Emerging processes for metallurgical coatings and thin films

Innovation in thin-film deposition processes, thermal spraying and cladding technologies mostly rely on evolutions of their previous iteration. Along with other examples, five case studies of emerging elaboration processes for metallurgical coatings are described coupled with their applications. In the frame of the lifetime extension of components exposed to aggressive media or their functionalization, this article depicts all the developments of the detailed processes. Physical vapor deposition (PVD) of coatings with exceptional properties is possible thanks to sources generating highly ionized metallic vapors. The control of the average energy per incident species and particularly metallic ions strongly influences the characteristics of the deposited layer obtained, for example, with HiPIMS (High Power Impulse Magnetron Sputtering). While PVD techniques are mainly directive regarding the growth of the coating, chemical vapor deposition (CVD) processes manage to homogeneously coat complex 3D shapes. The use of specific precursors in DLI–MOCVD (Direct Liquid Injection – MetalOrganic CVD), carefully selected from the whole metalorganic chemistry, allows one to efficiently treat heat-sensitive substrates and broadens their application range. The third detailed example of emerging technology is suspension plasma spraying (SPS). Projection of various solutions containing nanoparticles leads to the growth of unusual morphologies and microstructures and to the generation of porous coatings with multi-scaled porosity. On the other hand, cold-spray uses metallic powders with higher granulometry and does not modify them during the deposition process. As a result, high-purity and dense materials are deposited with properties similar to those of wrought materials. Whereas cold-spray is suitable only for ductile metals, laser cladding can be applied to ceramics, polymers and of course metals. Laser cladding is a key technology for advanced metallurgical engineering and alloy development due to its capability for functionally graded materials production and combinatorial synthesis

Oxidation of steels in liquid lead bismuth: Oxygen control to achieve efficient corrosion protection

International audienc

Influence of an original manufacturing process on the properties and microstructure of SiC/SiC tubular composites

International audienc

Corrosion of T91 and pure iron in flowing and static Pb-Bi alloy between 450 °C and 540 °C: experiments, modelling and mechanism

International audienceT91 (Fe-9Cr steel) and pure iron were corroded in pure dissolution domain in liquid lead bismuth eutectic (LBE) from 450 to 540°C in static and in dynamic LBE flow. The modelling showed that corrosion rates were controlled: (i) for LBE natural convection, by the iron diffusion in the diffusion boundary layer; (ii) for flowing LBE, by a mixed process combining both the interfacial reaction rate of iron dissolution and the iron diffusion rate in the diffusion boundary layer. By fitting the modelling on the experimental points, the iron dissolution reaction rate constant was determined

Optimization of HiPIMS metal coating interface and properties by in-situ plasma etching pretreatment

International audienceDeposition of dense Ti and Zr coatings by high power impulse magnetron sputtering (HiPIMS) was performed to enhance the lifespan of stainless steel 304L infrastructures and tools in corrosive environments. The effect of Ar+, Ti+ and Zr+ in-situ etching pretreatment on the substrate-coating interface and coating properties was investigated. Characterization by SEM and TEM shows the polycrystalline structure, high density and adhesion of metal coatings on the substrate. XPS analysis reveals surface modifications due to etching pretreatments. Electrochemical measurements quantify the improvement in corrosion resistance in saline environments due to etching and coating with a 200-nm-thick metal layer

Electrochemical impedance spectroscopy applied for investigating cathodic and anodic processes of corrosion in HNO3

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Corrosion et protection des matériaux à haute température

Cet ouvrage est issu des cours donnés lors de l'école thématique ''Corrosion et protection des matériaux à haute température'' qui s'est déroulée du 30 mai au 04 juin 2010 à Porquerolles. Il rassemble les contributions de scientifiques et d'industriels issus de communautés différentes, présente l'état de l'art des développements scientifiques et technologiques concernant le comportement des matériaux à haute température sous environnement agressif, dans différents domaines (aéronautique ; nucléaire ; valorisation énergétique ; chimie...). Il fournit, en outre, les outils pédagogiques pour appréhender la corrosion à haute température grâce à la compréhension des mécanismes d'oxydation, et propose des solutions de protection des matériaux et des structures

A step towards a better understanding of corrosion of zirconium in nitric acid with additions of fluorine: focus on the role of the presence of an initial oxide film

International audienceThe presence of fluorine is known to drastically reduce the corrosion resistance of zirconium in nitric acid. Nevertheless corrosion processes involved for this system appear controversial, especially concerning the role played by the initial oxide film (ZrO2) that can naturally be formed in nitric acid. To study the contribution of the initial oxide film, zirconium samples were pre-oxidized in several ways so as to obtain different thicknesses of the initial oxide film. Then, the corrosion evolution of these samples was studied in nitric acid with fluorine additions. It appears that the initial oxide film present on surface plays a protective role for corrosion. But as the oxide film slowly dissolves, this protective role may only be transitory (depending on the thickness of the initial oxide film). When the oxide film has been sufficiently dissolved, it breaks by a process of initiation, growth and coalescence of pits. Zirconium is then directly attacked by fluorine and its corrosion rate increases largely. After the complete vanishing of the initial oxide film, corrosion becomes uniform and the corrosion rate decreases slowly: the corrosion process is limited by the diffusion and the consumption of fluorine

Integrated approach to stainless steel 316L parts repair for pitting corrosion using laser metal deposition

International audienc

Influence of trapezoidal groove geometry on the microstructure and mechanical properties of stainless steel 316L parts repaired by laser metal deposition

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