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The need for materials with special and often unique functionalities is particularly felt in forefront domains, particularly in areas where materials are subjected to extreme erosion and/or corrosion. Coating technologies are becoming more widespread since they help to improve existing materials and products separating the structural performances from the surface-protection performances [1]. Refractory metals and their alloys constitute a class of particularly interesting materials because, thanks to their outstanding properties, they can be used in hazardous environments and extreme conditions. In this work, we present an investigation on W and Ta based coatings on stainless steel substrates. Among many different applications, tungsten is used in electronic industry for x-ray optics and in harsh environments such as thermonuclear fusion reactors (tokamaks) where it is generally considered to be the most promising plasma facing material (PFM). This is due to its high cohesive energy, which makes it resistant to erosion and ensures an high sputtering threshold under hydrogen bombardment, its high melting point (the highest one when considering refractory metals), low coefficient of thermal expansion, good electrical conductivity, low affinity with hydrogen and excellent thermal conductivity. Unfortunately tungsten finds just a few applications in the standard industrial fields because of the low stability of its oxides (WO3, WO2). Tantalum has properties that make it useful for many applications, from electronics to mechanical and chemical systems. Its high melting point, toughness, low ductile-to-brittle transition temperature and exceptional resistance to chemical attack make it an attractive coating material for components exposed to high temperature, wear, and harsh chemical environments. Its excellent resistance against corrosion is ensured by the formation of a stable passive oxide film (Ta2O5). Tantalum is also used to produce a variety of alloys that have high melting points, are strong and have good ductility. In particular W is alloyed with Ta to lower brittle-to-ductile transition temperature [2,3]. W rich alloys (W-Ta) are not very well known and, to the authors' knowledge, there are just a few papers in literature. On the contrary Ta rich alloys (Ta-W) are well known materials and they excel due to their good mechanical properties and excellent corrosion resistance. With the 10 % of W the resulting alloy is 1.4 times stronger than pure tantalum but it remains easy to work even at high temperature (up to 1 600 °C). Physical vapor deposition (PVD) is one of the most promising coating technology and it is widely employed to improve mechanical, wear and corrosion properties of materials. Moreover it is possible to tailor coating features (crystallinity, grain orientation, etc.) to obtain properties that can be far apart from the bulk material ones. In this work, different films, with different W and Ta contents, have been produced via PVD using Direct Current Magnetron Sputtering (DCMS) and Pulsed Laser Deposition (PLD) [4]. Moreover pure W and Ta samples have been deposited by High-Power Impulse Magnetron Sputtering (HiPIMS) [5,6]. For these samples the various deposition parameters have not been fully optimized. However, the preliminary results look very promising. DC Magnetron Sputtering is a traditional PVD technique extensively used in industry. PLD is a relatively new technique that permits to deposit films with very complex stoichiometry (e.g. YBCO). Moreover it is able to deposit nanostructured materials tailoring film features at the nanoscale. HiPIMS is an innovative technique which utilizes magnetron sputtering cathodes and high peak power density of up to 3 kW cm-2 on the target. The plasma produces a particle flux with high degree of ionization. HiPIMS has been successfully used to enhance coating adhesion. It produces high-density microstructure films with smooth surfaces. Moreover, it has a few industrial applications in hard, electronic, and optical coatings. The produced refractory metal based coatings have been extensively analyzed. Microstructural characterization activities consisted of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The nano-mechanical properties of the films (hardness and elastic modulus) have been analyzed by nanoindentation testing. Adhesion has been finally evaluated by scratch tests [7], using a fully-computerized UMT apparatus. The electrochemical properties of thin films have been also evaluated in 3.5 wt.% NaCl aqueous solution [8]. The goal of this work was to evaluate the properties of high tech nanostructured coatings of refractory metals. Moreover it was possible to stress how to drive the film characteristics needed for the specific application using three different techniques.

Superaustenitic stainless steels have become of growing interest in industrial and technological fields, but there is not a complete understanding on their fundamental properties and their performances. For this paper, AISI 904-L superaustenitic samples were nitrided and carburized in order to study the expanded austenite stability under severe deuterium and helium ion bombardment. Surface treatments were conducted using pulsed plasma glow discharges in a low pressure atmosphere, and a dense plasma focus device was used to irradiate the samples. Characterization techniques used were focused ion beam/SEM, energy-dispersive X-ray spectroscopy, and grazing incidence X-ray diffraction. Our results showed in carburized samples lattice expansion growth with the time treatment, but in nitrided samples, an expanded austenite reduction with time treatment was observed due to the formation of nitride nanoagglomerates. Moreover, this ion impingement provoked surface melting and a severe collision cascade, and a damaged bead located under the craters composed solely of minor alloying atoms. Furthermore, nitrided samples were more stable following ion bombardment than the carburized ones. When helium ions were used, the loss of expansion (triggered by diffusion processes of N or C to deeper regions) was more pronounced in the expanded austenite, but when deuterium ions were used to bombard the sample, there was a crystallite development of stressed austenite, which provoked a diffraction peak arousal at 43.3°. Fil: García Molleja, Javier. Universite de Nantes; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentina Fil: Milanese, Maria Magdalena. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Fisica Arroyo Seco; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gomez, Bernardo Jose Armando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentina Fil: Moroso, Roberto Luis. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Fisica Arroyo Seco; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Piccoli, M.. Università di Roma; Italia Fil: Niedbalski, Jorge Julio. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Fisica Arroyo Seco; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Burgi, Juan Mauel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentina Fil: Bemporad, E.. Università di Roma; Italia Fil: Feugeas, Jorge Nestor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentina

AlTiN is a promising anti-oxidation and corrosion protective material. Thanks to the formation of a coherent, compact and adherent alumina scale, it can be applied in harsh environments. In this work, the intrinsic properties of AlTiN films produced by reactive High Power Impulse Magnetron Sputtering (HiPIMS) have been investigated. Different substrates were chosen considering their technological interest: a common stainless steel (AISI 304), the T91 martensitic steel, which is conventionally used for nuclear fusion and fission plants, and, finally, a light alloy for aeronautic applications (g-TiAl), which represents a possibility to replace Ni based super-alloy in aircraft turbine engines. Working gas composition has been systematically changed (N2/(Ar+N2) atomic ratio 10, 25, 50 ,75, 100 %). Morphology, microstructure, hardness, elastic modulus, residual stress have been studied through high resolution methodologies. Microstructural analyses were carried out by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). Moreover, films nano-mechanical properties, as hardness (H) and Young's modulus (E), were estimated by nano-indentation tester, while adhesion was evaluated by scratch tests. In order to investigate the average residual stress in the produced coatings, a recently proposed approach was used, which involves an incremental FIB milling of annular trenches at material surface, combined with high resolution SEM imaging . Finally, AlTiN/T91 coatings were subjected to long duration tests for the evaluation of corrosion by molten metal (Pd or Pb-Bi alloy), while all the other films were tested in air at high temperature, to investigate the behaviors of AlTiN films subjected to thermal cycles. SEM and XRD results showed a significant modification of films' microstructure due to selected deposition parameters: it ranges from quasi-amorphous structure at high N2 percentage to crystalline one at low nitrogen content. This means that the energy flux carried to the substrate considerably changes. Mechanical properties were found to be extremely promising: measured hardness reached 40 GPa. Moreover, by optimizing N2 percentage during the deposition process, it is possible to maximize the H/E ratio, which provides an indicator of the coating's elastic strain at failure. Finally, it was found how microstructure and/or mechanical properties of the coatings help to foresee the film/substrate system adhesion. The possibility to choose different experimental conditions coupled with an extensive characterization of the deposited coatings, allows to obtain useful information about structure/properties correlations and then, to optimize deposition parameters to achieve the required characteristics for specific applications.

A TiO2 (anatase) nanopowder suspension was processed by High Velocity Suspension Flame Spraying (HVSFS). The resulting coatings were characterized and compared to conventional atmospheric plasma sprayed (APS) and HVOFsprayed ones. The HVSFS operating parameters can be adjusted in order to achieve dense coatings, with a fine (nearnanosized) structure and a homogeneous distribution of anatase and rutile: these coatings have lower pore interconnectivity and higher wear resistance than APS and HVOF ones. Alternatively, quite large unmelted agglomerates of anatase nanoparticles can be embedded in the coating, increasing the porosity and the anatase content for enhanced photocatalytic efficiency.

Recently introduced FIB/SEM analysis in microscopy seems to provide a high-resolution characterization of the samples by 3D (FIB) cross-sectioning and (SEM) high resolution imaging. The aim of this study was to apply the FIB/SEM and SEM/EDS analysis to the interfaces of a metal-ceramic vs. two zirconia-ceramic systems. Plate samples of three different prosthetic systems were prepared in the dental lab following the manufacturers' instructions, where metal-ceramic was the result of a ceramic veneering (porcelain-fused-to-metal) and the two zirconia-ceramic systems were produced by the dedicated CAD-CAM procedures of the zirconia cores (both with final sintering) and then veneered by layered or heat pressed ceramics. In a FIB/SEM equipment (also called DualBeam), a thin layer of platinum (1 μm) was deposited on samples surface crossing the interfaces, in order to protect them during milling. Then, increasingly deeper trenches were milled by a focused ion beam, first using a relatively higher and later using a lower ion current (from 9 nA to 0.28 nA, 30KV). Finally, FEG-SEM (5KV) micrographs (1000-50,000X) were acquired. In a SEM the analysis of the morphology and internal microstructure was performed by 13KV secondary and backscattered electrons signals (in all the samples). The compositional maps were then performed by EDS probe only in the metal-ceramic system (20kV). Despite the presence of many voids in all the ceramic layers, it was possible to identify: (1) the grain structures of the metallic and zirconia substrates, (2) the thin oxide layer at the metal-ceramic interface and its interactions with the first ceramic layer (wash technique), (3) the roughness of the two different zirconia cores and their interactions with the ceramic interface, where the presence of zirconia grains in the ceramic layer was reported in two system possibly due to sandblasting before ceramic firing.