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In this study, we investigated the effect of spray angle on the microstructure, bonding quality, and scratch resistance of cold-sprayed SS316L coatings on SS304 substrates. The coatings were deposited at spray angles of 45°, 60°, 75°, and 90° using a high-pressure cold spray system. A comprehensive analysis of the relationship between the spray angle and coating properties was conducted, with a particular focus on fracture toughness and porosity. Scratch testing, combined with real-time acoustic emission monitoring, enabled the precise identification of failure mechanisms and the assessment of coating integrity. The results indicate that microhardness and porosity are significantly influenced by the spray angle. The highest microhardness was achieved at a 45° angle, while a 90° angle resulted in the lowest porosity and superior bonding due to superior normal impact velocity. Fracture toughness was found to correlate with microstructural cohesion and particle deformation. Optimizing the incidence angle improved the coating performance by balancing strain hardening and ductility, thereby reducing the risk of premature failure. These findings are particularly relevant for industrial applications, where wear resistance and high-quality bonding are critical, such as in aerospace, automotive, and marine sectors. By adjusting the spray angles, manufacturers can enhance the longevity and reliability of the coated components, thus reducing maintenance costs and improving performance. This research highlights the importance of process parameters in achieving durable, high-quality coatings and emphasizes scratch testing as an effective, sustainable, and semi-destructive evaluation method for coating integrity. [ABSTRACT FROM AUTHOR]

Cold spray technology has become essential for industries requiring efficient material deposition, yet achieving optimal deposition efficiency (DE) presents challenges due to complex interactions among process parameters. This study developed a two-stage machine learning (ML) framework incorporating Bayesian optimization to address these challenges. In the first stage, a classification model predicted the occurrence of deposition, while the second stage used a regression model to forecast DE values given deposition presence. The approach was validated on Aluminum 6061 data, demonstrating its capability to accurately predict DE and identify optimal process parameters for target efficiencies. Model interpretability was enhanced with SHAP analysis, which identified gas temperature and gas type as primary factors affecting DE. Scenario-based inverse analysis further validated the framework by comparing model-predicted parameters to literature data, revealing high accuracy in replicating real-world conditions. Notably, substituting hydrogen as the gas carrier reduced the required gas temperature and pressure for high DE values, suggesting economic and operational benefits over helium and nitrogen. This study demonstrates the effectiveness of AI-driven solutions in optimizing cold spray processes, contributing to more efficient and practical approaches in material deposition. [ABSTRACT FROM AUTHOR]

This research work aims to study the drilling behaviour of hybrid composite structures made of glass fibre-reinforced polymer matrix metallised with a surface aluminium layer produced via cold spray technology. The metal deposition creating the coating was optimised by applying a thermoplastic layer to the thermoset composite structure using the co-curing technique. Aiming to highlight the influence of the metallic coating on the workpiece's response during drilling, this research systematically analyses the effects of drilling parameters such as feed rate and spindle speed on delamination, burr formation and hole quality. In-process monitoring techniques, including thermocouple temperature and thrust force measurements, as well as energy consumption estimation, were utilised to evaluate drilling performance. The main findings demonstrate that selecting the composite side as the inlet surface results in the highest measured force and reduced delamination, meaning that aluminium coatings significantly impact drilling dynamics. [ABSTRACT FROM AUTHOR]

The corrosion resistance of a Cr3C2-25(Ni20Cr) cermet coating applied to an Al7075 substrate (Cr3C2-25(Ni20Cr)/Al7075) was investigated. The coating was produced using a cold spraying (CS) method. The main aim of the research was to determine the effect of heat treatment on the properties of cermet coatings on the Al7075 substrate. The mechanical properties of the Cr3C2-25(Ni20Cr)/Al7075 composite were assessed through microhardness (HV) measurements. The surface morphology and microstructure of the specimens were examined using a scanning electron microscope (SEM). Electrochemical testing in an acidic chloride solution was employed to evaluate the corrosion behavior of the materials. The cermet coating effectively protected the Al7075 substrate from the aggressive corrosive environment. Heat treatment homogenized the structure of the cermet coating, eliminating microcracks and pores on the Cr3C2-25(Ni20Cr)/Al7075 surface. Notably, annealing at 300 °C in air significantly enhanced the corrosion resistance of the cermet coating. The corrosion rate was reduced by more than five times compared to the non-heat-treated Cr3C2-25(Ni20Cr)/Al7075 coating. [ABSTRACT FROM AUTHOR]

Cold spray additive manufacturing (CSAM) has gained significant attention for its rapid solid deposition capabilities. However, the presence of defects such as pores and voids limits its performance, particularly in electrochemical environments. In this study, a novel post-surface treatment, plasma electrolytic oxidation (PEO), was applied and investigated as a feasible solution to overcome these defects. Results demonstrated a successful PEO deposition on cold-sprayed 316L stainless steel (SS) due to the rapid formation and discharge of aluminate electrolytes along the surface. However, due to the severely strained and highly crystalline surface, the electric field that allows for the deposition of Al(OH)4− anions was reduced. As consequence, an uneven and rough deposition took place. Nonetheless, a successful Al2O3 film of 12.30 μm thickness was formed. Experimental tests were further conducted in simulated aqueous and biological-based solutions to test the electrochemical resistance of the deposit. Results reveal a noticeable enhancement in corrosion resistance for both solutions. This enhancement can be attributed to the "postponing" and "blocking" effect enabled by the Al2O3 film, which prevented the electrolyte solution from penetrating the CS surface. Collectively, these findings suggest that PEO is indeed a promising technique to mitigate the chemical degradation of CSAM'd 316L SS. [ABSTRACT FROM AUTHOR]

Magnesium (Mg) alloys are used more often today in the automotive and aviation industries. Owing to their many beneficial characteristics, such as higher thermal conductivity, greater strength, lower density and weight, etc., magnesium alloys tend to corrode when employed in particular moist regions, and their poor wear characteristics may reduce their lifespan. To deal with such challenges, a surface coating technique was used on the AZ31B Mg alloy with AA2024/Al2O3 coating powder through a cold spray process. The porosity, corrosion, and wear rate of the deposited Mg alloy are investigated. Box–Behnken designs (BBD) are used to plan the experimental investigation. The results were verified using the Mayfly optimization technique in MATLAB 2021, which relies on a hybrid deep belief network, and also through the BBD-response surface methodology (RSM) in Design Expert 11. The metal matrix composite coating has a minimal porosity, corrosion rate, and wear loss of 0.52%, 1.35 mm/year, and 0.52 mg, experimentally. As a result, the hybrid deep belief network-mayfly optimization estimated results are more similar to the experimental results compared to the BBD-RSM. [ABSTRACT FROM AUTHOR]

With the rapid growth of the lithium-ion battery (LIBs) market, recycling and re-using end-of-life LIBs to reclaim the critical Li, Co, Ni, and Mn has become an urgent task. Presently, high temperature, strong acid, and alkali conditions are required to extract blended critical metals (CM) from the typical battery cathode. Hence, there is a need for more effective recycling processes for recycling blended Li, Co, Ni, and their direct regeneration for re-use in LIBs. The goal of the offered paper is the development of recycling technology for degraded battery cathode-active materials based on the thermal decomposition of polyvinylidene fluoride (PVDF) using calcination and air-jet stripping of active materials. The proposed air-jet erosion method of calcined cathode material stripping from Al foil allows for the flexible industry-applicable separation process, which is damage-free for both particles and substrate. The CaO calcination air-jet separation process and equipment can significantly improve the PVDF decomposition and the separation efficiency of the cathode materials. It is demonstrated that low-temperature CaO calcination at 350–450 °C associated with air-jet separation of active material is characterized by low environmental impact, high purity of the recycled material, and low cost as compared to pyro- and hydrometallurgical methods. [ABSTRACT FROM AUTHOR]

A numerical study was performed to analyze the particle deposition of a cold spray process for the preparation of nickel electrocatalysts used in the Hydrogen Evolution Reaction (HER). The study focused on the creation of fin-shaped geometries with an optimal porosity on the electrode surface using a mask located between the nozzle exit and the substrate. Computational Fluid Dynamics (CFD) was performed on a three-dimensional high-pressure nozzle, with nickel powder used as the injection feedstock. The behavior of particles was effectively modeled through a two-way coupled Eulerian–Lagrangian approach. As per the parametric study, four masks of varying wire thicknesses and opening sizes were investigated. The masks were placed at 4 mm increments from the nozzle exit, with the substrate placed at standoff distances (SODs) of 10 mm and 20 mm. To capture the effects of the gas inlet operating conditions, two different nozzle inlet conditions were analyzed (2 MPa and 400 °C, 4 MPa and 800 °C). It was found that the nozzle inlet operating condition had the most significant impact, as it relates to the particle velocity and powder deposition. The high-pressure operating condition resulted in a deposition efficiency (DE) greater than 99.9% for all the test cases, with nearly all the impacted particles depositing on the substrate. For the medium-pressure operating condition, the DE increased linearly as the mask SOD was increased, due to the increase in the particle velocity upon impact. [ABSTRACT FROM AUTHOR]

Superficial depositions gain interest in various industries due to the significant improvement of the properties of the base material that is subjected to superficial depositions. The deposits can be made both in the technological process of manufacturing the various components and in the reconditioning processes of the components with high levels of wear. Superficial coatings are applied with the aim of creating a protective surface layer, that is hard and resistant to both external factors and various demands. Depending on the nature of the application of the component, to be coated the mechanical, microstructural, thermal, corrosion resistance, etc. properties can be improved. The objective of this work is to demonstrate the ability of thermal deposition to improve the mechanical and microstructural properties of materials used in the construction of armour for military equipment using the Cold Spray (CS) thermal deposition method. Among all the deposition methods, this method is the only one that manages to deposit the particles below their melting point, having the lowest deposition temperatures, thus preserving the properties of the deposited material. This paper presents experimental results for armor elements that are subjected to severe exploitation regimes and contributes to the scientific progress in the field of deposits applicable to most industries such as petrochemical, military, aerospace, automotive, and medical.

The effect of coating thickness (CT) on the microstructures, hardness, and wear of cold sprayed Ti-6Al-4V (CS-Ti64) coatings was systematically investigated since the prolonged high pressure CS deposition could change their microstructures and porosity levels. In addition, the CT was relatively important for their durability, performance, and service life. Therefore, the CS-Ti64 coatings with different CT of 100-3000 µm were prepared on commercially available Ti64 (CA-Ti64) substrates via high pressure CS processes. The CS-Ti64 coatings had low porosity levels wherewith severely deformed Ti64 particles with a crescent-shape could be seen in their cross-sectional microstructures. The hardness of the CS-Ti64 coatings increased with increased CT probably due to their lowered bulk porosity levels associated with longer high pressure CS deposition. As a result, the increased CT from 100 to 3000 µm resulted in a 9.8% decrease in the wear of the CS-Ti64 coatings. The wear of the CS-Ti64 coating with 3000 µm was 16.8% lower than that of the CA-Ti64 as all the CS-Ti64 coatings had lower wear than the CA-Ti64. It could be concluded that the prolonged high pressure CS deposition for the thick CS-Ti64 coatings had an influence on their porosity, hardness, and wear.

Cold spray additive manufacturing (CSAM) is a cutting-edge high-speed additive manufacturing process enabling the production of high-strength components without relying on traditional high-temperature methods. Unlike other techniques, CSAM produces oxide-free deposits and preserves the feedstock's original characteristics without adversely affecting the substrate. This makes it ideal for industries requiring materials that maintain structural integrity. This paper explores strategies for improving material quality, focusing on nozzle design, particle size distribution, and fine-tuning of process parameters such as gas pressure, temperature, and spray distance. These factors are key to achieving efficient deposition and optimal bonding, which enhance the mechanical properties of the final products. Challenges in CSAM, including porosity control and achieving uniform coating thickness, are discussed, with solutions offered through the advancements in machine learning (ML). ML algorithms analyze extensive data to predict optimal process parameters, allowing for more precise control, reduced trial-and-error, and improved material usage. Advances in material strength, such as enhanced tensile strength and corrosion resistance, are also highlighted, making CSAM applicable to sectors like aerospace, defense, and automotive. The ability to produce high-performance, durable components positions CSAM as a promising additive-manufacturing technology. By addressing these innovations, this study offers insights into optimizing CSAM processes, guiding future research and industrial applications toward more efficient and high-performing manufacturing systems. [ABSTRACT FROM AUTHOR]

This study employed a high-pressure cold spray to apply a Zn30Al alloy coating to Q235 steel substrates to provide corrosion protection for steel in marine environments. The corrosion resistance of the coatings was investigated through full immersion tests, and the corrosion mechanisms were further analyzed using electrochemical experiments. The results were compared with those of traditional flame-sprayed Zn30Al alloy coating. The findings indicate that the high-pressure cold-sprayed Zn30Al alloy coating possesses a dense microstructure with a porosity of only 0.32%, providing effective cathodic protection to the substrate during the immersion tests. The cold-sprayed Zn30Al alloy coating maintained good integrity after 720 h immersion in 3.5 wt.% NaCl solution, whereas the flame-sprayed Zn30Al alloy coating exhibited significant pitting corrosion. [ABSTRACT FROM AUTHOR]

Cold spray is a solid-state additive manufacturing technology and has significant potential in component fabrication and structural repair. However, the unfavourable strength–ductility synergy in cold spray due to the high work hardening, porosity and insufficient bonding strength makes it an obstacle for real application. In recent years, several methods have been proposed to improve the quality of the cold-sprayed deposits, and to achieve a balance between strength and ductility. According to the mechanism of how these methods work to enhance metallurgical bonding, decrease porosity and reduce dislocation densities, they can be divided into four groups: (i) thermal methods, (ii) mechanical methods, (iii) thermal–mechanical methods and (iv) optimisation of microstructure morphology. A comprehensive review of the strengthening mechanism, microstructure and mechanical properties of cold-sprayed deposits by these methods is conducted. The challenges towards strength–ductility synergy of cold-sprayed deposits are summarised. The possible research directions based on authors' research experience are also proposed. This review article aims to help researchers and engineers understand the strengths and weaknesses of existing methods and provide pointers to develop new technologies that are easily adopted to improve the strength–ductility synergy of cold-sprayed deposits for real application. [ABSTRACT FROM AUTHOR]

Superficial depositions gain interest in various industries due to the significant improvement of the properties of the base material that is subjected to superficial depositions. The deposits can be made both in the technological process of manufacturing the various components and in the reconditioning processes of the components with high levels of wear. Superficial coatings are applied with the aim of creating a protective surface layer, that is hard and resistant to both external factors and various demands. Depending on the nature of the application of the component, to be coated the mechanical, microstructural, thermal, corrosion resistance, etc. properties can be improved. The objective of this work is to demonstrate the ability of thermal deposition to improve the mechanical and microstructural properties of materials used in the construction of armour for military equipment using the Cold Spray (CS) thermal deposition method. Among all the deposition methods, this method is the only one that manages to deposit the particles below their melting point, having the lowest deposition temperatures, thus preserving the properties of the deposited material. This paper presents experimental results for armor elements that are subjected to severe exploitation regimes and contributes to the scientific progress in the field of deposits applicable to most industries such as petrochemical, military, aerospace, automotive, and medical. [ABSTRACT FROM AUTHOR]

Chromium carbide powder agglomerated with nickel/chrome was deposited using a cold spray process onto a mild steel substrate. The deposits were heat-treated at 650 °C and 950 °C in ambient conditions to reduce porosity and improve adhesion between powder particles. The corrosion behaviour of these cold-sprayed materials was studied in artificial seawater conditions using electrochemical techniques. Heat treatment at 650 °C was found to best improve corrosion resistance, while the 950 °C treatment performed better than the as-sprayed condition but lower than the 650 °C sample. Microstructural analysis revealed complex phase transformations and structural refinements with increasing heat treatment temperature. The crystallite size of both Cr3C2 and NiCr phases decreased, while microstrain and dislocation density increased due to heat treatment. The formation of and subsequent reduction in Cr23C6 content indicated a complex sequence of carbide dissolution, transformation, and precipitation processes. The 650 °C heat-treated sample demonstrated superior corrosion resistance, evidenced by the highest corrosion potential, lowest passive current, and largest charge transfer resistance. This enhanced performance was attributed to the formation of a more stable and protective passive film, optimal carbide dissolution, and a homogeneous microstructure. Meanwhile, the 950 °C treatment led to excessive carbide dissolution and formed increased interfaces between the carbide and matrix. Mechanical property changes were also observed, with carbide hardness significantly decreasing after corrosion testing. These findings highlight the critical role of controlled heat treatment in optimising the performance of cold-sprayed Cr3C2-NiCr coatings, demonstrating that achieving superior corrosion resistance requires a delicate balance between microstructural refinement, phase transformations, and preservation of coating integrity. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HA, Ca10(PO4)6(OH)2) composite coatings added in the second phase could improve the mechanical properties and bonding strength. The cold spraying technique, as a technology for the deposition of solid particles at low temperatures, is employed to deposit HA ceramic composite coatings. The nano HA material possesses characteristics that enhance properties and promote interface bonding. Due to the exceptional mechanical properties of Ti material, adding Ti particles could improve the mechanical properties of nano HA/Ti composite coatings. In order to explore the deposition deformation mechanism of composite particles under different cold spraying conditions, numerical simulation and experimental testing of deposition behaviors of dual nano HA/Ti composite particles were analyzed. As the particle velocity increased from 400 m/s to 800 m/s in the numerical simulation analysis, the more serious the deposition deformation. Meanwhile, more cracking and splashing phenomena occurred on the surface of the particle. By analyzing the stress value curve of Ti and HA units under different particle velocities, it was found that the adiabatic shear instability phenomenon occurred during the particle deposition on the substrate. In addition, the degree of particle deformation increased with the decrease in the particle size. The results of the experimental investigation were consistent with that of the numerical simulation. [ABSTRACT FROM AUTHOR]

Softening and subsequent deformation are significant challenges in additive manufacturing of thermal-curable thermosets. This study proposes an approach to address these issues, involving the preparation of thermosetting composite powders with distinct curing temperatures, the utilization of cold spray additive manufacturing (CSAM) for sample fabrication, and the implementation of stepwise curing for each component. To validate the feasibility of this approach, two single-component thermosetting powders P1 and P2 and their composite powder C were subjected to CSAM and stepwise curing. From the sample morphology observation and deposition/curing mechanism investigation based on thermomechanical analysis and differential scanning calorimetry, it is found that severe plastic deformation occurs during the CSAM process, accompanied by heat generation, leading to local melting to promote a good bond at the contact surface of the particles and form small pores. During the progressive curing, the samples printed using C demonstrate superior deformation resistance compared with those using P1 and P2, and the curing time is reduced from 16.7 h to 1.5 h, due to the sequential curing reactions of P1 and P2 components in composite C, allowing the uncured P2 and cured P1 to alternately remain solid for providing structural support and minimizing deformation. [ABSTRACT FROM AUTHOR]

The application of cold spray (CS) for 316L stainless steel (SS) has been an increasingly popular process in recent years. However, defects in the form of porosity hamper their frictional resistance. In an effort to enhance the frictional resistance of CS 316L SS, novel indirect-laser surface texturing without confinement (ILSTwC) and direct-laser surface texturing without confinement (DLSTwC) processes are introduced as viable surface texturing, densifying, and strengthening techniques. These techniques operate by taking advantage of the severe plastic deformation and heating kinetics of a pulsed laser to an externally applied mesh, thus creating a surface texture that is highly dense and work-hardened. For the ILSTwC treatment, utilizing a laser intensity of 6.13 GW cm−2 led to significant changes in surface properties. Compared to the non-textured CS surface, there was a 24.1% increase in surface roughness, a notable 262.2% increase in surface skewness, a 26.0% increase in surface hardness, and a substantial 54.4% decrease in frictional response. For the DLSTwC treatment at the same laser intensity, the surface properties exhibited contrasting behavior. There was a remarkable 80.4% reduction in surface roughness, accompanied by a 63.6% increase in surface skewness, a 26.4% increase in surface hardness, and a significant 65.1% decrease in frictional response compared to the non-textured CS surface. Between the ILSTwC and DLSTwC surfaces, the DLSTwC surface had the greatest reduction in friction due to the lessened tribological contacts from the negatively skewed surface. Based on these findings, this work indicates that laser surface texturing has an influential effect on enhancing surface hardness and density and is indeed a viable technique to control the tribological performance of harder materials such as CS 316L SS. [ABSTRACT FROM AUTHOR]

A GRCop-42 cylinder was produced by North American Manufacturing Pros using laser powder bed fusion to measure the residual stress at a bimetallic joint with NASA HR-1. Pure Ni was applied by ASB Industries as a diffusion barrier between the GRCop-42 and NASA HR-1 using cold spray. Residual stress measurements of the Ni layer in the as-cold sprayed and heat-treated conditions were collected on the top surface of the coating using x-ray diffraction with Co Kα radiation and the Sin2ψ method at multiple phi (φ) angles. Biaxial stress values and rotation angles between the original sample axes (φ = 0° direction) and the principal axes were calculated at three equally spaced locations around the perimeter of the cylindrical part. The stress measurements were plotted at their respective positions around a circle, and with the rotation angles for each, to reveal rotational symmetry in the tension and compression of the coating. [ABSTRACT FROM AUTHOR]

Cold spray additively manufactured (CSAM) aluminum 6061 components are characterized by heterogeneous compressive residual stresses induced during manufacturing. This heterogeneity is further compounded by spatial variations in microstructures and mechanical properties, leading to poor inter-particle (intersplat) bonding and significant marring of overall component performance. Thermal post-processing is a keenly researched method for recovering mechanical toughness by enhancing intersplat bonding and altering highly concentrated residual stress distributions. The current work incorporates a modified microscale–mesoscale material model into a viscoplastic self-consistent simulation framework to capture material response in the as-sprayed and post-processed states. The updated model incorporates physically informed parameters emphasizing residual stresses measured experimentally through X-ray diffraction. The model calibrated using experimental tests and published literature was able to predict the stress–strain response of CSAM parts at post-heat-treated conditions. Results of the parametric study showed the significance of intersplat boundary effects on the overall yield and strain hardening of the CSAM parts. Without any information on the processing conditions of CSAM parts, the modified plasticity model predicted the deformation response using information gathered from microstructure characterization. [ABSTRACT FROM AUTHOR]

This study employs neutron diffraction to investigate the relationship between residual stress and coating thickness in cold sprayed 304L austenitic stainless steel. Results show that shot peening predominantly impacts the residual stress profile, leading to substantial in-plane compressive force. The impact of laser heating, a widely used method to alter cold spray's microstructural properties, on the coating's residual stress is also analyzed. The findings indicate that the maximum compressive residual stress in the in-plane component is mainly independent of coating thickness, which suggests that the material properties determine the maximum residual stress. The cold sprayed deposits possessed compressive, nearly biaxial strain and stresses. After laser heating, these stresses were replaced by tensile residual stresses. Two analytical models, the Tsui and Clyne and the Boruah models, for predicting residual stresses are also evaluated, and both models provide reasonable fits to the experimental data. At this point, the deviations between the experimental results and the models are principally caused by the inability of the current models to address plastic deformation and relaxation, and the residual stresses generated by thermal gradients. [ABSTRACT FROM AUTHOR]

The cold spray (CS) process is an advanced material deposition method that has emerged as a versatile method to create high-performance coatings and functional components. This process offers unique advantages in achieving exceptional material adhesion and properties without needing high-temperature melting or heating. The CS process enables the deposition of cermets, allowing it to combine the favorable properties of their constituent phases. This review article explores the bonding mechanism specific to the CS deposition of cermets, highlighting its contrast with that of pure metals. It subsequently investigates the pivotal role played by ceramic particles in the overall efficiency of the CS deposition process, emphasizing the need for a comprehensive understanding of particle properties to achieve quality coatings for specific applications. The paper explores the challenges and limitations imposed by the CS process of cermets in optimizing the crucial parameters. It dissects the influence of interfacial bond strength and porosities on the tribological and corrosion properties of CS-deposited coatings. The discussion extends to the significant role played by substrate in shaping the coating's characteristics. The potential for enhancing coating properties through post-processing treatments is also thoroughly examined. The review article also discusses current advancements in the field and contemplates potential future directions, offering a comprehensive exploration of CS deposition of cermets and its multifaceted considerations. [ABSTRACT FROM AUTHOR]

The cold spray deposition technique has been used to produce a new class of solid lubricant coatings using powder feedstocks of the metal disulfides WS2 or MoS2, either pure or mixed with Cu and Ni metal powders. Friction and cycle lives were obtained using ball-on-flat reciprocating tribometry of coated 304 SS flats in dry nitrogen and vacuum at higher Hertzian contact stresses (Smax = 1386 MPa (201 ksi)). The measured friction and thickness of the coatings were much lower than for previous studies (COF = 0.03 ± 0.01 and ≤1 µm, respectively), which is due to their high metal disulfide:metal ratios. Cu-containing metal sulfide coatings exhibited somewhat higher cycle lifetimes than the pure metal sulfide coatings, even though the Cu content was only ~1 wt%. Profiling of wear tracks for coatings tested to 3000 cycles (i.e., pre-failure) yielded specific wear rates in the range 3–7 × 10−6 mm3N−1m−1, similar to other solid lubricant coatings. When compared to other coating techniques, the cold spray method represents a niche that has heretofore been vacant. In particular, it will be useful in many precision ball-bearing applications that require higher throughput and lower costs than sputter-deposited MoS2-based coatings. [ABSTRACT FROM AUTHOR]

The effect of niobium ion implantation on the surface and scratch properties of a WC-5wt.%Ni cold sprayed coating was investigated with accelerating energies of 60 and 170 keV and fluences of 5 × 1016 and 8 × 1016 ions cm−2, respectively. High-resolution Rutherford backscattering spectroscopy spectra revealed that Ni-Nb and WC-Nb amorphous layers had likely formed. Using ion implantation parameters of 60 keV with a fluence of 8 × 1016 ions cm-2 (coating 608-NB), higher Nb peak intensities were found. Oxide formation in the form of NbO, NbO2, and Nb2O5 was detected with high-resolution x-ray photoelectron spectroscopy spectra analyses on the 608-NB coating, in conjunction with the intermetallic, thereby having the best coating properties: higher hardness, low roughness, and scratch properties compared to the other ion-doped samples. The failure mechanisms of all the coatings were found to be similar, showing angular cracks, cone cracking, and primary delamination. [ABSTRACT FROM AUTHOR]

Cold spray technology, as an emerging surface engineering technique, effectively prepares hard coatings by high-speed projection of powder materials onto substrates at relatively low temperatures. The principal advantage of this technology lies in its ability to rapidly deposit coatings without significantly altering the properties of the substrate or powder materials. Carbon-based materials, especially carbides and diamond, etc., are renowned for their exceptional hardness and thermal stability, which make them indispensable in industrial applications requiring materials with high wear resistance and durability at elevated temperatures. This review elucidates the fundamental principles of cold spray technology, the key components of the equipment, and the properties and applications of hard coatings. The equipment involved primarily includes spray guns, powder feeders, and gas heaters, while the properties of the coatings, such as mechanical strength, corrosion resistance, and tribological performance, are discussed in detail. Moreover, the application of this technology in preparing metal matrix composite (MMC) materials with carbon-based reinforcements, including tungsten carbide, boron carbide, titanium carbide, and diamond, are particularly emphasized, showcasing its potential to enhance the performance of tools and components. Finally, this article outlines the challenges and prospects faced by cold spray technology, highlighting the importance of material innovation and process optimization. This review provides researchers in the fields of materials science and engineering with a comprehensive perspective on the application of cold spray technology in MMC materials with carbon-based reinforcements to drive significant improvements in coating performance and broaden the scope of its industrial applications. [ABSTRACT FROM AUTHOR]

This paper presents the results of an extensive investigation into the durability of cold spray repairs to corrosion damage in AA7075-T7351 aluminium alloy specimens where, prior to powder deposition, the surface preparation involved grit blasting. In this context, it is shown that the growth of small naturally occurring cracks in cold spray repairs to simulated corrosion damage can be accurately computed using the Hartman–Schijve crack growth equation in a fashion that is consistent with the requirements delineated in USAF Structures Bulletin EZ-SB-19-01, MIL-STD-1530D, and the US Joint Services Structural Guidelines JSSG2006. The relatively large variation in the da/dN versus ΔK curves associated with low values of da/dN highlights the fact that, before any durability assessment of a cold spray repair to an operational airframe is attempted, it is first necessary to perform a sufficient number of tests so that the worst-case small crack growth curve needed to perform the mandated airworthiness certification analysis can be determined. [ABSTRACT FROM AUTHOR]

This research investigates the influence of thickness on residual stress profiles in aluminum cold spray coatings using finite element analysis (FEA). Residual stress is a critical factor that impacts coating adhesion, fatigue life, and susceptibility to delamination in thermal spray processes. Despite its acknowledged importance, predictive analysis of these stresses on a layer-by-layer basis remains relatively unexplored. This study introduces an innovative numerical methodology to analyze the progression of residual stresses across various deposition efficiencies (10%, 40%, 60%, and 100%) and layer thicknesses, thereby enhancing predictive accuracy for cold spray coatings. The findings demonstrate that the number of deposited layers significantly affects residual stress profiles in both coatings and the substrate, with compressive residual stress predominating in the coatings and deeper tensile stress predominating in the substrate. Residual stress behavior near the last deposited layer aligns with the expected peening effect. Discrepancies in substrate stress distributions may arise from variations in deposition parameters and unconsidered temperature effects. While the model generally aligns with theoretical and some empirical data, observed discrepancies underscore the need for further validation. This study lays the groundwork for informed decision-making for cold spray processes by providing insights into stress management, thereby contributing to enhancing coating integrity and performance. [ABSTRACT FROM AUTHOR]

Aluminum alloys (Al) produced by fusion-based additive manufacturing techniques exhibit limited strength due to undesirable grain growth, porosity, and thermal gradient. To address these limitations, Scalmalloy (Al–Mg4.6-Sc0.72-Zr0.3 wt%) deposits of 5 mm thickness using helium and nitrogen gases were manufactured using a solid-state cold spray (CS) deposition. The microstructure of these deposits revealed a bimodal distribution of coarse and fine grains in the splat interior and jetting region, respectively, characterized by a higher degree of plastic deformation in the He-deposit. These bimodal grains resulted in a nanohardness of 1.2 GPa in the jetting region, 20% higher than that in the interior. The cumulative effect of these microstructural features resulted in a microhardness of 149 HV in the He-deposit, 1.1 times compared to that in the N2-deposit. The increased hardness is translated to a yield strength of 383 MPa and ultimate strength of 487 MPa in the He-deposit, 1.17 and 1.08 times of N2-deposit, respectively, estimated by Profilometry-based indentation plastometry (PIP). Across the hierarchical layers, profilometry-based indentation plastometry captured a consistent pile-up difference of ∼2 μm in the He-deposit and ∼3 μm in the N2-deposit on the plane perpendicular to build plane, a manifestation of in-plane anisotropy. This study advances the microstructural understanding and its relationship with observed mechanical properties, deformation behavior, and anisotropic response in high-strength Scalmalloy CS deposits.

To improve the wear resistance of CoCrFeNi high-entropy alloys (HEAs) for a wider range of industrial applications, the alloying strategy was applied to CoCrFeNi HEA by doping Mo element in various ratios, and CoCrFeNiMox (x = 0, 0.2, 0.5, and 1.0) HEA deposits were fabricated by cold spray. The microstructure evolution, mechanical properties, and tribological properties of cold-sprayed CoCrFeNiMox HEA deposits were systematically investigated. The results showed that Mo0, Mo0.2, and Mo0.5 deposits have a face-centered-cubic (FCC) single structure, while Mo1.0 deposit was composed of FCC matrix and hard brittle phases. The doping of Mo element into CoCrFeNi HEA deposits significantly increased the hardness due to the enhanced solid solution strengthening and precipitation strengthening. As a result, the anti-wear properties of Mo-doped CoCrFeNi HEA deposits were gradually improved with the increase in Mo ratios. To be specific, the Mo1.0 deposit exhibited the lowest specific wear rate of 5.1 × 10−5 mm3/N·m, which was reduced by 94.9% in comparison to the Mo0 deposit. Overall, the current study proposes a new strategy to manipulate the mechanical properties of cold-sprayed HEA deposits by alloying.

With the rapid growth of the lithium-ion battery (LIBs) market, recycling and re-using end-of-life LIBs to reclaim the critical Li, Co, Ni, and Mn has become an urgent task. Presently, high temperature, strong acid, and alkali conditions are required to extract blended critical metals (CM) from the typical battery cathode. Hence, there is a need for more effective recycling processes for recycling blended Li, Co, Ni, and their direct regeneration for re-use in LIBs. The goal of the offered paper is the development of recycling technology for degraded battery cathode-active materials based on the thermal decomposition of polyvinylidene fluoride (PVDF) using calcination and air-jet stripping of active materials. The proposed air-jet erosion method of calcined cathode material stripping from Al foil allows for the flexible industry-applicable separation process, which is damage-free for both particles and substrate. The CaO calcination air-jet separation process and equipment can significantly improve the PVDF decomposition and the separation efficiency of the cathode materials. It is demonstrated that low-temperature CaO calcination at 350–450 °C associated with air-jet separation of active material is characterized by low environmental impact, high purity of the recycled material, and low cost as compared to pyro- and hydrometallurgical methods.

In this research, a silicon-aluminizing diffusion coating constituted of homogenous Ti(Al, Si)3 phase was prepared on γ-TiAl alloy using cold spraying Al-40Si (wt.%) alloy coating followed by thermal diffusion treatment. The oxidation behavior of the diffusion coating was tested for 300 h at high temperatures of 900, 950 and 1000 °C. The differences in microstructure evolution at three different temperatures, as well as antioxidant properties of the coating, were investigated. The results showed that the weight gain of the coating after 300-h oxidation at 900, 950 and 1000 °C was sharply reduced to only 1.195, 1.550 and 1.925 mg cm−2, respectively. Although the alumina-based oxide scale formed on the coating became thicker with the increasing oxidation temperature, it had a good adherence to the coating even at 1000 °C. Thus, the coating can significantly improve the oxidation resistance of the γ-TiAl alloy at three temperatures because the generated oxide scale can act as a barrier to prevent the outward diffusion of Ti and the internal diffusion of O. The degradation rate of the coating also increased with the increasing oxidation temperature. Following 300 h of oxidation test at 1000 °C, the homogenous Ti(Al, Si)3 phase in the coating almost entirely degraded. However, the in situ formed Ti5Si3 diffusion layer maintained a good stability at 1000 °C, which can block the further invasion of O to a certain extent. [ABSTRACT FROM AUTHOR]

There are some important advantages presented by metal specimens coated with WIP-C1 (Ni/CrC)-type materials. However, given the coating methods and the stress under dynamic loads, there are issues that need to be taken into account, particularly in terms of the behavior at the interface between the two materials. Using standardized cylindrical 1018 steel specimens uniformly coated with WIP-C1 (Ni/CrC) by cold spraying, this study investigated the fatigue behavior of the specimen as a whole, focusing on the interface areas of the two materials. The fatigue life diagram is given, to a large extent, by the behavior of the base material. As a result, in this work, we have focused not so much on the fatigue behavior of the assembly as on the integrity of the coating material and the defects, failures, etc., that may occur at the interface after a certain number of cycles. The applied load was cyclic fatigue through alternating–symmetric cycles. Scanning optical microscopy was used to observe plastic deformations and crack propagation during the breakage process. It was found that both the base material zone and the cover material zone presented good performance when the maximum stresses were at low values. A fatigue durability curve was also plotted, showing a conventional appearance for a metallic material, slightly influenced by the destruction of the base material interface. At higher maximum stress and, consequently, to large strains, a series of destructions at the interface of the two materials, of different types, were observed and will be highlighted in the paper. [ABSTRACT FROM AUTHOR]

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In dye-sensitized solar cells (DSSCs), the counter electrode (CE) plays a crucial role as an electron transfer agent and regenerator of the redox couple. Unlike conventional CEs that are generally made of glass-based substrates (e.g., FTO/glass), polymer substrates appear to be emerging candidates, owing to their intrinsic properties of lightweight, high durability, and low cost. Despite great promise, current manufacturing methods of CEs on polymeric substrates suffer from serious limitations, including low conductivity, scalability, process complexity, and the need for dedicated vacuum equipment. In the present study, we employ and evaluate a fully additive manufacturing route that can enable the fabrication of CEs for DSSCs in a high-throughput and eco-friendly manner with improved performance. The proposed approach sequentially comprises: (1) material extrusion 3-D printing of polymer substrate; (2) conductive surface metallization through cold spray particle deposition; and (3) over-coating of a thin-layer catalyzer with a graphite pencil. The fabricated electrodes are characterized in terms of microstructure, electrical conductivity, and photo-conversion efficiency. Owing to its promising electrical conductivity (8.5 × 104 S·m−1) and micro-rough surface structure (Ra ≈ 6.32 µm), the DSSCs with the additively manufactured CEs led to ≈2.5-times-higher photo-conversion efficiency than that of traditional CEs made of FTO/glass. The results of the study suggest that the proposed additive manufacturing approach can advance the field of DSSCs by addressing the limitations of conventional CE manufacturing platforms. [ABSTRACT FROM AUTHOR]

Gas-atomization is extensively used to produce metallic feedstock powders for additive manufacturing processes, including gas dynamic cold spray processing. This work explores the potential utility of on-demand recycled titanium scrap feedstock powder as a viable substitute for virgin powder sources. Three recycled titanium powders were atomized from different battlefield scrap sources using a mobile foundry developed by MolyWorks Materials Corporation. Recycled titanium alloy powders were compared against virgin Ti-6Al-4V powder to verify there were no significant variations between the recycled and virgin materials. Powder characterization methods included chemical analysis, particle size distribution analysis, scanning electron microscopy (SEM), Karl Fischer (KF) titration moisture content analysis, X-ray diffraction (XRD) phase analysis, microparticle compression testing (MCT), and nanoindentation. Results indicate that recycled titanium powder provides a viable alternative to virgin titanium alloy powders without compromising mechanical capabilities, microstructural features, or ASTM-specified composition and impurity standards. The results of this work will be used to aid future research efforts that will focus on optimizing cold spray parameters to maximize coating density, mechanical strength, and hardness of recycled titanium feedstock powders. "Cold spray" presents opportunities to enhance the sustainability of titanium component production through the utilization of recycled feedstock powder, mitigating issues of long lead times and high waste associated with the use of conventional virgin feedstock. [ABSTRACT FROM AUTHOR]

High-strength, high-conductivity copper/silver-alloyed materials were prepared by cold-spray (CS) manufacturing. For DC high-field application at room temperature, bulk Cu/Ag (5% vol. Ag) alloys with high mechanical properties and high electrical conductivity can be obtained by CS and post-heat treatments. For pulsed-field application at liquid nitrogen temperature, bulk Cu/Ag (5% vol. Ag) alloys serve as precursors for room-temperature wire drawing. The Cu/Ag-alloyed bulk CS deposit presents a high yield strength of about 510 MPa with a corresponding electrical resistivity of 1.92 µΩ·cm (at 293 K). The Cu/Ag-alloyed wires show a very high ultimate tensile strength (1660 MPa at 77 K or 1370 MPa at 293 K) and low electrical resistivity (1.05 µΩ·cm at 77 K or 2.56 µΩ·cm at 293 K). Microstructural studies via STEM allow us to understand this very high level of mechanical strength. The results evidence that materials developed by CS exhibit very high mechanical properties compared to materials prepared by other routes, due to the high velocity of the deposited particles, which leads to high initial deformation rates and specific microstructural features. [ABSTRACT FROM AUTHOR]

For high-level radioactive waste, the French National Radioactive Waste Management Agency is currently developing a 500 m deep geological disposal facility called Cigéo. Carbon steel containers will be used to contain the wastes in the specific conditions of the disposal. The use of a sacrificial coating was studied as an additional protection for the containers against corrosion. A previous work had shown the possibility to use Zn-Al coatings in this specific medium. To optimize the coatings' performance, the cold-spraying process was considered instead of the previously used wire arc spraying because it can increase the cohesion between the particles in the coating. Moreover, three aluminum contents, i.e., 5, 15 and 25 wt.%, were considered. The characterization of the obtained coatings revealed a strongly heterogeneous composition for the lower Al content (5 wt.%), with local Al contents from 1.3 wt.% Al to 44.5 wt.% Al. The corrosion study was carried out in a specific solution mimicking the pore solution of the surrounding cementitious material designed for disposal at a temperature of 50 °C. First, the polarization curves acquired with coated steel electrodes revealed the pseudo-passive behavior of the 25 wt.% Al coating, while for the other compositions, the coating remained active. Moreover, the higher aluminum content (25 wt.%) induced an important decrease in potential, with a possible risk of hydrogen embrittlement for the protected steel. Secondly, the sacrificial properties were investigated through 6 months of experiments using coated electrodes with cross-like defects and coated electrodes coupled with bare steel electrodes. Whatever the composition of the coating, the protection was maintained, with the 15 wt.% Al coating giving the best performance. [ABSTRACT FROM AUTHOR]

Cold spray (CS) is a new kind of coating that has many potential uses, including functionalizing surfaces, doing localized repairs, and mass production. Its fast deposition rate and diverse feedstocks have led to its growing popularity as an additive manufacturing method, which has been driven by improvements in lateral resolution. CS materials have several uses in the transportation industry, and some of the most frequent ones include nickel super-alloys, titanium alloys, copper, aluminum and metal-ceramic composites. Nevertheless, the mechanical properties depend upon number of parameters involved during spraying process. Therefore, there is an immediate need for researchers and businesses to understand the various parameters affecting the adhesion strength of CS deposits. The current research presents an analysis of the adhesion behavior of coatings that have been deposited by CS methodology.

Spraying technical parameters are important factors that affect spraying efficiency. Most studies on spraying technical parameters use single-factor methods to study the speed of spray particles, and few scholars have studied the joint influence of multiple factors. This article uses gas temperature, particle size, and gas pressure as independent variables, and the independent variables interact. The design-expert method was used to establish a linear regression equation model of the velocity of sprayed Al and Cu particles at the Laval exit and the velocity before deposition with the substrate, and the response surface analysis method was used to predict the optimal spraying parameters of Al and Cu particles. The study found the contribution rate of three factors to particle velocity: the prediction of particle velocity at the exit of the Laval nozzle and before deposition with the substrate was realized; the error between the predicted value of particle velocity and the actual value obtained by simulation is less than 1.6 %, indicating that the speed linear regression equation established is effective and reliable in predicting the simulation results; the optimal spraying parameters and particle speeds of Al and Cu particles were obtained through response surface analysis.

Along with corrosion, erosion is one of the main causes of damage to civil infrastructures. The continuous impact of fine particles carried by the air produces a deterioration in the elements of these structures. When this damage is significant, these elements are replaced by new ones. In this work, the possibility of extending the useful life of these components by spraying coatings on the damaged areas is proposed. In this sense, repair techniques such as cold spray deposition are possibilities for this purpose. Therefore, this study focuses on evaluating the erosion behaviour of stainless-steel coatings deposited on structural steel. In addition, the erosion results have been correlated with the model proposed by Hutchings, and an energetic interpretation of the erosion process through this model has been proposed. To carry out this study, stainless steel coatings have been deposited on carbon steel substrates to improve their resistance to corrosion. Different spraying temperatures, from 800 °C to 1100 °C, combined with different pressures of the carrier gas, from 40 to 70 bar, have been analysed. The elastic moduli of the coatings, and their stress-strain curve, have been determined by depth sensing indentation tests with Berkovich and spherical tips, respectively. Erosion tests with normal incidence have been programmed to obtain the corresponding erosion rates. From the results of this work, the optimal projection conditions of stainless steel on carbon steel substrates for the repair of civil infrastructures subjected to erosion processes could be identified.

A numerical study was performed to analyze the particle deposition of a cold spray process for the preparation of nickel electrocatalysts used in the Hydrogen Evolution Reaction (HER). The study focused on the creation of fin-shaped geometries with an optimal porosity on the electrode surface using a mask located between the nozzle exit and the substrate. Computational Fluid Dynamics (CFD) was performed on a three-dimensional high-pressure nozzle, with nickel powder used as the injection feedstock. The behavior of particles was effectively modeled through a two-way coupled Eulerian–Lagrangian approach. As per the parametric study, four masks of varying wire thicknesses and opening sizes were investigated. The masks were placed at 4 mm increments from the nozzle exit, with the substrate placed at standoff distances (SODs) of 10 mm and 20 mm. To capture the effects of the gas inlet operating conditions, two different nozzle inlet conditions were analyzed (2 MPa and 400 °C, 4 MPa and 800 °C). It was found that the nozzle inlet operating condition had the most significant impact, as it relates to the particle velocity and powder deposition. The high-pressure operating condition resulted in a deposition efficiency (DE) greater than 99.9% for all the test cases, with nearly all the impacted particles depositing on the substrate. For the medium-pressure operating condition, the DE increased linearly as the mask SOD was increased, due to the increase in the particle velocity upon impact.

Chromium carbide powder agglomerated with nickel/chrome was deposited using a cold spray process onto a mild steel substrate. The deposits were heat-treated at 650 °C and 950 °C in ambient conditions to reduce porosity and improve adhesion between powder particles. The corrosion behaviour of these cold-sprayed materials was studied in artificial seawater conditions using electrochemical techniques. Heat treatment at 650 °C was found to best improve corrosion resistance, while the 950 °C treatment performed better than the as-sprayed condition but lower than the 650 °C sample. Microstructural analysis revealed complex phase transformations and structural refinements with increasing heat treatment temperature. The crystallite size of both Cr3C2 and NiCr phases decreased, while microstrain and dislocation density increased due to heat treatment. The formation of and subsequent reduction in Cr23C6 content indicated a complex sequence of carbide dissolution, transformation, and precipitation processes. The 650 °C heat-treated sample demonstrated superior corrosion resistance, evidenced by the highest corrosion potential, lowest passive current, and largest charge transfer resistance. This enhanced performance was attributed to the formation of a more stable and protective passive film, optimal carbide dissolution, and a homogeneous microstructure. Meanwhile, the 950 °C treatment led to excessive carbide dissolution and formed increased interfaces between the carbide and matrix. Mechanical property changes were also observed, with carbide hardness significantly decreasing after corrosion testing. These findings highlight the critical role of controlled heat treatment in optimising the performance of cold-sprayed Cr3C2-NiCr coatings, demonstrating that achieving superior corrosion resistance requires a delicate balance between microstructural refinement, phase transformations, and preservation of coating integrity.

In electromagnetic launching systems, arc erosion of rail material, such as Al2O3 dispersion-strengthened copper (ODS-Cu), remains a critical unresolved issue. Here, we report a cold-sprayed CuCrZr–W coating on ODS-Cu exhibiting enhanced arc erosion resistance. The coating was fabricated using a bimodal powder mixture comprising coarse CuCrZr and fine W particles, resulting in a dense structure with an embedded networks of fine W particles along intersplat boundaries. Compared to the ODS-Cu substrate, the CuCrZr–W coating displays superior arc erosion resistance, as evidenced by the reduced arc erosion area and depth, shorter arc duration, lower wielding force, and limited molten Al adhesion during arcing tests. The enhanced performance is attributed to a high density of W/CuCrZr interfaces that effectively disperse arcs, the W particle network that alters the flow path of molten Cu, lowering splashing and evaporation. This work provides valuable insights into developing high-performance, arc erosion-resistant coatings for applications where safeguarding against arc erosion is paramount.