bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation and Growth of Compound Layer on Nitrocarburizing Iron: Kinetics and Microstructural Evolution
Authors: Somers M. A. J. , Mittemeijer E. J.
Published: January 2014

A simple method for determining the hardness or thickness of very thin (few micrometre) ceramic coatings is described. The methods employed are demonstrated for hard, thin coatings of titanium nitride, deposited by physical vapour deposition on to high speed steel substrates. A procedure has been formulated, using the microhardness technique, to carry out thickness, hardness, and adhesion quality control checks on coated items.
Hardfacing using Bars
Authors:   none
Published: January 2014

In repairing heavily worn surfaces, significant benefits are demonstrated for incorporating preplaced solid bars along with standard weld deposition and hardfacing techniques.
Post-Treatment of Metal Composites by Hot Isostatic Pressing
Authors: Steffens H. D. , Dammer R. , Fischer U.
Published: January 2014

Metallic composites with specifically defined properties may be produced by various techniques. Thus, for example, high temperature materials can be covered by MCrAIY coatings by means of low pressure plasma spraying. These coatings offer considerable advantages with regard to high temperature oxidation resistance and generally lead to a longer useful life of the coated components. A further possibility to improve the properties of such composites is a post-treatment by hot isostatic pressing (hipping). The hipping process increases the density of the coatings and has so far proved itself in improving the mechanical properties of components made of nickel and cobalt base superalloys.
Guidelines for Testing of Arc and Flame Spraying Equipment
Authors:   none
Published: January 2014

This official document of the International Institute of Welding has been prepared by Dr E. Kretzschmar, of ZIS, Halle, on behalf of the German Democratic Republic Delegation, and has been accepted by IIW Commission 1 for comment by other Commissions, as the prelude to producing a final document for publication in ‘Welding in the World’. Modern spraying technology imposes important requirements on practitioners, including adherence to relevant national health and safety regulations, while a vital contribution to quality assurance and control is the correct and efficient operation of the process.
Boron Condensation from Glow Discharge
Authors: Filep E. , Farkas Sz. , Kolozsvary Z.
Published: January 2014

The efficiency and morphology of boron deposition have been investigated in a glow discharge, using a BCl3-H2 mixture. The efficiency of reaction depends on the initial BCl3 concentration and the gas flowrate. The maximum efficiency was 27% at 800° C using an initial BCl3 concentration of between 0.2 and 10 vol. -%. Under these conditions the boron condensed on the caihode as slightly overlapping spiral crystals. The quantity of condensed boron increases linearly with higher initial BCl3 concentration, and thus the reaction should be considered as being first order relative to the BCl3 concentration.
Cathodic Arc Evaporation as a Coating Technique
Authors: Rother B.
Published: January 2014

The fundamentals and applications of cathodic arc evaporation (CAE) are reviewed. Quantitative and qualitative estimates pernlit direct comparison with other high speed physical vapour deposition techniques. The potentials and limitations as well as recent developments of CAE are outlined.
Corrosion Behaviour of Stainless Steels Aner Plasma and Ammonia Nitriding
Authors: Flis J. , Mańkowski J. , Roliński E.
Published: January 2014

Steels Cr17Ni2 and Cr18Ni9Ti were plasma nitrided and nitrided in ammonia at 585°C for 16h, and the layers obtained examined by X-ray diffraction and microhardness measurements. Corrosion properties were determined in 0.05M Na2SO4 at pH 3.0 and 5.0, with and without added chloride, using a potentiodynamic polarisation method. Nitriding resulted in a deterioration of corrosion resistance, especially in the acidic (pH 3.0) solutions, whereas in the near neutral (pH 5.0) chloride free solution the deterioration was slight and limitea to the transpassive region. Ammonia nitrided layers with ε +γ nitrides had lower corrosion resistances than plasma nitrided layers with γ nitride alone. This can be explained by the high porosity of the ε nitride layers and the resultant exposure of diffusion zones. The corrosion resistance of diffusion zones with CrN precipitates was markedly lower than that of outer nitride zones and of steel cores.
Influence, of Ti Intermediate Layer on Properties of Tin Coatings Deposited on Various Substrates
Authors: Van Stappen M. , Malliet B. , De Schepper L. , Stals L. M. , Celis J. P. , Roos J. R.
Published: January 2014

The effect of a Ti intermediate layer on the properties of TiN coatings has been investigated for stainless steel AISI304 and high speed steel ASP 23 substrates. In this context surface morphology, crystallographic orientation, hardness, and adhesion to the substrate have been studied. A Ti intermediate layer of 0·1 to 0·2 μm thickness resulted in optimal adhesion of TiN on ASP 23. Earlier transmission electron microscopy findings on the growth mode of a TiN layer on AISI304 substrate were confirmed.
CERAMIC COATING TECHNIQUE USING LASER SPRAY PROCESS
Authors: Tsukamoto Koichi , Uchiyama Futoshi , Ohno Yoshihiro , Kaga Yasuo
Published: January 2014

A new ceramic coating technique using a high power density carbon dioxide laser has been developed, which makes possible the practical production of solid electrolyte layers for high temperature solid electrolyte fuel cells. Initial experiments have been performed using alumina and copper substrates, which were coated with 91ZrO2–9Y2O3. The crystal structure of the coated layer was cubic. No evidence of monoclinic or tetragonal crystals was found.
Plasma Assisted Deposition of Integrated Optic Waveguides
Authors: Gawne D. T. , Nourshargh N. , Kandasamy I. , Starr E. M.
Published: January 2014

A plasma assisted CVD technique for fabrication of optical planar waveguides on silica substrates is described. Silica films doped with germania have been deposited at 1000-1100°C with <0.3 dB cm-1 attenuation, sharp refractive index profiles, and satisfactory adhesion and integrity. Deposition has been achieved at temperatures down to 100°C, but resultant film attenuation, adhesion, and integrity are substantially inferior. Codeposition of fluorine is shown to improve the mechanical properties, while cladding and buffer layers are expected to enhance the optical performance of the waveguides.
Wear Behaviour of Stainless Steelafter Al2O3 Plasma Spraying for Biomedical Applications
Authors: Santos J. D. S. , Monteiro F. J.
Published: January 2014

A promising use of metallic alloys such as stainless steels, Cr-Co-Mo alloys, and titanium alloys coated with ceramics such as alumina or hydroxyapatite is in biomaterial applications. This procedure can lead to a good combination of properties: corrosion and wear resistance and beneficial bioreactivity from the coating, together with the necessary high yield strength and toughness of the metallic substrates. Results of wear tests on AISI 316L stainless steel, with and without alumina coatings, are presented. The adhesion of the coatings has also been evaluated.
Scratch Induced Subsurface Deformation Behaviour of Thin Ceramic Coatings
Authors: Knight J. C. , Page T. F.
Published: January 2014

Transmission electron microscopy has been used to study the subsurface deformation structures induced in ceramic coatings subjected to scratch testing. CVD TiN, CVD TiC (both ∼ 5 μm thick), and ∼ 2 μm thick PVD TiN coatings, all deposited on steels, were investigated. For behavioural comparison, a relatively soft, thicker ‘coating’ - an aluminised KEA28 steel of reacted layer (Al2O3) thickness ∼ 30 μm - was also studied. For the TiN and TiC samples, both grain boundary decohesion and in grain plasticity were found to feature prominently both in response to subsurface stresses and in contributing to friction by dissipating energy. For the coating on the aluminised steel, plasticity alone appeared as the dominant deformation mechanism. The results are discussed in relation to coating microstructure and wear performance.
Practical Assessment of Spraying and Welding Processes for the Hardfacing of Grey Cast Iron
Authors: Womersley D.
Published: January 2014

The results of a practical investigation into the potential assessment of spraying and welding processes for the hardfacing of grey cast iron to resist abrasive wear are reported. The choice of alloy, processes, operating techniques, and testing procedures are discussed.
Materials Science Aspects of Ion Beam Technology
Authors: Dearnaley G.
Published: January 2014

Ion beams can provide the most versatile and sophisticated family of methods for tailoring the surface properties of all classes of material (semiconductors, metals, ceramics, polymers, etc.). Their usefulness is due to the particle energies they carry which are much greater than conventional thermal energies or interatomic bond energies. Consequently, non-equilibrium modifications can be brought about, the results of which are rapidly quenched into place. This paper deals with the application of these methods for the improvement of tribological, optical, electrical, corrosion, and catalytic properties of material surfaces.
Laser Surface Alloying of Titanium with Silicon
Authors: Abboud J. H. , West D. R. F.
Published: January 2014

An investigation is reported of the laser surface alloying of titanium with silicon using a 2 kW carbon dioxide laser and continuous feed of silicon powder. Alloyed zones containing up to 20 at.-%Si were produced using the following processing parameters: 1·8 kW laser power, 2 mm beam diameter, 7mm S-l traverse speed, and powder feed rates ranging from 0·053 to 0·071 g S-1. Fine scale microstructures were produced by solidification sequences involving primary titanium dendrites or primary Ti5Si3, and β + Ti5Si3 eutectic. In the solid state, martensite formation and precipitation of Ti5Si3 occurred. The hardness increased with silicon content up to 620 HV at 20 at.-%Si.
Plasma Nitriding in a Low Pressure Triode Discharge to Provide Improvements in Adhesion and Load Support for Wear Resistant Coatings
Authors: Leyland A. , Fancey K. S. , Matthews A.
Published: January 2014

Wear resistant coatings produced by physical vapour deposition (PVD) techniques are gaining increasingly widespread industrial acceptance, particularly as a means of providing improvements in service life and product quality when used on cutting tools, on casting, moulding, and extrusion dies, and in a variety of other materials processing applications. Titanium nitride coatings are now widely used and second generation alloy coatings such as, for example, Ti(C,N), Ti(B,N), (Ti,Al)N, and (Ti,W)C are being considered for specific wear situations. The next stage in extending the applicability of plasma assisted P VD processing is likely to be in the area of third generation multicomponent coatings, which may incorporate multilayers and/or duplex diffusion/coating plasma treatments. These new combined treatments will primarily be designed to improve coating durability (particularly with regard to toughness and corrosion resistance). The use of alternative substrate materials which are cheaper, lighter, and/or more corrosion resistant than traditional tool steels will therefore also become increasingly important. In order to achieve good coating support with these ‘new’ materials, plasma diffusion or implantation treatments are likely to play a major role, especially if adequate coating-substrate adhesion is to be maintained. This paper investigates the duplex low pressure triode plasma diffusion/coating treatment of ASP 23 tool steel and demonstrates that plasma nitriding has the potential to provide substantial improvements in PVD coating support, if appropriate treatment conditions are employed. The plasma theory behind the suitability of low pressure triode plasmas for precoating diffusion treatments is examined, with particular regard to surface oxide removal by argon-hydrogen plasma precleaning and white layer control by adjustment of the nitriding discharge parameters. The performance of the nitrided/coated (TiN) system under scratch adhesion testing is also discussed.
Diffusion Chromising of Steel by CVD Using Chloride Compounds: 4 Influence of Steel Composition
Authors: Jyrkäs K.
Published: January 2014

The effects of carbon content and low titanium additions on the structure and thickness of chemical vapour deposited chromium coatings produced at 930°C have been studied. Diffusion of chromium in these steels has been examined by calculation of the average diffusion coefficients and determination of the concentration dependence of the interdiffusion coefficient by the Boltzmann- Matano method. The structure and thickness of the coating obtained depend largely on the amount of soluble carbon in the steel. The steels that contained 0.002–0.004% soluble carbon were most suitablefor chromising since only a very thin surface carbide layer was formed. Those steels which contained >0·05% soluble carbon at 930°C produced coatings containing dispersions of (Cr,Fe)23C6 carbide. Such coatings remain thinner and are no longer pure diffusion coatings.
Wear of Ion Implanted Pure Titanium and Ti6Al4V Alloy against Ultrahigh Molecular Weight Polyethylene
Authors: Lausmaa J. , Röstlund T. , McKellop H.
Published: January 2014

The wear of balls of N ion implanted Ti and Ti6Al4V alloy bearing against cups of ultrahigh molecular weight polyethylene was investigated using a simulator to approximate the conditions of an artificial hip joint. Differences in polymer wear rates related to variations in the surface finish of the balls, but not to ion implantation, were observed. The wear resistance of the femoral heads was significantly improved by ion implantation. Analysis of the lubricant showed lower concentrations of metal from the ion implanted specimens compared to non-implanted controls. After 106 cycles in the simulator, the equivalent of approximately 1 year's use of a hip prosthesis in a patient, significant parts of the specimens’ ion implanted layers had worn away. This metallic wear was more extensive with the Ti samples than those of Ti6Al4V. Since the wear conditions in the laboratory simulation may be more aggressive than is typical in patients, the rate of wear of the ion implanted layer in actual use needs to be established from measurements on components removed from patients.
Development of Cobalt Free Wear Resistant Alloys for Nuclear Applications
Authors: Burdett W. B.
Published: January 2014

The major source of shutdown radiation in PWR plant is the 60Co radio nuclide generated from Stellite alloys used for wear resistance in the circuit. Initial attempts to replace cobalt based alloys with materials based on the nickel-chromium-boron system were unsuccessful in prototype testing. A galling test applied to these alloys and a new range of iron based materials has revealed considerable differences in performance. Two iron based alloys, Delcrome 910 and Deloro EB 5183, have now been selected for testing in valves.
Mechanical Properties of Urea Nitrocarburised Nodular Graphite Cast Iron with Hard Eye Structure
Authors: Chen K. C. , Hon M. H.
Published: January 2014

The mechanical properties of urea nitrocarburised nodular cast iron with a hard eye structure have been studied and compared with the same urea nitrocarburised cast iron with a bull eye structure. If the hard eye structure was introduced before urea nitrocarburising, the impact strength and the elongation were higher while its wear resistance, fatigue strength, and tensile strength were lower than for material with the bull eye structure. In the case where the cast iron was heat treated to produce a hard eye structure after it had been urea nitrocarburised in the ferritic state, its impact strength was only slightly increased; but its toughness was improved significantly if it was subsequently subjected to this hard eye heat treatment. A hf hardened urea nitrocarburised nodular cast iron with a bull eye structure exhibited the best fatigue strength and wear resistance. It is then concluded that the toughness and elongation of the investigated cast iron could be improved by introducing a hard eye structure of tempered martensite, while the fatigue strength, tensile strength, and wear resistance were strongly dependent on the structures of the compound layer and of the matrix.
Filtered Arc Evaporation
Authors: Martin P. J.
Published: January 2014

Arc evaporation has been extensively used in the deposition of wear resistant coatings and metallisation. The methods used to improve the quality of arc evaporated films by macroparticle filtering are reviewed. The use of passive filtering, and internal and external magnetic fields are discussed. The technique of filtering using the magnetic plasma duct is reviewed in detail with emphasis on the properties of deposited films. The filtered arc technique is seen to be a useful method for the deposition of metal, nitride, and oxide films.
IOP Annual Congress/Physics World'93
Authors:   none
Published: January 2014

The Institute of Physics’ ‘festival of physics’, held in Brighton on 19–22 April, was the first to take place in conjunction with the Physics World exhibition. Sixteen individual seminars were available to delegates in the well appointed Brighton Centre together with daily plenary lectures. Otherevents included a civic reception at the Royal Pavilion and the Congress Dinner, at which the speaker was Professor Nicholas Kurti.
STRUCTURE AND PROPERTIES OF NICKEL ELECTRODEPOSITED USING SULPHAMATE-SULPHATE-ETHYLENE GLYCOL BATH
Authors: Singh V. B. , Sarabi R. Sadeghi
Published: January 2014

Bright smooth nickel was electrodeposited using a mixed electrolyte (nickel sulphamate–nickel sulphate) in an ethylene glycol solution under various plating conditions. The influence of current density and bath temperature on cathode current efficiency, microhardness, and microstructure was investigated. The effect of annealing of the deposits at various temperatures, on micro hardness and structure was also studied. The micro hardness of the deposits decreased with increasing annealing temperature and bath temperature. Transmission electron microscopy studies revealed that the deposits were fine grained, polycrystalline, randomly oriented, and almost free from defects.
LIGHT ELEMENT WAVELENGTH DISPERSIVE X-RAY ANALYSIS IN SCANNING ELECTRON MICROSCOPE
Authors: Hall M. G.
Published: January 2014

It is shown how the SEM equipped with a wavelength dispersive X-ray analyser may be used for the analysis of light elements in a range of metallurgical samples. The paper aims to help anyone wishing to set up a microprobe analyser for analysis and it describes the history, apparatus used, and the potential for the technique. Several practical analytical situations are explored that show how the technique may be applied to surface engineered components. The problems that can arise are illustrated and examples are given of the results that may be obtained.
EVALUATION OF HIGH ENERGY PLASMA SPRAYED WC-Co COATINGS USING EXPERIMENTAL DESI, GN
Authors: Nerz T. C. , Nerz J. E. , Kushner B. A. , Riggs W. L.
Published: January 2014

Experimental design is an effective means of producing optimum spraying parameters to enhance thermal sprayed coatings. A range of WC-Co coatings is widely used in the aircraft industry to resist severe wear environments. The Box, Bisgaard, and Fung experimental design method was employed to study the relationship between plasma spraying parameters and coating properties for WC-12Co coatings. The coating properties examined were hardness, bond strength, porosity, and microstructural evaluation.
Materials into the 21st century
Authors:   none
Published: January 2014

To coincide with the twenty-first anniversary of its formation, the Department of Materials Engineering at the University of Cape Town hosted a three day international conference in collaboration with the South African Institute of Mining and Metallurgy in October. The conference was broadly aimed at tracing major materials developments over the past two decades as well as addressing key issues into the twenty-first century.
Some recent applications of materials deposited by unbalanced magnetron sputiering
Authors: Kelly P. J. , Arnell R. D. , Ahmed W.
Published: January 2014

Surface coating technologies now play a vital role in many engineering applications, particularly in the areas of wear resistance and corrosion protection. The use of surface coatings can allow stringent specifications to be met by otherwise routine engineering materials. Unbalanced magnetron sputtering, a development of the basic sputtering process, is a highly versatile coating process which is now used to deposit high quality metal, alloy, and ceramic coatings on to a wide range of components. This paper discusses several recent applications of materials deposited by unbalanced magnetron sputtering, including coatings for wear and corrosion resistance, novel supersaturated alloys, and multilayer coatings with pyrotechnic properties.
Measurement methods in surface engineering
Authors: Saunders S. R. J.
Published: January 2014

Current developments in the measurement of the properties of surfaces are reviewed with emphasis given to ongoing work at the National Physical Laboratory. Much of the activity is concerned with devising methods of measuring the mechanical properties of surface coatings, although the significant research on quantification of surface analysis methods is also described. Nanoindentation (or the mechanical property microprobe), a relatively new technique that is gaining wide acceptance and which allows load-displacement measurements to be carried out at nanometre resolution, is also given special emphasis.
Effects of EDM and its mitigation by surface modification on thermal fatigue properties
Authors: Kim H.-J. , Wallace J. F.
Published: January 2014

Electrodischarge machining (ED M) reduces the thermal fatigue resistance compared to conventional machining. The most common corrective treatments employed are electropolishing, shot peening, and the melonite nitrocarburising process, all of which can improve the thermal fatigue resistance. This improvement is attributed to a smoother surface and the elimination of the overtempered layer as well as the removal of the brittle recast layer. The corrosion resistant oxide layer on the melonite treated specimens also has beneficial effects on the thermal fatigue behaviour. The Charpy V notch impact energy of ED electropolished and shot peened samples is slightly higher than that of conventionally machined specimens. However, melonite treatment lowers the impact energy of the specimens compared to conventionally machined samples.
21st International Conference on Metallurgical Coatings and Thin Films
Authors:   none
Published: January 2014

Dr-Ing ULRICH HOLZWARTH of Peter Brehm, Weisendorf, Germany picks out the important developments in wear resistant surface treatments reported in this year's thin film conference.
Zinc coated steel
Authors:   none
Published: January 2014

FRANK C. PORTER reviews the state of the art of zinc and zinc alloy coatings on steel in the light of two recent international gatherings in Paris, which covered the entire range of applications from strip coating to protection of fabricated components.
PVD Coatings for Tool Applications: Tribological Evaluation
Authors: Bromark M. , Larsson M. , Hedenqvist P. , Olsson M. , Hogmark S. , Bergmann E.
Published: January 2014

Four different PVD coatings; CrN, TiN, (Ti, Al)N, and Ti(C,N) have been evaluated with respect to their mechanical and tribological properties. Two different tool steels were used as substrate materials. Several modern analytical methods, including glow discharge optical emission spectroscopy, and three different aboratory wear tests (erosion, abrasion, and sliding wear) have been used. The investigation shows that in order to minimise wear in erosion of coated parts, a coating–substrate composite with high substrate and coating hardness and sufficiently high coating thickness should be chosen. In particular, it was found that theinfluence of coating hardness increases with substrate hardness. A high coating fracture toughness also aids erosion resistance. The difference in intrinsic abrasive wear resistance between the investigated coatings is small. This implies that other coating properties, e.g. oxidation resistance etc., are the limiting factors whenone of these coatings is selected for a given tribological application. From the results of the sliding wear studies it was concluded that the amount of wear of the coated specimen decreases with increasing coating fracture toughness and coating hardness. To retain these properties at high sliding speed the chemical and thermal properties of the coating-substrate composite are highly important. The present work highlights the importance of the coating fracture toughness. This is a property that needs to be more closely examined and, in particular, there is a clearly defined need fordevelopment of reliable, easy to use experimental methods for fracture toughness determination. It should also be noted that the overall performance of the (Ti,Al)N coatings proved to be the best of all tested coatings, which means that if an uncertainty as to which coating material to choose arises, (Ti,Al)N is likely to be a good first choice.
Surface modification by laser induced shock waves
Authors: Masse J.-E. , Barreau G.
Published: January 2014

Laser shock surface treatment is a recently developed process designed to improve component fatigue life in a manner similar to conventional treatments such as shot peening. Irradiation with a short, intense laser pulse can be used to induce plastic strains and compressive residual stresses in metallic substrates. At laser energy densities above the threshold for melting and evaporation a hot plasma can form, expansion of which will induce a shock wave in the substrate, creating plastic strains. The effect of laser induced stress waves on residual stress, micro hardness, and surface quality of a standard steel have been investigated.
Abnormal nitriding behaviour of a high chromium, high manganese austenitic steel
Authors: Gemma K. , Satoh Y. , Ushioku I. , Kawakami M.
Published: January 2014

The nitriding rate of a high chromium, high manganese austenitic steel has been found to exhibit abnormalbehaviour similar to that of austenitic stainless steels, i.e. a sudden decrease of the rate at about 870 K; marked acceleration between 670 and 870 K; a discontinuity at about 670 K; and formation of a nitrogen supersaturated nitrided layer below 670 K. These results require a new explanation, since previous theories address the abnormalities in austenitic stainless steels only. Accelerated nitriding is discussed with reference to the free energy of formation of chromium nitrides (Cr2N and CrN) on a T–∆G° diagram. The sudden decrease of the rate is attributed to the termination of accelerated nitriding.
FORMATION OF COMPOUND LAYERS ON IRON DURING GAS NITRIDING
Authors: Du H. , Lange N. , Ågren J.
Published: January 2014

Gas nitriding experiments were carried out for two series of iron specimens at 575°C: one was preheatedin air at 300°C for 1 h before nitriding, the other was nitrided directly. It was found that the pretreatment has a significant effect on the formation of the nitrides. Without preoxidation, the rate of nitriding was inhibited by a slow surface reaction such that the nitrides were formed on the iron surface inhomogeneously. With preoxidation, a homogeneous compound layer developed rapidly on the iron surface during the subsequentnitriding. The kinetics of the compound layer formation and the effect of the preoxidation on the subsequent nitriding process are discussed together with the previous findings.
9th International Conference on Surface Modification Technologies
Authors:   none
Published: January 2014

Dr PETER DEARNLEY of Leeds University reports on the latest in this series of international meetings covering developments in surface engineering processing, technology, and applications and reviews the newly published proceedings.
INVESTIGATION OF SURFACE SEGREGATION ON COLD ROLLED STEEL BY GLOW DISCHARGE SPECTROMETRY
Authors: Jyrkäs K. , Paavilainen J.
Published: January 2014

The composition of the uppermost surface layer of steel influences the coating properties. Surface segregation is generally considered to be one of the reasons for difficulties that can occur during hot dip galvanising. In the present work the surface composition of cold rolled, batch annealed steels and the change of composition after pickling, polishing, and shot blasting were studied using glow discharge optical emission spectrometry (GDOES) to explain the variations in the reactivity of the steels when undergoing hot dip galvanising. Surface segregation of all the elements included in the measurements (carbon, silicon, manganese, phosphorus, sulphur, chromium, nickel, aluminium, copper, and calcium) was observed. However, only silicon and phosphorus segregation clearly influenced the reactivity of the steel. Steel reactivity during galvanising could not be explained by the segregation of the outermost layer of the steel surface. Some elements (silicon, manganese, and aluminium) can have a relatively thick enrichment zone under the surface and, moreover, silicon concentration profiles can contain two peaks. These findings indicate internal oxidation of these elements, variation of which is a probable explanation for the different behaviour of the steels. Shot blasting, pickling, and polishing clearly influence the reactivity of the steels. Different pretreatments can remove the oxidised unreactive layer and/or increase the concentration of non-oxidised element (silicon). It is evident that the reactivity depends to some extent on the chemical composition of the steel under the topmost surface layer, a zone which is difficult to investigate by surface sensitive analysis methods (Auger spectroscopy, electron spectroscopy for chemical analysis). The present work showed that GDOES is a powerful tool for the analysis of relatively thick surface layers.
RESIDUAL STRESS CHARACTERISATION OF GRIT BlASTED STEEL SURFACES
Authors: Guilemany J. M. , Llorca-Isern N. , Szabo P. J.
Published: January 2014

With most surface engineering procedures it is necessary to create good initial surface conditions. In the case of thermal spraying processes it is recommended that a rough surface is created to enhance adhesion of the coating, especially when the coating contains ceramics. For optimum mechanical properties, in particular fatigue behaviour, the surface must remain in a compressive stress state. When high velocity oxyfuel spraying is used a compressive residual stress condition is strongly advised in view of the pressure and velocity with which the powder particles reach the substrate. The method of surface preparation employed can strongly affect the resultant compressive stresses. The effects of grit blasting conditions on the resultant residual stress state have been studied. Compressive residual stress in the surface layer increases with grit blasting time. Time, gun-specimen distance, and impingement angle have also been evaluated and show complementary behaviour.
FACTORS DETERMINING GROWTH OF DIFFUSION LAYERS ON LOW CARBON STEEL AND IRON DURING VACUUM CHROMISING
Authors: Kasprzycka E. , Tacikowski J. , Pietrzak K.
Published: January 2014

Layers produced on low carbon steel and Armco iron during vacuum chromising have been investigated. In particular, the influence of two fundamental factors, the surface area of the sublimating metallic chromium and the pressure within the furnace chamber, is discussed. Layer thickness and morphology, and the chromium and iron concentrations in the diffusion zone of chromised layers, have been studied. Layers consisting of solid solutions of chromium in iron resulted in all instances. Chromising conducted at low pressure, with a static rather than a dynamic vacuum, was found to be most effective for maximising the rate of growth of diffusion layers. Scanning electron micrographs of the surfaces of chromised low carbon iron alloys show the presence of microsteps characteristic of screw dislocations. Hence, it is concluded that the growth of diffusion layers during vacuum chromising depends on the generation and growth of dislocations according to Frank‘s spiral lnechanism model.
Corrosion behaviour and microstructure of two thermal spray coatings
Authors: Neville A. , Hodgkiess T.
Published: January 2014

Many of the state of the art thermal spray coatings (e.g. plasma, HVOF) have been developed with wear resistance as a primary aim. However, these coatings are increasingly being required to function in aqueous environments and, to date, their corrosion behaviour is not well defined. This paper comprises a description of a study of the corrosion behaviour of two types of thermal sprayed cermet coatings applied to a superduplex stainless steel (UNS S32760) substrate. Both coatings (86WC-10Co-4Cr and 50WC-50Ni-Cr-B-Si) were applied using a proprietary HVO F process. Each generic coating was studied in three forms: unsealed, sealed using a polymeric sealant, and with an interlayer of Inconel 625 applied between coating and substrate. Surfaces were tested in both the as sprayed condition and after abrasion and polishing to 1üm. The coatings were exposed to seawater and a low total dissolved solids (TDS) water at 18 and 50°C. The corrosion behaviour and detailed corrosion mechanisms were investigated using electrochemical monitoring techniques supported by precise post-test microscopical examination using light microscopy, scanning electron microscopy, and X-ray microanalysis. The two coatings studied are shown to be susceptible to corrosion after relatively short periods in both the low TDS water and seawater. Distinct differences in the extent and mechanisms of attack are demonstrated. In addition, the findings from electrochemical accelerated tests are shown to correlate well with the results of detailed examination of specimens after longer term exposure to the aqueous environments.
Influence of contaminants on gas nitriding
Authors: Irretier O. , Naber C. , Dong J. , Klumper-Westkamp H. , Haase B. , Bauckhage K.
Published: January 2014

Machining of steels not only affects the shape of the workpiece, but also influences surface structure and composition. At elevated temperatures and pressures during machining or the subsequent cleaning process cooling lubricants, hydraulic oils, machine greases, and cleaning residues can form stable adsorption or reaction layers. These layers can work as barriers and therefore inhibit surface modification reactions, as can be seen in the example of gas nitriding. The aim of the present investigation was to explore possible mechanisms of reaction inhibition and develop a nitriding process more reproducible in terms of reaction temperature and residence time. Samples prepared with residues of cleaning and machining processes on different alloy surfaces were nitrided under normal conditions and with extremely short residence times (1 < t < 20 min), in order to detect the effect of reaction and barrier layers on nitrogen acceptance during the initial stages of the nitriding process. For all alloys examined the samples with adsorbed cleaning agents showed the worst nitriding result. Volatile contaminations of industrial cleaners such as tens ides desorbed from the surface during gas nitriding. Non-volatile contamination and reaction layers such as phosphates and silicates are stable and hindered gas nitriding during the entire process period. The nitriding hindrance of non-volatile contaminants was found to increase with increasing chromium and aluminium content of the steel and decreasing nitriding time.
Microstructure and mechanical properties of Ni-Al composite coatings for tribological applications
Authors: Ding Y. , Northwood D. O. , Alpas A. T.
Published: January 2014

Composite coatings consisting of alternating layers of Ni and Al were fabricated using a radio frequencymagnetron sputtering system. The composite coatings, which were 15 μm thick and consisted of 30 layers with an average thickness· of 900 nm for the Ni and 200 nm for the Al layers, were fabricated and then annealed at temperatures from 200 to 750°C. In as sputtered coatings a metastable η phase (Al9 Ni2) was found at the interface between Ni and Al layers. In the coatings annealed at 550°C, there were the stable intermetallic phases, Al3 Ni and Al3 Ni2, and the metastable 1] phase. The as sputtered coatings had a hardness of 7·30 GPa and elastic modulus of 123·4 GPa; hardness was found to decrease with increasing annealing temperature. The strength decrease arose mainly from an increase in the grain size of the nickel and aluminium. The coefficients of friction of the as sputtered and annealed (at 550°C) coatings were 0·36 and 0·27, respectively, lower than that for an as sputtered Ni film (0·54). The improvement in tribological behaviour is mainly attributable to the production of the intermetallic phases.
Tribological evaluation of copper coated aluminium
Authors: Ashrafizadeh F.
Published: January 2014

The influence of copper coatings prepared by a pack diffusion method on tribological properties of aluminiumalloys has been investigated. Powder mixtures were used in order to form metallic copper and to diffuse it into an aluminium alloy. The treatments were carried out at a range of temperatures and times to optimise the coating thickness and to control the formation of intermetallic phases on aluminium. Coatings and interface regions were examined by scanning electron and optical microscopy, X-ray analysis, and microhardness measurements. Tribological tests were conducted on a reciprocating wear testing machine under dry conditions and the worn surfaces were examined by SEM. The results show that copper coatings produced by pack diffusion have good adhesion to the aluminium substrate, offer a low coefficient of friction, andprevent the galling of aluminium to steel. Near the interface regions, diffusion zones develop and hard intermetallic phases are produced. The effect of increasing thickness was to increase the load bearing capacity of the coating. Experimental findings also suggest that diffusion copper coatings make a suitable base on aluminium parts for soldering or plating operations.
INFLUENCE OF RF SUBSTRATE BIAS ON PROPERTIES OF REACTIVE SPUlTERED TiAlN FILMS
Authors: Shew B.-Y. , Huang J.-L. , Lii D.-F.
Published: January 2014

A thin coating of TiAIN was deposited on a high speed steel substrate by reactive sputtering. The effect of varying the rf substrate bias on microstructure, chemical composition, and mechanical properties of these films was investigated. The deposition rate and critical N2 jlowrate decreased with increasing bias voltage. A stoichiometric composition of TiAIN was obtained and the chemical composition was found to be independent of bias voltage if the N2 jlowrate exceeded a critical value. Large grained microstructure was developed with increased bias voltage, probably because of the larger size and smaller number of nuclei formed. A denser, harder film was obtained with increasing bias voltage, but adhesive strength decreased as substrate bias increased owing to the residual stresses developed. Optimum wear resistance occurred at a bias voltage of 80 ∼. this was probably a result of the combined effects of hardness and adhesive strength.
NUMERICAL MODELLING OF RESIDUAL STRESSES IN BORIDE lAYERS ON STEEL
Authors: Golański D. , Bieliński P. , Wierzchoń T.
Published: January 2014

The properties of boride layers produced by a plasma boriding process are described and the residual stressesin these layers are analysed using a numerical modelling method. It has been shown that a new method combining electroless nickel deposition and plasma boriding is possible. The results of the present study show that compressive residual stresses in the (Fe,Ni)2B layers are reduced by about 1500 MPa, relative to those in the thin surface (Fe,Ni)B layers. This should reduce the brittleness of the borided case and hence improve wear resistance, as was observed in the preliminary studies reported.
Fretting behaviour of TiN coatings
Authors: Wei J. , Fouvry S. , Kapsa P. , Vincent L.
Published: January 2014

Titaniunl nitride coatings are often used to increase the wear resistance of steel. In this study, the fretting ear of TiN coatings sliding against a 52100 steel sphere as a function of relative humidity, normal force, displacelnent, and reciprocating frequency was measured in the gross slip regime. The critical values for transition from the partial slip regime to the gross slip regime were determined and displayed in a running condition fretting map, which indicates the different contact conditions. No stick regime was observed for TiN coatings. The critical values of displacement were reduced by increasing the relative humidity. Curves of friction coefficient against number of cycles were characterised by an initial rapid increase, followed by a small decrease and a steady state. The profiles of fretting scars were characterised by a small wear depth in the central part and a locally large wear depth in the outer part. The coefficient of friction and wear decreased with increasing relative humidity. Other experimental parameters also had an influence on the fretting behaviour of TiN coatings. Debris played an important role in the fretting wear of the coatings. The effects of the experimental conditions are related to the morphology and composition of the debris and its formation and elimination.
Dry coating method for surface modification of particulates
Authors: Singh R. K. , Ata A. , Fitz-Gerald J. , Hendrickson W.
Published: January 2014

Surface modified particulates have many potential industrial applications, ranging from new technologies such as rechargeable batteries and fiat panel displays to a wide variety of unit operation processes such as dispersion, transport and handling, and separation of particulate systems. Owing to environmental constraints, there has recently been a strong interest in the development of dry methods (chemical and/or water free) for particulate coatings. This paper reports on the feasibility of a novel dry method based on a magnetically assisted impaction process for synthesis of surface modified particulates. In this process magneticparticles in the coating system accelerate and collide with the core and secondary particles to form composite particles. Experiments have been conducted on a variety of particle systems such as Si02–SiC, CoO–Ni(OH)2, Al203–PMMA, and Ti02–Al203. The composite particles were subjected to high frequency ultrasound so that weakly adhering particles could be removed from the surface. The experiments showed that adherent uniformly distributed coatings could be formed in a wide variety of systems. Magnetically assisted impaction coatings were found to be more adherent and possess a higher surface coverage than coatings produced by standard blending methods. Preliminary experiments have also been conducted to investigate the effects of variations in materials parameterssuch as hardness of core and secondary particles.
Processing and characterisation of diamondlike carbon films
Authors: Zhang S. , Wang B. , Tang J. Y.
Published: January 2014

In nature, carbon has two crystalline allotropes, diamond and graphite, with vastly different properties. However, through chemical or physical vapour deposition (CVD or PVD) a third state, diamondlike carbon (DLC), can be synthesised at low temperatures. There are two kinds of DLC films, one with a relatively large amount (up to 50 at.-%) of hydrogen which is thus named hydrogenated DLC, or a-C: H, and the other essentially without hydrogen inclusion which is thus named non-hydrogenated DLC or a-C (amorphous carbon). There are two basic ways to synthesise a DLCcoating: one is to dissociate a hydrocarbon gas (methane, ethylene, butane, etc.), and the other is by sputtering of a graphite target. Unbalanced magnetron sputtering, arc ion plating, and microwave, cathodic arc, and plasma assisted CVD are examples of suitable processes. The advantages and limitations of these processing methods are discussed. Methods which are often used to characterise DLC coatings are briefly described; advantages, limitations, and important influences on results are also outlined, with emphasis on Raman, infrared, electron energy loss, and NMR spectroscopy.
Composite DLC–metal/metal–carbide coatings produced by electron enhanced unbalanced magnetron sputtering
Authors: Rebholz C. , Ziegele H. , Voevodin A. A. , Schneider J. M. , Matthews A.
Published: January 2014

Composite coatings consisting of metal containing DLC were produced by unbalanced magnetron sputtering in a closed field magnetic configuration. Targets of Ti and W were poisoned with acetylene during the depositionprocess, enabling the formation of a carbon enriched surface layer, which was then sputtered to produce DLC–metal/metal–carbide composites. Target poisoning was controlled by plasma emission monitoring, and a hot filament was used to regulate the ion current to the substrates independently of the magnetron power and substrate bias. Coating morphology and composition were investigated using scanning electron microscopy techniques and glow discharge optical emission spectroscopy. Additionally the films were characterised by means of Raman spectroscopy. Microhardness, pin on disc, abrasive wheel, impact, and scratch tests were pelformed to evaluate the mechanical and tribological properties of the coatings. In pin on disc tests, dry sliding friction coefficients of less than 0·15 were recorded against an SAE 52100 steel ball, even after 1 km sliding distance. The implications of these extremely favourable tribological properties are discussed.
Investigation into Application of Electrodischarge Machining as Steel Surface Modification Technique
Authors: Pantelis D. I. , Vaxevanidis N. M. , Houndri A. E. , Dumas P. , Jeandin M.
Published: January 2014

The feasibility of surface hardfacing/alloying of tool steels using the EDM process has been studied. By this technique, material transfer from the tool electrode (made of sintered Fe–WC) to the steel substrate took place, leading to the formation of a surface alloyedlayer consisting of antiwear constituents (e.g. undissolved carbides). The parameters of the EDM process have been optimised and the microstructure and surface properties (roughness, microhardness, and wear resistance) of the treated material studied. Finally, the industrial potential of this technique is discussed.
Variation of friction coefficient with percentage of metallic matrix in WC–Co coatings sprayed by HVOF
Authors: Guilemany J. M. , de Paco J. M.
Published: January 2014

Hardmetal (WC–Co) coatings are widely used in industry for their good resistance to wear. The continuous improvement of these materials has producedvarious commercial coatings of different metallic matrix content. In the present work, the factors that affect the friction coefficient of HVOF sprayed coatings of WC–12Co and WC-17Co have been evaluated, as have the wear mechanisms taking place during wear testing. By modifying the spraying distance, the two powders were used to produce different coatings in order to study the changes produced on the friction coefficient. A ball on disc test was used to evaluate the specimens (ASTM Standard G99–90) and the resultant structures were observed using optical and scanning electron microscopy. Energy dispersive spectrometrywas used to analyse the wear products generated during testing. The WC–17 Co coatings exhibited higher friction coefficients than WC–12Co coatings. This behaviour was attributed to the larger amount of metallic matrix present. The wear mechanisms were identified as plastic deformation and adhesive wear.