, pearlite, and bainite transformations proposed by Kirkaldy et al. is employed. The coefficients for silicon, manganese, copper, and nickel calculated in the present study show good agreement with experiments, whereas a considerable discrepancy is observed for the coefficients for chromium and molybdenum. Prior austenite grain size, which influences hardenability, can be incorporated in the carbon equivalent using the method presented in this study.
High dilution submerged arc welding of Cr–Ni–Mo austenitic stainless steel
Authors: McPherson N.A. , Baker T.N. , Li Y. , Hoffmann J.
Published: January 2014

Improvements in the submerged arc welding (SAW) of Cr–Ni–Mo austenitic stainless steel have been achieved from a combination of simplified edge preparation, intermediate heat input, and high dilution (75–80%). The cost benefit is 83% compared with the previously used practice. Mechanical properties of the weld metal in a square edge preparation showed a decrease in yield and tensile strengths, but a significant improvement in toughness compared with the Y preparation weld metal. Thin foil transmission electron microscopy confirmed the presence of χ phase in some areas of the Y preparation weld metal, and M23C6 in some areas of the square edge preparation. This has been related to the incidence of fewer reheated and cooled areas in the square edge preparation weld. The reduced precipitation has influenced the toughness characteristics of the square edge preparation weld metal.
Analysis and optimisation of electrode life for conventional and compound tip electrodes during resistance spot welding of electrogalvanised steels
Authors: de A. , Dorn L. , Gupta O.P.
Published: January 2014

Rapid electrode wear is the major concern in resistance spot welding of galvanised steels. The electrode life in such instances is tremendously influenced by the continuous alloying reactions that occur between the molten free zinc and the copper electrodes. It is shown in the present work that the use of compound electrodes can considerably enhance the effective electrode life. The compound electrodes are fabricated by introducing a tungsten insert at the tip of conventional circular face electrodes. The performance of these new electrodes has been investigated under laboratory conditions during multispot welding. It is observed that the compound tip electrodes can offer superior electrode life only for a small insert size. A finite element method based numerical simulation has simultaneously been carried out. The results of the numerical calculation also indicate that the optimum design of the compound tip electrode depends on the insert size.
Analysis of toughness of welding alloys for high strength low alloy shipbuilding steels
Authors: Metzbower E.A. , DeLoach J.J. , Lalam S.H. , Bhadeshia H.K.D.H.
Published: January 2014

In previous work by the present authors a model was developed for the estimation of the tensile properties (strength and ductility) of ferrous alloys intended for the welding of high strength low alloy steels used in the construction of ships. The method used to model the properties as a function of a large number of variables was based on a neural network within a Bayesian framework. This method is particularly useful when attempting to understand complex non-linear phenomena where the distribution of data within the input space is not obvious. In the present work, a similar approach is used to model the toughness (characterised by Charpy and dynamic tear tests) of the same alloys. The level of noise in the experimental data is perceived to be high, but it has nevertheless been possible to recognise reasonable trends and uncertainties when making predictions. For example, the toughness shows a non-linear deterioration as the oxygen concentration is increased; this behaviour is expected but can now be expressed quantitatively.
Hydrogen attack on simulated weld heat affected zone of 3Cr–1Mo–0.25V steel
Authors: Kim D.J. , Lee W.J. , Kim B.H. , Kim J.T. , Jeong S.J. , Song J.S.
Published: January 2014

Hydrogen attack and the associated change in mechanical properties in a 3Cr–1Mo–0.25V steel subjected to a simulated welding thermal treatment were investigated to show the influence of welding conditions on the heat affected zone. The maximum peak temperature reached in the simulated welding process affected the microstructure, which in turn is related to the occurrence of different quantities of methane bubbles.
Structural stability of dissimilar weld joints of steel P91
Authors: Foret R. , Million B. , Svoboda M. , Stránský K.
Published: January 2014

The present paper addresses the issue of carbon and nitrogen redistribution in weld joints between creep resistant chromium steels. The redistribution of carbon and nitrogen was measured using the wave dispersive X-ray method. The conditions of the long term diffusion annealing process were: temperature 575, 625, and 700°C; and time 10, 100, 1000, and 5000 h. It was ascertained that carbon and nitrogen diffused from the low alloy steels to the high alloy steel P91. The carbon diffusion coefficients in the individual steels in 15128/P91 and SK3STC/P91 weld joints, the ratio between the thermodynamic activity coefficients of carbon in the joints, the diffusion interaction parameters βCr C, and their temperature dependencies were estimated from carbon concentration curves. The present paper also contains a microstructure analysis of decarburised and carburised zones in the weld joints studied.
Rake and Flank Wear Mechanisms of Coated Cemented Carbides
Authors: Dearnley P A
Published: January 2014

A series of commercially available cemented carbides coated with single or composite layers of TiC, TiN, and Al2O3 were used to cut three types of steel, En 8 (080M40), En9 (070M55), and En24 (817M40). For comparison, two uncoated cemented carbides and some Al2O3-ceramic inserts were also tested. The worn surfaces were examined using optical and scanning electron microscopy techniques and tool/work interfacial conditions were evaluated from ‘quick stop’ experiments and tool temperature estimates. By linking this information with observed wear rates, various rake and flank wear mechanisms are proposed.
Thermal Spray Coatings for High Temperature Protection
Authors: Nicoll A R , Gruner H , Prince R , Wuest G
Published: January 2014

Modern design philosophy of high temperature systems is based on the use of a substrate to provide the mechanical strength properties and a thin coating to inhibit oxidation and corrosion. The thin coating can be applied using a wide variety of processes. This paper describes the use of thermal spray processes and, in particular, the process of detonation gun and plasma spraying. The effects of the process environment, combustion system, powder properties, powder injection, and heat treatments are reviewed. Finally, the plasma spraying of thermal barriers is presented and discussed.
Plasma Heat Treatment of Titanium and Titanium Alloy Ti-6Al-4V: Effect of Gas Composition and Temperature
Authors: Rie K. -T. , Lampe Th. , Eisenberg St.
Published: January 2014

The results of investigations into the thermochemical heat treatment of titanium and the titanium alloy Ti-6Al-4V in a glow discharge are reported. The effect of the important process parameters, gas composition and temperature, on the microstructure, microhardness, and mechanism of layer formation has been studied by means of X-ray diffraction and electron microscopy. The microhardness (Knoop) profiles have been measured and related to various heat treatment conditions. It has been found that the microstructure and the microhardness profiles depend strongly on gas composition. The presence of hydrogen in the gas mixture led to hydride formation in pure titanium, while the microstructure of the titanium alloy Ti-6Al-4V was not affected by hydrogen. It was shown that plasma heat treatment in a gas mixture containing carbon resulted in the formation of titanium carbide. At high carbon contents, compound layer formation can be retarded by a deposit of soot on the surface. It has been observed that, in addition to the established methods of nitrogen mass transfer, i.e. implantation of reactive species and reactive sputtering, chemisorption of nitrogen at the surface plays a significant role in layer formation if pure nitrogen gas is used for the plasma heat treatment; however, the addition of carbon to the gas mixture causes variations in the layer formation mechanism.
Assessment of Coating Adhesion
Authors: Valli J. , Makela U. , Matthews A.
Published: January 2014

The main factor which has hitherto prevented the more widespread use of many coating processes has been poor adhesion. There is a real need for a standard test for adhesion to improve user confidence and avoid failure in service. We discuss the available adhesion test methods and recommend the scratch test as offering the best solution at this time, and a new laser photothermal technique as having good potential.
Argon Shrouded Plasma Spray Technology for Production Applications
Authors: Gill B. J. , Ridding F. L.
Published: January 2014

In order to meet the demand for improved performance from engineering components in aggressive environments, increasing attention is being paid to the design and production of surfaces with specific characteristics. One of the most effective means of producing special surfaces without affecting bulk substrate properties is to apply optimized materials in the form of coatings. There are many processes by which one material may be applied to another as a coating, but in the past 25 years plasma spray technology has advanced to become one of the most important. In this paper the principles of plasma spraying and the development of the Union Carbide argon shrouded torch process will be considered together with the methodology of materials and process control. Examples of production applications are taken from the field of gas turbine protection.
Scratch Adhesion Testing: A Critique
Authors: Perry A. J.
Published: January 2014

The method of testing the adhesion of a thin, strongly adhering film by scratching it with a loaded diamond stylus is currently the only really satisfactory test available. In this paper the critical load for coating loss and the accompanying so called acoustic emission are discussed critically, together with aspects of metallurgical interest.
Introduction to Surface Engineering for Corrosion Protection
Authors: Kolb-Telieps A.
Published: January 2014

The methods available to produce corrosion resistant coatings are considered. Although traditional methods such as dipping, electroplating, and painting are described, emphasis is given to recently developed surface engineering techniques, which are discussed under the categories: spraying, chemical vapour deposition, diffusion techniques, physical vapour deposition, mechanical plating, ion implantation, and electron beam and laser glazing. The advantages and problems relating to these approaches are reviewed with extensive reference to current literature. It is concluded that advances can be made by better use of available knowledge as well as by developments based on the surface engineering philosophy of enhancing the surface properties of materials to increase the corrosion resistance above that of the bulk substrate.
Microstructure and Properties of Nodular Cast Iron Surface Alloyed with Tungsten Carbide by Concentrated Solar Energy
Authors: Yu Zhong Kui , Lu Jin Tang
Published: January 2014

The surface of nodular cast iron was first coated with tungsten carbide powder, then melted by concentrated solar energy to form an alloyed layer on its surface. By scanning a high energy focal point over the surface, a predominantly alloyed surface was created after rapid solidification. The surface of the alloyed layer was quite flat, with a microstructure of very fine ledeburite. This alloyed layer possessed a very high hardness and high tempering resistance, and had greatly improved wear resistance compared to untreated nodular cast iron. In addition, excellent adhesive wear resistance is displayed by the alloyed material.
Characterization of Fe-Cr-Ni Alloys Produced by Laser Surface Alloying using Mixed Power Feed
Authors: Chande T. , Ghose A. , Mazumder J.
Published: January 2014

A screw fed, gravity flow, carrier gas aided powder delivery system was used to produce laser surface alloys using chromium and nickel powders on AISI 1016 steel. A 10 kW continuous wave CO2 laser was used for alloying, at incident power densities up to 1.2 × 1010 W m−2 and traverse speeds up to 0.03 m s−1. Ten overlapped passes were used to make alloyed zones 0.05 m long by 0·015 m wide. Alloys with up to 80 wt-%Cr and 58%Cr + 26%Ni were obtained. Surface roughness and corrosion resistance measurements were made. The microstructure was characterized by transmission and scanning electron microscopy. Smoother surfaces were obtained by increasing traverse speed and beam diameter. Corrosion samples passivated spontaneously in a 3.5%NaCI solution in distilled water, but were susceptible to pitting corrosion when uneven su;faces were subjected to corrosion testing. Microstructures were highly refined with a high dislocation density. These results are related to process mechanisms. The reported method of powder delivery is versatile, flexible, and reproducible, and can be used to make useful alloys.
Laser Deposited Austenitic Stainless Steel Clad Layers
Authors: Weerasinghe V. M. , Steen W. M. , West D. R. F.
Published: January 2014

An investigation has been made of some metallurgical features of an austenitic stainless steel (Type 316L) in the fonn of a laser deposited clad layer on a mild steel substrate. The substrate surface was clad by a series of partially overlapping tracks. The cladding material in the forn1 of a fine powder was injected into the laser generated melt pool on the moving substrate. Superior eatures in terms of good surface finish, low dilution, and refined structure have been found in relation to other comparable fusion processes.
Ion Implantation of Titanium Alloys for Biomaterial and Other Applications
Authors: Perry A. J.
Published: January 2014

The existing studies of the effect of ion implantation on the wear, fatigue, and oxidation resistance of titanium and its alloys are reviewed. The majority of the work deals with nitrogen implantation, and rather less with the effect of carbon. Both species lead to a zone immediately below the sample surface with enhanced hardness due to the fine precipitation of nitride or carbide together with dissolved nitrogen or carbon respectively. In addition, the nature of the oxide coating appears to be different from the unimplanted metal: a well adhering low friction TiO film is formed. The combination leads to good wear and repassivation properties. The fatigue properties of carbon implanted material appear to be distinctly superior, the reason, however, not being apparent. Among the implanted metal ion species studied, only barium and platinum have a positive effect: both improve the high cycle fatigue resistance and the former enhances wear and fretting resistance. The mechanism appears to be the blocking of oxidation paths into the metal by the formation of a perovskite phase. The improved properties apply in air or physiological fluids against wear bodies of polyethylene, steel, ruby, or titanium.
Auger Electron Microprobe Investigation of Nitrided Austenitic Stainless Steel
Authors: Chung M. F. , Lim Y. K.
Published: January 2014

Auger electron microprobe observations on plasma nitrided 304 austenitic stainless steel samples have confirmed previous results obtained by scanning electron microscopy and wavelength dispersive X-ray spectroscopy and have also shown some marked differences in micrograin structure between NH3 and plasma nitrided samples. The N H3 nitrided layer appeared to consist of a single layer with precipitate grains, if any, > 0.1 μm size, nitrogen concentration decreasing exponentially with depth. The plasma nitrided layer, on the other hand, consisted of two layers: a near surface layer with constant nitrogen concentration and precipitate grains of B1 (CrN) 1-2 μm in size, beneath which is a layer in which the nitrogen content decreases exponentially with depth, this layer being thinner than its equivalent in the NH3 nitrided material. The differences in nitrogen depth profile and nitriding rate between the two processes are explained in terms of the different resultant microstructures.
Laser Melting of Plasma Sprayed Ceramic Coatings
Authors: Sivakumar R. , Mordike B. L.
Published: January 2014

Improved and reliable ceramic materials are key elements for the development of many advanced energy systems, such as gas turbines and diesel engines. Laser melting of plasma sprayed ceramic coatings represents an important step in that direction. It can seal the pores that are present in the sprayed coatings and thus increase the life of coated components by eliminating the access of corrosive gases and molten salts to the underlying metallic substrate. One of the problems is the cracking of the melted layer during cooling. The objective of the present investigation is to develop an understanding of the effect of various processing parameters on· laser melting of various ceramic coatings based on ZrO2 Al2O3, and TiO2. It is shown that it is possible to produce crack free melted layers in the Al2O3 and TiO2 systems. Directions for future research to achieve this in ZrO2 systems are indicated.
Laser Beam Hardening of a Nitrocarburised Steel Containing O.50/oC and 1%Cr
Authors: Zenker R. , Zenker U.
Published: January 2014

The results of a study on the combined nitrocarburising and laser beam hardening of 50Cr V4 steel are presented. A normalising or hardening and tempering pretreatment was applied before nitrocarburising for 4 or 8 h at 843 K. Surface and cross-sectional microstructure, layer morphology, concentration-depth profiles for carbon, nitrogen, and oxygen, and hardness-depth profiles are presented. A ttempts to correlate laser beam power, traverse speed, and degree of defocusing with the microstructures and hardness profiles obtained are described and the microstructural transformations occurring during laser treatment are discussed. Optimum hardening was obtained when the compound zone has either just or almost been transformed completely, when any porosity present has yet to coagulate to fornz larger cavities, when fine martensite coupled with retained austenite exists near to the surface, when fine, lathlike martensite is found in the diffusion layer, and when nitrogen and carbon are found at levels below those of the compound layer but higher than those of the diffusion layer, across a region wider than the original compound layer. Recommendations for transferring this combined hardening treatment to industrial practice are given.
Selective stripping of high temperature turbine blade coatings and aerospace braze materials
Authors: Gysen B. , Malik M.
Published: January 2014

In the light of increased manufacturing costs for aerospace components and assemblies, methods of removing worn or damaged turbine blade coatings to allow recoating of the original component are assuming ever greater importance. In this contribution case studies are presented describing the development and refining of procedures for the selective chemical/electrochemical stripping of aluminised and PVD MCrAIY coatings from turbine blades. The disassembly of joints by selective stripping of the braze filler material is also considered.
Surface Deformation Behaviour of Tic and Tin Coated Steels: 1 Indentation Response
Authors: Knight J. C. , Page T. F. , Hutchings I. M.
Published: January 2014

Indentation hardness testing using loads of 25–1000 gf on a Vickers profile diamond indenter has been used to study the deformation and fracture behaviour of CVD TiC and CVD and PVD TiN coatings on a range of steel substrates. The coatings were prepared by proprietary processes and were 2–5 /lm thick. The variation of hardness with indentation size and depth has been compared with a number of models for the composite hardness behaviour of coated systems. Good fits were found both to a law of mixtures model incorporating indentation size effect behaviour, and to a simple empirical polynomial. In both cases, parameters can be calculated from which the hardness of the coating itself can be assessed for purposes of quality control etc. For the first time, the variation of hardness with temperature for coated systems has been investigated. For the coating/substrate composites studied here, hardness fell rapidly with temperature, and ‘displayed marked hysteresis of both hardness andfracture behaviour. This reduction in hardness can be so marked that the composite hardness can decrease to below that of the substrate itself above ∼ 300°C. Also, stress relaxation at elevated temperatures leads to copious cracking of the coating during indentation. The observations are discussed and the implications assessed for the tribological applications of coatings. A simple model relating the hysteresis in hardness with residual stress is also presented.
Plasma Sprayed Ni–Al Coatings
Authors: Sampath S. , Bancke G. A. , Herman H. , Rangaswamy S.
Published: January 2014

It is widely appreciated that Ni–Al can act effectively as a bond coat for thermal sprayed coatings. The origin of this technologically significant phenomenon is generally considered to lie in an ‘pexothermic process’ associated with solidification of the molten alloy droplets. This exothermic heat has been variously attributed to compound formation, yielding a high heat of reaction, or to heat of oxidation of aluminium. Experimental tests to date have led to ambiguous conclusions. The present study offers a re-examination of this subject using plasma spraying of Ni–Al, composite and prealloyed, in the presence and absence of oxygen. X-ray and electron microprobe analyses were used to characterise the phase structures of the coatings. Coatings plasma sprayed in air showed significant oxidation products, while those plasma sprayed in a vacuum showed the presence of compounds. The results indicate that for Ni–Al the heat evolved during conventional plasma spraying in air is principally due to partial oxidation of the components, and not to alum inide compound formation, as previously suggested. Mechanical property (tensile bond strength, hardness, and cavitation erosion) tests were performed to verify the microstructural findings.
Paper mill sweat dryer roll
Authors:   none
Published: January 2014

Work originated in Canada, as a result of liaison between the customer and the Technical Services and Sales Departments of Eutectic-Canada, is reported. A sweat dryer roll (model 953A (Table 1)), manufactured by Dominion Engineering, Montreal, experienced pitting and wear of the working surface after approximately 3 years of operation, due to corrosion activity and paper abrasion. Reclamation using a MicroFlo ™ alloy specially formulated for wear and corrosion conditions encountered in paper mills resulted in an estimated increase in service life of 2 years.
Diffusion Chromising of Steel by CVD Using Chloride Compounds: I Coating Process
Authors: Jyrkäs K. , Lajunen L. H. J.
Published: January 2014

A new coating method has been developed, by which a chromium coating 10-40 μm in thickness can be obtained on a steel sheet. The technique used is CVD with metallic chromium and iron (III) chloride reagents. Coating time is 1-4h at temperatures of 840- 980°C. The diffusion coating obtained by this method is uniform and ductile, and has a good adherence to the base metal. The effect of steel composition on chromium diffusion is discussed.
White Layers on Surface of Ground EN24 Steel:2 Effect of Grinding Conditions on Formation and Surface Metallography
Authors: Tomlinson W. J. , Blunt L. A. , Spraggett S.
Published: January 2014

The effect of infeed rate on the thickness of the white layer, surface metallography, and specific grinding energies during centreless grinding have been determined, and the maximum grinding zone temperature calculated. The average thickness of the white layer is a well defined function of the machining conditions, and increases approximately linearly from 0.24 to 1.53 μm as the infeed rate increases from 0.14 to 1-56 mm min−1. The surface roughness increases with the depth of white layer, which is formed essentially by a process of intense plastic deformation. The results are discussed in terms of Shaw's Brinell indentation model of grinding.
Quality Assurance Assessment of Thin Films
Authors: Bull S. J. , Rickerby D. S. , Gent J. T.
Published: January 2014

Thin films produced by a number of deposition technologies have found many applications over the past few years in a range of sectors of engineering. As the use of such coatings becomes widespread, the need to assess the quality and reliability of these films becomes more important, for both coating suppliers as a means of process monitoring and end users as a means of identifying if the properties of the coating are suitable for the intended application. There are a number of coatings evaluation tests which are used at present by both suppliers and end users as ranking tools and it would be an advantage if such tests could be extended to be used for quality assurance (QA) assessment. An ideal QA test would be nondestructive, rely on readily available equipment, be quick and easy to perform and interpret, nonsubjective, amenable to automation, and of relevance to the intended application. Unfortunately such tests do not exist and it is essential to make the best use of the tests that are available if QA assessment is to be attempted on test coupons which can be coated alongside real components. In tribological applications it is often the hardness of the coating which dictates component performance, provided that the adhesion of the coating to the substrate is sufficient. Thus it would appear that hardness testing and scratch adhesion testing might be useful bases for QA tests. A methodology by which both tests can be used for QA assessment, given a ‘standard’ coating for comparison which shows the required performance in the intended application, is discussed. The inferences which may be drawn about the reasons for deviations from the standard behaviour are discussed and illustrated for PVD titanium nitride films. This has highlighted the fact that suitable QA of the components before coating is essential if the coating quality is to be reliably assessed.
X-Ray Residual Stress Determination in Thin Chromium Coatings on Steel
Authors: Eigenmann B. , Scholtes B. , Macherauch E.
Published: January 2014

A method is presented to separate, for the purpose of residual stress analysis, superimposed X-ray diffraction patterns arising from thin surface layers and substrates with similar crystal structures or from multilayer coatings in which the individual layers are of similar structure. The method is also suitable for use on bulk materials in which the stress gradient is very steep. Residual stress determinations were carried out in single and multilayer electrodeposited chromium coatings on steel. In the single coating the maximum residual stress was found to exist in the centre of the coating, whereas in the three layered coating the maximum values were found close to the substrate.
Aluminium Nitride as a Corrosion Protection Coating for Steel: Selfsealing Porous Electrode Model
Authors: Tait W. S. , Aita C. R.
Published: January 2014

The use of aluminium nitride (AIN) as a corrosion protection coating for mild steel is discussed. For comparison, the corrosion protection capability of Al and AI–AIN cermet coatings on mild steel is also examined. The coatings, ∼1.0 μm thick, were grown on water cooled steel substrates by sputtering an Al target in 5N2–95 (Ne1-x + Arx) discharges. Coating crystallography, morphology, surface chemistry, and electrical resistivity were determined prior to corrosion testing. Surface chemistry was also determined after exposure to the electrolyte. Cathodic polarisation electrochemical measurements were used to determine the corrosion rate. Electrolyte pH measurements were carried out to measure 0H- ion concentration resulting from the interaction of the coating with the electrolyte. Microcrystalline AlN coated steel was found to corrode at a rate of 1.5 orders of magnitude slower than uncoated steel, and 2 orders of magnitude slower than Al coated steel. The selfsealing porous electrode model of the corrosion process is presented, which describes the AlN coating as a barrier to both H+ diffusion and electromigration.
Laser Cladding of Paste Bound Hardfacing Alloys
Authors: Lugscheider E. , Bolender H. , Krappitz H.
Published: January 2014

A new technique of laser cladding by a one step process, using paste bound hardfacing alloys, is presented. This process offers the possibility of exact positioning of the hardfacing alloy relative to the laser beam and thus close control of melting conditions. The possibility of prealloying the added hardfacing material with further elements (metals or metalloids) or with hard particles (e.g. carbides) is a further potential advantage. The process is introduced and examples of carbide/hard alloy claddings are given. Results of wear tests on Co–Cr–W–B–Si and Co–Ni–Cr–W–B–Si hardfacings produced by this method are reported. Compared with plasma sprayed hardfacings of the same composition, the laser clad paste bound materials produce coatings with improved wear resistance, provided dilution is kept low.
5th International Conference on Surface Modification Technologies
Authors:   none
Published: January 2014

Reproduced below are synopses of all papers and posters presented at the 5th International Conference on Surface Modification Technologies, organised jointly by The Institute of Metals and Dr T. S. Sudarshan and held at the University of Birmingham on 2–4 September 1991. A proceedings volume containing most of these contributions will be published by the institute early in 1992.
High Speed Laser Boronising of High Speed Steel Gear Cunlng Hobs
Authors: Zhi-fan Han , Zhi-gang Feng , Zhi-rong Zhou , Jang-long Liou
Published: January 2014

The simultaneous decarburising and boronising of high speed steel (HSS) gear cutting hob with 2 kW CO2 laser and a four dimensional machine tool is described. First, the HSS gear cutting hob is partially decarburised at the edge, which involves the use of a special decarburising agent. The edge is then partially boronised after coating with a boride based paste. The laser beam is moved across the hob at relative scanning speed of between 400-1800 mm min-1. Under conditions where surface melting does not occur a thin boride layer (FeB and Fe2B) only 0.08 mm deep is produced, but a transformation hardened layer of 0.9 mm is also produced beneath the boride surface. Good keying of the boride layer to the substrate is ensured due to the sawtooth microstructure of the duplex compound layer. Industrial trials have demonstrated a 100% increase in tool life after this treatment.
Microindentation and Tribological Study of Nitrogen Implanted Martensitic Steels
Authors: Oñate J. I. , Alonso F. , Dennis J. K. , Hamilton S.
Published: January 2014

Ion implantation is an established technique for the modification of the surface characteristics of materials by bombardment with high energy ions to improve properties such as wear resistance, hardness, fatigue, and friction behaviour. The low treatment temperatures involved in this technique ensure the avoidance of distortion and are ideal for components and tools finished to a high precision. Results obtained in the present work illustrate that wear resistance and surface hardness of AISI M2, D2, and 420 steels can be improved by nitrogen implantation at doses > 1017 ions cm -2. Lubricated Falex wear tests carried out using high loads showed an enhancement in wear resistance and a significant decrease in the coefficient of friction, especially for 420 and D2 steels. Use of an ultramicrohardness technique has shown that the true hardness of implanted surface layers is greater than the values obtained by conventional micro hardness methods that result in penetration below the implanted depth. Other mechanical property data, such as elastic recovery and elastic modulus, can also be obtained from the shallow implanted layer. The results indicate that implantation of nitrogen can bring about a significant change of the near surface region of steels, promoting a change in the dominant wear mechanism and thus improving tribological behaviour of the surface.
Effects of Vapour Deposited and Bulk Alloyed Ruthenium on Corrosion Resistance of a Duplex Stainless Steel in Sulphuric Acid
Authors: Potgieter J. H. , Wentzel E. , Myburg G.
Published: January 2014

An investigation was carried out to assess the corrosion resistance of duplex stainless steel that was surface alloyed with ruthenium. It was found that vapour deposited ruthenium on the surface of a duplex stainless steel improved the corrosion resistance, especially if the alloy is annealed after surface deposition has been carried out. The ruthenium apparently increases the corrosion potential to more noble values, and also inhibits anodic dissolution. This method promised a more economical technique of cathodic modification than bulk alloying.
Structure and Mechanical Properties of Coatings Produced by Dynamic Ion Mixing
Authors: Rivière J. P. , Delafond J.
Published: January 2014

Ion implantation is now applied on a wide scale for Si doping in the semiconductor industry but its application to other materials is more recent. The ion beam mixing of predeposited surface layers with substrate materials has expanded the potential uses of ion beams to modify material properties. However, the shallow implanted or mixed layers (about 0·1 μm) are often insufficient for many technological applications and a new method combining ion beam mixing with simultaneous deposition, dynamic ion mixing (DIM), removes the thickness limitation imposed by finite ion ranges and allows for the buildup of thicker coatings on engineering components. The characteristic of the DIM technique is the use of a high energy (100-400 keV) heavy ion beam (Ar + or Xe +) to produce localised energetic deposition of the target atoms. One of the most important features of this surface alloying process is to produce atomic mixing at the film/substrate interface which is important in the first stage of coating. This deposition results in an intermixed layer of graded composition which improves markedly the adhesion performance of the film. Moreover, the high atomic displacement rate achieved during heavy ion bombardment can also be considered to be a modification of the process itself which is used to control the microstructural state of the film. For instance, crystallisation of amorphous coatings can be obtained by DIM at temperatures much lower than those required in conventional thermal treatment. Some recent examples of coatings produced by this method on stainless steel and tool steel are described, including intermetallics (CuNi, FeAl) and ceramics (TiC, SiC, TiB2). The microstructural characteristics of the coatings were studied by TEM observations on crosssectional samples and composition-depth profiles were carried out by secondary ion mass spectroscopy. In all cases it was demonstrated that thick and adherent coatings with homogeneous and controlled structures could be produced. The adhesion performance of the coatings has been studied by means of scratch tests and the friction and wear behaviour assessed on a standard ball on disc tribometer. The hardness of the coatings was determined from nanoindentation experiments.
Surface Modification of Ceramic Materials Using Excimer Lasers
Authors: Schubert E. , Bergmann H. W.
Published: January 2014

In ceramics processing, the final machining steps for surface loaded devices have until now been mechanical in nature. Techniques such as turning or grinding, followed by finishing, lapping, honing, or polishing, are usually sufficient to produce the desired surface roughness. The lifetime of a ceramic component is in most cases determined by its surface features. Crack initiation often occurs at machining marks because the stress intensity factor of such defects results in higher stresses in the surface on loading. If these stresses exceed the material's strength, failure of the workpiece will occur. Depending on the actual conditions in service, various combinations of surface properties, e.g. roughness, coefficient of friction, or the absence of porosity, are required. Irradiating the surface with an excimer laser is a contact free, optical process that seals the surface with simultaneous smoothing and reduction in surface porosity. Results for laser treated alumina samples of different purities with as fired and diamond polished surface finishes are presented. The investigations show an improvement in both bending strength and Weibull modulus of the treated specimens.
KINETICS OF GROWTH OF PLASMA NITRIDED LAYERS ON A TITANIUM MODIFIED STAINLESS STEEL
Authors: Kuppusami P. , Terrance A. L. E. , Sundararaman D. , Raghunathan V. S.
Published: January 2014

The kinetics of growth of the subsurface layer containing CrN in plasma nitrided titanium modified stainless steel D–9 in the temperature range 773–923 K have been studied using the techniques of microhardness measurements, X-ray diffraction, and electron probe microanalysis. The hardness profile of D–9 exhibits a sharp boundary between the nitrided layer and the bulk and consequently, it has been analysed as one in which strong nitrogen-chromium interaction prevails. The kinetics of nitriding has been discussed according to a rate equation derived from an internal nitriding approximation. The growth of the thickness of the nitrided layer has been found to be parabolic with nitriding time in the temperature range of investigation. The calculated diffusion coefficients of nitrogen in the nitrided layer have been found to be larger than the reported diffusion rates in the austenite phase. The nitrogen concentration profiles have been explained on the basis of differing diffusion rates of nitrogen in the nitrided layer and the bulk.
EFFECT OF RARE EARTH ELEMENTS ON MICROSTRUCTURE AND WEAR RESISTANCE OF LASER REMELTED IRON ALLOY COATINGS CONTAINING METALLOIDS
Authors: Wang Y. , Liu J.-J. , Yu Z.-H.
Published: January 2014

The microstructure, hardness, and wear resistance of thermal sprayed and laser remelted M80S20 and M80S20–8CeO2 self-fluxing alloy coatings (where M signifies a metallic content, predominantly iron, and S represents a metalloid content specifically boron, silicon, and carbon) were investigated using SEM, an electron microprobe, a microhardness tester, and an Amsler wear testing machine. The results showed that the rare earth element can significantly improve the surface quality, microstructure, and wear resistance of laser remelted coatings.