bluuebunny/crossref_metadata_2025 huggingface dataset:
Modelling of austenite formation during rapid heating
Authors: Rödel J. , Spies H.-J.
Published: January 2014

Numerical models of austenite formation during rapid heating of steels are presented. Shifted transformation temperatures, diffusion controlled growth, impingement effects, and the possibility of diffusion less growth are considered. Local equilibrium at the phase interfaces is assumed. Further, the effect of alloying elements under paraequilibrium conditions is taken into account. The model is applied to electron beam hardening of hypoeutectoid steels in order to predict the properties of the hardened zone.
Effect of laser surface hardening on permeability of hydrogen through 1045 steel
Authors: Skrzypek H.
Published: January 2014

The effect of laser surface hardening on hydrogen permeability through AISI 1045 steel was measured and determination of the contribution of compressive stresses to this effect was attempted. Metallography and micro hardness measurements of the heat affected zone were performed to determine the depth of the most hardened zone. It was found that the steady state permeability of hydrogen through steel was reduced from 1·19 x 10-6 A cm-2in a normalised condition to 0·38 x 10-6 A cm-2 for a laser hardened specimen. But when compressive stresses in the hardened layer were relieved by cutting the layer off, the permeation rate of hydrogen increased to 1·74 x 10-6 A cm-2. After correctionfor the effect of membrane thickness on steady state permeability, and analysis of the effective diffusivity using Fick s first diffusion law, it was concluded that the effect can be attributed to compressive stresses in the hardened layer. It was also found that martensite reduces the effective diffusivity of hydrogen but does not affect steady state hydrogen permeability.
Al rich hard coatings on Al alloy by low pressure plasma spraying
Authors: Nakata K. , Ushiroda M.
Published: January 2014

In order to improve the wear resistance of an Al alloy surface, a low pressure plasma spray coating has been applied to make a hard coating. An A6063 alloy was used as the substrate, with coatings of rapidly solidified powders of the alloys Al–50Si, Al–17Si–15Fe, and Al–50Fe. Dense layers with high hardness of 200–240 and 450–530 HV were obtained with Al–50Si and Al–17Si–15Fe powders, respectively. The abrasive wear resistance of these coatings improved by two and three times respectively on that of A6063. A much higher hardness of 700–850 HV was obtained with Al-50Fe powder, but porosity and cracking occurred in the layer. These defects prevented an improvement of the abrasive wear resistance of the coatings compared to those of Al–50Si and Al–17Si–15Fe powders.
Effect of anodised coatings on fatigue crack growth rates in aluminium alloy
Authors: Cree A. M. , Weidmann G. W.
Published: January 2014

This paper reports the findings of fatigue crack growth measurements on a 2014 aluminium alloy that had been anodised using the recently developed boric acidsulphuric acid process. The results demonstrate that fatigue crack growth rates in this alloy can be markedly enhanced by the presence of a thin anodic oxide film. This enhancement can be explained in terms of reduced plasticity induced closure assisted by surface cracking of the brittle oxide film ahead of the propagating fatigue crack.
Surface modification by plasma ion and ion beam implantation
Authors: Husein I. F. , Zhou Y. , Qin S. , Chan C.
Published: January 2014

Plasma ion implantation (PII) is a relatively new technique for the surface modification of materials. It is emerging as a potential competitor for the conventional ion beam implantation technique in many semiconductor and non-semiconductor materials processing applications. The most attractive feature of the PII process is its efficiency in implanting large areas and three-dimensional objects at a rate orders of magnitude faster than conventional methods and without the need for sample manipulation. In this paper, the following PII applications are considered: doping shallow junctions and the etching effects of the doping gases; efficient hydrogenation of polycrystalline silicon thin film transistors; and modification of carbon thin film coatings and rubber materials. The results from investigations of these applications are compared to results obtained by conventional ion beam implantation methods.
Wear behaviour of carbon implanted hard chromium coatings
Authors: Rao Z. , O'Connor B. H. , Sood D. K. , Williams J. S.
Published: January 2014

Recent results are reported from a systematic study of the wear behaviour of carbon implanted hard chromiumcoatings. After carbon implantation to various doses, samples were characterised using ion beam analysis techniques and grazing incidence X-ray diffraction. A nanoindentation technique was utilised to measure near surface hardness and wear tests were carried out in a pin on disc configuration under various conditions; SEM was employed to examine the worn surfaces. Wear behaviour changed significantly and new phases formed as a result of high dose carbon implantation. Wear damage and friction coefficient were dependent on implantation doses as well as on test conditions. Only very high dose (4 × 1017 C cm–2) implantation could significantly improve wear resistance under mild wear conditions. The implications of these findings are discussed.
Evolution of microstructure in BaTiO3 thin films recrystallised by laser
Authors: Okutomi M. , Tsukamoto T. , Niki S. , Dahotre N. B.
Published: January 2014

Barium titanate ceramic thin films fabricated by the electrophoretic deposition technique were recrystallised using scanned CO2 laser irradiation. Conventionally the film is sintered at high temperature (1200°C) to increase adhesive forces between powdered ceramic film and substrate. During this process, however, many micropores and microcracks are produced owing to large shrinkage of fine aggregate grains in the film layer. In order to produce preferred orientation grainswithout these defects, the films were instantaneously melted by laser irradiation and recrystallised. The microstructure of the resulting thin film showed significant growth of platelike crystals and strip grain morphology on the surface. The recrystallised phase of BaTiO3 was tetragonal. Thus the laser scanning process appears to be suited to generating large grains with preferred orientation. In hysteresis D–E curve measurements, remanent polarisation of 48 mCm –2 and coercive field of 320 kVm–1 were the best dielectric and ferroelectric properties obtained in a film of 4 μm thickness.
Wear behaviour of mosaic shaped surfaces produced by laser hardening
Authors: Munteanu V. , Levcovici D. T. , Paraschiv M. M. , Levcovici S. M.
Published: January 2014

Surface heat treatment by laser radiation develops microstructural constituents with improved wear resistance. However, this technique is limited in terms of the depth of hardened layer achievable. For large wearsurfaces mosaic shaping is practised by the generation of bands, resulting in structural inhomogeneities that can affect tribological behaviour. This paper presents results of research performed to determine the optimum tribological operating conditions for mosaic shaped surfaces. Specimens were prepared by different combinations of volume and/or surface heat treatment; laser mosaic shaping generated bands inclined at various angles to the displacement directions. Loadbearing capacity, friction coefficient, and wear resistance have been investigated. The results demonstrate improvements to laser mosaic shaping techniques for large wear surfaces.
Surface Engineering for Improving Performance of Mining and Agricultural Implements
Authors: Dasgupta R. , Prasad B. K. , Modi o. P. , Das S. , Jha A. K. , Yegneswaran A. H.
Published: January 2014

Numerous implements used in the mining and agricultural sectors undergo constant wear and so require frequent replacement, resulting in significant financial losses. One way of reducing wear related problems is through surface engineering of the wear prone surface. A variety of surface engineering techniques are commercially available for tribological applications, although cost and convenience in repair and maintenance situations are of considerable importance in selecting a particular method. The most suitable surface modification methods for mining and agricultural implements are welding, hardfacing, and thermal spraying. In addition to attaining the desired wear resistance ofthese implements, improvements in properties such as corrosion resistance can be imparted through appropriate surface modification techniques. The techniques of surface engineering can also permit the use of a cheaper or inferior substrate material. This paper is an overview of the potential of the different surface engineering techniques for improving tribological performance. A number of case studies are discussed where these techniques have been applied successfully in themining and agricultural sectors.
IMPROVED ADHESION OF TiN DEPOSITED ON PRENITRIDED STEELS
Authors: Damaschek R. , Strydom I. LeRoux , Bergmann H. W.
Published: January 2014

This study investigates the deposition of TiN coatings on two stainless steels that have been plasma nitrided before coating deposition. The steels were plasma nitrided under several conditions, producing compound layers and diffusion zones of varying thickness. Subsequently, TiN coatings were produced by electron beam P VD on the nitrided steel substrates. The hardness, microstructure, and phase distribution of the surface regions of the nitrided steels with TiN coatings were investigated by optical metallography, micro hardness measurements, scratch adhesion tests, Auger electron spectroscopy, and X -ray diffraction.
CORROSION AND WEAR RESPONSE OF Cr–B COATED 316L AUSTENITIC STAINLESS STEEL
Authors: Dearnley P. A. , Dortmann N. , Dahm K. L. , Weiss H.
Published: January 2014

Results are presented of an investigation into the corrosion and abrasion response of 316L stainless steelwith and without a surface coating of chromium boride. The coatings were produced by unbalanced magnetron sputter deposition at a pressure of 5 mtorr. Full crystallisation of the coatings was suppressed by the very low homologous deposition temperature (about 0·2Tm). The exact Cr:B ratio was not determined and all coatings were found to be semicrystalline or amorphous; hence, they are referred to in this paper by the general formula Cr–B, rather than CrB. Anodic polarisation and simple abrasive wear testing indicated an improved performance for the Cr–B coated samples. However, under the severest corrosion immersion testing, carried out in 6%FeC13 at 50°C, the coated samples proved inferior to uncoated 316L. The passive nature of the Cr–B coatings resulted in preferential corrosion of the substrate (via galvanic action) which quickly undermined the integrity of the coating.Corrosion of the coating involved the formation of large pits developed by the growth of numerous near circular or Hertzian cracks. It is proposed that this phenomenon was triggered by the accumulation of corrosion deposits at the coating/substrate interface.
GLOW DISCHARGE ANALYSIS ON HARD SURFACE LAYERS
Authors: Ivankovic v. , Stupnisek M. , Cerjan-Stefanovic S. , Mahovic S.
Published: January 2014

Using by way of example an investigation of hard surface layers produced by chemical vapour deposition certain peculiarities in the use of GDS profile analysis are presented. Methods of quantification of the results are given. Of particular significance is the observation of non-uniform sputtering during the analysis.
Crater wear of TiN coated high speed steel tool inserts
Authors: Lim S. C. , Lim C. Y. H. , Lee K. S.
Published: January 2014

This paper reports the crater wear characteristics of TiN coated high speed steel (HSS) tool inserts during single point dry turning operations. Experimental data obtained from carefully executed single point dry turning tests as well as from the technical literature enabled the construction of wear maps showing the crater wear behaviour of these tools over a wide range of machining conditions. The maps show that there is a safety zone (defined by a range of feedrate and cutting speed) within which the rates of crater wear are the lowest. The concept of an overall wear damage map for TiN coated HSS tool inserts is discussed and such a map for this group of coated tools is presented for the first time.
Tribological properties of coating films synthesised by laser assisted plasma spraying
Authors: Sasaki S.
Published: January 2014

This paper reports a new surface modification technique that couples high power CO2 laser processing with low pressure plasma spray coating. In order to clarify the effect of laser irradiation on tribological properties, everal metal and ceramic films have been synthesised using a laser and plasma hybrid spraying (LP HS) system. Tribological characterisation of the films was achieved by a sliding test with oil lubrication. The results show that it is possible to produce a highperformance tribomaterial possessing good adhesion and little microporosity with the LP HS system. Analysis of X RD results suggests that a metastable state is formed by laser irradiation during the spraying process, which is closely related to the antiwear and low friction mechanisms of LP HS produced films.
Coating of SiC with ti by chemical vapour deposition
Authors: Umezawa A. , Yamaguchi M. , Murakoshi Y. , Maeda R. , Sano T. , Hirohashi M.
Published: January 2014

Silicon carbide particle reinforced aluminium alloy composites have been studied. One of the most important problems with metal matrix composites is low interfacial bonding strength between reinforcement and matrix, which results in poor mechanical properties. This work studied the coating method with the aim of improving interfacial bonding between SiC particles and Al alloy. Titanium coated SiC plates and particles were prepared by plasma enhanced chemical vapour deposition (PECVD) using the reactant system TiCl4–H2. Continuous and adherent films on the SiC plates and particles were obtained by PEC VD treatment for 2 min. Treatment by PECVD for periods greater than 2 min resulted in crack formation and agglomeration of particles. Chlorine content in the films was reduced by using laser CVD as compared with PECVD.
Laser surface modification for improving localised corrosion resistance of austenitic stainless steels
Authors: Dayal R. K.
Published: January 2014

Localised corrosion considerably affects the service life of austenitic stainless steel components. Laser surface modification offers a method of improving the corrosion resistance of the components without affecting the bulk properties by producing a novel microstructure having improved properties on the surface of a material. Surfaces of AISI type 304 stainless steel were laser melted in nitrogen using a continuous wave CO2 laser in order to introduce nitrogen into the surface layer. The pitting resistance, as determined by the potentiodynamic anodic polarisation method in 0·5M NaCl rnedium, indicated an improvement which was attributed to the increased content of nitrogen, confirmed by secondary ion mass spectrometry analysis. Using a pulsed ruby laser, Nd–YAG laser, and multibeam continuous wave CO2 laser, surfaces of sensitised AISI types 316 and 304 stainless steels were modified. The extent of sensitisation (susceptibility to intergranular corrosion) was assessed by the electrochemical potentiokinetic reactivation test, as well as by metallographic and immersion test methods. An improvement in the intergranular corrosion resistance was obtained after laser surface melting. This was attributed to the elimination of the sensitised heterogeneous microstructure at the surface. Pitting resistance also increased significantly, reflecting the formation of a homogeneous microstructure and elimination of susceptible sites for pitting corrosion.
Use of ion implantation in high temperature corrosion studies
Authors: Stroosnijder M. F.
Published: January 2014

Ion implantation has an important role in corrosion science as a research tool for studying the irifluence of various elements on the corrosion behaviour of materials. In the present paper this is illustrated by some high temperature corrosion applications, namely its use for studying the mechanisms underlying the so called reactive element effect, for developing more corrosion resistant TiAl based intermetallic alloys, and for addressing mechanistic questions concerned with mixed oxidation/sulphidation. It is shown that ion implantation can be a very efficient screening technique for evaluating the effect of possible alloying additions in materials. Additionally, it can play a role in studying the underlying corrosion mechanisms. It is concluded that ion implantation is apowerful tool in high temperature corrosion studies, and can thus be very helpful for material development.
Wear behaviour of coated sucker rod couplings
Authors: Sonego G. H. , Bellow D. G.
Published: January 2014

Excessive wear of sucker rod couplings and oil field tubing can cause mechanical breakdowns in conventionally pumped oil wells, especially where sand particles contaminate the crude oil. To reduce the wearof the standard AISI 8630 steel couplings they are sometimes coated with hard spray metal particles. Such coatings add an extra expense and it is questionable whether the improved wear resistance of the coupling is justified, especially if it will result in increased wear of the softer oil well tubing. This paper evaluates three such coatings: nickel tungsten, nickel chromium, and titanium oxide. These are compared with an uncoated coupling in a water and a water–sand environment. An economic assessment of the wear results is also presented.
Characterisation of Ni–P electroless deposits with moderate phosphorus content
Authors: Staia M. H. , Puchi E. S. , Castillo E. , Lewis D. B. , Jeandin M.
Published: January 2014

The influence of the phosphorus content on hardness, structure, and morphology of electro less Ni–P deposits on an AISI 1020 steel substrate was investigated. The deposits were prepared from acidic plating solutions based on nickel chloride, as the source of nickel cations, and sodium hypophosphite, as the reducing agent. Coatings with an average of 4·68 and 6·65 wt-%P were obtained, which were analysed using glow discharge optical emission spectroscopy. Variation of phosphorus content with coating thickness was observed when the pH of the solution was not controlled rigorously. The coated samples were annealed at 170°C for 1 h in order to eliminate hydrogen, then post-treated for 25 h at 260°C or 1h at 400°C. X-ray diffraction studies indicated that the as deposited coatings presented a microcrystalline/amorphous or an amorphous structure depending on the phosphorus content. After both heat treatments, a strong (111) preferred orientation was found and coarsening of the grain sizes occurred with increase in temperature. The maximum hardness achieved was 916 HK(100 g) (0.63 GPa). Scanning electron microscopy studies have revealed a nodular, cauliflower type morphology. Extended cracks through the coating surface were observed when the heat treatment was performed at 400°C. A crack free surface was obtained when the heat treatment was performed at 260°C.
Oxide layer phase structure of MCrAIY coatings
Authors: Czech N. , Kolarik V. , Quadakkers W. J. , Stamm W.
Published: January 2014

During operation, stationary blades and vanes of gas turbines are subjected to high thermal and mechanical stresses and severe oxidation. This situation can only be controlled by a composite approach in which the base material provides the necessary mechanical properties and coatings provide protection against oxidation, corrosion and, in the case of thermal barrier coatings, a part of the heat flux. For a better understanding of the oxidation processes on standalone MCrAIY overlays as well as MCr AIY used as a bond coat, in situ X-ray diffraction measurements of the formation and composition of the oxide scale at high temperatures are presented. The phase changes during oxide scale formation are discussed. Data are presented for MCrAlY coatings with 12%AI and 3%Re at three different temperatures versus time. At 950, 1000, and 1050°C a three phase oxide layer of Cr203‘ A1203, and NiCr2O4 was detectable. Rhenium could not be found in the oxide layer at any of the three temperatures.
Surface composites: Novel method to fabricate adherent interfaces
Authors: Singh R. K. , Gilbert D. R. , Fitz-Gerald J. , Lee D. G.
Published: January 2014

To integrate irreconcilable material properties into a single component, novel engineered materials termed ‘surface composites’ have been developed. In these engineered materials, the second phase is spatially distributed in the near surface region, whereas the phase composition is linearly graded as a function of distance from the surface. Surface composites are different from existing engineered materials such as bulk composites and functionally graded materials (FGM). Unlike in bulk composites, the surface phase in surface composites is present only in the near surface region. In contrast to FGMs, the graded properties of surface composites are achieved by unique morphological surface modification of the bulk phase. To fabricate surface composites, the initial surface of the bulk material is transformed using a novel multiple pulse irradiation technique into truncated conelike structures. The laser induced microrough structures possess surface areas which are up to an order of magnitude higher than that of the original sUljace. The second phase is deposited on the surface using thin or thick film deposition methods. A key characteristic of surface composites is the formation of a three-dimensional, compositonally and thermallygraded interface, which gives rise to improved adhesion of the surface phase. Examples of various types of surface composites such as W/Mo and diamond/WC–Co are presented. The unique properties of surface composites make them ideal engineered materials for applications involving adherent thick film coatings of thermally mismatched materials, compositional surface modification for controlled catalytic activity, and creating adherent metal–ceramic and ceramic–polymer joints.
Relationship between microstructure and erosive wear resistance of plasma sprayed alumina coatings
Authors: Zhang X. S. , Clyne T. W. , Hutching I. M.
Published: January 2014

Pure alumina coatings deposited on metallic substrates by plasma spraying in air (APS) and in low vacuum (VPS) were subjected to erosive wear by silica sand particles at 50 m s−1. The AP S coatings were porous and exhibited poor resistance to erosion. The VP S coatings produced at high substrate temperatures and lower chamber pressures exhibited low porosity and good erosion resistance, while those deposited at lower substrate temperatures and higher chamber pressures were more porous and eroded more rapidly, in some cases with erosion rates higher than those of the AP S coatings. A pronounced lamellar structure was found to be the most important factor in reducing the erosion resistance. The extent of the lamellar structure and the coating porosity depended on the spraying conditions. For VPS coatings the effects of residual stresses arising from differential thermal contraction were studied by using substrates with different thermal expansion coefficients and by controlling the substrate temperature during spraying. Microstructural effects in these experiments obscured any clear influence of residual stress on erosion behaviour, although there were indications that high residual stresses may lead to microcracking which in turn may promote more rapid erosion.
Surface modification using high power lasers: Influence of surface characteristics on properties of laser processed materials
Authors: Dubrujeaud B. , Fontes A. , Forget P. , Papaphilippou C. , Sainte-Catherine C. , Vardavoulias M. , Jeandin M.
Published: January 2014

Laser beams provide a highly concentrated energy source that can easily be transmitted and manipulated using fibre optics and other optical cOlnponents such as mirrors. Advantages of laser treatment of componentsinclude: lowdistortion of treated parts; the ability to treat specific areas accurately; flexibility compared with, for example, electron beams; and the ability to conduct treatlnent in air or in inert or reactive gases. Apart fr01n cutting and welding, the first application in the Inaterials field was for heat treatment and involved laser surface hardening in the solid state, based on the heating of a thin sUlface layer that was self quenched by the bulk of the cOlnponent. Numerous further treatments have since been developed that involve melting of the surface layer, with or without addition of material, and more recently purely mechanical processes based on the laser shock phenomenon have emerged. The main laser processes that have already been commercialised or are expected shortlyto be so are reviewed. In each case, the principle and some fundamentals, and the characteristics of the treated surface and their influence on mechanical properties are discussed. Specific applications, particularly in the aerospace industry, are then examined. The influence of sUlface dalnage caused during treatment and the ability of laser processing to repair this damage are also discussed.
Thermodynamics, kinetics, and process control of nitriding
Authors: Mittemeijer E. J. , Somers M. A. J.
Published: January 2014

As a prerequisite for the predictability of properties obtained by a nitriding treatment of iron based workpieces, the relation between the process parameters and the composition and structure of the surface layer produced 111ustbe known. At present, even the description of thermodynamic equilibrium of pure Fe–N phases has not been fully achieved. It is shown that taking into account the ordering of nitrogen in the ε and γ'iron nitride phases leads to an improved understanding of the Fe–N phase diagran1. Although consideration of thermodynamics indicates the state the system strives f01∼ the nitriding result is determined largely by kinetics. Nitriding kinetics are shown to be characterised by localnear equilibria and stationary states at surfaces and intelfaces, and the diffusion coefficient of nitrogen in the various phases, for which new data are presented. The necessary background for process control of gaseous nitriding by monitoring the partial pressure of oxygen in the furnace using a solid state electrolyte is provided.
Engineering the Subsurface of Borided Aisi H13 Steel
Authors: Chicco B. , Borbidge w. E. , Summerville E.
Published: January 2014

Boriding has been employed with some success to increase the service life of commercial forging dies fabricated from the hot work steel AISI H13. This steel is poorly suited to the treatment, however, since an undesirable intermediate layer is formed between the hard boride coating and the core. In practice, a boride coating thickness well below that required for the application has been imposed by the need to minimise the thickness of this layer. An experimental study was undertaken with the aim of improving the effectiveness of a boriding treatment by engineering the subsurface of AISI H 13 steel. It was established that a carburising pretreatment markedly improved the microstructural features of the steel subsurface. The formation of the undesirable layer was completely inhibited within the range of boride thicknesses employed in commercial practice and severely limited at the higher thicknesses better suited to forging applications.
Improved Ti1–xAlxN PVD Coatings for Dry High Speed Cutting Operations
Authors: Smith I. J. , Münz W. D. , Donohue L. A. , Petrov I. , Greene J. E.
Published: January 2014

Titanium aluminium nitride (Ti1–xAlxN) has been shown to enhance the performance of cutting tools in dry, high speed machining of cast iron and die steels when compared with TiN and TiCN coatings. The ultimate benefit of Ti1–xAlxN coatings depends on two main criteria: the microroughness of the coating surface has to be minimised, and the oxidation resistance has to be maximised. The microroughness is governed by the choice of deposition method whereas the oxidation resistance is controlled by the composition of the coating. In particular, the generation of macroparticles during the PVD process has to be suppressed and the Al content of the film metallic constituents has to be kept between 40 and 60 at.-%. To achieve these demands supplementary to excellent adhesion, a PVD deposition process has been developed based on combined steered arc and unbalanced magnetron sputtering techniques. Using Cr in the steered arc sustained metal ion etching process the desired adhesion criteria may be exceeded and the surface roughness is kept as low as Ra = 0·04 μm. Unbalanced magnetronsputtering takes place from 50: 50 (at.-%) TiAI alloy targets. Further improvement has been achieved by incorporation of 3 at.-%Cr and, in particular, about 2 at.-% Y into the TiA1N coating, leading to an optimised film composition of Ti0·42Al0.53Cr0.03 Y0.02N. Cross-sectional TEM analysis, SNMS depth profiling, and thermogravimetric evaluation reveal grain refinement, interface stabilisation, and reduced oxidation at temperatures up to 950°C. These coatings allow enhanced dry drilling performance in GG 25 grey cast iron at a cutting speed of 60 m min–1 and feed of 0·2 mm rev–1, and dry milling of 56 HRC die steel with a 300 m min–1 (12000 rev min–1) cutting speed and linear feeds up to 6 m min–1, with a total lifetime of more than 20 h for this latter application.
Industrial Surface C Leaning Using Halogen Free Cleaning Agents: Surfactant Solutions and Hydrocarbon Solvents
Authors: Haase B. , Dong J.
Published: January 2014

Minimising the health and environmental risks resulting from surface cleaning involves the design of suitable hardware but also the choice of a cleaning agent. As an alternative to chlorinated hydrocarbons, chlorine free hydrocarbons or surfactant cleaners in aqueous solution can be used. Whereas hydrocarbons work as solvents and remove mainly soluble oil or fat contamination, surfactant cleaners dissolve water soluble contamination and displace oils, fats, and insoluble particles, swarf, chippings, and cuttings. While it is advantageous to work with water as a solvent, many alkaline surfactant cleaners contain inorganic salts which leave non-volatile residues at metal surfaces ifthe parts are not rinsed sufficiently with desalinated water. Laboratory scale cleaning experiments with both types of cleaning agent have been carried out. Results were obtained by analytical means and modern surface analysis; in addition, gas nitriding, a surface modification process which is known to be sensitive to surface composition, was used to assess cleaning potential. For the total process of machining, cleaning, and nitriding, it is shown that it is neither possible nor sensible to define a standard of surface purity without considering the special demands of the surface modification process following.
Surface Modification of A Cr–mo Steel Using Laser Surface Alloying with B4C Powder Injection
Authors: Song G. Q. , Hlawka F. , Cornet A. , Marchione T.
Published: January 2014

Specimens of an AISI4135H steel were traversed across a focused laser beam and superficially alloyed using a co-deposition technique involving B4C powder injection. The metallurgical phases appearing at different depths in the laser surface alloyed steel have been identified using optical microscopy and SEM observations as well as X-ray diffraction analyses and Auger electron spectroscopy. A high hardness in the melted zone was generally obtained. Optimum process parameters including powder feedrate and specimen traverse rate have been determined to avoid porosity or cracks.
Novel powertrain applications of thermal spray coatings
Authors: Popoola O. O. , Zaluzec M. J. , McCune R. C.
Published: January 2014

Recent innovations in equipment, processes, and diagnostics make thermal spray coatings both practical and desirable for use in large scale automotive manufacturing.The advent of rotating devices and surface preparation methodologies such as high pressure water jet, electrodischarge machining, and chemical fluxes permit thermal spray coating applications on cylinder bore and valve seat areas of engines. Low carbon steel alloy composite and aluminium bronze coatings have been successfully tested on cylinder bores. The Fe–Fe3O4/Ni–NiO–CrO composite coating obtained by spraying carbon steel and nickel base alloy wires using a two wire arc gun works well as a valve seat material.
Advantages for automotive industry of plasma spray coating of Ai–Si cast alloy cylinder bores
Authors: Barbezat G. , Wuest G.
Published: January 2014

In the automotive industry the need for lower manufacturing costs, the use of fewer strategic materials, andthe need for easier, faster, and more environmentally sound coating processes is growing. This has led to the examination of a plasma powder spray process used in the application of coatings for surface modification. The present paper examines the use of the plasma powder spray process in coating aluminium-silicon cylinder block bores using a rotating plasma gun capable of producing coatings of reliable microstructure and integrity. Properties and microstructures of the applied coatings are presented and test results show that the necessary bond strength of the coating can be achieved without the use of a bond coat. Surface preparation before coating and surface finishing methods after coating are also discussed. Experience in Europe, Japan, and the USA shows that the plasma powder spray process offers a performance proven and cost effective solution for the coating of cylinder bores.
Corrosion resistance of HVOF WC–Co and TiC/Ni–Ti coatings sprayed on commercial steel
Authors: Guilemany J. M. , Fernández J. , de Paco J. M. , Sanchez J.
Published: January 2014

Corrosion, erosion, and abrasion damage arefrequently found in equipment used in service in the oil and gas industries. This represents a challenge to materials engineers because of the deterioration of equipment and increased maintenance costs. Much work is being done on the evolution of corrosion of different types of coatings. The aim of the present work is to study the corrosion behaviour of two different coatings sprayed using high velocity oxyfuel technology. A commercial steel was coated with a CDS 1927 (WC–12Co) or TiC/Ni–Ti powder using a Plasma-Technik CDS–100 thermal spray gun. The powder was sprayed on to a cylindrical specimen 25·4 mm in diameter and 25·4 mm high. The corrosion potential v. time and potentiodynamic polarisation were studied inan ASTM standard cell with three electrodes. Air saturated seawater was used as the electrolyte.
Improving wear and corrosion resistance of thermal sprayed coatings
Authors: Wielage B. , Hofmann U. , Steinhauser S. , Zimmermann G.
Published: January 2014

Thermal sprayed coatings are used in various applications often dedicated to corrosion and wear protection.Poresand other coating imperfections reduce corrosion and wear resistance and/or necessitate higher coating thicknesses. To improve the quality of thermal sprayed coatings, various post-treatment processes can be used. Characterisation of the efficiency of sealing was studied by metallographic examination andcomparative investigation of the corrosion and wear behaviour of the thermal sprayed coatings used with and without sealing and also by measuring the insulation resistance of the coating system. The results differ among the sealants. It is possible to remove the sealants from the coatings by mechanical treatment. Corrosion tests of the sealants demonstrate their efficiency in closing the interconnected pores and, consequently, preventing corrosion.
Effect of local thermal shock load on plasma sprayed thermal barrier coatings
Authors: Koolloos M. F. J. , van Liempd G. G. , Houben J. M.
Published: January 2014

The number of cycles to failure of plasma sprayed thermal barrier coatings (TBCs) during thermal shockexperiments gives an indication of their performance in a real environment. The authors have subjected 0·3 mm thick ZrO2–8Y2O3 TBCs to a local thermal shock load with maximum surface temperatureof 1300 and 1400°C. The diameter of the flame was about 15 mm. During cycling, the temperature drop through the specimen thickness and the temperatureprofile of the back of the substrate were measured. The number of cycles to failure and the type of failure appeared to be dependent on the maximum surface temperature of the coating. After failure, a phase analysis was performed. In addition, the residual stress profile of the top coat was determined after 200 cycles with Tsurf = 1300°C. It is concluded that at 1300°C bond coat oxidation is the main cause of failure, while at 1400°C top coatdegradation leads to failure.
Effect of process parameters during friction coating on properties of non-dilution coating layers
Authors: Shinoda T. , Li J. Q. , Katoh Y. , Yashiro T.
Published: January 2014

Few surface modification processes appear to coat a 1 mm thick compact layer on a substrate successfully, although several technologies have been proposed and applied. The present paper concerns a fundamental approach to establishing a friction surfacing technique that produces a 1mm thick hard coat. Experiments were carried out to clarify the effect of process parameters on the quality of coatings. Martensitic stainless steel with 1C-17 Cr was the coating material and low carbon structural steel the substrate, using a conventional friction welding machine equipped with a sliding stage. A 20 mm wide and 1 mm thick stable hardened layer was produced using a 20 mm dia. Rod of coating material. The dimensions of the layer depend on the rotational speed of the consumable rod, as lower rotational speeds produce thicker, wider coating layers. Calorimetric measurements revealed that the total heat input rate was not influenced by the frictional speed, however the ratio of thermal distributions on to the substrate and rod was significantly affected by rotational speed. Additional experiments were carried out to clarify the effect of edge preparation, rotational direction, and overlapping distance on defect formation in multilayer depositions by friction coating for wide area coating on steel plates. Results were optimised by grinding the edges of previous layers to prevent defects such as incomplete bonding.
Study on wear behaviour of hot working tool steels
Authors: Rosso M. , Scavino G.
Published: January 2014

An X37CrMoV5.1KU hot working steel was quenched and tempered, nitrided, overcarburised, overcarburised and nitrided, and nitrocarburised for 18 and 36 h. Wear tests at 50 and 100 kg loads were performed without lubricant on the treated specimens using an A135 Amsler machine in order to determine the most effective treatment. The quenched and tempered specimens showed the worst behaviour and the nitrocarburised specimens the best. Nitriding performed without or after overcarburising on the specimens tested at the lowest load appreciably increased wear resistance, while minor benefits resulted from overcarburising. For the specimens tested at high loads the benefits of nitriding after overcarburising remained, while the behaviour of nitrided or overcarburised specimens was similar. The wear resistance of the treated specimens was related to surface layer characteristics and in particular to the presence of intergranular precipitates.
Preparation and characterisation of electrolytically deposited ceramic coating on stainless steel
Authors: Aries L. , Jalama L. , Laaouini A. , Roy J.
Published: January 2014

Ceramic coatings are widely used to protect metals against oxidation at high temperatures. In order to obtain ceramic layers with strong metal substrate adhesion, an original method has been developed. It involves pretreatment of the metal surface to form a functional conversion coating, characterised by strong interfacial adhesion with the substrate and by a particular morphology. Its particular texture allows the cathodic deposition of alumina and/or zirconia during electrolysis of aluminium and/or zirconium salt solutions. After heating, the coating presents a continuous composition gradient with refractory compounds at the surface. This electrochemical method offers a relatively easy way to establish coating composition and enables the preparation of a mixed ceramic layer. Results for Al2O3-ZrO2 coating preparation are presented. The electrochemical behaviour and chemical composition are analysed. Electrolytic bath composition, electrochemical parameters, and coating composition are correlated.
Structural characterisation (AFM and XRD) and hardness of spultered CrxNy coatings
Authors: Bertrand G. , Savall C. , Meunier C.
Published: January 2014

Hard coatings for wear and oxidation/corrosion protection based on chromium nitride were deposited by means of a commercial rf magnetron sputtering unit with a mixture of nitrogen and argon from a target of the pure metal. The present paper reports on the influence of deposition parameters on coating morphology, crystallographic structure, and hardness. The coating surfaces viewed by atomic force microscopy showed that grain shape depends on the composition of the vapour phase, and especially on the presence or absence of reactive gas. In addition, special attention was paid to the first stages of growth. The crystalline phases Cr, Cr2N, and CrN were identified by X -ray diffraction analysis as a function of the film nitrogen content. Finally, hardness measurements were performed and compared to coating structure and composition.
Deposition of synthetic diamond films: PVD., CVD., and multiplexed lasers
Authors: Ali N. , Ahmed W. , Hassan I. U. , Rego C. A.
Published: January 2014

Diamond has so many exceptional characteristics (high thermal conductivity, chemical inertness, high hardness, excellent insulation, lowest compressibility of any known material, semiconducting properties when doped) that industrial applications would be numerous if natural diamond was not such a high value commodity. If synthetic diamond (rather than diamondlike carbon) could be readily produced it would therefore have an enormous potential worldwide market. Variants on the chemical vapour deposition process are some of the most promising techniques for synthesising diamond, although they suffer from a number of key drawbacks. A more recent development is a novel multiplexed laser deposition system which may offer solutions to many of these problems; work is currently under way to gain a better understanding of this new technique.
Wear behaviour of TiAIn films deposited on plasma nitrided high speed steel
Authors: Lii D.-F.
Published: January 2014

Titanium aluminium nitride films were deposited on a plasma nitrided high speed steel substrate by reactive sputtering. The hardness and nitriding depth of the plasma nitrided substrates increased with increase in N2/(N2 + H2) flow ratio because of the enhanced diffusion of nitrogen atoms. The hardness and adhesive strength of TiAlN films coated on the plasma nitrided substrate were also found to be higher than those of the unnitrided substrates. In addition, the hardness of the TiAlN films increased with increase in the N2 + H2) flow ratio. The wear resistance, which was principally dominated by the hardness of the TiAlN films, was also enhanced by an increase in theN2/(N2 + H2) flow ratio.
Spatial distribution of active species during post-discharge nitriding
Authors: Salas O. , Figueroa U. , Oseguera J.
Published: January 2014

The spatial distribution of active species during nitriding in a plasma post-discharge flow was investigated in a microstructural study linked with models to predict the atmospheric density of atomic nitrogen. Pure iron pieces were nitrided at 560°C for 10 min in an N2-H2-Ar mixture in the post-discharge flow of a microwave plasma reactor. The distribution of the species was experimentally evaluated in terms of the nitriding precipitation behaviour at different positions along the quartz tube of the reactor. The nitrided specimens were analysed by optical and scanning electron microscopy as well as X-ray diffraction. The treated pieces developed a microstructure with a nonuniform distribution of nitrides over the surface. These results indicate that there is a gradient in nitrogen potential along the length of the quartz tube of the post-discharge reactor and are consistent with the nitrogen atomic density distribution values estimated using the models.
Cavitation erosion of steels processed with laser beam and optical discharge plasma
Authors: Gireń B. G.
Published: January 2014

The response of a solid state body to cavitation attack depends on impingement parameters as well as the properties of the eroded material. Changes to steel surface structural features intended to give cavitation resistance were induced by laser methods in order to test the usefulness of laser beam and optical discharge plasma surface remelting in protecting a 0·45% carbon steel and a 13% chromium steel against cavitation damage. Some light is also shed on the correlation between the performance of hardened layers during the incubation period of cavitation erosion and their physical properties.
Interface strengthening by mechanical surface treatment of substrates
Authors: Tönshoff H. K. , Mohlfeld A. , Oberbeck-Spintig I. , Marzenell C.
Published: January 2014

Today's cutting tool research activities are concentrated on improving the properties of tools by optimizing manufacturing technologies and tool geometries, by alloying special cutting materials, and by coating tools. During dry drilling of tempered steel the wear mechanisms of (Ti1−xAlx)N coated WC carbide tools were investigated. Effects of coating composition, sputter technologies (magnetron sputter ion plating and high ion sputtering), and substrate machining on cutting performance were examined. Topics considered include influences of surface properties of wc carbides on film adhesion and effects on wear behaviour. Residual stress measurements and SEM images were used for characterization of surface properties. Film adhesion was analysed by scratch and indentation tests. Because of increasing interfacial strength of microblasted tools, superior wear behaviour in dry machining was observed. The best wear resistance during dry drilling of tempered steel was found for (Ti,Al)N compositions of high microhardness (Al/Ti ratio of about 1).
Surface alloying of iron by laser melting: Microstructure and mechanical properties
Authors: Cordier-Robert C. , Crampon J. , Foct J.
Published: January 2014

Superficial laser induced melting produces non-equilibrium phases without changing the microstructure of the bulk and therefore alters specimen properties. Nitrided steels are of interest in a wide range oftechnological applications because of increased hardness and corrosion resistance as well as interesting magnetic and electrical properties. The aim of the present study was to determine the influence of nitride coatings (y’-Fe4N, ε-Fe3–2N, α″′-Fe8N, BN, AlN, and Cr2N) on the superficial alloying, microstructure, and microhardness of Armco iron melted with a continuous CO2 laser beam at a power level of 400 W Depending onmelting conditions as well as thickness and chemical composition of the coating, ferrite, martensite, austenite, γ’, or ε phases are detected at the surface of laser alloyed iron using Mossbauer spectroscopy, X-ray diffraction, and optical microscopy. The microhardness can be considerably increased depending on the microstructure and residual stresses in the surface layers.
Laser treatment of vacuum plasma sprayed CoCrAIY alloy
Authors: Wielage B. , Steinhäuser S. , Pawlowski L. , Smurov I. , Covelli L.
Published: January 2014

Coatings of the alloy Co–17Cr–12·5Al–0·45Y were vacuum plasma sprayed on to steel substrates. A CO2 high power continuous wave laser with a Gaussian rectangular beam was applied to treat the coatings after spraying. The treatment was carried out using 7·5 kW cm−2 power density and a relative beam scan speed in the range O.7–1.3 m min−1 and resulted in themelting of the coatings. The microstructure of the treated alloy and the heat affected zone was analysed using optical and scanning electron microscopy. Finally, the wear resistance of the coatings was tested using sliding wear, oscillating wear, and scratch tests.