Complex and high entropy alloys are attracting much attention currently thanks to their mechanical and corrosion resistance properties in harsh environments, in particular needed for carbon-free energy applications. However, their elaboration in bulk and in thin film form in a trial-and-error approach is impractical due to their complexity and the cocktail effect. The recent development of artificial intelligence brings a new possibility for their elaboration and adjustment of their properties. Firstly, we present an overview of Materials and data science research. Then we describe how DIADEM - French initiative for Materials and Data science convergence - tackles the development of innovative coatings for carbon-free energy applications (nuclear, high temperature electrolysis, ...) thanks to the development of a nationwide network of synthesis and characterization platforms - the DIADEM discovery hub. We describe in particular DIADEM-2D, an AI-driven Hybrid HiPIMS/Pulsed-DC PVD process using 4 cathodes in confocal combinatorial configuration. We present the high entropy alloy determination using data from the literature for corrosion resistance in molten salt media and nuclear accidental conditions. An element-independent model gathering deposition parameters and coating properties has been implemented allowing the design of protective coatings with a particular composition. We demonstrate the feasibility of this process and its accuracy.

This work uses the direct current magnetron sputtering (DCMS) of equi-atomic (AlTiZrHfTa) and Si targets in dynamic sweep mode to deposit nano-layered (AlTiZrHfTa)Nx/SiNx refractory high-entropy coatings (RHECs). Transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) are used to investigate the effect of Si addition on the oxidation behavior of the nano-layered coatings. The Si-free nitride coating exhibits FCC structure and columnar morphology, while the Si-doped nitride coatings present a FCC (AlTiZrHfTa)N/amorphous-SiNx nano-layered architecture. The hardness decreases from 24.3 ± 1.0 GPa to 17.5 ± 1.0 GPa because of the nano-layered architecture, whilst Young’s modulus reduces from 188.0 ± 1.0 GPa to roughly 162.4 ± 1.0 GPa. By increasing the thickness of the SiNx nano-layer, kp values decrease significantly from 3.36 × 10−8 g2 cm−4 h−1 to 6.06 × 10−9 g2 cm−4 h−1. The activation energy increases from 90.8 kJ·mol−1 for (AlTiZrHfTa)Nx nitride coating to 126.52 kJ·mol−1 for the (AlTiZrHfTa)Nx/SiNx nano-layered coating. The formation of a FCC (AlTiZrHfTa)-Nx/a-SiNx nano-layered architecture results in the improvement of the resistance to oxidation at high temperature.

This work focuses on the influence of the feedstock powders on the microstructural properties and corrosion behavior of 316 L stainless steel (SS) produced by laser powder bed fusion (L-PBF) from two different suppliers. Microstructural investigations conducted after additive manufacturing reveal many particularities depending on the powders. These microstructural differences lead to a different corrosion behavior in boiling nitric acid containing oxidizing ions. The presence of the triple structuration (grains, large cells, small internal cells) shows a positive effect on intergranular and cellular corrosion resistance. In both cases, L-PBF 316 L SS provides better resistance to intergranular corrosion than wrought 316L SS.

The influence of cobalt and cobalt–manganese oxide coating thickness on its ability to be a good diffusion barrier against Cr outward diffusion was investigated for stainless steel interconnects (AISI 441) of a solid oxide cell (SOC). The coatings were all synthesized using a DLI-MOCVD (Direct Liquid Injection-Metal Oxide Chemical Vapor Deposition) hot wall reactor. The study shows that a minimum cobalt oxide thickness of 300 nm was needed to be a good diffusion barrier against Cr for the 500-h exposure test. This observation was linked to the Mn concentration reached in the cobalt spinel during exposure. Indeed, during exposure at high temperature, Mn diffused from the substrate into the cobalt coating and transformed cobalt spinel into Co-Mn spinel. Whereas pure cobalt spinel was a good Cr diffusion barrier, cobalt-manganese spinel, Co3-xMnxO4, was not when x > 2. The thickness of the cobalt coatings must be chosen so that the Mn quantity coming into it from diffusion from the substrate does not degrade the protectiveness of the coating.

Multi-material Directed Energy Deposition of new high-performance components is limited by phase incompatibilities between metals and by the composition variations which complicate parameter optimization. In this work, a methodology of incorporation of a graded Multi-Material Compatibility Interface (MMCI) was employed to allow deposition of tungsten layers (melting at 3410 °C) on a much less refractory metal, copper (boiling at 2562 °C). The manufacturing of parts combining tungsten and copper is of interest for components designed to dissipate heat in extreme environments, such as the divertor for tokamak fusion reactors. A succession of miscible filler metals rationally selected from thermodynamics were printed by laser and powder injection, with optimization of energy and material inputs for each layer, supported by material characterization and physical numerical analysis of the process phenomenology. 90 %wt. tungsten layer deposition on a copper initial substrate is achieved using an MMCI with 6 intermediate layers and 1.6 mm total thickness. The results reveal the importance of controlling the dilution ratio to achieve stable depositions of multi-material with compositional gradients, with a progressive increase in melt pool temperatures. The numerical analysis highlighted the important role of the dissolution and mixing of partially melted refractory powders, and the selective vaporization of volatile elements.

Introduction: The quest to develop efficient, sustainable materials from non-critical, non-toxic resources is one of today's most formidable challenges in the current context of energy, transport, digital or healthcare transitions. In response, France launched the pioneering Priority Equipment and Research Program (PEPR) DIADEM in 2022. This innovative initiative, focused on DIscovery Acceleration for the Deployment of Emerging Materials (DIADEM), leverages Artificial Intelligence (AI) to accelerate the innovation chain from conception to realization, revolutionizing Materials Science sustainably. With a strategic emphasis on scientific synergy, PEPR DIADEM aims to expedite the discovery and development of novel materials essential for contemporary and future societal challenges. To achieve this, the program seeks to catalyze breakthroughs in areas ranging from energy efficiency to transportation, digitalization, and healthcare, covering a broad spectrum of materials from metallic alloys to functional nanostructures. Aligned with the Green Deal framework's ambitious targets, PEPR DIADEM addresses the urgent need for accelerated sustainable materials research. By utilizing cutting-edge technologies like rapid synthesis and characterization tools, automation, digital simulations, data management, AI, additive manufacturing, and thin film engineering, the program is set to significantly reshape the materials science landscape. As PEPR DIADEM embarks on its journey of innovation, it not only advances scientific knowledge but also holds the promise of addressing current global challenges and paving the way for a more sustainable and prosperous future.

(AlTiZrHfTa)1-xNx refractory high entropy films (RHEFs) were deposited by direct current magnetron sputtering in various nitrogen ratios (RN2 = N2/(Ar+N2)) on flat glass, silicon and sapphire substrates. The nitrogen-free film is amorphous while the nitrides are single-phased solid solutions with Face-Centered Cubic (FCC) structures. The hardness increases from 6.4 GPa for the nitrogen-free film to 25.3 GPa for the film obtained at RN2 = 20%. A preferred orientation from (111) to (200) occurs when RN2 increases from 5% to 50%. H/E and H3/H2 reports show high values for the film deposited at RN2 = 20% compared to that at 10%. However, this latter has the best compromise in terms of mechanical properties related to a lower residual stress value. The nitrides films obtained with RN2 >= 5%, are thermally stable at 800 degrees C for 3 h under vacuum. Compared to the metallic film they show an improved oxidation resistance. In fact, the Kp constant of the nitride (RN2=20%) is lower (1.22 10-7 g2 cm-4 h-1) than that of the nitrogen-free film (1.77 10-6 g2 cm-4 h-1). The corresponding activation energies (Ea) are respectively calculated at 94.8 KJ. mol-1 and 45.5 KJ.mol- 1. After oxidation process, TEM analysis reveal the formation of homogeneous mixed oxide.

Powder reuse is essential in laser powder bed fusion (L-PBF) to limit material waste and improve the process sustainability. However, complex laser-material interactions result in an inevitable alteration of the attributes of the recovered powder at the end of the fabrications. Powder degradation is influenced by numerous factors including the processing parameters but also the build topology. In this work, various build characteristics were studied to develop a better understanding of the effects on powder degradation, with the aim of minimizing it. LPBF prints with different melted volume fractions, part spacings and fabrication heights were conducted using stainless steel 316L (SS316L) material. Powders recovered on the build platform, as well as in zones of interest directly adjacent to solidified areas were characterized to investigate the changes in particles characteristics, with special regards to powder oxidation. In combination with these geometrical features, the effect of the oxygen concentration in the build chamber was also studied. The results allow to identify the relation between the oxygen content of recovered powder and the volume fraction of printed parts. It also highlights the presence of heat-affected zones in the near vicinity of the parts with a strong oxygen pick-up in a 500 mu m wide zone around the consolidated material. The results also show the significance of the oxygen concentration in the process

After Zr+ HiPIMS etching, four Zr-based substrate/coating systems were synthesized on 304L stainless steel by hybrid pulsed DCMS/HiPIMS. SEM-BSE images showed an open columnar structure. The coating effect on corrosion was investigated in nitric acid and compared to tantalum considered as reference material in terms of corrosion behavior. Electrochemical measurements in nitric acid at boiling temperature showed that the corrosion resistance of Zr-based coatings was similar to tantalum (coating and bulk) and better than uncoated 304L steel after 2 d of immersion. Longer immersion tests confirmed these results. No intergranular corrosion was observed on coated samples compared to uncoated 304L.

Costs and resource efficiency of laser powder bed fusion (L-PBF) are highly dependent on the ability to produce high quality parts with recycled powders. There is a need to control the quality of the material, which has a direct influence on the performance of the printed parts. Particles oxidation is known to increase with repeated powder recycling and can be a good indicator of powder degradation. The characterization of powders oxygen content is time-consuming, expensive, and usually carried out ex-situ on non-reusable quantities that are not necessarily representative of the entire feedstock. In this work, a new methodology was developed to measure the oxygen content of powders by in-line scanning of powder bed layers. The method takes advantage of stainless steel particles coloration related to their oxidation level in order to assess their oxygen concentration as a function of Red, Green and Blue channel values of image scans. The calibration procedure once carried out, several recycled powder samples were scanned and analyzed, and the determined powder beds oxygen contents were demonstrated to be in accordance with ex-situ measurements. The results highlight a new opportunity to monitor and evaluate powder degradation in-situ on powder bed layers by image analysis.

High entropy alloy nitrides (AlCrTiV)N coatings were deposited by cathodic arc evaporation at various deposition bias and temperature. The mechanical properties of the as-deposited coatings and their oxidation resistance after annealing at various temperatures were analysed. X-ray analyses show in all coatings a FCC structure with a (111) preferred orientation up to 750 degrees C Up to 600 degrees C, no oxygen penetration is measured in the films while at 800 degrees C, critical spalling occurs for all samples. The coating deposited at a temperature of 300 degrees C and negative bias of 100 V exhibits the most interesting compromise in both oxidation resistance and mechanical performances with a hardness of 40 GPa, a friction coefficient of 0.44 and a wear rate of 5.8 .10(-7) mm(3).N-1.m(-1). Annealing in air at 600 degrees C for 2h reduces the wear rate to 2.1 . 10(-7) mm(3).N-1.m(-1) and the surface hardness to 17 GPa. Although annealing forms a thin oxide layer that reduces the hardness on the surface of the coating, it also averages the hardness inside the film to 33 GPa regardless of the deposition bias.

There is a growing interest in the design of high entropy alloys due to their remarkable properties and applications in various fields such as aerospace, medical and automotive. AlTiTaZrHf(-N) high entropy metalsublattice nitrides were deposited in various argon-nitrogen gas mixtures on glass and silicon substrates. X-ray diffraction analyses reveal a transition from amorphous to an FCC single phase by increasing the nitrogen content. The films have compact or columnar morphology depending on the nitrogen flow rate. Energy dispersive spectroscopy analysis shows a decreasing of the matals content as the nitrogen flow rates ratio R-N2 = N-2/Ar + N-2 increases. XPS surface analysis reveal the formation of nitrides when the nitrogen is introduced. Evolution of hardness and Young's modulus are discussed and the maximum values are obtained for a flow rates ratio R-N2 of 10% at 27.67 GPa and 205.56 GPa respectively. The same film reveals good tribological properties compared to other films. This work conclusively demonstrates that high entropy metal-sublattice nitrides can be generated in an efficient way with tunable properties.

The data presented in this article are related to the published research of “Effect of nitrogen content on structural and mechanical properties of AlTiZrTaHf(-N) high entropy films deposited by reactive magnetron sputtering”. This database contains X-ray photoelectron spectroscopy (XPS) measurements, performed in order to determine the extents of nitrides formed in AlTiTaZrHf high entropy films. The latter were prepared by DC magnetron sputtering technique in reactive mode by adding the nitrogen to argon gas. The nitrogen flow rate is calculated by RN2 = N2/(N2+Ar). XPS measurements were done one month later. Oxides were detected on the top surface of the samples. 2p, 3d and 4f core level peaks were fitted in order to determine accurately the chemical composition of the nitride films. Al2p, Ti2p, Zr3d, Ta4f, and Hf4f reveal the formation of nitrides of all elements constituting the films. Atomic percentage of each element was calculated revealing an increase of nitrogen loading and decrease of the metallic fractions of the elements as RN2 grows from 5% to 50%. Nitridation behaviour of each element, as a function of the nitrogen flow rate, is investigated and presented.

A clean and defect-free substrate/coating interface is required to guarantee good adhesion of coatings under service conditions. For this purpose, an etching pre-treatment using High-Power Impulse Magnetron Sputtering (HiPIMS) was performed to modify the surface of 304L stainless steel. The effect of three etching procedures on the substrate properties, such as corrosion resistance and adhesion, was investigated with unprecedented spatial resolution and spectroscopic details. Glancing angle X-ray diffraction showed modification in phase content but no neoformation after steel etching. X-ray photoelectron spectroscopy confirmed the presence of etchant species (6–7 at.%) on the extreme surface of the substrate. Transmission Electron Microscopy and Atomic Probe Tomography showed that the interface was less than a few nanometers wide. Polarization curves in a nitric acid solution at boiling temperature showed, for the first time, that the Ti+ and Zr+ etchings decreased the corrosion current density compared to the untreated original surface. Scratch-test measurements indicated better substrate/coating adhesion using HiPIMS metal ion etching. Electrochemical characterization revealed that Zr etching and thin coating improve the anti-corrosion properties of stainless steel in strong nitric acid conditions.

As a mainstream metal additive manufacturing technique, laser metal deposition (LMD) opens up new possi-bilities for the repair of damaged metal parts. The repair process is composed of different steps, such as three-dimensional scanning, defect detection, pre-repair machining, material addition, post-repair finishing machining, and material testing. In this work, the steps of pre-repair machining and material addition of stainless steel (SS) 316L powder on SS316L substrate using LMD were studied. Three types of grooves with different opening angles (105 degrees, 120 degrees, and 135 degrees) were machined. Both the substrate and the repaired parts were charac-terized to investigate the influence of the opening angles on the relative density, microstructure, and mechanical properties. As compared to the substrate, the repaired parts feature heterogeneous microstructure, a peak in microhardness in the heat-affected zone, similar ultimate tensile strength but low elongation at break for tensile tests, and reduced absorbed energy for Charpy impact tests. The decrease of the opening angle decreases the relative density and tensile properties but increases the energy absorption of the repaired parts.

Surface coating is of a great interest to increase the performances of the materials and extend its lifetime. High entropy films (HEFs) become the hot spot for developing surface engineering applications due to their good performances. They are reported to have superior properties such as good corrosion, wear resistance and excellent high temperature oxidation. Various deposition techniques have been exploited to fabricate HEFs such as laser cladding, spraying, sputter deposition and electrochemical deposition. These techniques are known to be an easy process to achieve a rapid quenching. Magnetron sputtering is seen as the most efficient methods to deposit the HEFs. Different gas can be used to prepare the ceramic materials. Besides, the deposition parameters reveal a strong influence on the physicochemical properties of HEFs. Working pressure, substrate temperature, bias voltage and gas mixture flow ratios have been reported to influence the morphology, microstructure, and functional properties of HEFs. The chapter overviews the development of the recent HEFs prepared by magnetron sputtering technique. First, it describes the principal of the technique. Then, it reports the classes of HEFs followed by the effect of the deposition parameters on their different properties. Applications have been developed using some HEFs for biomaterials and machining process.

The LFPECVD (Low-Frequency Plasma-Enhanced Chemical Vapor Deposition) technique is now used on an industrial scale for the deposition of carbon-based coatings for several applications. This short review recalled the main principles of LFPECVD and provided examples of DLC-based films. The main differences between low-frequency (LF) and radio-frequency (RF) discharges were also recalled here and examples of deposition and characterization of carbon-based films were proposed. The influence of the bias voltage or the temperature of the active electrode on the deposition rate and the structure of a-C: H films obtained in cyclohexane/hydrogen mixtures was first discussed. Next, the properties of carbon-based films doped with silicon were described and, finally, it was shown that multilayer architectures make it possible to reduce the stresses without altering their tribological properties.

In Laser Powder Bed Fusion (L-PBF) of metallic materials, costs and material yield strongly depend on the ability to reuse powder efficiently, as a significant amount is not solidified as part by the laser beam. However, some of the powder is nevertheless exposed to high temperatures during the manufacturing process resulting in an alteration of the feedstock properties if reused. Therefore, there is a need to study and understand powder degradation during the L-PBF process and its direct effects on the printed parts. In this study, gas-atomized 316 L stainless steel powder was used, recovered, sieved and reused up to 15 times in order to produce successive L-PBF prints without adding any virgin powder. Both recycled powders and elaborated parts were fully characterized at each iteration to investigate changes in particles (morphology, rheology, microstructure and chemical composition) as well as printed parts (porosity, microstructure, microhardness and tensile properties). Recycled powder exhibited larger particle size and an improved flowability. A gradual increase in oxygen content was observed, along with the presence of colored and oxidized particles, as well as magnetic particles. Parts density slightly decreased with powder reuse and their microstructure featured more numerous and finer grains along reuse cycles. On the other hand, no significant difference was found on the microhardness and the tensile properties of the L-PBF components.

The effect of low temperature deposition on the quality and the microstructure of hard a-CrCx coatings grown by Direct Liquid Injection Metal-Organic Chemical Vapor Deposition (DLI-MOCVD) was investigated. At deposition temperatures higher than 525 degrees C, the coatings are bi-phased and polycrystalline, essentially composed of Cr7C3 with Cr3C2 as a minor phase. By decreasing the temperature in the 525-350 degrees C range, they are amorphous and exhibit a monolithic glassy-like microstructure without grain boundary. For temperatures lower than 350 degrees C, the uniform amorphous microstructure changes for a lamellar multilayer structure, while the composition of the gas phase was kept constant at the inlet of the reactor for all these CVD runs. The origin of this surprising lamellar structure has been investigated. After having discarded the idea of a self-organized multilayer growth, sometimes encountered in CVD processes, evidence was found for rapid changes in the deposition mechanism. They are induced by oscillations of the surface temperature around a critical value due to the regulation of the furnace used for such large-scale reactors. These almost periodic temperature changes lead to modulations in the surface composition of nutrient species, and subsequently, to the growth of multilayers. The individual composition of lamellae changes regularly, while the overall composition of the coatings remains identical to that of uniform monolithic coatings. For growth conditions leading to local temperature close to the critical value, a regular and controlled nanostructuring can be obtained with a period close to a hundred nanometers. Similar to monolithic a-CrCx coatings, these a-CrCx multilayer coatings exhibit a good barrier behavior against high temperature oxidation, according to the test performed. As future prospects, the main interest for these lamellar coatings could be their mechanical properties thanks to the numerous interfaces capable of deflecting and dissipating the propagation of cracks.

Directed energy deposition (DED) with laser and powder allows the manufacturing of multi-metallic near net shape structures, with control over the feedstock composition and intense liquid mixing of elements. To better understand the multi-physical aspects of the melt pool and strive toward local composition prediction, a 3D finite element model of the laser deposition of chromium on stainless steel has been developed. A modified v2-f model is implemented to investigate the effect of melt pool turbulence on heat, momentum, and mass transport. The model is formulated in the moving frame of the laser, which allows reducing the domain size and the computation time. Overlapping on previous tracks is included by updating the upstream face boundary conditions with the composition and free-surface shape of the calculated molten cross section. This allows for fast computation of the steady-state solution of the layer formation. Simulation results are compared to the composition analysis of a part containing an interface between chromium and stainless steel manufactured using a controlled atmosphere laser powder-DED system. The diffusive effects induced by turbulence are analyzed with regard to a laminar simulation and are found to have a significant impact on the maximum fluid velocity and temperature. Melt pool turbulence thickens the flow vortices and homogenizes the core of the melt pool, which is consistent with the experimental results. Chemical heterogeneities can be seen at the boundary with the substrate and are reviewed in light of the simulation results.