bluuebunny/crossref_metadata_2025 huggingface dataset:
Consideration of fretting fatigue properties of plasma nitrided En19 steel: Second Prize
Authors:   Li C.-X., Sun Y. , Bell T.
Published: May 2005

Fretting fatigue behaviour of plasma nitrided En19 steel was examined in the present study. It was found that a 10 h plasma nitriding treatment improved the fretting fatigue strength of the steel by 245% and the plain fatigue strength by 70%. However, extending the nitriding time had different influences on fretting fatigue as compared with those on plain fatigue. Long nitriding times resulted in higher plain fatigue strength, but this was not so in fretting situations. The present work demonstrates that short time nitriding is as effective as long time nitriding in improving the fretting fatigue strength of the investigated steel. The results can be explained in terms of the compound layer, the residual stresses, and the strengthening of the materials (increase in microhardness) in the nitrided case.
Plasma immersion ion implantation: Innovative technology for surface treatment of stainless steels: Third Prize
Authors: Blawert C.
Published: May 2005

Plasma immersion ion implantation technology was used to produce expanded austenite and to study the influence of treatment conditions and starting material on its formation and structure. Standard materials characterisation techniques, XRD, TEM, conversion electron Mössbauer spectroscopy, and Rutherford back scatter spectrometry analysis were used to determine the structure of the layers, thereby revealing the complex structure of expanded austenite. The properties of the expanded austenite layers (hardness, wear, and corrosion) were determined and correlated with the structure. Most work was concentrated on the austenitic stainless steel X6CrNiTi1810 after treatments at 300 and 400°C. Based on these results, the possibilities of influencing properties by varying the process conditions are discussed.
Thermalstability of Al–O–N PVD films and comparison with Al2O3 films as diffusion barriers: Shortlisted
Authors: Reichert K.
Published: May 2005

The use of Al–O–N films as diffusion barriers for components with a high thermal load, e.g. in gas turbines, was investigated. Films with compositions along the quasibinary section Al2O3–AlN were deposited onto Ni based superalloy (CMSX–4) substrates by means of magnetron sputtering ion plating at 373 K substrate temperature and characterised with regard to their composition and structure using X-ray photoelectron spectroscopy and grazing incidence XRD. The phase stability of the films was examined by annealing under inert atmosphere at temperatures up to 1473 K for 4 h and by subsequent XRD analyses. To investigate the possible application of these films as a diffusion barrier between Ni based superalloys and MCrAlY, with the latter serving in technical applications as corrosion protection for superalloys, an NiCoCrAlY coating was deposited onto selected specimens. Without a diffusion barrier and operating temperatures of and above 1373 K, noticeable interdiffusion was observed. After annealing the CMSX–4/Al–O–N/NiCoCrAlY composites for 4 h, the CMSX–4/Al–O–N and Al–O–N/NiCoCrAlY interfaces were investigated by XRD and energy dispersive X-ray spectroscopy. The analyses showed that interdiffusion between CMSX–4 and NiCoCrAlY was observed in the case of the Al2O3 during annealing, and was especially evident in titanium. In contrast to this, ternary Al–O–N films showed better performance as diffusion barriers, i.e. no titanium was detectable in the Al–O–N or NiCoCrAlY film. A possible explanation is that the ternary films were grown in an amorphous structure and remained in that state after annealing the CMSX–4/Al–O–N/NiCoCrAlY composites, whereas Al2O3, which at the low substrate temperature was supposedly deposited nanocrystalline in the cubic γ-Al2O3 structure, converted into the hexagonal α modification. This transition is assumed to be responsible for the permeability of interdiffusing elements.
Silane based metal pretreatments as alternatives to chromating: Shortlisted
Authors: Subramanian V. , van Ooij W.J.
Published: May 2005

Novel silane based metal pretreatments have been developed as cost effective alternatives to the chromating process. The new process is a simple solution dip process, is non-carcinogenic, and has outperformed chromated systems under different test conditions. The system provides superior corrosion and adhesion per formance. The process has been developed by optimising parameters such as choice of silane, silane concentration in the solution, extent of hydrolysis, pH of application, coating method, solution contact time, and nature and extent of curing. The pretreatments are versatile and can be modified to accommodate different top coat systems including paints. The performance of this new pretreatment has been tested on a number of metal and alloy substrates including aluminium and aluminium alloys, various steels, copper and copper alloys, brass, zinc, and several automotive and aircraft alloys. The superior performance is confirmed by using accelerated ac and dc electrochemical techniques, ASTM B–117 salt spray tests, and a variety of other corrosion and adhesion tests. Protection against forms of corrosion such as general, pitting, galvanic, stress corrosion cracking, and dezincification is established. Character isation and modelling were performed using advanced techniques including SEM, EDX, XPS, AES, SIMS, RA–IR, Raman spectroscopy, spectroscopic ellipso metry, EIS, AFM, and contact angle measurements. The unique nature of these chemicals and the adopted methodology are explained and the possible impact of the new development assessed.
Effects of additives in electrolyte on characteristics of ceramic coatings formed by microarc oxidation
Authors: Wang Y.K. , Sheng L. , Xiong R.Z. , Li B.S.
Published: May 2005

The effects of adding Na2 WO4. 2H2O and SiC powder to the electrolyte on the characteristics of ceramic coatings on Al based alloys formed by microarc oxidation were studied. The ceramic coating quality was improved by the two additives, but the addition of Na2 WO4. 2H2O was more effective, as it improved the formation of Al2O3 phase in the ceramic coating, increased the ratio of the internal dense region to the whole ceramic coating, optimised the ceramic coating phase structure, and improved its wear resistance. The SiC powder was able to enter into the ceramic coating and improve its wear resistance, at the same time increasing the friction coefficient of the coating.
Study of ceramic coatings formed by microarc oxidation on Al matrix composite surface
Authors: Wang Y.K. , Sheng L. , Xiong R.Z. , Li B.S.
Published: May 2005

Research was conducted on the microstructure, composition, and properties of a ceramic coating deposited on the surface of an aluminium matrix composite (10Al2O3f –ZL109) using microarc oxidation. The influence of different matrixes and reinforcements on the microstructure, properties, and deposition parameters of the ceramic coatings was studied. Both factors showed considerable effects, though the matrix composition had more influence. The results also showed that mullite ceramic coatings can be successfully deposited on the surfaces of aluminium matrix compos ites. The coating was composed of two layers, a porous layer and a dense layer.
Microstructure and mechanical properties of laser surface alloyed coatings prepared on cast Al–Si
Authors: Cai X. , Yang X. , Wang J.
Published: May 2005

Laser surface alloyed (LSA) layers were obtained on cast Al–Si using a CO2 continuous transverse flow laser beam with maximum power of 10 kW. The microstructure of the modified layers was examined using scanning electron microscopy and transmission electron microscopy. Surface alloying with Ni based powder generated a layer composed of γ-Ni(Cr,Fe), Ni3 Al, T(Al,Fe,Si), CrB, and Cr23 C6. The matrix phase in the modified layer was γ-Ni(Cr,Fe), with strengthening phases present. Microhardness and wear resistance tests were also performed: the average microhardness is around 3·1 to 3·6 GPa, three times higher than in the substrate. The antiwear properties of the LSA modified layers were also greatly improved, with relative wear resistance approaching 10 to 12. Finally, the wear mechanisms of LSA modified layers were studied by surface morphology analysis.
Fatigue life enhancement by laser surface treatment
Authors: Konstantino E. , Altus E.
Published: May 2005

A laser surface treatment (LST) which can enhance fatigue resistance of metallic parts has been developed. The LST is useful both for improving the surface microstructure of undamaged specimens, thereby increasing the original fatigue life, and for healing in service metallic parts subjected to cyclic loading. The LST method was applied to three point bend specimens of Ti–6Al–4V alloy at different stages of fatigue life. Results show a significant improvement in fatigue resistance, with a distinct treatment optimum point at about two-thirds of the original lifetime. In addition, changes in the near surface microstructure, including grain size and shape distribution, phase ratios, etc., have been studied. The relative α phase surface area, as well its grain size, decreased considerably, showing large perimeter curvatures and larger total grain border lengths.
Abrasive wear behaviour of detonation sprayed WC–Co coatings on mild steel
Authors: Roy M. , Rao C.V.S. , Rao D.S. , Sundararajan G.
Published: May 2005

The main objective of the present investigation is to evaluate the abrasive wear behaviour of detonation sprayed WC–Co coatings and to compare them with plasma sprayed WC–Co coatings and carburised and nitrided surfaces. Mild steel was coated with WC–12Co and WC–17Co using detonation and plasma guns. The abrasive wear rates of these coatings were determined at three different loads and compared with wear rates of as received, carburised, and nitrided mild steel. The abraded surfaces and the surfaces beneath the abraded surfaces were characterised by SEM. The results indicate that the detonation sprayed WC–12Co coating has the best abrasive wear resistance at all loads. Maximum improvement in wear resistance is obtained at an intermediate load (i.e. at 5 kg). The wear of detonation sprayed coatings is by abrasion of the soft Co matrix followed by the pullout of hard WC particles.
Residual stress profiles of plasma nitrided steels
Authors: Loh N.L. , Siew L.W.
Published: May 2005

It is well documented that plasma nitrided steels exhibit superior fatigue resistance by virtue of induced compressive residual stress. In the present paper, six steels with different alloying elements and contents were plasma nitrided for 4 and 9 h at 580°C. These were then analysed in terms of microstructural features, microhardness profiles, and residual stress distribution. A Philips X-ray diffractometer was used for phase determination and residual stress measurement. The paper discusses the use of X-ray diffractometry to measure residual stress, emphasising the significance of K calibration, choice of ψ angle, and validation of 2θ measurement. Results showed a close relationship between microhardness profiles and residual stress distribution. Effects of the various alloying elements such as Cr, Al, Ti, W, and V were explored in terms of their plasma nitrided microstructural features as well as their contribution to surface hardness and case depth.
Nanostructured ceramic coatings: Engineering on an atomic scale
Authors: Aita C.R.
Published: May 2005

In recent years, nanostructured coatings have emerged as technologically important materials. The production and analysis of nanostructured ceramic coatings bring new challenges to the materials science and engineering community. In this review, it is shown how two characteristic features of nanoscale morphology, large internal surface area and metastable phase formation owing to the finite crystal size effect, can be exploited to produce ceramic coatings with unique and useful properties.
Modification of reactive metals by aqueous electrochemical process
Authors: Iroh J.O. , Su W.
Published: May 2005

Polypyrrole coatings have been successfully formed on steel from aqueous oxalic acid–pyrrole solutions by electrochemical polymerisation. The formation of the coatings was found to be dependent on the pH of the reaction solution and the applied current. In an acidic medium, the formation of polypyrrole was characterised by an induction (passivation) period before electro-polymerisation of pyrrole. At the end of the induction period, a crystalline passive interphase was formed. The morphology and composition of the electrodeposited passive interphase and the resultant polypyrrole coatings were investigated by scanning electron microscopy, reflection–absorption infrared spectroscopy, and X-ray photoelectron spectroscopy. The results reveal that the chemical composition of the passive interphase was similar to that of iron (II) oxalate dihydrate (FeC2O4.2H2O) crystals. The size and orientation of the crystalline passive interphase varied with the electrochemical process variables.
Control of surface structure of graphite fibres for improved composite interfacial properties
Authors: Iroh J.O. , Wood G.A.
Published: May 2005

The properties of carbon fibres modified by aqueous electrochemical synthesis of pyrrole have been determined by using a dynamic contact angle analyser, scanning electron microscopy, and Fourier transform infrared spectroscopy (FTIR). Electrochemical process parameters such as initial pyrrole concentration, electrolyte concentration, applied voltage, electrolyte type, and reaction time were systematically varied and their impacts on the polypyrrole–carbon fibre interphase surface free energy and morphology ascertained. The surface free energies of the polypyrrole–carbon fibre interphases were obtained using single fibre filaments. SEM analysis of the interphases revealed several distinct surface structures, including smooth, porous, granular, microspheroidal, and plateletlike morphologies. Non-coated, commercially surface oxidised carbon fibres have smooth surface morphology with occasional longitudinal striations. FTIR analysis of the polypyrrole interphases confirmed that the counterions derived from the electrolytes were incorporated into the film. The surface free energies of the electrochemically formed polypyrrole–carbon fibre interphases (0·06–0·075 J m-2) were determined to be up to 40% higher than those of surface oxidised but unsized carbon fibres (0·05 J m-2). This improvement in the surface free energies of the polypyrrole–carbon fibre interphases suggests easy wettability by polymer matrices such as epoxy resin and polyimide (surface free energies around 0·047 and 0·045 J m-2 respectively).
Application of ceramic thermal spray coatings for molten metal handling tools and moulds
Authors: Wang Y.
Published: May 2005

This paper discusses the application of ceramic thermal spray coatings on tools such as cast iron ladles, heat element protectors, and steel moulds to replace pure ceramic and ceramic slurry coated tools for extended life and lower light metal casting operation cost. Numerous ceramic coating materials were tested based on thermodynamic and mechanical properties, as well as commercial availability and cost. The work involved thermodynamic modelling, coating microstructure optimisation of ceramic/metallic and bond layers on different substrates, as well as the thermal spray processes. Two coating materials offered much better corrosion resistance to molten aluminium than the rest. The optimised coating microstructures showed much better thermal shock resistance. The ceramic thermal spray coated tools had much longer life than ceramic slurry coated tools. Issues associated with the application of ceramic thermal spray coatings were also addressed.
Addition of ceramic particles to TIG melted titanium surfaces
Authors: Mridha S. , Ng B.S.
Published: May 2005

A surface layer metal matrix composite has been developed by using a tungsten inert gas (TIG) arc with an operating current of 60 A. The 0·5 mm thick coating of a powder mixture containing 80 vol.-% titanium and 20 vol.-% 40 μm SiCp particles was pre-placed on commercially pure titanium surfaces using a suitable binder. The powder coating was then melted by traversing specimens beneath a Miller TIG arc using 110, 90, 55, and 45 MJ m-2 energy densities. Glazing at energy densities from 55 to 110 MJ m-2 completely dissolved the powder mixture and produced 1 mm deep hard (500 to 600 HV) layers which were free from pores, cracks, and cavities. The tracks had smooth and reflective surfaces. The microstructure developed in the tracks is dominated by the reaction of SiCp particles with the molten titanium layer to form titanium carbide (dendrites), Ti5 Si3, and titanium. Processing with 45 MJ m-2 energy density arc produced pores and cavities in the melt pool; the microstructure consisted of agglomerated and partially dissolved SiCp, fine dendrites, and globular particles with hardness ranging from 800 to 1600 HV over a 500 μm thickness.
Plasma source ion implantation: Applications in metal forming
Authors: Leung C. , Elmoursi A. , Malaczynski G. , Hamdi A. , Mantese J. , Speck C.
Published: May 2005

The use of ion implantation to modify surface properties has always been considered too expensive in the metals industry. However, with the advent of plasma source ion implantation (PSII) the economics can be improved, especially when coupled with the highly desirable properties associated with diamondlike carbon (DLC) and many carbide and nitride coatings. The use of PSII to grow DLC films on aluminium alloys, to form hard coatings such as vanadium carbide on forming tools and die casting tools, and to nitrogen implant steel forming tools and chromium plate is reported in this paper. The commercialisation of PSII is the goal of the Advanced Technology Program with over 17 participating members, including national laboratories, corporate research centres, end users, equipment manufacturers, system component suppliers and integrators, and process providers. This multidiscipline cooperation has resulted in more effective research and development of coatings and commercial products, along with easier adaptation of processes and deployment of PSII.
Advances in PSII deposited DLC coatings for use as barriers to corrosion
Authors: Lillard R.S. , Butt D.P. , Baker N.P. , Walter K.C. , Nastasi M.
Published: May 2005

Plasma source ion implantation (PSII) is a non-line of sight process for implanting complex shaped targets without the need for complex fixturing. The breakdown initiation of materials coated with diamondlike carbon (DLC) produced by PSII occurs at defects in the DLC, which expose the underlying material, thus establishing a galvanic couple between the coating and exposed material at the base of the defect. Pitting and oxidation of the base metal leads to the development of mechanical stress in the coating and eventually spallation of the coating. This paper presents current progress in attempting to mitigate the breakdown of these coatings by implanting the parent material before coating with DLC. Ideally the parent material would be implanted with chromium or molybdenum, which are known to improve corrosion resistance, however the necessary organometallics needed to implant these materials with PSII are not yet available. Here the effects of carbon, nitrogen, and boron implantation on the susceptibility of PSII DLC coated mild steel to breakdown are reported.
Metal film deposition on carbon anodes for high rate charge–discharge of Li–ion batteries
Authors: Takamura T. , Suzuki J. , Yamada C. , Sumiya K. , Sekine K.
Published: May 2005

Carbon is the most promising active material for the anode of Li–ion secondary batteries because of its reliability. The high rate characteristics of carbon, however, are not satisfactory to meet the requirements of advanced appliances. An attempt has been made to improve the high rate capability by modifying carbon surfaces by heat treatment, but with limited success. In addition, a novel method based on metal film coating of carbon surfaces has been developed. Graphitised mesophase carbon fibre was used as the carbon sub–strate and several metals were examined, including Au, Bi, Pd, and Sn. A metal film was deposited on the carbon fibre surface with a thickness of 5 to 100 nm. The electrochemical charge–discharge cycle test was performed in a non-aqueous electrolyte containing 1M LiClO4. The presence of the metallic film increased the charge–discharge current for all metals examined.
Carbon nitride thin films and nanopowders produced by CO2laser pyrolysis
Authors: Alexandrescu R. , Cireasa R. , Cojocaru C.S. , Crunteanu A. , Morjan I. , Vasiliu F. , Kumar A.
Published: May 2005

Nanocrystalline CNx particles and thin films were produced in a flow reactor system by the CO2 laser pyrolysis of sensitised NH3–N2O–C2 H2reactant gas mixtures. Depending on the substrate nature (silicon or quartz) the SEM and TED analysis of the CNx thin films revealed specific nucleation and growth morphologies of crystallites, resembling the β-C3 N4 phase. In the case of C3 N4 nanopowder synthesis, the relative concentration of the sensitisers (SF6 /C2 H4) was varied to minimise SF6 decomposition. The majority of the data obtained from powder analysis (XRD, XPS, and ir transmission measurements) suggests the presence of CN bonded phases and the formation of α-and β-C3 N4 structures.
Self-replenishing solid lubricant films on boron carbide
Authors: Erdemir A. , Eryilmaz O.L. , Fenske G.R.
Published: May 2005

This study introduces a simple annealing procedure that leads to the formation of a self-replenishing solid lubricant film on bulk boron carbide (B4 C) and its coatings. The procedure uses short duration annealing at 800°C for 15 min. Subsequently, the specimens are cooled to room temperature and tested in a pin on disc machine. During annealing, B4 C reacts with oxygen in air and forms a glasslike boron oxide (B2 O3) layer on the exposed surface. Eventually, this layer reacts spontaneously with moisture in the surrounding air, thus forming a thin boric acid (H3 BO3) film. The friction coefficients of 440C steel and zirconia pins against this film are 0·04–0·06. Electron microscopy and Raman spectroscopy were used to elucidate the formation and self-lubricating mechanisms of this solid boundary film on sliding B4 C surfaces.
High cycle fatigue behaviour of Ti–47Al–2Cr–2Nb and Ti–6242s with (Al,Cr)3Ti plasma spray protective coating
Authors: Wood T.D. , Dewald D.K. , Mikkola D.E.
Published: May 2005

Certain γ-TiAl alloys are slated for use in aeroengines where they will serve in intermediate temperature environments (500–650°C). Under these conditions, such alloys will provide long service life with substantial weight savings over current materials and designs. With use, it is expected that there will be interest in extending the use of γ-TiAl alloys to more aggressive engine environments where protective coatings will be necessary. Likewise, high performance Ti alloys used in certain other applications could benefit from an effective protective coating. Several very successful plasma spray coatings based on cubic trialuminide alloys, i.e. (Al,Cr)3 Ti, have been developed to fill these needs. However, to properly design these coating–substrate systems, it is necessary to understand the influence of the coatings on the mechanical properties of the substrates. Recent high cycle fatigue (HCF) tests performed on three (Al,Cr)3 Ti based coating designs applied to γ-TiAl and a Ti alloy show that effective protection can be provided without compromising HCF response.
Adhesion and raman studies of magnetron sputtered amorphous carbon on WC–Co
Authors: Zhang S. , Xie H. , Hing P. , Mo Z.
Published: May 2005

Amorphous carbon coatings up to 2 μm thick were deposited on WC–Co substrates by magnetron sputter ing of a graphite target in Ar and Ar–Ht2 atmospheres. The Raman peak intensity ratio of the D band to the G band Id /Ig and the G band peak shift decreased initially but subsequently increased with bias power. Chamber pressure directly influenced the adhesion and hardness of the coating. It was established that below a certain minimum chamber pressure, there was spontaneous coating detachment. X-ray photoelectron spectroscopy depth profiling was used to quantify the cobalt depletion at the substrate surface as a function of sputter cleaning bias power. It was found that scratch adhesion strength increased with sputter clean ing power and reached a maximum at about 200 W, or -210 V in terms of induced voltage. The increase in adhesion strength was attributed to better cleaning of the interface cobalt.
Evaluation of thin film coatings for erosive–corrosive wear prevention in die casting dies
Authors: Gopal S. , Lakare A. , Shivpuri R.
Published: May 2005

Die casting dies are exposed to an extreme erosive–corrosive environment during a typical die casting operation using aluminium alloys. The erosive actions are primarily due to the high velocity injection of the liquid melt through narrow gates. This molten spray of liquid droplets attacks surfaces in front of the gates and normal to the flow front and is called ‘washout’ by die casters. The corrosive action on the other hand is governed by the solubility of the die material (often H13) in the molten aluminium alloy and is controlled by the composition of the cast metal and the die steel, and causes ‘soldering’ in die casting. To protect die surfaces from these erosive–corrosive actions, surface treatments and thin film ceramic coatings applied by PVD and CVD techniques have been evaluated using both laboratory tests and production evaluation. This paper provides details of the coating candidates, the tests, and the analysis of coating failure. It presents the results of these tests and explains the mechanisms for erosive–corrosive failure of H13, and the PVD and CVD coatings in the die casting environment.
Tribological behaviour of Si–DLC coatings
Authors: Varma A. , Palshin V. , Meletis E.I. , Fountzoulas C.
Published: May 2005

Amorphous silicon containing diamondlike carbon (Si–DLC) films were prepared by Ar+ ion beam assisted deposition (IBAD) on silicon wafers, with coating thickness ranging from 0·6 to 4·0 μm. The films were examined with SEM, TEM, and FTIR spec troscopy. The TEM analysis showed that the films were mainly amorphous and composed of diamondlike and graphitelike domains. The relative amounts of sp3 and sp2 bonding types in Si–DLC were determined by IR spectroscopy and the sp3/sp2 ratio was found to depend strongly on the current density in the ion beam, ranging from 1·4 for 163 μA cm-2 to 5·4 for 85 μA cm-2. Infrared absorption features correspond ing to Si–H and Si–C bonds were observed, illustrating the role of Si atoms in a DLC structure. Pin on disc experiments were conducted to characterise the tribol ogical behaviour of the Si–DLC films. The results showed that the films exhibit high wear resistance and low coefficient of friction. The results suggest that the wear behaviour is affected by film thickness and its diamondlike character. Thick films with low sp3/sp2 ratios demonstrated ultralow wear rates in short duration tests. However, films with high sp3/sp2 ratios may be suitable for long duration applications since they exhibit slower transformation kinetics.
Wear characteristics of WC–6Co coating deposited using pulsed electrode surfacing technique
Authors: Stiglich J. , Campillo B. , Rosales I. , Perez R.
Published: May 2005

An assessment of the wear performance of coatings produced by pulsed electrode surfacing was carried out. The PES technique is based on the transfer of coating material from an electrode to a substrate by means of an electric arc. A major advantage of this process is that a true metallurgical bond to the substrate results during coating application, in contrast with other coating techniques such as plasma spray, sputtering, etc. Initial experimental wear resistant coatings of WC–6Co have been applied to several steel substrates. Substrate steel pins were 1045, M2, 304SS, and 9840 (or 4140). Substrate bars were M2 and 9840 (or 4140). Wear tests were carried out using a pin on rotating bar system. After the tests, the surfaces were observed with an analytical SEM. Specimen cross- sections were characterised using SEM and microhard ness measurements. All coatings formed strong, adher ent metallurgical bonds to their substrates. Wear test results showed superior performance of all coatings to uncoated and to TiN coated substrates in the high stress, unlubricated environment of the pin on rotating bar test.
Tribological properties of pulsed ion nitrided AISI 4140 steel
Authors: Staia M.H. , Fragiel A. , Machado J. , Brühl S.P. ,   Feugeas J.., Gomez B.J.
Published: May 2005

The present study was conducted in order to investigate the tribological behaviour of plasma nitrided AISI 4140 steel by using a dc pulsed glow discharge technique. Microstructure and structural characterisations were performed by using scanning electron microscopy and X-ray diffraction techniques. A compound layer with a thickness between 6 and 8 μm containing ɛ (Fe3 N) and to a lesser extent γ′ (Fe4 N) was identified. Wear tests were performed with a pin on disc configuration. The tests were carried out at room temperature in air using two different pin materials (AISI 1086 and WC–6Co). A sliding speed of 0·1 m s-1, 5 N load, and 700 m maximum sliding distance were used on both substrate and nitrided specimens. The friction coefficients found for the tribological pairs under study, tungsten carbide pin and plasma nitrided disc, AISI 1086 pin and plasma nitrided disc, and AISI 1086 pin and AISI 4140 disc, were 0·34–0·6, 0·49–0·6, and 0·475–0·57 respectively. Wear volumes of 0·0453, 0·0511, and 0·00077 mm3 have been determined for the tribological pairs mentioned above. The surface top ography of the wear scars on both specimens and pins have been determined using scanning electron micros copy and three-dimensional stylus profilometry.
Improvement of ion plated Ag and Au film adhesion to Si3 N4 and SiC surfaces for increased tribological performance
Authors: Spalvins T.
Published: May 2005

A modified dc diode plating system, utilising a metallic screen cage as a cathode and designated screen cage ion plating, is used to deposit Ag and Au lubricating films on Si3 N4 and SiC surfaces. When deposition is performed in Ar or N2 glow discharge, the surface displays poor adhesive strength (<5 MPa). A dramatic increase in adhesive strength (>80 MPa) is achieved when plating is performed in a reactive 50O2–50Ar glow discharge. The excited/ionised oxygen species (O+2 /O+) in the glow discharge contribute to the oxidation of the Si3 N4 or SiC surfaces as determined by X-ray photoelectron spectroscopy depth profiling. The reactively sputter oxidised Si3 N4 or SiC surfaces and the activated oxidised metastable Ag or Au species formed in the plasma, cooperatively contribute to the increased adhesion. As a result, the linear thermal expansion coefficient mismatch at the interface is reduced. These lubricating Ag and Au films under sliding conditions reduce the friction coefficient by a factor of 2·5–4.
Rolling contact fatigue behaviour of Pyrowear 675
Authors: Wells M.G.H. , Beck J. , Middleton R.M. , Huang P.J. , Wert D.E.
Published: May 2005

This work represents one phase of a comprehensive gear and bearing materials programme, involving both substrates and coatings. The programme is directed at enhancing both the performance and durability of gears and bearings for insertion into military systems. This paper deals specifically with the Pyrowear 675 alloy, a carburising stainless steel recently developed by Carpenter Technology Corp. The rolling contact fatigue (RCF) performance of steel specimens with four different heat treatments is presented. The optimum heat treatment produced a fivefold increase in both B10 and B50 lifetimes compared with M50 steel, the standard turbine engine bearing steel. Thus, the improved RCF performance combined with good corrosion resistance make Pyrowear 675 alloy an attractive candidate for advanced bearing applications.
Hardness of submicrometre abrasive particles and polish rate measurements
Authors: Ramarajan S. , Hariharaputhiran M. ,   Her Y.-S., Babu S.V.
Published: May 2005

Metal surfaces (copper and tantalum) and films (copper and tungsten) and silicon dioxide films were polished in deionised (DI) water using submicrometre sized alumina particles of varying density in benchtop Struers and Strasbaugh polishers. The polish rates for copper and tantalum in DI water increase significantly when the abrasive particle density exceeds a threshold value that correlates with the reported microhardness values of the (bulk) materials obtained using classical diamond pyramid microindentation measurements. Since it is expected that the density values are indicative of the particle hardness, this suggests, as might be expected, the existence of a threshold in the abrasive particle hardness for obtaining measurable polish rates. Based on this observation, the change in the relative hardness of thin films of copper exposed to two different chemical reagents in the chemical polishing of copper films was evaluated.
Characterisation and applications of electrodischarge machined cast aluminium alloy surfaces
Authors: Popoola O.O. , Zaluzec M.J. , Haack L.
Published: May 2005

Scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectrometry have been used to characterise cast aluminium surfaces after electrodischarge machining (EDM) using copper electrodes. Depending on the machining conditions EDM produces a surface recast layer, about 20–100 μm thick, with significantly higher hardness than the underlying substrate. For example, the surface hardness of Al 319 was increased from 45 to 65 HK by EDM. HREM and XPS analyses showed that the increase in surface hardness was a result of the formation and dispersion of fine SiC particles in a rapidly resolidified solid solution of Cu–Al. Important tribological applications of electrodischarge machining of aluminium alloys include surface preparation for enhanced thermal spray coating adhesion and abrasive wear resistance improvement on parent aluminium surfaces.
Acoustic Emission Analysis of Wear in Hacksaw Blades
Authors: Ahmed W. , Farooq M.K. , Hassan I.U. , Ali N.
Published: May 2005

The performance and reliability of cutting tools depend on a number of variables such as cutting conditions, tool material, tool geometry, and the properties of the workpiece material. Acoustic emission analysis is a method that may be used to examine the in process progressive wear of cutting tools. This paper presents results of a study of wear processes associated with hand hacksaw blades using acoustic emission analysis. A direct relationship between the mean acoustic signal and the rate of wear has been established for hand hacksaw blades used for metal cutting. This is supplemented by results obtained from SEM and EDAX, which reveal wear in the cutting teeth. Acoustic emission analysis is an attractive technique that can be used to monitor wear processes online and non-obstructively, making it extremely useful for performance and life prediction of hand hacksaw blades. The method may also be applied to other single and multipoint cutting tools.
Influence of heat treatment on tribological behaviour of Ni–P autocatalytic coatings
Authors: León O.A. , Staia M.H.
Published: May 2005

Pin on disc tests were performed on Ni–P coatings, as deposited and heat treated at 200, 300, and 400°C for 1 h, to study the influence of heat treatment on the friction coefficient and wear resistance of the coatings. X-ray diffraction studies indicate thermally induced structural changes, which increase the hardness and wear resistance of the coatings. Heat treatment at 400°C induces complete crystallisation of the ductile Ni–P matrix to Ni3 P and Ni (fcc), which are responsible for the highest hardness and wear resistance. Scanning electron micrographs of the wear tracks of the coatings show that adhesive and abrasive wear are the wear mechanisms involved in the wear of Ni–P autocatalytic coatings under dry non-lubricated conditions.
Development of electrodeposited Fe–Cr–P amorphous metallic alloys
Authors: Kunioshi C.T. , Correa O.V. , de Lima N.B. , Ramanathan L.V.
Published: May 2005

The main characteristic of amorphous materials is the lack of long range crystallographic order in their structure that confers chemical and physical properties different from their crystalline counterparts. One such property is the superior corrosion resistance of certain Cr containing Fe based amorphous alloys. Conventional electrodeposition from aqueous solutions is one of the techniques that has been used to obtain these alloys. This paper represents a study of the influence of various process parameters on the composition, morphology, and properties of electrodeposited Fe– Cr–P amorphous alloy coatings. The effect of ion selective membrane, formic acid (a Cr3+ complexant), sodium lauryl sulphate (a surfactant), and aging time of the formic acid containing bath were investigated. The results show that it is possible to obtain these coatings under certain experimental conditions. Electrochemical tests, carried out in sulphuric acid, revealed corrosion behaviour intermediate between the carbon steel substrate and the amorphous alloy.
Growth of rutile TiO2 thin films by laser ablation
Authors: Escobar-Alarcón L. , Haro-Poniatowski E. , Camacho-López M.A. , Fernández-Guasti M. , Jímenez-Jarquín J. , Sánchez-Pineda A.
Published: May 2005

Thin films of TiO2 on glass substrates were grown by the laser ablation technique using the second harmonic (532 nm) of a pulsed Nd–YAG laser as the evaporation source. During deposition, various substrate temperatures and oxygen pressures were used to optimise the growth of rutile TiO2 thin films. Raman spectroscopy and X-ray diffraction measurements showed that crystalline thin films were obtained at a substrate temperature as low as 100°C. The films show smooth surface morphology and good adhesion.
Development of polishing technology for titanium used in surgical implants
Authors: Kenny E.D. , Da Silva J.M. , Henke S.L. , Lazaris J. , Onnoda R.T. , Maistrovicz J.V.
Published: May 2005

Currently, in the Brazilian market, the reservoirs implanted for chemotherapy are being manufactured and commercialised in stainless steel (ASTM F138), which supplies the demand in adult patients. Lighter reservoirs, which are made with biomedical grade titanium (ASTM F67), are needed to treat infants and babies. In this case, the national production is still custom made owing to the manual polishing which requires some 2–3 h to provide a mirror finish. Besides that, the cost of the imported models is very high. Therefore, the main purpose of the present work is to improve the polishing technology for the biomedical grade titanium used for surgical implant applications through the electrochemical polishing technique. With the application of this technique an Ra value of 0·3 µm on the internal surface of the reservoirs should be reached. This degree of finishing is necessary on all the titanium surfaces that will come into contact with the blood stream, in order to prevent or to reduce the risk of thrombus formation. This study makes the production of these titanium reservoirs two-thirds less expensive than the imported models and they will be available in a shorter time.
Models for hardness and adhesion of coatings
Authors: Lesage J. , Chicot D.
Published: May 2005

Indentation tests are widely used because they are apparently very simple to interpret in terms of mechanical properties. In the special case of coatings, indentation tests may be performed in order to determine hardness (even when the substrate interferes in the measurement) or adhesion properties, as long as some problems of interpretation are solved. In the first part of the paper, it is shown that existing models are not satisfactory for predicting hardness and instead a new model is presented based on the plastic deformation volumes under the indenter. The second part of the paper examines how the indentation is capable of creating and propagating a crack at the interface between the coating and the substrate, and the applied load–crack relation is interpreted in terms of an apparent interfacial toughness which can be correlated with adhesion.
Surface treatment of aluminium alloy by laser shock processing
Authors: Zhang H. ,   Zhang Y.-K.,   Yu C.-Y.
Published: May 2005

Laser shock processing is a novel surface treatment, distinct from shot peening, explosive treatment, and high power continuous laser treatment, for improving the fatigue resistance of metals. The effects of laser shock treatment on the fatigue life of 2024–T62 aluminium alloy have been studied. The fatigue test results show that the average life of laser shock treated specimens is six times that of unshocked ones. The fatigue life improvement is attributed to the combined effects of reduced surface roughness, increased dislocation density, and compressive surface residual stress.
Comparison of yttrium implantation effect on pure iron and various steels
Authors: Caudron E. , Buscail H. , Haanappel V.A.C. , Jacob Y.P. , Mignot A. , Stroosnijder M.F.
Published: May 2005

Specimens of pure iron and various steels were yttrium implanted using ion implantation. Specimen compositions and structures were investigated before and after yttrium implantation to determine the influence of specimen material on the resulting yttrium distribution. Yttrium implantation effects were characterised using scanning electron microscopy and analytical and structural techniques (Rutherford backscattering spectrometry, reflection high energy electron diffraction, X-ray diffractometry, and glancing angle X-ray diffraction). This paper demonstrates that correlation between compositional and structural analyses permits understanding and comparison of the surface and bulk modification effects of yttrium implantation on pure iron and various steels.
Investigation of plasma spray ceramic coatings on austenitic manganese and mild steels
Authors: Venugopal K.A. , Bandyopadhyay P.P. , Chattopadhyay A.B. , Chakrabarti A.K.
Published: May 2005

An investigation was conducted to explore the feasibility of applying plasma spray ceramic (alumina) coatings to Hadfield manganese and mild steels. The results suggest that an intermediate bond coat of Ni–Al alloy is necessary for satisfactory coating adhesion on both the mild and manganese steel substrates. The coating chemistry is altered by large scale diffusion of elements from the substrate to the coating and counterdiffusion of elements from the coating into the substrate, both of which adversely affect coating bond strength and abrasive wear resistance.
Fatigue strength of nitrided 18Ni250 and 18Ni300 grade maraging steels
Authors: Karliński W. , Tacikowski J. , Wojtyra K.
Published: May 2005

An investigation into the nitriding of maraging steels 18Ni250 and 18Ni300 has been conducted. Preliminary investigations of the nitriding parameters were carried out on 18Ni250 grade steel in an atmosphere of partially dissociated ammonia at temperatures within the range 450 to 520°C and for times from 1 to 24 h. Hardness, depth, and microstructural characteristics of the case were determined. The results of preliminary tests served to facilitate the selection of nitriding process parameters for fatigue test specimens. Specimens were nitrided at 470 and 480°C (grade 18Ni250) and 450 and 470°C (grade 18Ni300). An increase of the bending fatigue limit by 45% was noted in comparison with unnitrided specimens. Within the selected range of nitriding parameters, no effect of nitriding on fatigue strength was observed.
Corrosion and abrasive wear behaviour of laser consolidated plasma sprayed sic coating on Fe–15Cr–25Ni alloy
Authors: Tjong S.C. , Lau K.C. ,   Ku J.., Ho N.J.
Published: May 2005

Silicon carbide powders (75 μm) were plasma sprayed on austenitic Fe–15Cr–25Ni alloy. A continuous wave CO2 laser was used to consolidate the plasma sprayed layer and to decompose SiC particles during glazing. Optical and scanning electron microscopic techniques revealed that the structure of the laser consolidated layer consisted of cellular dendrites with M7 C3 carbides dispersed mainly at the dendritic boundaries. Consequently, the surface hardness of the Fe–15Cr–25Ni alloy improved considerably. Abrasive wear tests showed that the laser modified specimen exhibited lower wear mass loss and a lower coefficient of friction than the raw Fe–15Cr–25Ni alloy. Potentiodynamic and cyclic polarisation behaviour of the laser modified and raw Fe–15Cr–25Ni alloy specimens in 0·5M H2 SO4 and 0·5M NaCl solutions was also investigated.
Contribution of Hfe expression in macrophages to the regulation of hepatic hepcidin levels and iron loading
Authors: Makui Hortence , Soares Ricardo J. , Jiang Wenlei , Constante Marco , Santos Manuela M.
Published: May 2005

Hereditary hemochromatosis (HH), an iron overload disease associated with mutations in the HFE gene, is characterized by increased intestinal iron absorption and consequent deposition of excess iron, primarily in the liver. Patients with HH and Hfe-deficient (Hfe-/-) mice manifest inappropriate expression of the iron absorption regulator hepcidin, a peptide hormone produced by the liver in response to iron loading. In this study, we investigated the contribution of Hfe expression in macrophages to the regulation of liver hepcidin levels and iron loading. We used bone marrow transplantation to generate wild-type (wt) and Hfe-/- mice chimeric for macrophage Hfe gene expression. Reconstitution of Hfe-deficient mice with wt bone marrow resulted in augmented capacity of the spleen to store iron and in significantly decreased liver iron loading, accompanied by a significant increase of hepatic hepcidin mRNA levels. Conversely, wt mice reconstituted with Hfe-deficient bone marrow had a diminished capacity to store iron in the spleen but no significant alterations of liver iron stores or hepcidin mRNA levels. Our results suggest that macrophage Hfe participates in the regulation of splenic and liver iron concentrations and liver hepcidin expression. (Blood. 2005;106:2189-2195)
Reduced frequencies and suppressive function of CD4+CD25hi regulatory T cells in patients with chronic lymphocytic leukemia after therapy with fludarabine
Authors: Beyer Marc , Kochanek Matthias , Darabi Kamruz , Popov Alexey , Jensen Markus , Endl Elmar , Knolle Percy A. , Thomas Roman K. , von Bergwelt-Baildon Michael , Debey Svenja , Hallek Michael , Schultze Joachim L.
Published: May 2005

Globally suppressed T-cell function has been described in many patients with cancer to be a major hurdle for the development of clinically efficient cancer immunotherapy. Inhibition of antitumor immune responses has been mainly linked to inhibitory factors present in cancer patients. More recently, increased frequencies of CD4+CD25hi regulatory T cells (Treg cells) have been described as an additional mechanism reducing immunity. We assessed 73 patients with B-cell chronic lymphocytic leukemia (CLL) and 42 healthy controls and demonstrated significantly increased frequencies of cytotoxic T lymphocyte-associated protein 4 (CTLA4+)–, Forkhead box P3 (FOXP3+)–, glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR+)–, CD62L+–, transforming growth factor β1 (TGF-β1+)–, interleukin 10 (IL-10+)–Treg cells in patients with CLL, with highest frequencies in untreated or progressing patients presenting with extended disease. Most surprisingly, in the majority of patients with CLL treated with fludarabine-containing therapy regimens the inhibitory function of Treg cells was decreased or even abrogated. In addition, frequencies of Treg cells were significantly decreased after therapy with fludarabine. In light of similar findings for cyclophosphamide the combination of fludarabine and cyclophosphamide might be further exploited in strategies reducing immunosuppression prior to cancer immunotherapy.