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Cold spray is a rapidly developing solid-state deposition technology in recent years. It has the characteristics of low spraying temperature and high velocity of spraying particles, hence showing a good prospect for preparing metal matrix composite (MMC) coatings and bulk materials. In particular, aluminum matrix composites have received great attention in electronics, aerospace and automobile industries due to their excellent physical and mechanical properties. In this paper, the research progress of cold-sprayed aluminum matrix composite coatings and materials was systematically introduced. Firstly, state of the art on cold sprayed coatings and materials with different reinforcing phases was presented. Then, research progress on different post-spray treatments, to improve the properties of as-sprayed deposit, was briefly discussed. Finally, the application fields and problems of cold-sprayed aluminum matrix composite coatings and materials were summarized. [ABSTRACT FROM AUTHOR]

The cold spray (CS) process is the latest solid-state deposition method that has gained significant awareness for the metallization of polymer matrix composites (PMCs) materials to modify their surface properties, including electrical or thermal conductivity and electromagnetic shielding. In comparison with other coating processes, CS allows for the production of metallic coatings without the necessity to reach the melting temperature of the sprayed particles and provides a way to deposit resistant materials with improved properties onto various components to minimize wear, erosion and corrosion. For the first time in the literature, this work has the innovative goal of applying the life cycle assessment methodology to the case study of the CS production process in order to ascertain whether CS could be framed in the realm of green technologies offering interesting opportunities to improve manufacturing sustainability. In particular, the environmental impact of CS associated with the metallization process of PMCs was considered in terms of energy consumption and CO2, NOx and SO2 emissions, which are used as indicators in the life cycle assessment. When compared to different coating processes, the results suggest that CS has a large potential to reduce the environmental effects connected with the products in terms of the amount of CO2 and hazardous emissions created throughout the process. [ABSTRACT FROM AUTHOR]

The production of Inconel 718 coatings using the cold spray process is often challenging due to the limited plastic deformation of particles upon impact associated with its mechanical properties. This leads to the requirement of high spray parameters to achieve dense coating build-up that may result in high and complex residual stresses that can also affect negatively the substrate and lead to nozzle clogging. In this work, the role of the coating and particle impact temperatures is investigated while ensuring they are decoupled from the particle impact velocity. This allows starting to explore potential ways to produce a sound and quality Inconel 718 coating at reduced spray parameters. To decouple and evaluate the role of the particle impact temperature, powder preheating units with downstream injection are used to decouple the particle impact temperature from the particle impact velocity. Three initial particle temperatures are studied: 25, 400 and 750 °C. The effect of the coating temperature on the deposition process is investigated by controlling this temperature independently of the gas stagnation temperature through the use of induction heating. Deposition efficiency, porosity, and micro-hardness are used to assess the coating quality. The coating time–temperature history is measured to better understand its influence on the deposition of Inconel 718. In this work, an enhanced understanding of the effect of both particle and coating temperatures on the coating process is obtained, and the findings allow the establishment of a potential approach to produce dense coatings using reduced spray parameters. [ABSTRACT FROM AUTHOR]

Vacuum chambers used in high-energy particle accelerator experiments are conventionally made of bulk beryllium, which shows significant drawbacks due to cost and toxicity. An alternative solution could be to develop chambers made of polymer-based composites. Since these materials exhibit high outgassing not compatible with an ultra-high vacuum environment, a suitable gas-tight coating is required. Cold spray deposition of aluminum can be a solution, provided that the coating behaves as a perfect vacuum barrier. Porosity, especially percolating porous networks, is key to coating gas tightness issues. This work addresses the relationship between porosity and gas-tightness in cold spray coatings. To do so, coatings with different porosity were achieved playing with powder morphology, composition, and process parameters. Their gas tightness was evaluated by helium leak tests. Classical microscopy, being essentially a 2D analysis, is strongly limited when dealing with 3D properties as porosity percolation. For this reason, 3D X-ray microtomography images of coatings were obtained and treated by image analysis methods: pores were compared in terms of size and shape. Overall porosity properties, including percolation and a homogeneity criterion, were also investigated. Percolating porosity was highlighted for several samples which showed poor gas-tightness properties. The permeability of percolating pore structures was then numerically computed by a fast Fourier transform-based method, to quantify the mass flow through the coating. Results of those computations were finally compared to experimental coating leak rate measurements, in an effort to elucidate the link between gas tightness and morphology of the pore space. [ABSTRACT FROM AUTHOR]

Cold spraying is receiving increasing attention as a method for metallizing polymer surfaces. Although metallic coatings on polymer surfaces have been successfully prepared in several studies, these are currently only in the experimental stages. In this study, the impact behaviour of copper particles deposited on polyether ether ketone (PEEK) substrates by cold spraying was investigated, and the deposition mechanism of the coatings was elucidated based on numerical simulations. Computational fluid dynamics simulations were used to determine the impact velocity of the particles, initial temperature of the particles, and surface temperature of the substrates. An Eulerian–Lagrange three-dimensional finite element model was developed to simulate the impact behaviour of single and multiple copper particles on the PEEK substrate. The numerical simulation results showed good agreement with the experimental data reported in the literature. This indicates that the thermal softening and melting of the material provide good conditions for mechanical interlocking of the particles with the substrate. Based on the results, the effects of particle velocity, particle temperature, and substrate temperature on the cold spray deposition behaviour of copper particles on PEEK substrates are discussed. [ABSTRACT FROM AUTHOR]

Increasingly, due to their interesting applications, research on metal/ceramic interfaces created by cold spray is being undertaken. Metal matrix composites and metal coatings on ceramic substrates are two examples with interesting applications for tribology and power electronics among many others. By the cold spray process, adhesion of particle to substrate or particle to particle is achieved by means of high-speed impact while remaining in the solid state. For metal/ceramic interfaces, where the ceramic is not expected to plastically deform, adhesion is poorly understood. Adhesion is considered to be the result of a combination of mechanical interlocking and physicochemical interactions occurring as a result of high-speed impact. The formation of physicochemical interactions and their contribution to adhesion remain of interest to create performant coatings with high adhesion. This review article provides an overview of the current state of knowledge regarding the deposition of metal on ceramic. This review includes a summary of the materials tested, the testing methodology and findings as well as an overview on the effect of deposition parameters on adhesion, the role of jetting in the interface and outlook regarding potential local changes occurring at the interface promoting adhesion. [ABSTRACT FROM AUTHOR]

Cold spraying metallic coatings on ceramics (Ceramics Metallization) are widely concerned in electrical industry due to its high density, low oxidation and high electrical conductivity. However, the bonding reliability of the cold spraying coating on ceramics is usually considered to be poor since the metal particles don't experience melting. In the present work, the bonding quality of a cold spraying copper coating on a thermal sprayed alumina layer was examined. A pure copper coating was successfully deposited on Al2O3 coated Q235 steel substrate by cold spraying at 260 °C and 1.6 MPa using a pure copper powder. The bonding characteristics were studied by analyzing the surface, the cross-sectional microstructure of the coating and its interface after pull-off test. The results indicate that the high bonding quality (ranging from 8.26 MPa to 11.35 MPa) between copper coating and Al2O3 layer attributes to both metallurgical and interlock effect, which is mainly influenced by the hardness of the copper powders instead of Al2O3 surface roughness. The soft character of the pure copper powder makes it ready for deformation, subsequently interlocks with Al2O3, fills into the pores more completely, which increases the bonding quality between the copper coating and the Al2O3 layer. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced plastic (CFRP) is a competitive and promising material that is employed in various industries, including the aerospace industry. Metallized CFRPs and multimaterials based on metals are highly attractive for such applications. In this study, we deposited Sn on an epoxy-based CFRP via cold spraying and investigated the effects of gas temperature on Sn deposition behavior. A continuous Sn coating was successfully obtained on the CFRP at gas temperatures ranging from 473 to 523 K. By contrast, severe erosion of the CFRP substrate occurred at 623 K, making the cold spray coating of Sn difficult. The relationships between the processing temperature, surface topology, and erosion state are examined from the perspective of the CFRP surface temperature. The results indicate that a higher gas temperature leads to a greater surface temperature, resulting in an uneven surface topology with more severe erosion accompanied by a gradual decrease in coating thickness. [ABSTRACT FROM AUTHOR]

The present study compares prerequisites for cavitation-resistant bronzes production by different coating techniques, namely cold spraying, HVOF spraying, warm spraying and arc spraying. If optimized to maximum cavitation resistance, the deposited coatings can increase the service life of ship rudders significantly. Furthermore, these methods could enable repair processes for ship propellers. This study is meant to help selecting the right coating technology to achieve best cavitation protection for a given set of requirements. Using high-pressure warm spraying and cold spraying, properties similar to those of cast nickel aluminum bronze are achieved. Also, coatings produced by using HVOF and arc spraying have erosion rates that are only about four, respectively, three times higher as compared to cast nickel aluminum bronze, while by far outperforming bulk shipbuilding steel. Their properties should be sufficient for longer service life, i.e., less docking events for ship rudder repair. Hence, with respect to costs, HVOF and arc spraying could represent a good compromise to reach the specified coating properties needed in application, potentially even for propeller repair. [ABSTRACT FROM AUTHOR]

Induction heating cold spray has recently been proposed as a new hybrid additive manufacturing technique and a possible solution to avoid the delamination of soft material coatings from hard substrates. This process relies on the combined contributions of substrate preheating and in situ coating heating as a result of the alternating electromagnetic field applied that generates eddy currents. However, fundamental studies at the micron-scale explaining the role of substrate preheating on the adhesion strength of the soft/hard (particle/substrate) material combination are scarce. Therefore, this study focuses on investigating the role of substrate preheating in induction heating cold spray on bond formation and adhesion strength at the individual particle level by removing sprayed single soft particles (pure aluminum) from hard substrates (Ti-6Al-4V) using the splat adhesion test. Substrate preheating improved the splat adhesion strength by 30% and the bonded area sixfold. In addition, due to an increase in the splat adhesion energy, the failure mode changed from brittle to a more ductile type of failure when the initial substrate surface temperature was increased from 25 to 600 °C. These results are attributed to a combined effect of a more effective oxide removal on the substrate surface due to enhanced localized deformation, and a local heat treatment process in the vicinity of the particle/substrate interface that induces recovery, and, possibly, static recrystallization. [ABSTRACT FROM AUTHOR]

Thermite materials, which are a pyrotechnic composition of metal and metal oxide, can create bursts of heat and high temperature thanks to an exothermic reduction–oxidation reaction. Fabrication methods of bulk thermite materials should preserve the reactivity of the materials and ensure a sufficient mixing of components. This work investigated the use of kinetic spraying and ball milling to overcome the limitations of existing preparation methods. Aluminum–molybdenum trioxide (Al-MoO3) was selected as thermite material. Ball milling and the fractions of metal and oxide were chosen as the variables of the study. The mechanical properties and reactivity of various powders and coatings were evaluated. The milled powders and coatings were successfully fabricated without reactivity loss by properly controlling the process parameters. The bond strength of the Al-MoO3 coating was however weaker than that of a pure Al coating because the MoO3 powder interrupted the intimate bonding between the Al splats. A reactivity analysis demonstrated that ball milling improved the reactivity of both the powders and the coatings by increasing the exothermic value, decreasing the reaction onset temperature, and decreasing the activation energy required for the thermite reaction. The mechanical properties and reactivity of coatings did not vary significantly with the MoO3 fraction. [ABSTRACT FROM AUTHOR]

Polymer coating by cold spray presents interesting features such as the possibility of protecting metallic substrates or adding functionalities to a structure. However, it is characterized by a low deposition efficiency and a weak interface between the substrate and the coating. In this study, we performed fluoropolymer coatings by the cold-spray process. Analysis of the particle deposition during cold spray highlighted the importance of the particle size, substrate temperature and inlet gas temperature and pressure on the adhesion polymer/substrate. The addition of hydrophobized fumed nano-ceramics (FNC) to the polymer feedstock enhances the deposition efficiency and polymer adhesion on the substrate. The addition of fumed nano-alumina (FNA) to the polymer feedstock tends to give better results than fumed nano-silica in terms of deposition efficiency thanks to (1) the difference in surface charge leading to the attractive force between the polymer and the FNA during the powder preparation stage and (2) a homogeneous repartition of the FNA on the polymer particle surface. In addition, the hydrophobization of the FNC maintains and enhances the hydrophobicity and water repellency properties of the fluoropolymer coating. [ABSTRACT FROM AUTHOR]

Cold spray (CS) has been proven a promising manufacturing process for the MCrAlY coatings deposition. In this study, NiCoCrAlTaY coatings were deposited on single-crystal nickel-based superalloy (CMSX-4) substrates using the CS technique. Nitrogen and moderate spray parameters were used, and the resulting MCrAlY coatings were compared to coatings sprayed using helium under similar spray conditions. It was found that, contrary to general expectation, favorable coating characteristics were achieved when nitrogen was used. This is attributed to low deposition efficiency under the studied spray conditions, resulting in significant particle impingement that promotes overall particle deformation in the coatings sprayed using nitrogen. However, low deposition efficiency may lead to elevated process cost, despite great gas cost savings by using nitrogen, due to significant increases in powder waste and cost. As such, recycling of the non-deposited powder was explored in an aim to reduce powder cost when using nitrogen. A general cost model that considers the benefits of powder recycling was proposed for the CS process. It was demonstrated that the use of nitrogen and powder recycling can be economical over CS using helium, while producing MCrAlY coatings with desirable properties that are potentially beneficial to the oxidation performance of the coatings. [ABSTRACT FROM AUTHOR]

Two kinds of composite coatings, Zn 4 5 Al 3 5 Mg5ZnO 1 5 and Zn 6 5 Al 1 5 Mg5ZnO 1 5 , were prepared on steel matrix (Q235) by cold spraying. The Zn, Al, Mg, and ZnO in raw materials were calculated by percentage of mass. The morphology of the original coating was observed by scanning electron microscopy (SEM) and characterized by energy dispersive spectroscopy (EDS). It was found that the microstructures of Zn 4 5 Al 3 5 Mg5ZnO 1 5 and Zn 6 5 Al 1 5 Mg5ZnO 1 5 composite coatings prepared by cold spraying were compact without oxidation products, and the plastic deformation of powder particles was significant. The friction and wear test data of the two coatings showed that the Zn 4 5 Al 3 5 Mg5ZnO 1 5 coating had longer-lasting protective properties and wear resistance under the same conditions. Neutral salt spray test (NSS) and electrochemical accelerated corrosion test were carried out on samples at different time periods. The results of samples' corrosion microstructure and electrochemical curves showed that Zn 4 5 Al 3 5 Mg5ZnO 1 5 and Zn 6 5 Al 1 5 Mg5ZnO 1 5 have good electrochemical protection performance, and Zn 4 5 Al 3 5 Mg5ZnO 1 5 coating has better protection effect. [ABSTRACT FROM AUTHOR]

A methodical procedure for designing molds for cold spray additive manufacturing has been developed and validated. In a preliminary trial, a cold-sprayed part was shown to deform beyond the spatial tolerances of its defined shape. Based on these data and utilizing a linear elastic model of deformation, a new "compensated" mold with a modified shape was generated. The shape of the part deposited onto the compensated mold was measured to have, at maximum, approximately half the error as in the original trial, demonstrating the potential of such mold compensation as a means of achieving the final dimensional accuracy requirements of cold-sprayed parts. [ABSTRACT FROM AUTHOR]

This paper examines the residual stresses generated by laser-assisted cold spray deposition of an iron-based oxide dispersion strengthened alloy (Fe91Ni8Zr1 at.%) on an AISI 1018 mild steel substrate, as well as studies of the effect of the laser heating on the substrate alone. The in-plane residual stress values were determined by X-ray diffraction-based measurements. In the top section of the layers, established at a raster deposition rate of 25 mm/s and simultaneous surface heating temperatures of 650 and 950 °C, stresses were compressive ranging from − 170 to − 440 MPa. For the substrate only study, a larger span of surface temperatures from 350 to 950 °C and scan rates of 5 and 25 mm/s were investigated. Here, the stresses in the laser tracks were tensile, of the order of + 400 MPa, with both "W''- and "M"- shaped profiles about the laser centerline. It was found that the stress profile shape was influenced by the Gaussian power distribution across the laser spot diameter which correlated with microstructural changes (martensite formation) in the substrate. [ABSTRACT FROM AUTHOR]

In cold spray, high gas temperatures and high velocity impact of particles introduce complex thermal and stress histories in the coating layers and the substrate. It is crucial to understand the interplay between temperature evolution and residual stress development as the residual stresses could potentially cause distortion and/or delamination. In this study, a system-level cold-spray deposition model is developed. The model includes a moving heat source, material addition and thermo-mechanical stress analyses. The heat source model is first validated by qualitatively comparing the thermal history with experimental measurements from literature. The system-level model is then used to calculate the residual stresses and distortion in the cold-sprayed Cu/steel system. The influence of the spray path on the residual stress development is systematically analyzed. The corresponding interface residual stress states are also examined for the different spray paths. Simulation results indicate that the thermo-mechanical analysis using the developed system-level model can provide an effective way to assist in optimizing the cold-spray coating deposition strategy and improve the coating performance. [ABSTRACT FROM AUTHOR]

In cold spray additive manufacturing (CSAM), the severe plastic deformation of the input powder particles leads to an accumulation of residual stresses, the magnitude of which is affected by process conditions. In the current study, the effects of traverse speed and powder feed rate on the residual stress state were investigated in commercially pure titanium cylinders produced by CSAM. Residual stress measurements were made in a grid pattern covering the 2D cross section using the KOWARI neutron diffractometer at ANSTO, Australia, and selected results were validated using the contour method. It was found that the thermal effect was dominant on the residual stress state generating a tensile state near the inner and outer surfaces of the cylinder walls while compressive residual stresses tend to accumulate in the center of the wall. The residual stresses were dominated by thermal stresses at low traverse speed, while peening becomes more critical at high traverse speeds. Increasing the powder feed rate increased the magnitude of the residual stresses. High traverse speeds and low feed rates are beneficial for producing 3D parts by CSAM. However, slow traverse speeds are more detrimental than high feed rates for a given layer thickness. [ABSTRACT FROM AUTHOR]

Cold spray has been developed recently to be used as an additive manufacturing technology in order to fabricate bulk components. Residual stresses are known to build up in coatings made by cold spray; therefore, cold spray additive manufacturing (CSAM) is also expected to generate residual stress in bulk parts and components, and that residual stress can lead to shape distortions or component cracking. The residual stress analysis has been applied to some generic sample shapes, a thick patch deposit and a vertical wall, produced by CSAM out of Ti powder. The residual stress mapping has been achieved using neutron diffraction technique and analyzed within a modeling approach. The analysis allowed it to be determined as to what were the major contributions into the overall stress field and to establish the main sources of the residual stress, providing an analytical tool for prediction of the residual stress buildup in more complex shapes. [ABSTRACT FROM AUTHOR]

This paper examines the residual stresses generated by laser-assisted cold spray deposition of an iron-based oxide dispersion strengthened alloy (Fe91Ni8Zr1 at.%) on an AISI 1018 mild steel substrate, as well as studies of the effect of the laser heating on the substrate alone. The in-plane residual stress values were determined by X-ray diffraction-based measurements. In the top section of the layers, established at a raster deposition rate of 25 mm/s and simultaneous surface heating temperatures of 650 and 950 °C, stresses were compressive ranging from − 170 to − 440 MPa. For the substrate only study, a larger span of surface temperatures from 350 to 950 °C and scan rates of 5 and 25 mm/s were investigated. Here, the stresses in the laser tracks were tensile, of the order of + 400 MPa, with both "W''- and "M"- shaped profiles about the laser centerline. It was found that the stress profile shape was influenced by the Gaussian power distribution across the laser spot diameter which correlated with microstructural changes (martensite formation) in the substrate. [ABSTRACT FROM AUTHOR]

Delamination of soft and ductile materials from hard substrates is a challenge when using the cold spray process. Additionally, the as-sprayed coatings often exhibit a significant reduction in ductility and a brittle behavior upon fracture. As a potential solution to these problems, a tunable hybrid additive manufacturing process was developed by coupling induction heating and the cold spray process. Pure aluminum was used as the soft feedstock powder, while Ti-6Al-4V was used as the hard substrate. In situ induction heating and substrate preheating temperature effects on the coating's properties were evaluated: micro-hardness, adhesion and tensile strength were assessed and compared to traditional cold spray coating's properties. A reduction of up to 20% was found in the coating's micro-hardness produced by the hybrid process. Additionally, the adhesion strength was drastically increased when using the hybrid process while tensile strength reached almost 3 times the total elongation of the specimens produced using the traditional cold spray process. These results open up the possibility of using this hybrid technique as an additive manufacturing process for bulk parts and coating production. [ABSTRACT FROM AUTHOR]

The prevention of delamination of soft and ductile materials from hard substrates is a challenge when using the cold spray process. As a potential solution to this issue, a tunable hybrid additive manufacturing process was developed by coupling induction heating and cold spray processes. Pure aluminum was used as the soft feedstock powder, while Ti-6Al-4V was used for the hard substrate. The effects of induction heating and of the substrate initial temperature on the deposition process were evaluated. Single-particle impact tests suggested metallic bond formation at the particle/substrate region as the bonding mechanism. Deposition efficiency, coating thickness and porosity levels were evaluated to characterize the induction heating and initial substrate temperature effects. The deposition efficiency and the coating thickness were doubled with the hybrid additive manufacturing process compared to the traditional cold spray process. Moreover, the presence of eddy currents in the coating (in situ induction heating of the coating) was confirmed by an electromagnetic analysis which modeled the interaction between the coating and the electromagnetic field. Findings demonstrated that substrate preheating has little influence on the overall deposition process and coating quality compared to in situ induction heating effects. [ABSTRACT FROM AUTHOR]

The cold spray (CS) process is unique due to its high strain rate deformation and particle deposition in solid state. In situ investigation of this process is challenging. Therefore, numerical methods have been used to simulate this process and provide a better ground for furthering the understanding of the process physics. Metallurgical bonding occurs during the deformation process at the particle/substrate interface during coating build-up. Up to now, several studies have been performed to predict the material behavior during this process. Although several studies have been done to predict the bonding in CS, none of them was able to show the occurrence of localized metallurgical bonding. In this study, a novel modeling method is proposed to predict the occurrence and strength of localized metallurgical bonds in the CS process through finite element method. The process physics and implementation method are explained in details. Critical velocities of aluminum, copper, and nickel were predicted and compared with experimental data to validate the method. In addition, the proposed method is able to show the localized metallurgical bonding at the interface between particle and substrate. Comparison between the predicted bonding area with the proposed method and experimental data from the literature showed good agreement. [ABSTRACT FROM AUTHOR]

Cold spraying is a new additive manufacturing method capable of producing titanium alloy parts at a high production rate under ambient conditions. In this work, encapsulated hot isostatic pressing (HIP) was applied to reduce the porosity and improve the mechanical properties of cold-sprayed Ti6Al4V deposits. Encapsulated HIP at 110 MPa and 1173 K was found to significantly change the microstructure of the deposits owing to enhanced diffusion and material recrystallization. The total porosity decreased from 7.5 to 0.2%. The measured ultimate tensile strengths of the as-built and HIP-treated samples were ~ 70 and ~ 950 MPa, respectively. The elongation at break also increased, from less than 1% to ~ 13%. [ABSTRACT FROM AUTHOR]

Cold spray process principles allow the production of near-net-shape metal parts with a fast layer deposition by using 3D printing techniques via supersonic 3D deposition (SP3D). This innovative additive manufacturing process allows an easy and quick production of copper and aluminium parts with future possibilities to expand materials and alloys. The speed and materials enable the application of this cold spray based 3D printing process for the production of tools. In this paper, Electrical Discharge Machining (EDM) electrodes were fabricated by using SP3D to investigate its application in tool production. Requirements for the materials of electrodes and some existing solutions for the production of EDM electrodes with additive manufacturing methods are described first. The fabrication and experimental results are then presented for 3D printed copper EDM electrodes that were tested by using St 37-2 (DIN 17100) steel as the workpiece. [ABSTRACT FROM AUTHOR]

In this study, Fe and 316L powders with two different particle sizes were used as the feedstock. They were also premixed using different mixing ratios and combinations: (i) either 316L or Fe powder with large particles blended with small ones and (ii) a blend of 316L and Fe powder using three particle size combinations. Both single-component and mixed powders were deposited by cold spray, and the deposition efficiencies (DEs) were calculated and discussed. The results show that the DE of a mixture of large and small particles of the same powder follows the Rule of Mixtures, whereas the variation of the DE of the 316L and Fe mixture depends on the particle size combinations; specifically, mixtures with smaller-sized particles show better DEs than the respective Fe powder. The difference in the DEs of different Fe/316L mixtures can be explained by the particle–particle interactions (i.e., tamping and retention) upon impact. In addition, a relationship between the average particle size and density is proposed to determine the occurrence of particle–particle interactions in cold spray of mixed generic powders. The industrial significance of the knowledge of particle–particle interactions is finally explained in the context of the fabrications of metal matrix composites. [ABSTRACT FROM AUTHOR]

This work examines the fatigue behaviour of additive cold spray (CS) repairs of AA7075 and AA2024 fastener holes. Structural ring repairs around fastener holes were made by machining blend‐outs ranging from 1/8 to 1/2 the thickness of the plate, then refilling the section of removed material with CS deposition. The repairs were then tested in a lap shear geometry with the repair on both the free (outside) and the mating (inside) surfaces, as well as in remote uniaxial tension. CS repairs for the inside lap shear AA7075 repair configuration and the outside lap shear AA2024 repair configuration were found to have significantly increased fatigue lives even exceeding the number of cycles to failure of the undamaged, unrepaired control plates. Further, none of the CS repairs caused any detrimental impact on fatigue life, and microhardness results indicate that no thermal damage to the substrate occurred. Some interface cracking was seen in the CS repairs; however, no separation of the repair from the substrate was observed. [ABSTRACT FROM AUTHOR]

Single-component tin coatings have successfully been cold sprayed onto carbon fiber reinforced polymers in previous studies at McGill University. Coatings with mixed metal powders were also sprayed to improve the deposition efficiency and coating conductivity. The results indicated a noticeable improvement in deposition efficiency related to the addition of a secondary metallic powder (aluminum, copper and zinc); this study is focused on the effect of aluminum. Following cold spray of various Sn/Al mixtures over a wide range of gas pressures, unusual coating morphologies were observed. The study of these morphologies leads to the description of two distinct deposition phases depending on the spray pressure: a direct deposition effect and an indirect deposition effect. The presence of submicron particles also supports the occurrence of a powder melting phenomenon during the process. Numerical simulations were conducted to support the description of these phenomena. [ABSTRACT FROM AUTHOR]

The cold spray process can be used to form three-dimensional objects following the layer-by-layer approach which is called cold gas dynamic manufacturing or cold spray additive manufacturing (CSAM). In this study, a three-dimensional simulation of CSAM for a high-pressure nozzle with axial powder injection is investigated. During the manufacturing of a desirable object by CSAM, formation of the sharp edges, inclined surfaces, stagnation points, and corners will inevitably influence the trajectories of the particles. This leads to dispersion and lack of particle deposition in these areas which can eventually reduce the precision and efficiency of the deposition process. Three different objects of a cylinder and two frustums with different angles have been numerically simulated on a substrate to represent typical additively manufactured parts. Particle trajectories and impact conditions, i.e., size and velocity distributions, with and without these objects, have been compared. The results of numerical modeling provided useful information for understanding the limitations and challenges associated with CSAM, which can help us to improve the quality and precision of particle deposition. [ABSTRACT FROM AUTHOR]

Cold Spray (CS) technology enables structural reinforcement, coating and repairing of metal-based components. The deposition occurs by the impact of small particles accelerated at supersonic velocity on the deposition surface. While processing stainless steel material the CS must be run in high-pressure conditions, thus making any in-situ repairing prohibitive and risky. This paper presents a novel CS deposition method to coat stainless steel with a compact and transportable system infrastructure. The final part of the paper shows the advantages of the proposed CS deposition system against existing methods, in relation to industrial coating applications. [ABSTRACT FROM AUTHOR]

With the global trend towards electrification of transport, the interest for various configurations of electric motors is growing. Unfortunately, the low versatility of the motor magnet fabrication technologies limits the development of new motor geometries. Cold spray additive manufacturing was used for shaping permanent magnets for the direct fabrication of electric motor parts without the need for additional assembly steps. This novel technique allows an increase in the design flexibility of electrical machine geometries targeting improved performance. The permanent magnets were deposited from a NdFeB-Al composite powder mix featuring high raw theoretical remanence and coercivity. The role of the process parameters such as powder mix composition, binder granulometry and gas temperature on the magnetic volume fraction and the resulting magnetic properties will be investigated and compared with data from the literature. The use of complex robot toolpath programming necessary to spray on motor parts will be illustrated through an example of the fabrication of a complex shape rotor. The obtained magnetic properties demonstrate the feasibility of using cold spray additive manufacturing as an effective technology to fabricate motor parts without additional assembly steps. [ABSTRACT FROM AUTHOR]

The feasibility of depositing aluminum onto thermoplastic substrates via cold spray (CS) was investigated. Dense coatings of 7075 Al and CP Al (commercial purity) were achieved on three substrates—polyetheretherketone (PEEK), polyetherimide (PEI), and acrylonitrile butadiene styrene (ABS) using an iterative optimization process. 7075 Al deposition yielded low deposition efficiencies (DEs) and low thicknesses but high adhesive strengths, while CP Al deposition led to high DEs and thicknesses but relatively low adhesive strengths. PEEK and PEI were more suitable substrates for cold spray than ABS, which suffered from surface erosion and substrate distortion. Two key factors were identified that influenced the DE and adhesive strength of the coating. The first factor was the bond layer, the initial few particle layers that fused with the substrate to allow subsequent buildup. The bond layer was influenced by the substrate hardness, yield strength, glass transition temperature, and impact strength, as well as the differences in thermal expansion coefficients of Al and the polymer substrates. The second factor was the CS process parameters selected, as the bond layer and the build-up layers may require different process conditions in order to optimize both bonding strength and coating strength, respectively. [ABSTRACT FROM AUTHOR]

The impact of porous WC-12wt%Co and WC-17wt%Co particles onto homologous, smooth surfaces is simulated through a coupled Eulerian-Lagrangian, three-dimensional finite element model, in order to study the build-up mechanisms of cold sprayed WC-Co coatings. Deformation of hardmetal particles upon impact involves compaction and spreading of a rim, whose bottom face experiences heating, close to or even above the melting point of the matrix, and develops large equivalent plastic strain. The rim therefore adheres strongly to the underlying hardmetal. SEM observations of cold sprayed WC-Co particles deposited onto a smooth hardmetal surface show metallurgic bonding of the heated matrix and mechanical fixation as WC grains from the particle indent and penetrate into the underlying material. Little deformation and heating are instead seen in the middle of the contact surface, where adhesion is limited. Deformation of the particle requires the criterion for ductile failure of the hardmetal to be exceeded. This means the deformed rim is also extensively failed and ejects fragments as it spreads. Increasing the momentum of the particle enhances the spreading of the rim and promotes its bonding to the underlying surface, but also causes ejection of larger fragments, as well as the elastic storage of a greater amount of rebound energy, which can result in eventual rebounding of the entire particle or its poorly bonded central portion. It is therefore inferred that the deposition efficiency of cold sprayed hardmetals cannot increase linearly with impact velocity, and it is further impaired with stiff, dense particles and/or with very hard materials (e.g. WC-12Co as compared to WC-17Co). Unlabelled Image • Cold sprayed WC-Co particles flatten onto a relatively undeformed hardmetal surface. • Ductile failure of the hardmetal is an integral part of the particle flattening process. • The particle rim is deformed and heated; it bonds metallurgically to the underlying surface. • The rim ejects material fragments during its spreading process. • Deposition efficiency does not increase linearly with particle impact velocity. [ABSTRACT FROM AUTHOR]

Cold spray (CS) is a solid-state additive material deposition technique, which has gained attention in the aerospace industry as a potentially viable technology for structural repair of high-value parts made of high-strength alloys such as Ti-6Al-4V (Ti-64). Residual stresses build up in the substrate and deposited materials resulting from the CS process can influence the integrity of a coating or repair. However, the nature, magnitude and distribution of residual stresses in Ti-64/Ti-64 CS repairs are currently unknown. This study aims to evaluate the effects of geometrical variables (i.e. the number of CS layers, CS layer thickness, and substrate thickness) and track pattern on the magnitude and distribution of residual stresses in CS deposit-substrate assemblies. Through-thickness stress distributions were measured experimentally by neutron diffraction and contour method. Furthermore, a comparison among different residual stress build-up mechanisms induced by CS processes has been discussed for different combinations of substrate and deposit assemblies. An analytical model based on the force and moment equilibrium requirements was used to interpret the experimental stress profiles and to predict the residual stress distribution. It was found that residual stresses are highly tensile near the free surface of the Ti-64 deposits as well as towards the bottom of the substrate, and compressive near the interface region. Although all the specimens showed similar stress distribution, the magnitudes were found to be higher in one or more of the following cases: specimens with a higher number of CS layers, lower substrate thickness, higher layer thickness (i.e. at lower scanning speed), and deposited with a horizontal track pattern. • Residual stresses induced by cold spraying of Ti-6Al-4 V were evaluated using neutron diffraction and contour method. • A parametric study was performed on the influence of geometrical and process variables on residual stresses. • An analytical method was used to interpret the experimental results and to compare different stress build-up mechanisms. [ABSTRACT FROM AUTHOR]

As a precipitation-hardening nickel-based superalloy, Inconel 718 has decent corrosion resistance, high strength at ambient temperature, excellent creep and fatigue strengths at high temperature. In this work, high performance Inconel 718 alloy was fabricated by cold spray process. The microstructure evolution, hardness, adhesive strength and tensile strength were investigated systematically on the cold-sprayed Inconel 718 in as-sprayed and heat-treated conditions. The N 2 -processed Inconel 718 samples demonstrate a decreasing porosity with the increasing gas pressure, whereas the fully dense coating was obtained by using He gas. Consistent with the particle velocity measurement, higher adhesive and tensile strength were obtained at higher pressure of N 2 propelling gas. Through the heat treatment at 990 °C for 4 h, the adhesive strength of N 2 and He-processed Inconel 718 reached as high as 435.4 and 899.4 MPa, which is comparable with the tensile strength of bulk material. The microstructure and EBSD examination indicate the disappearance of particle boundaries after the diffusion during heat treatment. Besides, the He-processed Inconel 718 samples show a significantly improved ductility and ultimate strength comparable and even higher than those of bulk material. The results show that the high-performance Inconel 718 alloys can be fabricated by CS process for the application of damage repair and additive manufacturing. • High performance Inconel 718 alloy was fabricated using cold spraying. • Microstructure evolution was studied using SEM and EBSD. • Finite element analysis was used to investigate the deposition behavior. • High adhesive strength (899.4 MPa) was achieved using helium as propelling gas. • Tensile properties of In718 close to bulk material was obtained by cold spray. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to examine the performance of cold-sprayed Zn15Al alloy coating whether it is capable of protecting magnesium alloy from corrosion, and to compare it with arc-sprayed Zn15Al alloy coating. Design/methodology/approach: In this paper, Zn15Al alloy coating was prepared with CS-6000 cold spraying system and HDX-800 arc-sprayed system. Corrosion behaviors of the two kinds of coatings were examined with potentiodynamic polarization curves methods combined with SEM, EDS, XRD, etc. Findings: Corrosion behavior of cold-sprayed Zn15Al alloy coating is superior to arc-sprayed Zn15Al alloy coating. The bonding strength and density of cold-sprayed Zn15Al alloy coating is much higher than that of arc-sprayed Zn15Al alloy coating. The cold-sprayed coating has a dense structure which separate magnesium from corrosion medium completely. The samples behave as Zn15Al instead of AZ91D alloy. The coating has a low probability of pitting corrosion comparing with cold sprayed Al coating through potentiodynamic polarization curve. Practical implications: Cold-sprayed Zn15Al coating can be used to improve the anticorrosion performance of magnesium significantly and low down the risk of pitting corrosion of coating. Social implications: Cold-sprayed Zn15Al coating is an environmentally friendly anticorrosion method for light alloy, which is also the most effective way among thermal spray, chemical vapor deposition, sol–gel, plating and anodizing or microarc oxidation. Originality/value: The present paper used cold spray method to deposit Zn15Al coating, which has an overwhelming performance both in physical and anticorrosion to traditional thermal spray method. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Cold spray can be used to fabricate highly reflective Al coatings. • Increasing the gas heating temperature results in higher deposition efficiencies. • Low coating densities were delivered under the highest gas heating temperatures. • Porosity is the dominant factor that affects the reflectivity of the coatings. Abstract This research presents the results of an investigation into the additive manufacture of reflective Al coatings using cold spray (CS). This work is the first time that CS technology has been used to fabricate highly reflective surfaces. The coatings were characterised with respect to total reflectivity within the wavelength range of 400–1800 nm, surface roughness, particle deformation levels, and density. The experimental results indicate that raising the gas heating temperature increased the porosity and that the lowest gas heating temperature delivered the highest spectrally average reflectivity of 93.4% which was within 1% of bulk Al. This investigation demonstrates that CS can be used to coat thin layers of Al onto various materials, which can be subsequently polished to create composite reflectors. Hence, a reflector with the reflectivity of Al and the structural and thermal properties of the substrate material can be fabricated, allowing for greater design flexibility and the rapid manufacture of multi-material reflectors. [ABSTRACT FROM AUTHOR]

An innovative cold spray method for the deposition of ferromagnetic particles is presented. A magnetic field is used to magnetize and then accelerate the sprayed particles towards the substrate. In addition, the magnetic attraction focuses the trajectories of the particles so that their spreading is reduced. This magnetic assisted cold spray achieves higher deposition efficiencies in comparison with the conventional process. The quality of the produced coatings, as regard their porosity, is increased too. The proposed method shows promises of being a useful tool to expand the industrial applications of cold spray. [ABSTRACT FROM AUTHOR]

W Cu composite coatings with different tungsten (W) contents were fabricated by cold spraying. The morphology and microstructure were studied using scanning electron microscopy (SEM), with W content and porosity of the final coatings being measured by an Image analysis software program equipped with SEM. Results showed that a dense coating with very low porosity, and free of impurity phase can be obtained by cold spraying. The porosity and thickness of the coatings decreased with the increasing of W content in the starting blend powders. The deposition efficiency of W was improved with the addition of soft particles. The wear behavior and possible bonding mechanisms of W Cu composite coatings were also investigated. • W Cu coatings with different W contents were fabricated by cold spraying. • The porosity of the W Cu composite coatings is less than 2 vol%. • The maximal deposition efficiency of tungsten is around 72%. [ABSTRACT FROM AUTHOR]

Cold spraying of dissimilar materials have been addressed to understand the role of deposition sequence on the characteristics of the coating/substrate interface. Nickel and titanium coatings were sprayed onto the substrates of the opposite material under different conditions. The samples were subsequently heat treated, to better reveal the quality of metallic bonding at different locations, and examined by mechanical testing and microstructural analysis. The results show that the bonding characteristics of the Ni(coating)/Ti(substrate) pairs are significantly different from those of the Ti(coating)/Ni(substrate) pairs. Mechanical interlocking and intermixing instabilities were observed only at the interfaces of the Ni/Ti pairs, which also showed a more uniform and higher fraction of intermetallics compared to the Ti/Ni pairs in similar spraying conditions. This was attributed to higher degrees of particle/substrate deformation in the Ni/Ti pair. Also, the bond strength of the Ni/Ti pair appeared to be almost three folds of the Ti/Ni pair (64.31 MPa vs. 22.8 MPa). These findings are considered to have implications in cold-spray additive manufacturing of hybrid components or bimetals. Unlabelled Image • Cold spraying of Ni/Ti pairs was done to realize the role of deposition sequence. • Annealing experiments were used to form and study interfacial intermetallic layers. • Ni/Ti and Ti/Ni showed different interfacial intermetallic growth morphology. • Asymmetrical bond strengths of dissimilar pairs were measured. • Higher bond strength values were obtained for Ni/Ti pairs compared to Ti/Ni pairs. • Spraying Ni on Ti leads to significantly better coating features than the opposite. [ABSTRACT FROM AUTHOR]

This paper presents a geodesic-based robot trajectory planning approach to fulfill the increasingly high reproducibility and coating quality requirements for cold spray applications. First, on the basis of Gauss–Bonnet theorem, the selection of a reference curve is discussed with the aim of minimizing the entire length of subsequent offset curves. An index sequence-based offset curve is created, and its discrete algorithm is then introduced to generate the optimal trajectory. Finally, a comparative experiment and analysis indicate that the presented trajectory planning approach can achieve coating thickness homogeneity. [ABSTRACT FROM AUTHOR]

Cold spraying is a coating technology where the temperatures of the sprayed particles are kept low (below 1000 °C), and compensated by high impact velocity (300–1400 m/s). Although many particle and substrate variables are important under cold spray conditions, the particle temperature, Tp, and impact velocity, Vp, to a large extent control the quality of coatings. In this study, a cold spray coating diagram (CSCD) using Tp and Vp as coordinates is proposed. The cold spray coating process is characterized by a critical velocity, Vcr, beyond which Vp > Vcr adhesion and bonding of particles to the substrate will take place. If Vp is very high and crosses the erosion velocity, Vero, of the substrate, bonding will not occur. Both Vcr and Vero are dependent on the particle temperature Tp. The ratios Vp/Vcr = 1.0, 1.5, 2.0 and 2.5 were drawn as contours in the CSCD. Coating properties like deposition efficiency, cohesive strength, and flattening ratio have unique relationships with the impact velocity, Vp, expressed as the ratio Vp/Vcr; they are also depicted on the contours of Vp/Vcr in the cold spray coating diagram. In addition, the bonding mechanisms responsible for the adhesion of the particles on the substrate were also identified and indicated in the cold spray coating diagram. [ABSTRACT FROM AUTHOR]

The feedstock powder morphology has an important effect on the deposition behavior of cold spray coatings, and this effect is even more significant while spraying cermet coating by the mixture powders. The effect of alumina powder morphology on the deposition efficiency and coatings mechanical properties is investigated in the cold spray deposition of aluminum–alumina cermets. The deposition of aluminum mixed with spherical and angular alumina is studied and compared for six different feedstock powder compositions for each particle morphology. The addition of angular alumina particles in the feedstock powder induces an increase in deposition efficiency followed by a decrease as the alumina content increases beyond a specific value. This effect is not observed when spherical alumina is used. The creation of asperities during deposition was explored for the two alumina powder morphologies, and it was determined that spherical alumina does not produce intricate asperities at the coating surface, explaining the difference in deposition efficiencies. Coatings produced with spherical alumina were harder and showed a greater increase in adhesion strength than coatings produced with angular alumina for similar coating alumina content. These differences are attributed to a larger amount of plastic deformation of the matrix material in coatings sprayed with spherical alumina. [ABSTRACT FROM AUTHOR]

Abstract Cold spray technology is a recently developed surface modification method, which is widely used in various fields including the catalyst industry. Owing to their low reaction temperature, high activity, and high hydrogen selectivity, Cu-based catalysts are widely used in methanol steam reforming for hydrogen production. Cold spray is an efficient method for fabricating supported Cu-based catalysts for hydrogen production. However, in the cold spray process, the feedstock powder shape significantly affects the coating formation. In this study, we used two types of feedstock powders (consisting of dendritic Cu and clustered Al 2 O 3) with different morphologies for fabricating Cu and Al 2 O 3 coatings by cold spray on an Al substrate. A Cu + Al 2 O 3 composite coating was also prepared by the cold spray method. The microstructures of the Cu, Al 2 O 3 , and Cu + Al 2 O 3 coatings were investigated before and after methanol steam reforming. All the three feedstock powders were successfully deposited on the Al substrate. The coatings formed using the Cu and Cu + Al 2 O 3 feedstock powders were multilayered and highly porous. Only slight deformation was observed in the micro-spherical structure of the Cu particle branches. In the case of the composite coating, Al 2 O 3 particles were broken into pieces and were non-uniformly distributed. The bonding strength between the coating and the substrate was strong enough. After the methanol steam reforming process, the quality of the composite coating improved; however, the Cu coating showed carbon deposition. In order to obtain high-quality coatings, special attention should be paid to the feedstock particle shape and deposition of easily broken feedstock materials. The microstructural investigation of such coatings can be useful for understanding their fabrication mechanism. The fabrication method used in this study can be used as a novel method for fabricating supported catalysts. Highlights • Cu, Al 2 O 3 and Cu + Al 2 O 3 coatings were fabricated by cold spray. • Microstructure of the coating was investigated before and after treatment. • Deformation behavior of particles was analyzed. • Comparison of the coatings and its application have been discussed. [ABSTRACT FROM AUTHOR]

Abstract In this study, the feasibility of employing friction stir processing (FSP) as a post-spray method to augment the corrosion resistance of cold sprayed (CS) AA2024/Al 2 O 3 metal matrix composites (MMCs) was investigated. The effect of the FSP passes on the electrochemical properties of composites in a 3.5 wt.% NaCl solution was studied with cyclic polarization and electrochemical impedance spectroscopy (EIS). Microstructural evolution were employed to analyze and identify the corrosion mechanisms of the CSed and FSPed composites. Results demonstrated an improvement of the corrosion resistance of the AA2024/Al 2 O 3 coatings for the low pass number FSP (1 and 2 passes), with the best corrosion performance occurring at 2-pass FSP. The improved surface condition is the main improvement mechansim of corrosion resistance. Whereas for the high pass number FSP (4 passes), the corrosion resistance was reduced due to the combined effect of the improved surface condition and deteriorated interfaces of inside coatings. Highlights • FSP was employed to augment corrosion resistance of CSed AA2024/Al 2 O 3 MMCs. • Effect of FSP passes on corrosion performance was investigated. • Microstructural evolutions were analyzed to identify corrosion mechanisms. • 2-pass FSP effectively improved corrosion performance. [ABSTRACT FROM AUTHOR]

Abstract For the moment, the additive manufacturing (AM) of maraging steel has attracted increasing attention due to its outstanding mechanical properties. As a recently-emerged AM method, the solid-state cold spray has been widely used to fabricate the metallic components. In this work, the maraging steel 300 (MS300) was fabricated by cold spray additive manufacturing followed by solution-aging treatment. Analyses based on X-ray computed tomography (XCT) and optical microscope (OM) show a densified microstructure with a minimum porosity of 0.168%. Phase analysis through XRD and EBSD exhibits that as-fabricated samples possess well-retained phase composition compared with feedstock material, and the solution-aging can lead to a highly martensitized microstructure in the prepared samples. EBSD analysis shows the ultrafine grain structure of as-fabricated samples indicating the formation of dynamic recrystallization during the CS deposition. Tensile tests show that through the cohesive diffusion and precipitation-strengthening, the solution-aging treatment can lead to a significantly improved tensile properties (ultimate tensile strength and elongation) with the fracture morphology featured by extensive dimples. The wear resistance of CS MS300 was also significantly improved through the precipitation-hardening. As a summary, this study demonstrates cold spray as a promising AM method can fabricate high-performance grade 300 maraging steel parts. [ABSTRACT FROM AUTHOR]

Abstract The low retainability of reinforcing particles in functional composite coatings fabricated by cold spray (CS) is a major problem in maximizing coating properties. In this work, the Ni-coated FeSiAl composite powders were used to fabricate soft magnetic composite (SMC) coatings via CS. The feedstock particles were preheated prior to the entrance of nozzle to improve the retainability of FeSiAl particles and the coating properties. Our results showed that the dense Ni/FeSiAl coatings containing the uniformly-dispersed and crack-free FeSiAl particles were produced. The thermal softening effect of Ni layer, as a result of particle preheating, can effectively increase the volumetric content of FeSiAl particle (from 24.3% to 46.2%) in the composite coating. Particle preheating also conducted to the significant improvement of coating thickness due to enhanced deposition efficiency. Dry-sliding test showed that the tribological performance of SMC coating with particle preheating weakens, owing to lowered microhardness. Enhanced magnetic property was achieved with higher soft ferromagnetic characteristic and decreasing coercivity value at higher particle preheating temperatures. The study on coating formation mechanism highlighted that thermal softening effect can give rise to adiabatic shear instability of Ni layer. This results in the significantly improved retainability of FeSiAl particles and soft magnetic performance. Graphical abstract Unlabelled Image Highlights • Ni-coated FeSiAl powder was used to fabricate soft magnetic composite coating by cold spraying. • Higher retainability of FeSiAl particles was achieved by particle preheating. • Tribological performance of the Ni/FeSiAl composite coatings with particle preheating was studied. • Soft magnetic performance was enhanced at higher particle preheating temperatures. • The thermal softening effect of preheated composite particles was discussed. [ABSTRACT FROM AUTHOR]

• Metal composite coating deposited by cold spray post-treated by laser melting and friction stir processing. • After both post-treatments the formation of new intermetallic phases was observed. • The coating integrity is higher after friction stir processing than after laser melting. Friction stir processing (FSP) is applied for the post-treatment of an Al-Cu-Ni cold spray metal composite in order to produce an alloy coating. The results are compared with laser remelting of the same material. It was shown that both post-treatment procedures form an alloy containing new intermetallic phases AlNi and Al 2 Cu initially absent in the as-sprayed material. The integrity of the coating treated by FSP was significantly higher than the laser-treated one due to the absence of material melting, which can introduce significant porosity. Thus, FSP could be considered an efficient post-treatment process of cold sprayed composite coatings leading to the improvement of the coating uniformity and modification of the phase composition. [ABSTRACT FROM AUTHOR]

This study investigates the microstructure, the mechanical properties, the topography and the tribological behavior of a composite coating obtained by cold spray, as a potential candidate for its use in internal combustion engines in the automotive sector. The coating consists of a 410 L matrix and M2 tool steel reinforcements. For comparison, a single component 410 L cold sprayed coating and a wire arc coating, used in some of today's car engines, are also studied. Post-spraying, the coatings underwent specific surface finishing. Their microstructure and topographies were observed. A lubricated reciprocating sliding test was performed, resulting in an exceptionally low friction coefficient and negligible wear, even in harsh conditions for the composite coating. The analyses revealed that the surface finish creates protuberances due to the presence of hard M2 particles, activating a series of mechanisms bringing to the stabilization of a tribofilm. This can be considered responsible for the exceptional tribological properties observed. This study proposes the application of surface textures with protuberances, in particular, their use in lubricated contacts in presence of fully formulated oils, and how cold spray is a suitable process to easily produce them. [Display omitted] • Metal-metal composite coatings were applied on cylinder bores by cold spray. • Protuberances emerge after the surface finishing of the composite coating. • Low friction and negligible wear were measured in tribological tests. • Coating performance is due to the formation of a particular tribofilm. • Protuberances are essential for the formation of the tribofilm. [ABSTRACT FROM AUTHOR]