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Lithium metal batteries are promising next‐generation rechargeable batteries with high energy density. However, the high reactivity of lithium metal leads to an undesirable growth of high surface area lithium during electrodeposition and ‐dissolution and remains a key challenge that must be addressed to enable commercialization. Modification of the Li metal surface to obtain protective coatings is a common method to overcome these challenges. In this study, the influence of the thickness of an intermetallic coating on Li metal is investigated after application by means of thermal evaporation. In addition, the relevance of pre‐treatments in reducing the native layer thickness and surface roughness by roll‐pressing Li metal prior to coating is demonstrated. Morphological analyses are performed on cross‐sections prepared under cryogenic conditions to investigate the origin of high surface area lithium growth and coating cracks after electrodeposition and ‐dissolution processes. The results obtained support the conclusion that the exclusive combination of roll‐pressed Li metal foil followed by coating reduces overvoltage and improves cycle life at elevated current densities. Modification of the lithium metal surface by protective coatings is inevitable to reduce undesirable growth of HSAL during electrodeposition/‐dissolution, which represents a key challenge for lithium metal batteries. Herein, the thickness of a LiZn‐intermetallic coating is optimized and combined with mechanical pre‐treatment of Li metal via roll‐pressing to homogenize the native layer thickness to obtain excellent deposition behavior and performance.

High-entropy alloys (HEAs) are a new generation of materials that exhibit unique characteristics and properties, and are demonstrating potential in the form of thermal spray coatings for demanding environments. The use of HEAs as feedstock for coating processes has advanced due to reports of their exceptional properties in both bulk and coating forms. Emerging reports of thermal sprayed HEA coatings outperforming conventional materials have accelerated further exploration of this field. This early-stage review discusses the outcomes of combining thermal spray and HEAs. Various synthesis routes adopted for HEA feedstock preparation and their properties are discussed, with reference to the requirements of thermal spray processing. The HEA feedstock is then compared and correlated with coating microstructure and phase composition as a function of the thermal spray processing route. Subsequently, the mechanical behavior of thermal spray HEA coatings is summarized in terms of porosity, hardness, and tribological properties, along with their oxidation and electrochemical properties, followed by their potential applications. The thermal spray methods are contrasted against laser cladding and surface alloying techniques for synthesizing thick HEA coatings. Furthermore, HEAs that have displayed excellent properties via alternative processing routes, but have not been explored within the framework of thermal spray, are recommended.

Laves phases with their comparably simple crystal structure are very common intermetallic phases and can be formed from element combinations all over the periodic table resulting in a huge number of known examples. Even though this type of phases is known for almost 100 years, and although a lot of information on stability, structure, and properties has accumulated especially during the last about 20 years, systematic evaluation and rationalization of this information in particular as a function of the involved elements is often lacking. It is one of the two main goals of this review to summarize the knowledge for some selected respective topics with a certain focus on non-stoichiometric, i.e., non-ideal Laves phases. The second, central goal of the review is to give a systematic overview about the role of Laves phases in all kinds of materials for functional and structural applications. There is a surprisingly broad range of successful utilization of Laves phases in functional applications comprising Laves phases as hydrogen storage material (Hydraloy), as magneto-mechanical sensors and actuators (Terfenol), or for wear- and corrosion-resistant coatings in corrosive atmospheres and at high temperatures (Tribaloy), to name but a few. Regarding structural applications, there is a renewed interest in using Laves phases for creep-strengthening of high-temperature steels and new respective alloy design concepts were developed and successfully tested. Apart from steels, Laves phases also occur in various other kinds of structural materials sometimes effectively improving properties, but often also acting in a detrimental way.

High-entropy alloys (HEAs) have great potential to be used as high-temperature materials and in coating material applications due to their combination of strength, ductility, thermal stability, wear, and oxidation resistance. In this work, a new HEA alloy based on NiCoCrAlSi composition was designed and deposited into metallic coatings by high-velocity oxy-fuel (HVOF) and air plasma spray (APS) processes, with the aim of developing new HEA bondcoats for thermal barrier coating (TBC) systems. The HEA coatings were analyzed for phases, microstructure and composition using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The results showed that the BCC phase is the major phase present in the as-applied HVOF coating that was vacuum diffusion treated at 1080 °C. APS coatings of the same composition HEA alloy showed a two-phase structure consisting of the L12 and BCC/B2 phases. The HEA bondcoats produced by HVOF were tested for oxidation resistance at 1050 °C in air, and for thermal cycling resistance of the TBC comprising of the HVOF-applied HEA bondcoat and standard 8YSZ ceramic topcoat. The results showed internal oxidation in the HEA bondcoat during the high-temperature oxidation exposure, but no significant coating failure after 100 thermal cycles at 1150 °C.

Ceramic-coated metals with enhanced properties such as chemical and environmental deterioration resistance and high thermal stability have previously found widespread uses in various industries. However, their application was limited due to weak bonding at the interfaces of dissimilar materials. To achieve the necessary interfaces and bonding qualities, a variety of procedures, primarily mechanical treatments, were used. Interface structure and composition, transition temperature, and wettability are important characteristics. In this review, extensive study has been carried out for several thermal spray methods, such as flame spray, electric arc spray, and plasma spray technology. The study explores microstructural elements of plasma-sprayed coatings, including bonding mechanisms, pore creation, oxides formation, and other important process parameters. The study emphasizes how crucial wetness is to coating development. It looks at what affects wetting, how interfacial reactions affect reactive wetting, and how important additives or reactive materials are to encouraging wetting. In conclusion, the authors suggest the next studies and technological developments in coating technologies and thermal spray procedures. The study contributes to the continuous advancement of these processes and their applications by pointing out opportunities for more research and development.

Owing to low-temperature deposition conditions and high deposition rate, cold spray offers unique advantages in manufacturing a wide variety of metallic and composite coatings including metal matrix composites produced from physically blended powders. One of the challenges of producing composite coatings using cold spray is the deviation of coatings composition from the blended feedstock powder composition. This is of utmost importance as it affects the composition and phase evolution of intermetallic forming coatings during post spray heat treatment. In this work, cold spray of composite Ni-Ti coatings and formation of intermetallics from post spray heat treatment were investigated as a first step to examine the potential of producing equiatomic bulk Ni-Ti by cold spray. Three different physically blended Ni and Ti powders mixtures were sprayed on titanium substrates to address the coating composition variation from the blended feedstock powder and study its influence on phase evolution during post spray heat treatment. High-density and well-dispersed composite coatings were achieved for each case. EDS analysis revealed as-sprayed coatings with 10.5, 35.9 and 56.9 at.% Ni (and with balanced Ti ratios) from the three powder mixtures. Annealing treatments were conducted at 400, 500 and 900 °C for 1 and 2 h and comparative studies of the intermetallic compound formations were carried out. Microstructural investigation showed that all three equilibrium intermetallics phases of binary Ni-Ti phase diagram (Ni3Ti, Ti2Ni and NiTi) formed in the two Ni-rich composite coatings with NiTi phase being maximum in the coating with the closest composition to equiatomic ratio while only Ti2Ni phase formed in the Ti-rich coating after annealing. Thermal etching analysis of coatings showed that NiTi phase forms with a gradient microstructure from Ti splats boundary toward the center of splats, which is attributed to the grain refinement of CS samples at splat boundary and intermetallic nucleation mechanism.

Modeling the structure not only of whole metal products, but also of the protective coatings with which they are coated, brings a number of economic benefits through more resistant coatings and coatings that can be produced by simplifying manufacturing technology or reducing material consumption in the process. This paper presents the results of a study of dip metallization in zinc baths with Ti additions. Both steel and cast iron substrates were coated and similar results were obtained. The obtained coatings were subjected to SEM analysis with chemical composition studies, TEM characterization with selected area electron diffraction (SAED), and corrosion studies. Particle models of the elementary phases present in the zinc coating made with CaRine 3.0 software were presented and used for phase analysis. It emerged that coatings obtained in zinc baths with the addition of Ti are characterized by a more varied microstructure, the occurrence of phase separations to which Ti segregates, and higher corrosion resistance than classical zinc coatings. The higher corrosion resistance is prompted not only by the Ti content in the intermetallic phases, but also by the observed nanostructure favorably located in the alloy layer.

In recent years, cold spray technology has attracted more and more attentions. After more than 30 years of rapid development, research focus of cold spray technology is gradually shifting from fundamental and theoretical studies to application developments, some of which have been industrialized and mass-produced. In this paper, the characteristics of cold spray technology, cold spray materials perspectives and cold spray system developments were briefly introduced. Besides, the recent developments of cold spray applications in different fields including aerospace, biomedical, energy, electronics, semiconductor fields were discussed. Although cold spray technology is in the early stages of implementation, it has demonstrated a great potential to reduce costs and improve performance. World-wide awareness of ongoing and planned cold spray programs is critical to expand its applications and benefits.

Recently, the materials research community has seen a great increase in the development of multicomponent alloys, known as high entropy alloys (HEAs) with extraordinary properties and applications. In surface protection and engineering, diverse applications of HEAs are also being counted to benefit from their attractive performances in various environments. Thermally sprayed HEA coatings have outperformed conventional coating materials and have accelerated further advancement in this field. Therefore, this review article overviews the initial developments and outcomes in the field of HEA coatings. The authors have also categorized these HEA coatings in metallic, ceramic, and composite HEA coatings and discussed various developments in each of the categories in detail. Various fabrication strategies, properties, and important applications of these HEAs are highlighted. Further, various issues and future possibilities in this area for coatings development are recommended.

Hot-dip Al–Si alloy coatings with excellent resistance to corrosion and high-temperature oxidation have emerged as promising lightweight substitutes for conventional corrosion-resistant coatings. The introduction of Mg can be an effective strategy for enhancing the sacrificial protection capability of Al–Si coatings. In this study, the effects of Mg addition on the morphology, electrochemical behavior, and mechanical properties of Al–Si coatings were investigated, along with the Mg-content optimization of the coating layer. Adding Mg promoted the formation of finely distributed eutectic intermetallic phases, such as Al/Mg2Si and the primary Mg2Si phase. Notably, the Mg2Si phase coarsened significantly when ≥15 wt.% of Mg was added. In addition, an Al3Mg2 intermetallic compound was observed in coating layers containing >20 wt.% of Mg, reducing the adhesion of the coating layers. Samples containing 5–10 wt.% of Mg exhibited excellent corrosion resistance (owing to a uniform distribution of the fine eutectic Al/Mg2Si phase and the formation of stable corrosion products), whereas those containing 20 wt.% of Mg exhibited unremarkable corrosion resistance (owing to the formation of an Al3Mg2 phase that is susceptible to intergranular corrosion).