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This paper reports the use of the Layer-by-Layer self-assembly (LbL) as an efficient technique for the fabrication of thin-films with antibacterial activity. The LbL coatings are composed of a positive polyelectrolyte such as Poly(allylamine hydrochloride) (PAH) and an anionic polyelectrolyte such as Poly(sodium 4-styrene sulfonate) solution (PSS). In addition, these polyelectrolytes can be also used as an adequate encapsulating agent of specific metal oxide precursors such as titanium dioxide (TiO2) and iron oxide (Fe2O3) nanoparticles, making possible the fabrication of hybrid thin films composed of organic polymeric chains related to the polyelectrolytes and inorganic structure associated to the metal oxide nanoparticles. Four different LbL coatings have been fabricated and a comparative study about the resultant topographical, optical and wettability properties is presented by using light interferometry, atomic force microscopy (AFM), UV-Vis spectroscopy and water contact angle (WCA) measurements. In addition, X-ray fluorescence (XRF) has been also employed in order to corroborate the presence of metal oxide precursors inside the polymeric chains of the polyelectrolytes. Finally, the antibacterial tests have demonstrated that LbL coatings composed of metal oxide nanoparticles produce an enhancement in the efficacy and antibacterial activity.

Diamond-like carbon (DLC) coatings have been extensively studied over the last two decades in the field of materials engineering. The addition of effective bactericidal agents like silver suggests the potential application of silver-doped DLC coatings in the biomedical sector. In this paper, DLC coatings containing about 2 at. % Ag were grown on CoCrMo substrates by pulsed filtered cathodic arc co-deposition using pure graphite and silver targets. Morphology, structure and chemical composition of the coatings were characterized by SEM, XPS, XRD, Raman and HRTEM. Wettability and surface free energy were also measured. Mechanical properties were analyzed by means of nanoindentation and Rockwell-C adhesion tests. Corrosion resistance of coated and uncoated samples was determined by potentio-dynamic polarization tests in Hank's solution. Cytotoxicity and antibacterial activity against S. aureus and P. aeruginosa were also studied. For comparative purposes, nitrogen-doped DLC coatings obtained by RF magnetron sputtering were also prepared and characterized. Well-adhered and corrosion resistant Ag-DLC nanostructured coatings of up to 1.5 µm thick and 21 GPa in hardness were obtained. The doping concentration of silver studied in this work seems to be optimal for the preparation of non-cytotoxic coatings with a significant bactericidal activity. This work has been financed by the Ministry of the Economy, Industry and Competitiveness of Spain under the project BIOPLASMA (MAT2015-67103-C4).

El presente trabajo muestra una metodologia de preparacion superficial previa a ensayos de nanoindentacion que permite reducir las imprecisiones producidas por una rugosidad superficial excesiva. En aplicaciones en las que el tamano maximo de indentacion es dimensionalmente comparable con la rugosidad de la muestra, la dispersion y falta de exactitud de los resultados puede resultar excesiva. Son estos casos a los que se dirige la metodologia desarrollada. El desarrollo del metodo se ha realizado para capas finas en las que el recubrimiento presenta mayor dureza que el sustrato. Para ello, este se ha validado y aplicado utilizando recubrimientos PVD de TiO2 depositados sobre Inconel 718, los cuales han sido posteriormente sometidos a temperaturas entre 600 °C y 1100 °C, produciendose un aumento en la rugosidad de las muestras. Modificando diferentes parametros del ensayo ha sido posible analizar la mejora en los resultados que aporta el procedimiento y sus fuentes de incertidumbre, y compararlo con la metodologia habitual de nanoindentacion. PALABRAS CLAVE/KEYWORDS: Nanoindentacion, capas finas, rugosidad, abrasion superficial, PVD, oxido de titanio. Nanoindentation, thin coatings, roughness, surface abrasion, PVD, titanium oxide.

In this study we have analysed the indentation hardness and modulus of cathodic arc deposited CrTiAlN coatings as a function of the stoichiometric variables Ti/Cr, Al content and cation mix. The coatings have been prepared using a combinatorial cathode composition approach, leading up to 14 different stoichiometries produced in 5 batches. The coatings have been inspected by glow discharge optical emission spectroscopy, scanning electron microscopy, X-ray diffraction and nanoindentation techniques. The coatings develop crystalline structures compatible with solid solutions of face-centered cubic unit cells for all the compositions produced. Such unit cells exhibited a downwards lattice parameter dependency on the aluminum concentration of the coatings (from 0.417 nm down to 0.413 nm). The indentation hardness as a function of the Ti/Cr is compatible with other previous studies reported. The films hardnesses and moduli also increase as the aluminum concentration increases (21 GPa up to 34 GPa). Both indentation responses upon Ti/Cr and Al are attributed to solid solution strengthening. However in order to prove this statement, the indentation hardness and modulus were studied as a function of the mixing term of the cations, as this term is well representative of the solid solution compositional map. The observed results unambiguously evidence that the solid solution strengthening effect is confirmed on the basis of the dependency between the indentation hardness and the so called degree of mixing. This work has been funded by the Spanish Ministry of Science and Innovation of Spain through the project PGC2018-096855-A-C44. The authors also acknowledge the Centro para el Desarrollo Tecnológico e Industrial (CDTI) for the support of the excellence program CERVERA through the project CER2019-1003.

Due to its resistant to thermal shock and strength at elevated temperature, Titanium-Zirconium-Molybdenum (TZM) alloy is used for hot-work tooling up to 1500 °C. The friction and wear behaviour of the TZM alloy reciprocating against Al 2 O 3 and Si 3 N 4 in different conditions were investigated. It has an adhesion and/or oxidation character with a high coefficient of friction when dry sliding against an alumina ceramic ball. It is characterised with reduced wear in an abrasion mode when reciprocally sliding against a Si 3 N 4 ceramic ball. In addition, the friction and wear between TZM and an Al 2 O 3 ball under unidirectional sliding conditions can be reduced when lubricating molybdenum oxides was formed at higher temperature i.e. 600 °C. Finally, the friction and wear mechanisms involved are discussed.

Maraging steels combine excellent mechanical properties at medium-high temperatures with good fracture toughness, but they usually require the aid of thermochemical treatments to enhance superficial properties such as resistance to abrasive wear and corrosion resistance. In particular, plasma nitriding, due to its duration and temperature, which are compatible with the age-hardening cycles of maraging steels, permits the realization of both processes simultaneously. In this work, simultaneous ageing and arc-activated plasma nitriding of maraging steel grade 300 were studied as a function of the working pressure of the gases (N2 and Ar) present in the vacuum reactor chamber. In addition, the influence of the operating pressure was established by analysing the capacity of the plasma to penetrate in 2.5 mm in diameter blind holes. In-depth chemical composition, hardness and micro-hardness profiles, X-Ray diffraction, roughness, tribological characterization and corrosion tests were carried out to compare maraging steel samples treated in one simultaneous plasma nitriding and ageing process and in two-step processes. Metallographic tests and nanoindentation measurements were performed to study how the plasma penetrates and diffuses into the blind holes and how the nitride case layer thickness formed at the inner surfaces of the holes changes as a function of the distance to the surface for various working pressures.

In this work, cathodic arc evaporation CrTiAlN coatings have been deposited on H13 hot work steel and the tribological behavior investigated at room temperature and at 400 °C. The microstructure, composition, roughness, indentation hardness and lattice parameter have been measured as a function of the deposition conditions, mainly given by the different Cr and TiAl vapour fluxes coming from the cathode arrangement in the vacuum reactor. The coating microstructures showed dense, compact columnar growth and a good film adhesion. The lattice parameter measured over the (002) diffraction peaks exhibited a quasi lineal correlation with the Ti/Cr+Al atomic ratio of the samples. In addition, the indentation hardness also increased as the lattice parameter increased. The coefficients of friction unveiled the different tribological behavior of the samples depending on the stoichiomentry and the temperature. At 400 °C, the coefficients of friction showed high dispersion, in contrast to the coherent evolution observed at room temperature. The wear damage at 400 °C was more intense than that observed at room temperature in agreement with the friction evolution observed. The coating with a stoichiometry of Cr0.23Ti0.13Al0.22N0.42 showed a good wear performance at 400 °C.

Incineration units for sewage sludge disposal require a 40% minimum of dry solid content to obtain an ignitable material for energy recovery. Electro-dewatering (EDW) process could be useful to accelerate and improve the removal of adsorbed/interstitial water from sludge, but this application must be as cheap as possible and, further, the use of noble metals as electrodes to avoid corrosion is not appropriate. With these constraints, the use of an organic conductive coating could be suitable to protect low carbon steel electrodes. In this work, we investigated the chemical, electrical and mechanical characteristics of coatings obtained with epoxy resin/multi-walled carbon nanotube (MWCNT) composites, with the aim to design a protective film. The filler/resin ratio is the main parameter to be considered because at high ratio the electrical conductivity increases and, on the reverse, the physical and mechanical performances worsen. Specimens with different concentrations of carbonaceous filler have been produced and their characteristics have been discussed in relation to the critical pigment volume concentration (CPVC) and to the percolation limit.

The application of surface treatments that incorporate silver or copper as antibacterial elements has become a common practice for a wide variety of medical devices and materials because of their effective activity against nosocomial infections. Ceramic tiles are choice materials for cladding the floors and walls of operation rooms and other hospital spaces. This study is focused on the deposition of biocide physical vapor deposition (PVD) coatings on glazed ceramic tiles. The objective was to provide antibacterial activity to the surfaces without worsening their mechanical properties. Silver and copper-doped chromium nitride (CrN) and titanium nitride (TiN) coatings were deposited on samples of tiles. A complete characterization was carried out in order to determine the composition and structure of the coatings, as well as their topographical and mechanical properties. The distribution of Ag and Cu within the coating was analyzed using glow discharge optical emission spectrometry (GD-OES) and field emission scanning electron microscope (FE-SEM). Roughness, microhardness, and scratch resistance were measured for all of the combinations of coatings and dopants, as well as their wettability. Finally, tests of antibacterial efficacy against Staphylococcus aureus and Escherichia coli were carried out, showing that all of the doped coatings had pronounced biocide activity. This research was funded by Departamento de Innovación, Empresa y Empleo from Gobierno de Navarra and Fondo Europeo de Desarrollo Regional. Project EUROINNOVA EP-2 NANOCONS (IIM10784.RI1-02182).

This study reports the synthesis and characterization of ternary Cr-Al-O and quaternary Cr-Al-O-N coatings deposited by cathodic arc physical vapour deposition, for various nitrogen and oxygen mass flow ratios during the growth process. The composition, microstructure, indentation hardness and modulus of the films have been characterized by scanning electron microscopy, electron probe micro-analysis, X-ray diffraction, and nanoindentation techniques. The evolution of the microstructure and mechanical properties of the coatings after ambient air annealing from 800 °C up to 1100 °C have been investigated. As the oxygen to nitrogen mass flow increases, the as-deposited coatings exhibit lower hardness, higher roughness, lower crystallinity and a more marked columnar structure. At oxygen to nitrogen mass flow ratios bigger than 10/90, the coatings exhibit a stoichiometry of the type (CrAl)2+εO3−ε. Only the coatings with an oxygen to nitrogen mass flow ratio smaller than 10/90 retained nitrogen in their compositions. In all cases, the coatings developed a cubic fcc lattice structure. After annealing at 1100 °C the resulting microstructure showed a clear dependency upon the initial composition of the films. The evolution of the microstructure during the high temperature tests, as well as the analysis of the nanoindentation hardness, composition and thickness also provided valuable information about the combined effects of the thermal stability and the oxidation of the deposited coatings. This work has been funded by the Spanish Ministry of Economy and Competitiveness through the project PROTEOX MAT2013-45391-P. The European Commission is also acknowledged through the FP7-FOFNMP project MICROFAST under contract Nr 608720. The Research Group of Surface Engineering and Nanostructured Materials in the Universidad Complutense de Madrid also acknowledges financial support of the Spanish MINECO (project MAT2015-65539-P).

In this work CrAlO and CrAlO/CrAlN multilayers deposited by cathodic arc evaporation are evaluated as protective films in metal and ceramic powder FAST sintering tool dies fabricated in titanium-zirconium-molybdenum allows (TZM). The films have been characterised in terms of their composition, microstructure, mechanical properties and thermal stability in air at high temperatures between 800 °C and 1100 °C; in addition the tribological performance has been analysed at room temperature and at 400 °C. The crystalline structure and composition of the CrAlO based coatings are compatible with the formation of a mixture of α-corundum and a cubic fcc (Cr,Al)2O3. The crystalline structure of the multilayer is, on the other hand, dominated by the cubic fcc lattice plane reflections of the CrAlN. The deposited specimens have high hardness, between 25 and 30 GPa, which are stable even after annealing at 1000 °C. Even more, the multilayer coating also exhibited good mechanical stability at 1100 °C. The multilayer coating also exhibited an excellent behaviour against wear at 400 °C. Sintering trials using coated TZM dies have been carried out using Ti90Sn10 and Al2O3 high energy ball milled powders. The experimental results show that the oxide based coating formulations are potentially able to protect the tools from wear, sticking and oxidation of their surfaces. This may allow the use of TZM material as an alternative to other substrates such as graphite. The authors acknowledge the financial support of the European Commission through the FP7 Grant Agreement 608720 (Micro-FAST), and the MINECO (Spain) in the frame of the PROTEOX project (MAT2013-45391-P).

The deformation and failure mechanism of a multilayered thin film consisting of alternating soft Cu and hard TiN interlayers has been studied by in situ SEM compression of micro-pillars and finite element simulations. While the yielding of the multilayer is governed by the 'size-dependent' strength of Cu, the failure was found to occur by shearing of the columnar grains of TiN. At elevated temperatures of 200 and 400 °C, the yielding of the multilayers is governed by the stress-assisted diffusion of the Cu interlayers, which coalesce into microcrystals and grow into larger faceted crystals.

Plasma immersion ion implantation technology has been utilized to enhance the photocatalytic activity of the anatase phase of TiO thin films deposited by cathodic arc evaporation PVD. The main objective of this study is to shift the light absorbance of the titania in order to obtain antibacterial activity under visible light irradiation. TiO thin films, deposited on polished stainless steel AISI 304 and silicon wafers, were implanted with nitrogen ions (N/N ) at 20 kV energy and different temperatures between 250 and 350 °C. The antibacterial activity of nitrogen implanted titania coatings has been monitored for Escherichia coli under visible light irradiation. Additionally ultra violet/visible spectrophotometry tests have been carried out to measure the changes in the light absorbance of the doped films. Further characterization has been performed, including X-ray photoelectron spectroscopy, X-ray diffraction and glow discharge optical emission spectrometry. As a result of Nitrogen implantation, the light absorption peak shifted from ultra violet region (UV-A) to visible wavelength range, which led to an increase of the antibacterial efficacy under visible light irradiation., This work was developed in the framework of the industrial project ACTIONIC (IDI-20140-230-231) supported by the Ministerio de Economía y Competitividad (MINECO), through Centro Desarrollo Tecnológico Industrial (CDTI), and the Government of Navarra through the project DECOBAC.

The sewage sludge dewatering produced by wastewater treatment plants (WWTP) is a multifaceted process due to the presence of colloid fractions. Electro-osmosis could be a suitable technique to reduce the water content of the final sludge. Electric fields of 10, 15, and 20 V/cm have been studied for electro-osmosis tests under the pressure of a static or rotating piston, obtaining a dry solids content up to 40–45%, with respect to 25–30% obtained by mechanical methods. In order to optimize the process, the corrosion behavior and the wear of the anodic material appear to be the main critical aspects, due to the high circulating current density and the use of a rotating electrode. We compared the efficiency and the corrosion resistance of dimensionally stable anodes (DSA) with respect to bare stainless steel (AISI 304) and stainless steel coated by PVD technique with TiN, AlTiN, and DLC. Characterization of the anode surfaces by SEM and potentiodynamic tests show that DSA is the most suitable materia...

Los aceros maraging son aleaciones Fe-Ni, con concentraciones de Ni de entre 15-25% en peso, y con concentraciones de carbono muy bajas (

In this article, a mathematical algorithm is derived to accurately determine the critical load of indentation for the initiation of cracks on the surface of a hard coating on a soft substrate, based on the measurement of the diameter of circumferential cracks in micro-indentation impressions. The critical load required for the initiation of the first crack predicted using this technique is shown to be in good agreement with experimental results, indicating the feasibility of the technique proposed. The rationality of the approach proposed was further explored by investigating the fracture mechanism of the surface in a multilayer-coated surface using a finite element model, which was developed with the parameterised modelling approach, in combination with the cohesive-zone model.

In this work, a successful sequential co-implantation treatment of Cr+ and N2 + ions into electrodeposited nickel plates is presented. The goal of this treatment is the simultaneous enhancement of the wear resistance, mechanical stability and corrosion-protection properties of the Ni surfaces. The ion-implanted surfaces have been characterized by glow-discharge optical-emission spectroscopy, X-ray diffraction, nano-hardness, roughness, nano-wear and potentio-dynamic corrosion tests. It has been observed that the implantation of Cr+ or N2 + alone is not sufficient to achieve simultaneously the enhancement of both the wear-resistance and the corrosion-protection properties. Conversely, the sequential implantation of Cr+ and N2 + at 140keV and fluencies of 3×1017 and 1.5×1017ions/cm2 respectively, permits the formation of a functional surface capable of reducing both the corrosion rate and the wear rates, with respect to those exhibited by the un-implanted Ni surfaces.This treatment can be used to protect the surfaces of micro-embossing/stamping dies based on electroformed Nickel, as an alternative to other coating strategies. Furthermore, the ion implantation assures the non-modification of the net-shape and surface finish of these types of dies, which is of crucial importance when they are used for high-precision micro-texturing/imprinting applications. © 2011 Elsevier B.V.

This paper reports on tribological properties of magnetron-sputtered WC–C and chemical vapour-deposited diamond-like carbon films coated onto hard-metal surfaces when sliding on aluminium foil (0.2 mm nominal thickness) at different temperatures. The study addresses the evolution of the coefficient of friction at the interfaces of the coated hard metal and the aluminium foil under dry-lubrication conditions, in a ball-on-disc configuration. The wear mechanisms of the aluminium foil and the damage produced on the coated surfaces due to the sticking of aluminium were evaluated as a function of the deposited coating and the temperature at their interfaces. Aluminium-transfer to WC–C coated hard-metal surfaces during the sliding operation seemed to be a non-continuous process, which appeared after a certain number of sliding cycles. Temperatures above 70°C accelerated the transfer of aluminium to the WC–C tool surfaces. Chemical vapour-deposited diamond-like carbon films hindered the transfer of aluminium to the hard metal even at temperatures of around 125°C. At greater temperatures, an aluminium–aluminium tribosurface is formed at the interface, which increases the wear rate of the foils and rapidly degrades the quality of coatings of the hard-metal surfaces.

This work reports on the growth and properties of Cathodic Arc Physical Vapor Deposition of low friction-coefficient CrCN coatings, as deposited on the basis of complementary carbon/nitrogen gradient concentrations through the film thickness. The coatings developed in this study exhibited friction coefficients ranging from 0.2 to 0.6, against 100Cr6 bearing steel, depending on the preparation conditions. Gradient CrCN films with COF of 0.35 and comparable mechanical strength to that of CrN were achieved. The adhesion rate of metallic elements such as Fe during the sliding process of CrCN coated tools on AISI316L steels were monitored using a pin-on-disc experimental set-up. The results demonstrated a low tendency of the gradient CrCN deposited films to pick up material from the AISI316L steels surfaces, in contrast to that found when using standard CrN cathodic arc PVD films.

The use of ion implantation as a surface treatment technology has been dominated by its applications to prevent wear and oxidation in metal alloys, although some early works already pointed out that ion implantation could also be effective as a surface treatment for other materials, including polymers. Further research has shown that low-dose implantation of energetic light ions could be very effective for improving properties such as hardness and wear resistance in many different polymers. Cross linking of polymeric chains due to ionization energy provided by the stopping process is the main mechanism to explain the changes in mechanical properties. According to this model the lighter the ion is, the stronger is the effect: hydrogen and helium ions would be the ideal options to be employed in the treatment of polymers. This paper presents the results obtained by helium implantation in ultra high molecular weight polyethylene (UHMWPE). He+ ions were at 90 and doses between 5 × 1015 and 2 × 1016 ions/cm2. Nitrogen was also implanted in separate samples, under the same conditions, as a reference. Universal Hardness was measured using micro indenter at a maximum load of 2 mN. The results clearly show a higher increase in hardness and surface elastic modulus for samples implanted with helium, in comparison to those implanted with nitrogen or unimplanted. The effect also increases with the dose, although it saturates at 1 × 1016 ions/cm2.

Cr, CrN, TiCr coatings have been investigated as potential anti-multipactor coatings. The coatings were synthesized by cathodic-arc reactive evaporation in Ar–N 2 atmosphere where the ion energy is controlled by substrate biasing. Chemical state analysis and surface composition were studied by X-ray photoemission spectroscopy (XPS), whereas bulk composition and depth profile were studied by glow discharge optical emission spectroscopy (GDOES). The surface morphology was studied by optical profilometry (OP) and scanning electron microscopy (SEM). The compositions of the coatings were CrN and Ti 40 Cr 60 and they were homogeneous in depth. Surface oxidation was higher in Ti 40 Cr 60 than in CrN. Coatings deposited at high negative bias show lower deposition rate and had lower surface roughness than those obtained at low bias. Secondary electron emission yield (SEY) was higher for CrN than for Ti 40 Cr 60 , both before and after low-energy Ar + ion bombardment. The SEY of Ti 40 Cr 60 (1.17 maximum) was clearly smaller than the others. The maximum yield, σ m , and the first crossover electron energy, E 1 , are the most important parameters, and ( E 1 / σ m ) 1/2 is a good figure of merit. This quantity was approximately 3 eV 1/2 for Cr and CrN and 4 eV 1/2 for Ti 40 Cr. After Ar + ion bombardment, the average value improved significantly to 8.9 eV 1/2 for Cr and CrN and 10.2 eV 1/2 for Ti 40 Cr 60 . The radio-frequency multipactor performance of these materials was simulated using the experimentally determined SEY parameters.

Nickel based superalloys have good oxidation and creep resistance and hence they can function under high mechanical stress and high temperatures. However, their undesirable tribological behaviour is the major technical barrier to the challenging high-temperature, lubricant-free plasma sintering tool application. In this study, nickel based CM247 superalloy surfaces were co-alloyed using innovative active screen plasma technology with both interstitial element (e.g. N) and substitutional alloying elements (e.g. V and Ag) to provide a synergy effect to enhance its tribological properties. The tribological behaviour of the plasma co-alloyed CM247 superalloy surfaces were fully evaluated using reciprocal and pin-on-disc tribometers at temperatures from room temperature to 600 ∘C. The experimental results demonstrate that the co-alloyed surface with N, Ag and V can effectively lower the friction coefficient, which is expected to help demoulding during lubricant-free plasma sintering.

CrN multilayer coatings are possible replacements for hard chromium because of their good mechanical and chemical properties. This paper focuses on X-ray photoelectron spectroscopy (XPS) to study the mechanism of electrochemical stripping of multilayered Cr-N based coatings. The samples were produced by electron beam (e-beam) physical vapour deposition (PVD), on mirror polished M2 steel. Multilayers constituted three separate layers of CrN with intermediate interlayers of Cr (0.1 μm). The total coating thickness was in the range 4.5-5.5 μm. Under galvanostatic conditions, anodic oxidation of CrN leads to replacement of nitrogen in the CrN coating by oxygen, forming oxy-nitrides on the samples surface. Contrary to findings described by some authors, we have not detected Cr6+ in this research. © 2006 Elsevier B.V. All rights reserved.

Diamond-like carbon (DLC) coatings have found great applicability in the automotive industry because of their low friction coefficient and high wear resistance. Nevertheless, their tribological performance can be greatly reduced on soft substrates such as titanium alloys. The hard DLC coating cannot usually follow elastic and plastic deformation of the substrate without failing. In order to overcome this property mismatch between hard coating and soft substrate, triode plasma nitriding was applied as a pre-treatment to improve the mechanical properties of the Ti6Al4V alloy and further enhance the load support for the DLC coating. DLC and multilayered TiN/DLC, CrN/DLC CrAlN/DLC coatings were deposited onto “standard” and plasma nitrided Ti6Al4V substrates. Triode plasma nitriding increased the load-bearing capacity of the coating/substrate system, as higher critical adhesion loads were recorded for DLC coatings on plasma nitrided Ti6Al4V substrates. This treatment also reduced the wear rate of the DLC coating/substrate. Further load support and lower wear rates were achieved by using TiN, CrN and CrAlN as intermediate layers on plasma nitrided Ti6Al4V substrates.

En los ultimos anos se ha venido estudiado la aplicabilidad de las tecnicas de depositos mediante metodos fisicos en fase vapor (PVD), para la realizacion de recubrimientos sobre ceramicas y otros substratos con fines decorativos. Los recubrimientos estandar por PVD como el TiN, CrN, TiCN, etc, ofrecen la posibilidad de conseguir acabados de apariencia metalica, de una amplia gama de colores, y con buenas propiedades mecanicas y quimicas, como resistencia a la abrasion, estabilidad termica, o resistencia a la corrosion. En este trabajo se recogen las experiencias realizadas en el recubrimiento y caracterizacion de ceramicas decorativas, durante los tres ultimos anos, en el Centro de ngenieria de Superficies de la Asociacion de la ndustria Navarra. Los distintos tipos de recubrimientos se han realizado mediante un equipo de PVD modelo METAPLAS 232, con seis evaporadores de arco electrico y sistema de limpieza ionica patentado AEGD. Los recubrimientos han sido caracterizados, tanto quimica como mecanicamente, empleando las mas modernas tecnicas tribologicas (ultramicrodureza, scrascth tests, resistencia al desgaste...) y espectroscopicas optica por descarga luminiscente (GDOES). Los resultados obtenidos muestran que las tecnicas de PVD son una interesante via para la obtencion de recubrimientos decorativos, de excelente resistencia tanto mecanica como quimica, y que los metodos de caracterizacion empleados son adecuados para el control de calidad industrial.

This paper reports an investigation on the tribological properties of Al thin foils (0.2 mm nominal thickness) in sliding contact with PVD-coated carbide forming-tools, with reference to the applications in the manufacture of miniature/micro-products, particularly through micro-forming. The study addresses the evolution of the friction coefficient between both surfaces under dry lubrication conditions, its influence on the surface quality of the processed material and the damage produced on the tool due to sticking phenomena. Uncoated, CrN-coated and WC-C-coated tools were tested, using a pin-on-disc configuration to monitor the evolution of the relative friction coefficients under different contact pressures. It was shown that the contact sliding of Al foils on the untreated carbide tool produced a significant transfer of Al to the tool, leading to a rapid degradation of both tool and foil surfaces, even faster than that produced on bulk aluminium. Conversely, the sticking of Al was retarded using low friction magnetron sputtered WC-C-coated carbides. Other PVD coatings such as CrN failed under similar operation conditions. Aluminium transfer to the WC-C-coated tool surfaces during sliding seemed to be a non-continuous process, which appeared after certain sliding distances. Temperature accelerated the Al transfer to the WC-C tool surfaces, probably due to the increase of the thermoplastic behaviour of Al above 100 °C, which led to an increase of the adhesive interaction with the WC-C coating.

Plasma nitriding of different substrates such as Ti6Al4V and AISI M2 steel was achieved by means of D.C. glow discharges assisted by thermionic emission (triode configuration). The higher ionisation levels achieved using a D.C. triode configuration reduced the treatment time and nitriding temperature required to obtain hard and reasonably deep nitrided cases in the Ti6Al4V alloy. For this alloy, surface hardness values of 560–600 HV 0.05 and nitrided layer depths of 30–40 μm were achieved at 700 °C. Up to this nitriding temperature, hardening seemed to be mainly accomplished by incorporation of nitrogen in the α-Ti phase, as the formation of a titanium nitride layer on the surface could not be detected by SEM. For the AISI M2 steel, hard (1379–1524 HV 0.05 ) nitrided layers of 100–150 μm were obtained at 480–500 °C for 240 min, depending on total pressure, gas composition and substrate bias. For the highest nitrogen concentration and lowest bias voltage, no compound layer was formed. The triode plasma nitriding process allowed a significant reduction in processing time for both M2 steel and Ti6Al4V alloy in comparison to conventional D.C. diode plasma nitriding.

This paper is focussed on the characterisation of electron beam evaporation plasma-assisted physical vapour deposition Cr–N coatings deposited on AISI M2 steel and hardmetal (K10) substrates in two different conditions: Pristine (i.e., coated) and Recoated (i.e., stripped and recoated). Analytical methods, including X-ray diffraction (XRD), scanning electron microscopy, scratch adhesion and pin-on-disc tests were used to evaluate several coating properties. XRD analyses indicated that both Pristine and Recoated coatings consisted of a mixture of hexagonal Cr2N and cubic CrN, regardless of substrate type. For the M2 steel substrate, only small differences were found in terms of coating phases, microstructure, adhesion, friction and wear coefficients between Pristine and Recoated. Recoated on WC–Co (K10) exhibited a less dense microstructure and significant inferior adhesion compared to Pristine on WC–Co (K10). The wear coefficient of Recoated on WC–Co was 100 times higher than those exhibited by all other specimens. The results obtained confirm that the stripping process did not adversely affect the Cr–N properties when this coating was deposited onto M2 steel substrates, but it is clear from the unsatisfactory tribological performance of Recoated on WC–Co that the stripping process is unsuitable for hardmetal substrates.

Cr–N benefits from good oxidation and corrosion resistance, which has, until recently, caused difficulties in removing the coating without damage to substrates. Consequently, the industrial use of Cr–N coatings, particularly on expensive tools, has been limited. As a new commercially viable wet-stripping process has been developed that causes little or negligible damage to steel substrates, it is appropriate to investigate the effect of coating thickness and structure on the stripping rate of different Cr–N films. In this work, Cr–N coatings deposited by magnetron sputtering, arc and electron beam evaporation, having different thicknesses, was wet-stripped. The stripping rate was evaluated by statistical analyses for each deposition method and thickness. The stripping rate for the various deposition methods was correlated to the coating phases, structure, morphology, and surface roughness, which varied depending on the deposition process. For all deposition methods, the stripping rate was constant at a given as-deposited coating thickness. Regardless of the deposition method, the stripping rate for all different as-deposited thicknesses was statistically similar within the same deposition process, indicating that the stripping rate was independent of the coating thickness. Moreover, the stripping rate was not influenced by changes in the coating structure with increased thickness, which occurred in arc and electron beam Cr–N coatings. For coatings having similar as-deposited thicknesses, the highest stripping rate was obtained in magnetron sputtered Cr–N (∼ 4.4 μm h − 1 ), followed by electron beam and arc Cr–N coatings, which displayed similar stripping rates (∼ 3.3 μm h − 1 ). The highest stripping rate recorded for magnetron Cr–N coatings could not be explained by changes in coating structure/morphology and surface roughness. The differences in the stripping were attributed to the amount of CrN phase present in the coatings.

This work reports a comparative investigation on tribological performance enhancement induced by nitrogen Plasma Immersion Ion Implantation (PI3) and conventional Nitrogen Ion Implantation (I2) on Ti and Al based alloys. The study has been carried out on the basis of the surface modification produced by both treatment techniques, in terms of the implanted nitrogen in-depth profiles, and its effect on surface hardening and wear resistance increase of the treated samples. Under the experimental conditions described, PI3 Ti-based alloys treated samples evidenced slightly better tribological performance than those subjected to I2 treatments. In the case of Al alloys, however, PI3 caused strong detrimental modification on the treated samples as revealed in the increase by a factor 100 of its surface roughness. Consequently, different criteria should be deemed in order to establish the adequacy of one or other technique, not only taking into account set up costs but also considering specific applications.

Recent breakthroughs in wet-stripping Physical Vapour Deposited (PVD) CrN coatings on standard high speed and stainless steels and on hard metal substrates are reported in this work. Validation of the stripping processes was evaluated in terms of substrate damage after exposure to the chemical agents and also in terms of the tribological properties of the PVD CrN layers before (Pristine) and after stripping and re-coating (Recoated). The investigation was focussed on the influence of the stripping process on the hardness, roughness, adherence and wear resistance of the Recoated CrN coatings deposited by electron beam PVD (e-beam) after stripping. Analysis of the chemically stripped and Recoated steel substrates showed that: (a) hardness and elastic modulus of the Recoated e-beam CrN did not change significantly compared to Pristine e-beam CrN, and (b) surface roughness of the Recoated e-beam CrN layers was greater by a factor of 50–60% than the initial. For hard-metal substrates, the surface damage and its effect on the re-deposited coating performance in terms of the chemical reactions during the stripping process were discussed. It was observed that wet-stripping in a basic solution led to depletion of tungsten and carbon at the surface of the stripped WC-Co specimens. D 2004 Elsevier B.V. All rights reserved.

This work reports on the preparation and characterization of hard (Ti,Si)N nanocomposite coatings as a function of composition and ion bombardment during growth. The energy delivered to the growing film was changed using both bias voltage change and solenoid coils placed between the targets and the substrate holder. The stoichiometry of the films was investigated by Rutherford backscattering spectrometry (RBS). With reduced energy delivered to the growing film and low deposition temperatures, the coatings developed an fcc Ti1xSixNy phase (a=0.416 nm in a sample with 18 at.% of Si) where some Si atoms are probably occupying Ti positions in the TiN1x matrix, and can be identified as a metastable phase. With higher levels of ion irradiation, an fcc TiN phase with higher lattice parameters was developed, and a significant increase in hardness was obtained. The enhancement in species mobility at the film surface is enough to ensure an effective phase segregation, leading to the formation of an nc-TiN/a-Si3N4 nanocomposite. In spite of the development of some degree of residual stresses, the overall results confirm the potential benefits of ion bombardment during film growth. The fact that these high compressive stresses can be released through thermal annealing in vacuum, keeping the coating hardness values of about 45 GPa even after thermal treatments at 900 8C, is an example of these benefits. D 2004 Elsevier B.V. All rights reserved.

In this contribution, we report on the structural and the tribological characterisation of low-energy nitrogen-ion-implanted Vanadium Titanium (V5Ti) alloys as a function of the annealing temperature during the bombardment process. The surface of the alloys was bombarded with N 2 + ions accelerated at 1.2 keV in a vacuum chamber equipped with a Kaufman-type ion source. The temperature during the low-energy ion implantation were 480, 500, and 575 °C. In this temperature range, the penetration depth reached by the implanted ions is not only exclusively ballistic (i.e., kinetic energy dependent), but diffusion effects also play a decisive role. The structural changes can be drawn as the formation of a nitrogen diffusion layer containing a blend of pristine bcc V5Ti and a solid nitrogen solution having an expanded bcc phase. It has been found that the temperature favours the increase of both, the thickness of the diffusion layer and the relative nitrogen content in the solid solution. We have investigated the microhardness, friction and wear coefficients of the implanted V5Ti surfaces as a function of the annealing temperature. The reported results indicate that both hardness and wear resistance against mechanical abrasion increase as the temperature during the bombardment increases. This increment of the hardness and wear resistance could be directly correlated to the amount of the expanded phase exhibited by the V5Ti surfaces, as observed by X-ray diffraction. The hardness and wear resistance modification upon annealing temperature are discussed in terms of the plastic deformation undergone by the expanded bcc phase to release the accumulated lattice stresses.

The present paper reports on the tribological analysis of high-performance magnetron sputtered metal-carbon multilayered coating WC:H/Cr, in particular on the effect of the different process parameters on the final coating properties. A detailed mechanical and tribological analysis in terms of hardness, elastic modulus, friction coefficient and wear coefficient for the different coatings have been carried out and discussed. The mechanical test have indicated an overall good tribological behaviour for all the deposited coatings. In particular, we have found that, when the deposition parameters are optimised, these present very low abrasive wear. In these conditions, we report wear coefficients as low as 10−16 m3/N m, which can be attributed to a combination of relative high hardness and very low roughness.

We have applied factor analysis to the study of the valence band resonant photoemission spectra of a TiO 2 thin film. Classical analysis of the photoemission spectra as a function of the photon energy through the Ti 2p → 3d absorption edge does not give a clear understanding of the resonant process, because the resonance phenomenon is present along the valence band and the only differences on the resonance are related to the distribution of cationic d-states. However, factor analysis of the spectra allows a more quantitative analysis of the resonance phenomena. Using theoretical partial Ti 3d and O 2p density of states as starting bases in principal component analysis, it is shown that only the hybridized Ti 3d states at the valence band resonate. The Ti 3d constant initial state (CIS) curve maps the Ti 2p x-ray absorption spectrum. Experimental relative photoemission cross-sections of the Ti 3d states at the absorption edge (455-470 eV) have been obtained. It is shown that resonant photoemission gives a sixfold enhancement of the Ti 3d cross-section at 463 eV with respect to the values at energies off-resonance.

Soft x-ray absorption spectroscopy (XAS) has been used to perform chemical analysis of oxide films formed after contact with air, both at room temperature and at 750° C, on three titanium alloys. The alloys investigated were Ti–13Nb–13Zr, Ti–15Zr–4Nb and Ti–7Nb–6Al. Soft x-ray absorption spectra were taken at the Ti 2p and O 1s edges. The spectra corresponding to the room-temperature-oxidized samples are similar for the three alloys and show the presence of native oxide with a small metallic contribution. For the heat-treated samples, the alloying elements as well as element diffusion play a significant role in the formation of the oxide layer. In this case, the spectra exhibit clear differences between the TiNbZr alloys and Ti–7Nb–6Al. The oxide layer of the two TiNbZr alloys for the different heat treatment times is composed of TiO2 in the form of rutile. However, for Ti–7Nb–6Al short heat treatments give rise to the formation of Al2TiO5. By increasing the oxidation time, an Al2O3 layer grows on the initial oxide film, becoming thicker as the exposure time is enhanced. Copyright © 2002 John Wiley & Sons, Ltd.

The stoichiometry, structure and mechanical properties of ion beam sputtered TiC x N y thin films have been studied as a function of the assistance conditions. Tuning the ratio between the current density of assisting N 2 + ions and the target sputtering rate allows us to achieve films with stoichiometries in the range of 0.6> x >0.25, keeping x + y ≈1. The surface topography is also sensitive to the assisting conditions where the RMS roughness is an increasing parameter as the ion beam bombardment increases. In terms of the Ar + ion beam assistance, the films undergo a significant amorphisation and a steep increase in lattice strain as the current density and energy of the impinging ions are increased. The observed changes are discussed in terms of the energy transfer of the bombarding Ar + ions to the layers below the surface of the growing films, leading to vacancies and defects and to a sharp decrease in film crystallinity.

The nano-hardness (HV) of TiCxNy (x+y≈1) thin films has been investigated by nano-indentation as a function of the ion beam assistance for different contact depths and annealing temperatures. The hardness at low indentation depths (i.e. 10 nm) is observed to decrease abruptly from 55 down to 26 GPa when the carbon content in the films decreases from x≈0.2 to x≈0.05 (∼TiN). On the contrary, hardness measured at penetration depths of 40 nm is observed to decrease very slightly. After annealing in UHV the hardness of the coatings becomes independent of the penetration depths. Moreover, the values of the hardness of the annealed coatings are similar to the values measured for the untreated coatings at high penetration depths. All this suggests that, the surface of the films are hardened significantly, and that this hardening can be reduced not only by annealing but also by increasing the ion beam bombardment during the growth process. The mechanism of the film hardening has been addressed in terms of the content of lattice defects and its dependence on the ion bombardment.

SUMMARY AND CONCLUSIONS Electron energy-loss functions of Ti, TiC, TiN and TiO 2 in the energy range 3–60 eV have been determined fromexperimental REELS spectra in terms of the model proposedby Yubero and Tougaard. 23 These ELFs have been used tocalculateelectronIMFPs foreachmaterialinthe250–2000 eVenergy range and as a function of the depth travelled by theelectron, ( E 0 , x ). In the limit of x × 1 , we obtain theusual IMFP for an infinite homogeneous medium. We haveintroduced REELS as a modified IMFP that includes surfaceeffects as they appear in REELS experiments. The differencesbetween 1 and REELS areobservedtobe¾0.2 nm forthe materials studied here. A comparison of the calculatedIMFPs with values predicted by the TPP-2M formula showsgood agreement for Ti, TiN and TiC (5–10% deviations) butdifferencesofupto40%forTiO 2 ,whichapparentlycannotbeassociatedwithuncertaintiesintheproposedELF.Ingeneral,for a determined primary energy the IMFPs are observed todecrease as the density of valence electrons increases, i.e.

We have studied the implantation of 2 keV N2+ ions in TiC. Both the shape and binding energy of the different core levels, as well as their modification, have been analysed during the implantation process. In order to quantify the implantation steps as a function of the N2+ dose, we have used a Monte-Carlo-based TRIM code to simulate the implantation profile of the nitrogen ions, except for the absolute atomic concentration, which is then determined by making use of the usual equations for quantitative XPS. We have derived the atomic concentration of implanted nitrogen atoms, i.e. N(z, DN), as a function of depth and the N2+ ion dose in terms of TRIM simulated in depth profiles and the usual equations for quantitative XPS analysis. Owing to the accumulation effect and the sputtering of the target surface, the static nitrogen profiles NN(z) derived by TRIM evolve to an erf(z) distribution with increasing ion dose DN. A proper analysis of the Ti 2p, C 1s and N 1s peaks also allows different species to be distinguished and their distribution in depth. Copyright © 2002 John Wiley & Sons, Ltd.

The optical and electronic properties of TiCxNy(x+y∼1,0

The aim of this work is to investigate the mechanical and tribological properties of Tic x N 1-x wear resistant coatings grown on a Ti-0.2 Pd alloy substrate. Films were deposited by dual ion beam sputtering (DIBS) system with different proportions of N 2 and Ar in the assisting beam. The friction tests have been carried out with a pin-on-disc tribometer with different applied loads. The films present high hardness and elastic properties whose values depend upon preparation conditions. The mechanical properties and the tribological behaviour of the coatings seem to depend on their stoichiometry and microstructure. The coating TiC 0.5 N 0.5 shows less hardness and better wear resistance than the coating with stoichiometry Tic 0.15 N 0.85 . The influence of the stoichiometry and the local structure of the films on its mechanical properties have been ruled out.

The electronic structure of the TiO2−SiO2 interface has been investigated using X-ray absorption spectroscopy (XAS). TiO2 overlayers have been grown on two substrates, amorphous SiO2 and highly oriented pyrolytic graphite (for comparison), by evaporation of Ti in an oxygen atmosphere at room temperature. The evaporation rate was low enough to allow a detailed study of the early stages of growth, i.e., the submonolayer regime (θ < 1). The Ti 2p XAS spectra of the TiO2 overlayers have been measured for different coverages. The spectra corresponding to the submonolayer regime show an unusual shape not reported up to now. A comparison with existing atomic multiplet calculations indicates a significant decrease of the crystal field (≈0.7 eV) as compared with bulk TiO2 (≈1.7 eV) due to strong electronic interactions at the interface. The presence of the SiO2 substrate and the covalent character of the Si−O bonds lowers the crystal field of the TiO2 overlayer at the interface. In contrast, the graphite substrate...

Amorphous carbon nitride thin films were prepared in a dual ion beam sputtering (DIBS) system. The N/C atomic concentration ratio ranged between 0.3 and 0.5 as determined by quantitative X-ray photoelectron spectroscopy (XPS) of the surface. Fourier Transform Infrared spectroscopy (FT–IR), XPS and X-ray Absorption Spectroscopy (XAS) were used to obtain information about the different types of bonding present in the films. The hardness and the Young's modulus of the samples were determined by nanoindentation measurements. The hardness varied in the range 15–30 GPa with Young's modulus between 170 and 250 GPa. In order to explain the measured hardness, some of the films are considered as heterogeneous, in good agreement with the XPS, FT–IR and XAS data.

In this work, dual implantation of Cr + and N 2 + ions on electroplated Ni substrates have been investigated for N 2 + implantation energies of 140keV, 100keV and 60keV. The implanted specimens have been analyzed by glow discharge optical emission spectroscopy, X-ray diffraction, nano-indentation, coefficient of friction, nano-wear and potentiodynamic corrosion curves. The properties of the dual implanted samples have been compared to Cr + or N 2 + implanted specimens.The microstructural and mechanical properties of the Ni plates depend on the penetration ranges of the Cr and N atomic profiles obtained after the implantation process. The increase of hardness reduced the coefficient of friction of the samples and the wear rates. Preferential formation of Cr-N over Ni-N compounds has been observed when the Cr and N atomic profiles coexist within the Ni matrix.The potentiodynamic corrosion curves in acidic solutions revealed that the presence of Me-N species is detrimental for the chemical stability of the plates. Both nano-wear and corrosion properties are optimized when a Ni-N sublayer is formed underneath a top Cr-Ni implanted film. This is achieved by tuning the implantation energies of Cr + and N 2 + ions at 140keV. This bilayer structure could be a suitable treatment for micro-embossing dies for plastic texturing processes. © 2012 Elsevier B.V.

We report the Ti 2p X-ray absorption (XAS) and resonant photoemission (RPES) spectra of one equivalent TiO2 monolayer grown on MgO, Al 2O3 and SiO2 substrates. The Ti 2p XAS spectra of these systems were compared to atomic multiplet calculations projected in different octahedral crystal fields. The comparison indicates that the crystal field splitting and the Ti-O hybridization decrease along the MgO, Al 2O3 and SiO2 series. The analysis of the RPES spectra provides the Ti 3d contributions to the valence band in these systems. These were compared to configuration interaction calculations of a TiO 6 cluster for different Ti 3d-O 2p hybridizations. The Ti 3d states in the valence band shift to lower binding energies along the MgO, Al 2O3 and SiO2 series. These effects are attributed to changes in the electronic structure at the interface, which, in turn, are related to the formation of cross-linking Ti-O-M (M = Mg, Al, and Si) bonds. © 2010 Elsevier B.V. All rights reserved., This work has been financially supported by the Spanish Ministerio de Ciencia e Innovación (MICINN) through contracts FUNCOAT-CSD2008-00023, MAT2007-66719-C03-03 and MAT2008-01497. The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007–2013) under grant agreement no. 226716.

This work reports on the surface characterisation of 2,2-bis[4-(2-hydroxy- 3-methacryloxyl-oxypropoxy)phenyl]propane/triethylene glycol dimethacrylate bio-compatible resins after high energy He+ ion implantation treatments. The samples have been characterised by diffuse reflectance FT-IR, X-ray photo-electron spectroscopy, ultramicro-hardness and nano-scratch wear tests. In addition, osteblast cell assays MG-63 have been used to test the bio-compatibility of the resin surfaces after the ion implantation treatments. It has been observed that the maximum surface hardening of the resin surfaces is achieved at He-ion implantation energies of around 50 keV and fluences of 1 × 1016 cm-2. At 50 keV of He-ion bombardment, the wear rate of the resin surface decreases by a factor 2 with respect to the pristine resin. Finally, in vitro tests indicate that the He-ion implantation does not affect to the cell-proliferation behaviour of the UV-cured resins. The enhancement of the surface mechanical properties of these materials can have beneficial consequences, for instance in preventing wear and surface fatigue of bone-fixation prostheses, whose surfaces are continuously held to sliding and shearing contacts of sub-millimetre scale lengths. © 2010 Elsevier B.V. All rights reserved.

In this work, two nitride coatings deposited on aluminum-based bipolar plates via cathodic arc evaporation physical vapor deposition (CAE-PVD) have been evaluated using two different techniques. The coating materials, a multi-layer chromium-zirconium nitride (ZrN–CrN) and a monolayer chromium nitride (CrN) have been exposed to electrochemical polarization tests for corrosion resistance simulating the typical environment in the anode and cathode sides in polymer electrolyte membrane fuel cells (PEMFC). Besides, two 3-cell PEMFC stacks, one per each coating material, have been formed. The migration of metal cations toward both the gas diffusion layers (GDL) and catalyst layers have been analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), after 100 h of continuous operation of the stacks. Results have shown that the two coatings applied over the Al-plates satisfy the corrosion resistance requirements in the short-term tests performed at the two stacks. Moreover, results obtained from electrochemical polarization tests have revealed that the CrN-coating confers a good corrosion resistance to the Al-based metal plate, achieving values of corrosion potential and corrosion current two orders of magnitude lower than the ones obtained for the Al alloy as-received.

The improvement of the corrosion, wear and tribological behaviour by searching for new materials has entailed a greater expansion of PVD technology. Introduction of PVD systems in the industry is a real fact because this technique has been able to develop coatings whose response for many applications goes beyond used them until now. However the evolution of this technology requires minimize the economic costs in order to be a competitive process. A way to achieve this objective consists on recover the tool when the life time of the coating has finished or when deposition process has failed. Bringing this idea in the industry requires the stripping methods’ development due to surface’s tool must be clean —without coating’s remainders—, before a new deposition process. Current work shows galvanostatic stripping of chromium nitride coating deposited by two different PVD techniques: cathodic arc and magnetron sputtering. The electrochemical method has exhibited more advantages than chemical methods reported in literature, such a high sensitivity to detect final point of CrN coating stripping, capability to determinate structure of the coating —number of coatings, chemical composition, thickness…—, short times of the process and minimum damage on the substrate. These entire characteristics do possible think about a new deposition process on the stripped tool.

This paper reports on the tribological properties of commercial Cr-N physical vapour deposition (PVD) processes for enhanced mechanical protection of forming and machining tools. The study is carried out on conventional tooling materials as substrates, i.e. high speed steels (M2) and cemented tungsten carbide. Electron beam (EB), magnetron sputtering (MS) and cathodic arc (CA) commercial Cr-N PVD processes from three different EU coating centers/companies are evaluated in terms of their tribological behaviour by standard characterization techniques for material properties: surface hardness and roughness, film adherence strength and wear resistance under sliding conditions. The results are discussed on the basis of their current applications and their influence on tool performance for manufacturing processes. Moreover, film tribological performance is correlated with their microstructural properties as obtained by electron microscopy and X-ray diffraction. In terms of surface hardness and adherence strength, CA Cr-N seems to outperform EB and MS coatings. However, EB and MS exhibit enhanced surface finish which might be more appropriate for some applications. © 2005 Published by Elsevier B.V.