Cold spray additive manufacturing (CSAM) is an emerging process that has garnered significant attention from researchers due to its unique advantages. These include higher deposition rates, no need for a protective atmosphere, and the ability to connect or combine dissimilar materials. While CSAM allows for near-net-shape fabrication of workpieces, the accuracy and properties of the final products often fall short of user requirements. Furthermore, there is an urgent need to develop a generalized manufacturing strategy for workpieces with complex geometries. It appears that integrating various processes throughout the entire manufacturing workflow, from design to delivery, could address these challenges. However, few researchers have explored this area. To fill this gap, this study presents an integrated modular CSAM system designed for efficient and flexible workpiece fabrication. The system comprises two main components: software for modeling and simulation, and hardware for precise fabrication, each containing multiple modules. These modules do not operate independently but are coupled through direct or indirect decentralized and event-driven physical links. The system described in this paper offers a generalized strategy for precision manufacturing of workpieces using CSAM, potentially advancing the field and addressing current limitations in accuracy and versatility.

Thermal spray (TS) technology has attracted the attention of numerous industrial sectors due to its apparent simplicity and versatility. It has been used across the world for over 80 years in the conservation and creation of art. Despite the creativity involved in the creation of an art piece, the TS artistic endeavors are limited and insufficiently explored. Unique material combinations, usually not observed in conventional engineering applications, can be achieved with TS technology. Although the material amalgamation possibilities are infinite, their combined deposited characteristics, interfacial compatibility and color palette require further study. In this work, the fields of photography, image processing and TS are combined to produce a large art-piece using the cold gas dynamic spray (CGDS) process. Aluminum, zinc, nickel, alumina, steel and titanium alloy powders are sprayed to replicate in three-dimensions a photograph of a crinoid from the Silurian period found on the Anticosti Island, located in the Gulf of St. Lawrence in Canada. The numerous steps required to produce the artistic 3D piece, namely numerical segmentation of the photograph, conversion to a computer-assisted design (CAD), manufacturing of steel masks and CGDS deposition of the selected powders to reach the sought color palette are described. Powder deposition efficiency, material compatibility and microstructural characteristics are analyzed. and the resulting art piece is presented.

Cold spray is an emergent sold-state manufacturing process based on high-speed consecutive collision of small sized particles powders. Such a cold process principle led to the recent development of coatings for various surface functionalization and direct component manufacturing applications. This study investigates the mechanisms of porosity formation during the additive growth of Al1050 powders. To this end, a thermo-mechanical computational model based on the Eulerian computational approach using the Johnson-Cook constitutive law is applied on the case of an additive growth from a stacking of powder layers. The model uses in-flight velocities measured by a DPV2000 system during a cold spray test and an isentropic gas flow model. The measurements show the velocity distribution within the powder jet at the nozzle exit and consists of a Gaussian-like distribution within the typical range of 450-650m/s. The centerline zone at the nozzle exhibits the highest velocity. These data used as input data of the model allowed to apprehend some circumstances of pore formation, in terms of site occurrence, pore behavior over time, and deficient in-flight velocity.

In the cold spray additive manufacturing (CSAM) process, layer-by-layer stacking is a good method to achieve coating AM. Different from AM processes such as selective laser cladding, which can quickly realize trajectory planning based on commercial software, the spraying trajectory of the CSAM process cannot be created easily due to the “one-stroke” character. The spray path cannot be intersected and the coating deposition cannot be interrupted during the spraying process. What’s more, the spray gun or the workpiece held by the robot usually needs to be deflected by a certain angle to compensate the coating edges. An accurate and efficient spraying trajectory for a given workpiece is the most basic and important part in CSAM process. This article proposes a novel parametric layered slicing algorithm for STL files and an optimized rapidly exploring random tree (RRT) algorithm, so as to generate spraying trajectory accurately and quickly, especially for a part with multiple features. The simulation results revealed that the algorithms can efficiently generate the corresponding spraying trajectory for CSAM.

Cold Spraying (CS) is a thermal spray process capable of producing dense and thick coatings by the spraying of powders under high velocity and relatively low temperature. The high deposition efficiency and the thickness of each pass make possible the use of CS to produce freestanding parts, as an additive manufacturing process (CSAM). Traditionally, CS is performed spraying perpendicularly to the substrate, which ensures maximum deposition efficiency among other benefits. This, however, presents two main disadvantages for CSAM. First, by keeping the spraying angle constant, there is not much control on the final geometry of the part being built, and, second, the resultant part’s properties show anisotropy depending on whether this property is measured along the spraying axe or not. In this work, we present a method (Metal Knitting) that aims to help reduce both disadvantages. Metal Knitting is based on the performance of certain spraying movements that build near squared shapes step-by-step like in a knitting process. The principle of the method and examples are presented in this work, as well as some results on the anisotropy of 316L stainless steel freeform parts obtained by CSAM, measuring the tensile stress, hardness, and evaluating the microstructure in different directions of the material. The effect of annealing on the material properties is also investigated.

In line with the industrial trend of additive manufacturing, cold spray as a non-laser-based process is becoming increasingly important for many fields of application. For the evaluation of additive manufacturing of winding components made of copper for large electrical high-voltage machines, material and component properties such as electrical conductivity, mechanical load capacity and the component size that can be produced are of particular importance. In this context, the cold spray process offers advantages over laser-based additive manufacturing processes such as laser powder bed fusion (LPBF) or laser cladding by using the kinetic energy of the copper powder particles to generate particle bonding. To investigate the electrical conductivity as well as the mechanical load capacity of cold spray parts, specimens were machined out of cold sprayed bulk copper deposits. The characteristic values were obtained with regard to the direction of deposition, which is defined by the direction of the robot’s movement. Thus, for the investigation of the component properties, specimens were provided that had been produced both aligned lengthwise and crosswise as well as vertically to the direction of deposition. The results of the investigations show that both the electrical conductivity and the mechanical load capacity of the specimen have a strong dependency of the specimen orientation with respect to the direction of deposition. Furthermore, it could be shown that by increasing the deposition height, there is an increasing oxygen content in the sample material, combined with increasingly significant defect networks. These effects have a negative impact on the electrical conductivity as well as on the mechanical load capacity. As a conclusion, further need for investigation is identified in the optimization of the process parameters as well as in the deposition strategy for the additive manufacturing of large-volume components with cold spray.

Cold spray additive manufacturing is an emerging solid-state deposition process that enables large-scale components to be manufactured at high production rates. Control over geometry is important for reducing the development and growth of defects during the 3D build process and improving the final dimensional accuracy and quality of components. To this end, a machine learning approach has recently gained interest in modelling additively manufactured geometry; however, such a data-driven modelling framework lacks the explicit consideration of a depositing surface and domain knowledge in cold spray additive manufacturing. Therefore, this study presents surface-aware data-driven modelling of an overlapping-track profile using a Gaussian Process Regression model. The proposed Gaussian Process modelling framework explicitly incorporated two relevant geometric features (i.e., surface type and polar length from the nozzle exit to the surface) and a widely adopted Gaussian superposing model as prior domain knowledge in the form of an explicit mean function. It was shown that the proposed model is able to provide better predictive performance than the Gaussian superposing model alone and purely data-driven Gaussian Process model, providing consistent overlapping-track profile predictions at all overlapping ratios. By combining accurate prediction of track geometry with toolpath planning, it is anticipated that improved geometric control and product quality can be achieved in cold spray additive manufacturing.

As an emerging additive manufacturing method, cold spray additive manufacturing (CSAM) has attracted more and more researchers’ attention due to its unique advantages. However, only a few researchers have studied the fabrication of complex structural components. Therefore, it is important to develop a general CSAM framework that is suitable for the fabrication of different shapes of workpieces. In particular, the choice for the optimal kinematic spraying parameters, the prediction of deposit evolution and the planning of spraying trajectory are the most basic and crucial. Different sub-modules are integrated in the proposed framework to solve these problems. In detail, the modeling methodology is used to obtain the optimal kinematic spraying parameters and to predict the deposit evolution in the simulation. Based on the feasible parameters, the trajectory planification methodology is used to generate the spraying trajectory for the workpiece being manufactured, especially the workpiece with complex structure. Finally, the simulation and experimental results of a fabrication for a workpiece with complex structure provide the developed system is reliable and effective. The framework developed in this paper can considered as a general tool for additive manufacturing of with complex structural workpieces in the CSAM.

High-performance polymers such as poly(ether ether ketone) (PEEK) are appealing for a wide variety of industrial and medical applications due to their excellent mechanical properties. However, these applications are often limited by relatively low thermal stability and conductivity compared to metals. Many methods developed to metallize polymers, including vapor deposition and thermal spray processes, can lead to poor quality control, low deposition rate, and high cost. Thus, cold spray is a promising potential alternative to rapidly and inexpensively produce polymer-metal composites. In this study, we investigated the deposition characteristics of metalpolymer composite feedstock, composed of PEEK powder with varying volume fractions of copper (Cu) flake added, onto a PEEK substrate. We prepared the Cu-PEEK composite powder in varying compositions by two methods: hand-mixing the powders and cryogenically milling the powders. Scanning electron microscopy (SEM) of the feed mixtures shows that cryogenically milling the polymer and metal powders together created uniformly distributed micron-scale domains of Cu on PEEK particle surfaces, and vice versa, as well as consolidating much of the porous Cu flake. In lowpressure cold spray, the relatively large volume fractions of PEEK in the composite mixtures allowed for lower operating temperatures than those commonly used in PEEK metallization (300-500 °C). While the deposition efficiencies of each mixture were relatively similar in single-layer experiments, deposits formed after multiple passes showed significant changes in deposition efficiency and composition in PEEK-rich feedstock mixtures. SEM of deposit surfaces and cross-sections revealed multiple co-dominant mechanisms of deposition, which affect both the porosity and final composition of the deposit. Though present in all samples analyzed, the effects of cryogenic milling were more prevalent at lower Cu concentrations.

Cold spraying (CS) has proved as an attractive and rapidly developing solid-state material deposition process that allows for fast formation of high quality, large 3D volume objects. Low risks of undesirable heat effects lead to increased interest in CS-based rapidly additive manufacturing (AM). However, by continuous powder spraying and high-pressure gas operation, cold spray additive manufacturing (CSAM) in terms of shape building is rather sensitive to operating parameters and imposes high requirements on the control of process conditions and locally needed kinematics. Every step of the manufacturing process therefore needs to be well conceived and planned, especially with regard to the toolpath planning and implementation. This is not only essential to meet basic performance requirements, but also needed to realize the desired accuracy. In order to tackle above needs, the present study presents a new toolpath planning method for 3D volume build-up to improve manufacturing accuracy and flexibility by cold spray additive manufacturing. Applied benchmarking tests prove acceptable shape accuracy and demonstrate that the current method can enhance the capabilities of CSAM for nearnet shape construction. This implies that careful planning and manufacturing strategies should enable to overcome the challenges associated with CSAM.

The clogging, a frequent gas passage deformation phenomenon because of powder accumulation on inner nozzle wall, is a major issue in long duration Cold Spray (CS) operations and a major challenge for Cold spray technology to be adopted for additive manufacturing. This study aims to design and integrate new nozzle design in Cold Spray operations for addressing the clogging issues in traditional circular convergent-divergent (CD) nozzles. The concept of the Aerospike nozzle is proposed for that purpose and is investigated using numerical simulation methods in this paper. An aerospike nozzle allows gases to accelerate externally bounded by environment on one-side and contoured spike wall on other side. After accelerating along the spike wall, aerospike nozzle can generate a longer supersonic gas stream. The spike region can be truncated near the tip to provide a flat face for powder injection. This proposed strategy will allow powder particles to accelerate through a longer supersonic core region, without interacting with nozzle wall. With appropriate operating parameters, an aerospike nozzle can reduce or eliminate the clogging issue completely. The efficiency and operation of aerospike nozzle is compared with same Mach number C-D nozzle using numerical simulations at stagnation pressure of 30 bar and temperature of 623K, where the aluminium powder particles are injected at 30 g/min in the centerline of both nozzles and are accelerated to similar velocities. The powder particles are accelerated in supersonic core region of aerospike nozzle without interacting with nozzle wall, it is concluded that the aerospike nozzle can be a promising nozzle design to provide clogging free long duration CS operations.

As a result of the rise in processing power demands of today’s personal computers, water cooled pin fin heat sinks are increasingly being employed for the cooling of graphical processing units. Currently, these high performance devices are manufactured through high-cost, high-waste processes. In recent years, a new solution has emerged using the cold gas dynamic spray process, in which pin fins are directly manufactured onto a base plate by spraying metallic powder particles through a mask. This process allows for a high degree of adaptability to different graphics processing unit shapes and sizes not achievable by any other process to date. One drawback of this new additive manufacturing process is reduced deposition efficiency, resulting in a fair portion of the feedstock powder being wasted as substrate sensitivity to heat and mechanical residual stresses requires the use of reduced spray parameters. This work aims to demonstrate the feasibility of using powder recycling to mitigate this issue and compares coatings sprayed with reclaimed powder to their counterparts sprayed with as-received powder. In so doing, cold gas dynamic spray is shown to be a highly flexible and economically competitive process for the production of pin fin heat sinks even when spray parameters result in reduced deposition efficiency.

In this work, advanced Al/diamond wear-resistance composites were fabricated by solid-state cold spray additive manufacturing using core-shell-structured diamond powders. Based on the experimental results and thorough discussion, it is found that core-shell-structured diamond powders were much easier to deposit than pure Al by cold spray, showing great potentials as feedstock for cold spraying. The deposition mechanism of the Al/diamond composites were dominated by the true metallic bonding between Al matrix and Cu layer, which is different from other conventual cold sprayed metal matrix composites. Tensile tests indicated that the tensile strength of the Al/diamond composites can be higher than cold sprayed pure Al. In addition, the Al/diamond composites had super wear-resistance performance. The wear rate was reduced by 17.8 times for the N 4-1 composite and by 37.5 times for the N 1-1 composite as compared with cold sprayed Al/Al 2 O 3 composite.

In this work, hot isostatic pressing (HIP) is used to reduce interior defects, adjust the microstructure, and improve the tensile properties of cold-sprayed Ti6Al4V. Optical microscope and X-ray tomography were used to characterize pore morphologies and porosity evolution. XCT reconstructions show that fully dense Ti6Al4V alloy with an equiaxed microstructure were achieved. Tensile testing shows that strength and ductility were improved as well because of enhanced diffusion and resultant metallurgical bonding.

The use of cold spray in metal additive manufacturing (AM) offers well recognized advantages with typical commercial drivers being a rapid build rate, low process temperature, and wide range of usable alloys. Cold spray AM to date has often employed a methodology of rapid material deposition, with or without masking, into relatively simple shapes and wide tolerances that can lead to constraints in part geometries and/or significant post-spray machining. In this work, an investigation has been performed into producing more complex geometries and improving shape fidelity using a conventional AM strategy; namely, starting with a CAD drawing, slicing the CAD geometry into a layered structure, and performing a layer-by-layer build. For cold spray, technology-specific considerations must be factored into each of these steps and in particular, an effective build strategy and toolpath are critical to moving towards near-net shape parts. This requires, by extension, precise manipulation of the spray gun, or part as applicable, which was performed using industrial robot offline programming via commercially available software. Various cold spray 3d builds are used to demonstrate developments in toolpath planning and build strategy.

Cold spray is continuously expanding for the repair of parts made of aluminum-based alloys. Beyond repair applications, the process is now expected to be exploited efficiently for the additive manufacturing of shaped parts. However, up to now, cold spray is limited to the achievement of rather simple shapes due to a lack of basic knowledge on coating build-up mechanisms to result in dimension-controlled deposition. The objective of this work is to fill that gap through an experimental and modeling study of the coating build-up in cold spray for this specific application. Experimentally, Al-based coatings were deposited for a large range of particle velocity due to the use of low-pressure, medium-pressure and high-pressure cold spray facilities. Particle velocity was monitored as a function of cold spray conditions. Two different types of Al 2024 (Aluminium 2024 Alloy) powders were tested. Coating porosity and microhardness were studied as a function of (both morphological and metallurgical) powder characteristics and spray conditions, primarily in the light of particle velocity. Various correlations could be exhibited. Finite element (FE) simulations of particle impacts were developed, including particle velocity from experimental measurements. These will be used as inputs in an in-house morphological model, the first stages of which could be established successfully.

This present work investigates the effect of electromagnetic fields on cold spray processes by means of an induction-heating cold spray (IHCS) system. Aluminum powder was cold sprayed onto inductively heated Ti6Al-4V (Ti64) substrates. These materials were selected to minimize the mechanical contribution to coating adhesion. As a result, changes in coating adhesion strength can be attributed to improved metallic bond formation due to the effect of the electromagnetic field. Four different initial substrate surface temperatures were used in the study to assess the role of initial temperature as well. Deposition efficiency and adhesion and tensile strength measurements were recorded and are used to characterize the hybrid coating process and compare it with traditional techniques.

This study employs a three-dimensional simulation to investigate the cold gas dynamic manufacturing process. During the buildup of the desired object, sharp edges, stagnation points, and corners are likely to form that can 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 build process. A cylindrical and frustum-shaped object are numerically simulated on a substrate to represent typical additively manufactured parts. Particle trajectories and impact conditions with and without these objects are compared. The results provide useful information for understanding the limitations and challenges associated with cold gas dynamic manufacturing, which can help improve the quality and precision of the process.

In this work, fully dense titanium parts are fabricated by cold gas dynamic spraying (CGDS). Titanium powder is deposited using a low-pressure CGDS process with nitrogen as the carrier gas. The density, porosity, hardness, and tensile properties of the parts produced are determined and discussed.

Cold Spray is a solid-state Additive Manufacturing process of 3D near-net-shape parts which requires the implementation of a good spraying strategy and the choice of the right operating parameters. This paper is the result of empirical studies on the determination of the optimal processing conditions (spraying and kinematics) for the Cold Spray Additive Manufacturing (CSAM) of pure aluminum powder using a stable layers building strategy. Vertical 3D deposits (thick walls) with a height and thickness of 13-100 mm and 5-11 mm, respectively, were obtained through a series of tests that consider an effect of some kinematic parameters. The visual analysis of the deposits shows that the nozzle traverse speed as well as middle/edge pass number ratio constitute the two most influential parameters on the final shape of the deposits (flatness and straightness). All these results prove the potential of the Cold Spray Additive Manufacturing (CSAM) process as fast 3D additive method using micron sized powders, and particularly for Al powder.