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[CoN/AlN]n multilayer coatings with different bilayer numbers (n = 10, 20 and 30) were developed, showing an interesting evolution in the mechanical properties and tribological behavior. These coatings were deposited by pulsed laser deposition technique with a Nd: YAG laser (λ = 1064 nm) on Silicon (100) and AISI 302 steel substrates. The structural and chemical composition analysis was performed by (XRD) and (XPS), showing characteristic phases and the stoichiometry of AlN (111) and CoN (200) materials. The surface morphology by (AFM) presented a reduction in grain size and roughness as a function of the bilayer number. The mechanical evaluation found an increase of 40% in the hardness and 19.4% in the elastic modulus when comparing [CoN/AlN]30 to the cobalt nitride (CoN) single layer. The tribological analysis evidenced the values of 0.33 for the friction coefficient and 57 N for the critical load at which the adhesive failure of the coatings (LC2) appeared. The mechano-tribological results found in these transition metals-based multilayer nitrides open a possibility of future applications in mechanical devices that require high demands in service conditions due to the high mechanical performance observed in the [CoN/AlN]n multilayers. [ABSTRACT FROM AUTHOR]

Yttria-stabilized zirconia (YSZ) is the most common material used as a thermal barrier in several engineering applications. In order to improve the insulator potential of these thin films, an oblique-angle deposition approach was used to grow YSZ with tilted columnar structures. Initially, the period (n) was defined as the repetition unit composed of two layers each with different columnar growth directions, and then, n was increased (n = 1, 2, 10, 30, and 50), keeping constant the total thickness (~3.50 µm). The influence of (n) on the structure, roughness, grain size, microstructure, and thermal conductivity (κ) of thin films deposited was determined by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy, and hot-plate technique, respectively. For all the samples, XRD patterns indicate the presence of the characteristic 8YSZ tetragonal phase peaks. Through AFM analysis, it was established that the roughness of the films deposited decreases from (4.0 ± 0.6) to (2.0 ± 0.6) nm when n is increased. Cross-sectional images recorded by SEM corroborate the formation of marked interfaces when growth direction changes occur, allowing to identify a multilayer system with a "zigzag" microstructure and an evolution towards more refined and isolated columns. Moreover, the SEM images reveal that for n = 10, 30, 50, and 70, the growth direction of the column is perpendicular to the substrate plane, losing its tilted form and the "zigzag" behavior becomes intracolumnar, reaching nanometer scale. Finally, analyses by hot-plate technique for different n repetition units showed that the thermal conductivity of YSZ films decreases from 0.151 W/m K to 0.064 W/m K, establishing the direct influence of the "zigzag" microstructure on the j value. This study shows the potential of growing YSZ thin films by oblique-angle deposition as an effective method to improving the thermal insulator potential of this material. [ABSTRACT FROM AUTHOR]

This study presents a detailed analysis of the wear presented in [8YSZ/α-Al2O3] multilayer coatings as a function of the bilayer number when exposed to a corro-erosive environment. In this study, the roughness and grain size decreased by 58 and 30%, respectively when comparing the 70 bilayers system with the 1 bilayer system. The surface factors and the higher bilayer number of the n = 70 system, influenced the 67.33% decrease in corrosion rate compared to the 1 bilayer system. Subsequently, by means of SEM and optical microscopy, the degradation of the coatings due to the impact of abrasive particles and the generation of oxides on the substrate surface caused by a partial delamination of the coating was evidenced. This wear was calculated by means of the mass loss after the corro-erosive test, obtaining a decrease of 55.25% for the system with 70 bilayers with respect to the system with 1 bilayer. The results obtained showed that the system with 70 bilayers presented the best set of electrochemical properties and lower wear in corrosive environments, which makes it the best candidate to be used as a protective coating. [ABSTRACT FROM AUTHOR]

Al2O3 and Si3N4 coatings have been extensively studied separately, showing excellent performance in resistance to corrosion and wear. In the present work, the structural, morphological, mechanical and tribological properties of Al2O3 and Si3N4 single-layer coatings deposited on AISI 316 stainless steel substrates were studied by means of the R. F. Magnetron Sputtering technique. By X-ray diffraction (XRD) The structures of the coatings were determined, the chemical composition was studied by X-ray Photoelectron Spectroscopy (XPS). By means of Atomic Force Microscopy (AFM) the grain size and roughness were analyzed, through Scanning Electron Microscopy (SEM) the wear surfaces produced by the Pin-On-Disk and the Scratch tests were studied. By nanoindentation technique the behavior in hardness and elastic modulus was evaluated, finding better performance in the Si3N4 coating. The friction coefficient was evaluated by Pin-On-Disk tests in dry and lubricated environments. The critical load against adhesive wear was determined for Al2O3 and for Si3N4. This study develops a comparison between the mechanical and tribological properties of the mentioned coatings, proposing their possible application in components of the food and pharmaceutical industry that are subjected to phenomena where Al2O3 and Si3N4 coatings could mitigate. [ABSTRACT FROM AUTHOR]

Were produced TiO2 thin coatings prepared, on substrates pure Titanium using a deposition by magnetron sputtering technique, the percentage of oxygen was varied, to study the behavior in terms of friction coefficient corrosive fluids such as those related to the human body. Electrochemical Impedance Spectroscopy (EIS), wear tests with a tribometer, were performed to obtain the tribo-corrosion mechanism of deterioration, taking into account the dual corrosion wear system. The phases were identified by X-ray Photoelectron Spectroscopy (XPS) high resolution. It is determined through the tests performed that the surface treatment has a different effect for each percentage of oxygen influenced by the simulated body environments. The wear performance analysis indicated that the TiO2 film's protection had increased as the percentage of oxygen in the gas mixture (Ar/O2) varied and other synthesis parameters such as deposition time, target power, and substrate temperature remained constant. [ABSTRACT FROM AUTHOR]

Rhenium was the most interesting material because it can be oxidized at high temperatures, so it is a promising applicant in biomedical applications. Its high melting point requires techniques such as electro-coating to produce it in thin-film formation, using a current of 40 mA/cm2, in a cathode pulse and 4 mA/cm2, in anodic form, the variation in temperature of the acid electrolytic bath being realized in a range of 60 to 85±2 °C. The temperature variation of the samples allowed to correlate their response to the degradation phenomenon. The topographical evaluation using atomic force microscopy on the surface of the samples permitted to indicate that a tendency of the roughness to reduce with the increase of the temperature up to 80 °C existed, an electrochemical evaluation was generated using Tafel polarization curves, immersed in a Ringer's lactate solution with a temperature of 37 °C, has now been subsequently performed using the scanning electron microscope, the surface analysis of the coatings, demonstrating that at deterioration is negligible, but when increasing the temperature to 80 °C, the deterioration is imperceptible when the type of surface damage is unobservable, however in the case of 85 °C the deterioration is observable. [ABSTRACT FROM AUTHOR]

Multilayer coatings [Si3N4/Al2O3]n have generated great interest due to their intriguing properties which have made them a potential candidate to be implemented in different processes within the food and pharmaceutical industries. Unfortunately, this multilayer system based on [Si3N4/Al2O3]n does not have strong tribological studies that could express in an emphatic way its own tribological characteristics. For this reason, the aim of this research consisted of a detailed study of the evolution of the mechanical and tribological properties of the [Si3N4/Al2O3]n coatings as a function of the bilayer number n=1, 10, 30 and 70, with special emphasis on the tribological analysis in a dry and lubricated environment. It was determined that the mechanical properties such as the hardness and the elastic modulus increased by 29% and 6.3%, while the friction coefficient in a dry and lubricated environment decreased by 33% and 81.8%, respectively, when increasing the bilayers from n=1 to n=70. Thus, the present study determined that the coating [Si3N4/Al2O3]70 presented ideal properties that make it a promising candidate to be implemented as a protective coating on processing devices within the food and pharmaceutical industry. [ABSTRACT FROM AUTHOR]

The improvement of corrosion performance at high temperatures of coatings in which the alumina composition in Yttria-stabilized zirconia (YSZ-Al2O3) was varied in 3 different percentages was studied. These systems were deposited on AISI 304L stainless steel substrates using plasma spraying. The determination of the corrosion rate was performed in a corrosive environment containing 20% Na2SO4 and 80% V2O5, at temperatures ranging from 800 °C to 900 °C. The structural characterization was determined by X-ray diffraction (XRD), and the analysis of the surface after exposure at 900°C was performed by scanning electron microscopy (SEM). The best performing system was the one containing 40% alumina, due to the morphology and structural change. [ABSTRACT FROM AUTHOR]

Anodized AZ31 Magnesium Alloys was synthesized via electrodeposition processes. The aim of this work was to determine the mechanical and tribological response of the anodized AZ31 Magnesium alloy with different current densities immersed under cement concrete paste with different solidification times. The samples of the anodized alloy were characterized by microindentation so, the mechanical properties (micro-hardness) was increased by 32% when the magnesium alloy was anodized with a current density of 25 mA/cm2, in this sense the friction coefficient between the anodized AZ31 magnesium (MgO) obtained with the highest current density and the metallic AZ31 alloy exhibited a reduction of 54.5%. The scratch test and wear rate (abrasive sliding of cement concrete) show an increase in the critical load and a reduction of weight loss as a function of the applied current density around of 49% and 92.3%, respectively. Scanning electron microscopy was performed to analyze morphological surface changes on the anodized AZ31 alloy after tribological tests. The tribological behavior of the anodized AZ31/MgO system indicates that the AZ31/MgO coatings can have a promising future in applications for the civil construction industry. [ABSTRACT FROM AUTHOR]

In this investigation, the use of thin films of tungsten-titanium carbide as electro-catalysts for the evolution reaction of hydrogen (HER) was evaluated. Thin films, with a different number of layers, were deposited on titanium substrates by cathodic arc deposition. The samples were structurally characterized by X-ray diffraction (XRD) and the surface roughness was analyzed by Atomic Force Microscopy (AFM). The HER kinetics were analyzed with 0.5 M sulfuric acid as an electrolyte on films supported on titanium substrates. With EIS together with AFM, the relationship between surface roughness and the electrochemical response was determined, indicating that as the number of layers increases, the capacitive activity increases and the grain size decreases, associating with the generation of hydrogen production. It was concluded that the coatings generate catalytic activity when subjected to 1000 voltammetric cycles. [ABSTRACT FROM AUTHOR]

This paper shows tribological compatibility enhancement in dry turning of a low carbon steel (AISI 1020) with High-speed steel cutting tools, due to physical vapor deposition (PVD) of hafnium and vanadium nitride multilayer coatings ([HfN/VN]n), with different bilayer number system in each tool (n = 1, n = 30, n = 50, and n = 80). Tool wear mechanisms were assessed by means of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) techniques, and surface integrity by roughness measurement and SEM inspection. Results show these multilayer coatings increase tool life up to 43%, and modify contact at tool/workpiece interface, as a function of bilayer number (n), due to their outstanding mechanical and tribological properties as a low coefficient of friction, high thermal conductivity, and high hardness; this produces a decrease of chip compression ratio, from 3.6 to 2.7, and workpiece roughness almost 1.6 μm lesser with the tool [HfN/VN]80. Moreover, improvement of workpiece integrity includes its corrosion resistance, from a corrosion rate of 1.5 mmy, which decrease exponentially with higher bilayer number, to a corrosion rate lower than 0.1 mmy obtained with 80 bilayers, due to the change of chip morphology. Therefore, [HfN/VN]n coatings could enhance productivity and quality in an industrial manufacturing application, as these protective thin films increase tribological compatibility of tool/workpiece system. [ABSTRACT FROM AUTHOR]

A simultaneous evaluation was done of the wear-corrosion of the coatings of beta-tricalcium phosphate on titanium (Ti) substrate deposits obtained by the magnetron sputtering technique. The characterization was developed by a tribometer system coupled to an electrochemical cell. This system allows the combination of corrosion and friction tests between the surface of the coating and the spherical bone pin. The synergy of the two wear phenomena was characterized, which were monitored by means of the electrochemical response as a function of the value of the friction coefficient. It was determined that the system generates a gradual film accumulation process, followed by an instantaneous loss after a critical period. Additionally, it is concluded that the increase in the coefficient of friction is not immediately followed by the increase in wear rate. [ABSTRACT FROM AUTHOR]

The current work presents a comparative study of niobium, niobium carbide, and niobium nitride coatings deposited on AISI 316LVM stainless steel. The investigation was based on the synergy between corrosion and wear; therefore, the coating application was focused on future biomedical implants. The experiments were conducted under conditions of simulated biological fluid, with load and speed parameters of an average person. The tribo-corrosion tests were done by adapting an electrochemical cell to a pinon- disk tribometer. The surfaces were characterized through optical means and scanning electron microscopy while the corrosion phenomenon was studied by potentiodynamic polarization curves. As a result, it was found that these coatings protect the surface against corrosion showing no evidence of degradation and lower corrosion rate value compared with the uncoated steel substrate. Moreover, the coatings show diverse wear mechanisms including abrasion wear and plastic deformation. The microstructure of the niobium coating was modified by the addition of carbon or nitrogen, improving the surface performance. Furthermore, in all the studied cases the coatings showed better behavior in tribo-corrosion phenomena in relation to the AISI 316LVM stainless steel substrate. [ABSTRACT FROM AUTHOR]