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The objective of this study is to explore and compare the mechanical response of AlCrSiN coatings deposited on two different substrates, namely, WC-Co and cBN. Nano-indentation was used to measure the hardness and elastic modulus of the coatings, and micro-indentation was used for observing the contact damage under Hertzian contact with monotonic and cyclic (fatigue) loads. Microscratch and contact damage tests were also used to evaluate the strength of adhesion between the AlCrSiN coatings and the two substrates under progressive and constant loads, respectively. The surface damages induced via different mechanical tests were observed using scanning electron microscopy (SEM). A focused ion beam (FIB) was used to produce a cross-section of the coating–substrate system in order to further detect the mode and extent of failure that was induced. The results show that the AlCrSiN coating deposited on the WC-Co substrate performed better in regard to adhesion strength and contact damage response than the same coating deposited on the cBN substrate; this is attributed to the lower plasticity of the cBN substrate as well as its less powerful adhesion to the coating.

Proton exchange membrane water electrolysis (PEMWE) is a promising technology to be incorporated in the production of green hydrogen, but one of its limitation to market penetration is the cost of bipolar plates (BPP). Aiming to reduce the cost of PEMWE stack, different surface engineered coating systems based on CrN/TiN, Ti/TiN, Ti and TiN deposited by physical vapor deposition on SS 316L, SS 904L and SS 321 were tested, as potential cost effective solutions to be implemented on bipolar plates. A corrosion evaluation has been carried out in anodic PEMWE conditions in order to determine the best substrate/coating combination for bipolar plates. Ti/TiN multi-layered coating on SS 321 shown the best performance with −0.02% weight loss, current at 2 VSHE to 436 μA cm−2 and ICR after corrosion test to 9.9 mΩ cm2.

Diamond-like carbon (DLC) coatings are very interesting due to their extraordinary properties, their excellent wear resistance, very low friction coefficient, great hardness, high elastic modulus or biocompatibility can be highlighted, as can their multifunctionality. Because of this, over recent decades they have been widely used in tribological applications, improving the performance and the useful life of machining tools in an effective way. However, these coatings have a disadvantage compared to other coatings deposited by commercially available techniques&mdash, their resultant adhesion is worse than that of other techniques and limits their industrial applications. In this work, tribological results of a scratch test, wear resistance and nanoindentation of tetrahedral amorphous carbon (ta-C) and tungsten carbide:carbon (WC:C) DLC coatings deposited by means of novel high-power impulse magnetron sputtering (HiPIMS) technology with positive pulses are reported. The coatings were deposited in three different tools steels: K360, vanadis 4 and vancron. These tools&rsquo, steels are very interesting because of their great and wide industrial applicability. Experimental results showed excellent tribological properties, such as resistance to wear or adhesion, in the two types of DLC coatings.

This study aims to investigate the improvement of the tribocorrosion properties of WC-TiC-Co substrates by coating them with hard coatings such as AlCrSiN using cathodic arc deposition. WC-TiC-Co is commonly used in the fabrication of machining and cutting tools; however, there are some materials such as titanium or stainless steel that are difficult to work with; furthermore, in aggressive environments or under high temperatures the performance of the machining tools can be affected, and a failure may occur. This coating is intended to ensure the correct performance of the tools in any conditions. The coatings were characterized by glow discharge optical emission spectroscopy (GDOES), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Tribocorrosion, tribology and corrosion tests were performed to evaluate the tribocorrosion properties of the samples. Furthermore, mechanical and adhesive properties of the coating were studied using scratch and nanoindentation tests. The results showed improved tribocorrosion properties in the samples combined with good adhesive and mechanical properties. These results show the possibility of using these coated materials in the most demanding cutting and machining applications. Funded in part by the Spanish Ministry of Science, Innovation and Universities through grant PGC2018-096855-B-C43 and PGC2018-096855-A-C44.

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.

Hard coatings, such as AlTiN-TiSiN, deposited by Physical Vapor Deposition (PVD) techniques are widely used in industrial applications to protect and increase the lifetime of industrial components, such as cutting tools, dies, and forming tools. Despite their great properties, such as high hardness and wear and oxidation resistance, they are limited in cases of severe conditions due to the poor adhesion between the coating and the substrate. Duplex treatments have commonly been used to improve the adhesive properties of PVD coatings, especially those of the cathodic arc evaporation type. The purpose of this study is to achieve coatings with the good properties of the Magnetron Sputtering processes but with higher adhesion than that achieved with these techniques, thus achieving coatings that can be used under the most severe conditions. In this work, an AlTiN-TiSiN coating was deposited by a combination of DC Magnetron Sputtering (DCMS) and High-Power Impulse Magnetron Sputtering (HiPIMS) after a gas nitriding pretreatment on 1.2379 and Vanadis 4 tool steels. Mechanical (ultra-microhardness and scratch tests) and tribological tests were carried out to study the improvement in the properties of the coating. Duplex-treated samples showed improved adhesion between the coating and the substrate, with second critical load (Lc2) values greater than 100 N. Furthermore, they showed great toughness and wear resistance. These results show that this type of coating technique could be used in the most extreme applications and that they can compete with other techniques and coatings that to date they have not been able to compete with. This research was funded in part by the Spanish Ministry of Science, Innovation and Universities through grants PGC2018-096855-B-C43 and PGC2018-096855-A-C44.

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.

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.

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.

Accurately predicting the failure of multilayered surface systems, including coatings on tools or products, is of significance for all of the parties concerned within the chain of design, manufacturing and use of a product. Previous modeling work has, however, been focused largely on the effect of individual parameters rather than on the performance of a multilayered system as a whole. Design and manufacture of multilayered surface systems, currently, still relies largely on experiments and failure tests. A parameterized approach which considers geometrical, material, interfacial and loading variables, processing history, thermal effects, surface-failure modeling, etc. has therefore been developed to address the situation in order to be able to improve the efficiency and accuracy of the analysis and design of multilayered coating-systems. Material property values for the hardened case of the substrate are described with a function of the hardened depth and defined with a field method. Initial residual stresses calculated using a newly developed theoretical model are incorporated into the model as initial stress conditions. Thermo-mechanical coupled modeling is incorporated into the model so as to be able to consider temperature effects. These are associated with a cohesive-element modeling approach, which has been used to predict indentation-induced crack initiation and propagation within the coating layer. The comparison of experimental results with those of numerical modeling affords excellent agreement. The parameterized modeling method developed allows for the parameters to be changed easily during a series analysis. Combined with the capability of the prediction of cracking of the coatings, the developed method/model provides an efficient way for investigating the effects of these parameters on the behavior of multilayered systems, which is demonstrated by the analysis of three cases of the coated tool steels (H11): (i) a substrate without being pre-heat-treated; and (ii) two substrates with a shallow and a deep hardened-case, respectively, (both are treated by plasma-nitriding). The results showed that the case-hardening of a substrate has a significant influence on the performance of the surface system with coating, especially on its load-bearing capacity and the cracking of the coating.

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.

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.

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.