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Cold spraying methods are used to prepare Cu/Ni composite coating on Q235 substrates. The porosity, micromorphology, and microhardness and corrosion properties of the copper coating prepared by cold spraying are studied. This experiment mainly explores the microstructure and corrosion resistance of Cu/Ni composite coatings prepared by different composition powder ratios. The heat treatment process of the coating was carried out to explore the effect of the heat treatment process on the microstructure and corrosion resistance of the coating. The results indicated that the porosity of the coating increases slightly with an increase in nickel powder content. The metal nickel plays an anodic protection role in the Cu/Ni battery. However, too much nickel will lead to too much anode material, and the overall structure of the coating will be destroyed after anode corrosion. The composite coating prepared with 40 wt% nickel powder has the best corrosion resistance. After heat treatment, the corrosion resistance of copper/nickel composite coatings is reduced, and the quality of the coatings is improved. [ABSTRACT FROM AUTHOR]

Cold spray technology is a multifaceted, environmentally friendly, and very promising method utilised for the aim of applying coatings onto complex geometries. This research examines several challenges pertaining to cold spray coating that have the potential to restrict its practical application. The application of this methodology enhances the depth of understanding of the fundamental process, allows for precise control of coating properties, and supports the refinement of cold spray treatments. Furthermore, it exhibits the supplementary benefit of being environmentally friendly because of its eradication of hazardous emissions and utilisation of flame. Moreover, the application of gas-turbine-driven cold spray equipment provides improved accuracy in controlling the coating thickness. Additionally, it has the capability to be combined with other methods such as laser cladding and thermal spraying to enhance its overall efficiency. [ABSTRACT FROM AUTHOR]

The cold-spray technology has been rapidly gaining in popularity, especially over the last two decades, due to its ability for depositing coatings at relatively low temperatures in contrast to other thermal spray methods. A key challenge for this technique lies in optimization of process parameters. Particle deposition occurs by plastic deformation of the particle and the substrate, which requires a high kinetic energy of impact. This calls for a minimum threshold velocity called the critical velocity and happens to be a key factor affecting process efficiency. In this review, we focus on numerical, theoretical and experimental approaches towards measuring the critical velocity (vcr) and subsequently elucidate the factors affecting vcr. [ABSTRACT FROM AUTHOR]

The grain structure evolution and nanomechanical behavior of cold-sprayed Al coating on Ti substrate with friction stir spot processing (FSSP) were studied by the electron backscatter diffraction and nanoindentation methods. The low-angle boundaries (LAGBs) fraction and the density of the geometrically necessary dislocations (GNDs) decreased from the base zone (BZ) to the stir zone (SZ). The average grain size, the LAGBs fraction and the density of the GNDs were various in different locations of the SZ, which can be attributed to the variety of local shear strain and temperature gradient during FSSP. The B/ B - component, the C component, and the A*1/ A*2 component were mainly developed in the SZ. The highest intensity of the B/ B - component appeared in the 3/8D of the SZ, indicating that the plasticized materials flowed downward experienced the highest shear strain. The materials in the heat affected zone (HAZ) underwent static recrystallization, while the continuous dynamic recrystallization (CDRX) and the geometric dynamic recrystallization (GDRX) occurred in the thermo-mechanically affected zone (TMAZ) and SZ. The nano-hardness and elastic modulus of the cold-sprayed Al coating after FSSP were comparable to those of pure Al bulk. The grain size and dislocation density were the main factors affecting the nano-hardness in the SZ. [ABSTRACT FROM AUTHOR]

This study investigated the effect of powder pre-oxidation on the microstructures and mechanical properties of cold-sprayed nickel coatings. The artificially pre-oxidized nickel powders at 200, 300 and 400 °C for 5 h show the resulting oxygen contents of 0.27, 0.36 and 0.41 wt.%, as compared to 0.21 wt.% in the feedstock powder. Microstructurally, the higher oxygen contents of the impact particles significantly increased in both the number and size of the pores in the as-sprayed coatings by using the pe-oxidized powders, as a result of the porosities of 0.7, 1.5 and 3.3% compared to 0.4% by using the as-atomized powder (natural oxidation condition). Mechanically, the increased oxygen contents of powders result in the reduced properties for the as-sprayed Ni coatings, as the microhardness of 263.2 HV0.1, 245.3 HV0.1 and 236.3 HV0.1 and the tensile strength of 94, 76 and 61 MPa by using oxidized powders compared to those of 289.2 HV0.1 and 208 MPa by using natural oxidation powder. In addition, post-spray heat treatment at 800 °C for 2 h effectively reduces the small-sized pores and nonbonded particle-particle boundaries within the coatings, which is attributed to a combination effect of annealing twins and dislocation slip during heat treatment. As a result, the microhardness significantly decreased to 135.3 HV0.1, 126.7 HV0.1, 124.5 HV0.1 and 114.7 HV0.1, while the tensile strength is increased to 210, 166, 133 and 117 MPa, respectively. [ABSTRACT FROM AUTHOR]

7-Series aluminum (Al) alloys have been widely used in aircraft and high-speed train manufacturing owing to its excellent mechanical properties and fracture toughness. However, surface problems of corrosion, wear and fatigue failure of Al alloy parts seriously affect the service life. In the present study, the noncontact laser shock peening (LSP) was applied to improve the fatigue life of the substrate before the coating deposited by cold spraying (CS). The effect of LSP on the interfacial bonding behavior between CS Al with 50 vol.% Al2O3 composite coatings and 7075 Al alloy substrate was comprehensively investigated. Results showed that after LSP treatment, the tensile strength is reduced from 47 to 34 MPa and 32 MPa when the laser shock energy was 2 and 3 J, respectively. Under the condition of shear strength, it decreases from 41.5 to 30 MPa and 26 MPa, respectively. In addition, numerical simulations were conducted on LSP and CS processes, and the results showed that with the increase of laser shock energy, the plastic deformation dissipation energy of Al particles increases gradually, while the plastic deformation dissipation energy of the matrix decreased. Therefore, the surface hardening caused by LSP treatment is the main reason for the decrease of interfacial bonding strength. [ABSTRACT FROM AUTHOR]

In this study, a comprehensive set of characterization techniques are employed to demonstrate that the cold spray deposition process can result in a significant increase in martensite in austenitic stainless steel. The lack of consensus in the literature on the formation of strain-induced martensite in cold spray can be attributed to the diverse processing conditions and measurement techniques used in different studies. In this work, EBSD, neutron diffraction, TEM imaging, and precession electron diffraction were used in combination to examine whether strain-induced martensite is formed during cold spray deposition of 304L stainless steel powder and to give further insight into possible mechanisms controlling this phenomenon. Cold spray was performed at both 350 °C and room temperature (25 °C) to investigate the effects of spray temperature on the martensite transformation. It is shown that the strain-induced martensite formation is significantly suppressed compared to that which would be expected for comparable levels of plastic strain at quasi-static strain rates. Additionally, the spray gas temperature is shown to directly impact the microstructure formed at the prior particle interface and the formation of dynamically recrystallized regions. [ABSTRACT FROM AUTHOR]

A computational framework is proposed for modelling particle bonding in cold spray. The model is based on the commonly-held view that bonding is a consequence of jetting, namely, the large plastic strains occurring at extreme rates upon particle impact. The model incorporates a bonding criterion at contacting boundaries by introducing a novel strain-like history variable referred to as the bonding parameter conjugate to a rate-dependent evolution law. In doing so, an analogy is made with classic damage mechanics where bonding is viewed as a similar but opposite process to fracture. Two new material constants are introduced, namely, the bonding toughness and the bonding toughness rate. Furthermore, a numerical implementation of the model in the Material Point Method (MPM) is presented which, thanks to a proposed regularization technique, is free of non-physical dependence on discretization parameters. The mesh-free nature of the MPM allows avoiding the numerical issues in conventional Lagrangian and Eulerian methods such as mesh distortion and artificial dissipation. The model is calibrated numerically for aluminum-aluminum material pair using an in-house computer program. Several numerical results are presented to demonstrate that the model can accurately capture material jetting and directly relate it to bonding within the simulation. [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 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]

With the widespread use of nuclear energy, the storage of surplus spent fuel has emerged as a critical issue that needs to be solved, especially for the efficient absorption of neutron radiation and secondary γ-rays generated by spent fuel produced when 10B absorbs neutrons. In this work, B4C/Al and W/B4C/Al coating were prepared on 316 L stainless steel by cold spraying. The microstructure and tensile properties of the coatings were investigated. The performance of the thermal neutron and secondary γ-rays absorption of the two coatings were simulated using the Monte Carlo approach. The results indicated that, compared to the B4C/Al coating, the W/B4C/Al coating exhibited better mechanical properties due to the tamping effect of the W particles. In addition, the secondary γ-rays absorption property was improved due to the addition of W. [ABSTRACT FROM AUTHOR]

This study establishes a machine learning (ML) model utilizing the expectation-maximization approach to predict maximum residual stresses, encompassing both tensile and compressive states, in the cold spraying process across various substrates. The main feature of the ML algorithm lies in its two-step iterative process, where the Expectation (E step) refines latent variable estimates, and the Maximization (M step) optimizes the model's parameters, aligning them with the data. Based on the results, regression analysis highlighted the predictive capabilities of the proposed model for tensile and compressive residual stresses, exhibiting root mean square error values of 8.8 and 3.5%, along with determination coefficient values of 0.915 and 0.968, respectively, indicating higher prediction performance in the compression mode. This suggests higher predictability for residual stress within the depth of material's body. Moreover, analyzing low residual stress levels underscored the significant impact of substrate and particle mechanical strength on prediction performance, whereas higher residual stress levels highlighted the strong influence of thermal conductivity. This correlation suggests that high stresses during the cold spray process generate more heat, thereby emphasizing the crucial role of thermal conductivity in predicting resultant residual stresses. Furthermore, a notable trend emerges as tensile stress increases, spotlighting the augmented influence of processing parameters in the prediction process. Conversely, at elevated compressive stresses, material properties' weight factors assume a vital role in predictions. These findings offer insights into the intricate interplay between processing parameters and materials properties in determining resultant residual stresses during cold spraying. [ABSTRACT FROM AUTHOR]

This paper offers a concise critical review of finite element studies of the jetting phenomenon in cold spray (CS). CS is a deposition technique wherein solid particles impact a substrate at high velocities, inducing severe plastic deformation and material deposition. These high-velocity particle impacts lead to the ejection of material in a jet-like shape at the periphery of the particle/substrate interface, a phenomenon known as "jetting". Jetting has been the subject of numerous studies over recent decades and remains a point of debate. Two main mechanisms, Adiabatic Shear Instability (ASI) and Hydrodynamic Pressure-Release (HPR), have been proposed to explain the jetting phenomenon. These mechanisms are mainly elucidated through finite element method (FEM) simulations, a numerical technique rooted in continuum mechanics. However, it is important to emphasize that FEM is limited by the equations established for analysis, and as such, its predictive capabilities are confined to those principles clearly defined within these equations. The choice of employed equations and approaches significantly influence the outcomes and predictions in FEM. While recognizing FEM's capabilities, this study reviews the ASI and HPR mechanisms within the context of CS. Additionally, this paper reviews FEM's algorithms and the core principles that govern FEM in calculating plastic deformation, which can lead to the formation of jetting. [ABSTRACT FROM AUTHOR]

Cold spray is an additive manufacturing and coating process in which powder particles are accelerated to supersonic speeds without melting them and then deposit on a surface to form a layer of a coating. Process parameters and materials affect the characteristics of manufactured parts and therefore must be chosen with care. Machine learning (ML) techniques have been specifically applied in additive manufacturing for tasks such as predicting and characterizing porosity. Machine learning algorithms can learn how a variation in the input spray parameters affects annotated output data, such as experimentally measured part properties. In this work, a dataset was developed from experiments reported in published academic papers, to train ML algorithms for the porosity prediction of cold spray manufactured parts. Data cleaning steps, such as null value replacement and categorical feature handling, were applied to prepare the dataset for the training of different ML models. The dataset was split into training and testing portions, and floating feature selection and hyperparameter optimization were performed using parts of the training set. A final evaluation of all trained models, using the test portion of the dataset, showed that a prediction accuracy with an average deviation of 0-2% porosity of the predicted values compared to the true values can be achieved. [ABSTRACT FROM AUTHOR]

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]

With multiple merits compared with thermal spray, cold spray technology is widely applied for various application fields. As part of an intelligent cold spray repair system, an approach for three-dimensional (3D) damage region contour extraction is proposed, which is without nominal Computer-Aided Design models and prior knowledge of damaged workpieces. Moreover, due to partially image processing based, the computation load of the proposed method is lower caused by partially avoiding the 3D point cloud processing. According to the results, it is capable to handle the uneven, sparse and unorganized point cloud to precisely extract 3D contour of damage region. The effectiveness of the proposed approach is highlight. Furthermore, the proposed methods on 3D cloud point to grayscale conversion, two-dimensional (2D) edge detection on images, 3D contour reconstruction from 2D edge are also promising for point cloud processing in other application fields. [ABSTRACT FROM AUTHOR]

The main objective of this work is to investigate the microstructure, mechanical and corrosion properties of 304 stainless steel-H13 composites produced using high pressure cold spray process. 304 stainless steel powders with varying amount of H13 tool steel powders (0, 25, 50 and 75 wt.%) were pre-mixed and cold spray deposited using nitrogen process gas to produce metal-metal composites. H13 tool steel addition improved plastic deformation, reduced porosity, increased microhardness, and tensile properties of 304 cold spray coatings. The tensile properties increased with the increase in H13 tool steel content and with post deposition heat treatment. Post deposition heat treatment at 900 °C significantly improved the tensile strengths and ductility of the composite coatings. However, the wear rate and corrosion susceptibility increased with the tool steel addition in the as-deposited condition, but improved when heat treated to 900 °C. The overall results suggest that the addition of H13 in 304 cold sprayed coatings deposited with nitrogen process gas could be used as a cheaper alternative to helium as well as improve both the microstructure and mechanical properties over pure 304 cold spray coatings. [ABSTRACT FROM AUTHOR]

In this study, a method is demonstrated for predicting defect-laden areas within deposits produced by cold spray additive manufacturing that are caused by substrate geometry and robot tool path. Leading edge shapes were used as the test bed for this method, and porosity was selected as the metric by which defects are quantified. A porosity model was developed based on the observation that porosity is significantly influenced by particle impact velocity normal to the surface and is therefore highly correlated to particle impact angle. The model outputs deposit shape and a probability map of porosity based on initial substrate geometry and robot tool path as inputs. The model was calibrated by experimental deposits formed at varying impact angles. To validate the method, the model was applied to three airfoil leading edge geometries and was shown to qualitatively estimate the density of pores in the deposit. The study also revealed that robotics alignment is an important factor in causing defects within highly curved geometries. The mathematical construct of the model is applicable to other applications outside of leading edges and deposit properties beyond porosity, but other applications and properties are not evaluated in this study. [ABSTRACT FROM AUTHOR]

Cold spray metallization of polymers is a promising surface engineering technique that enables the deposition of metal coatings onto polymer substrates at low process temperatures, resulting in improved surface properties, thus enhanced functionality of the polymeric material. However, deposition of well-adhering metallic coatings without causing surface damage to the polymer substrate is still a challenge. In this work, copper-polyamide composite coatings with different copper concentrations between 30 and 75 vol.% in the starting powders were deposited on polyamide substrates using a low-pressure cold spray system with two nozzle geometries of short and long diverging sections. The spray parameters were first developed for the deposition of polyamide powder (at gas temperature of 260 °C and gas pressures ranging from 0.41 to 1.37 MPa), and then used to spray the composite powder mixtures where the polyamide particles were acting as a binder for copper particles. Inflight and impact particle characteristics (velocity and temperature) of the polyamide powder were simulated to better understand the deposition properties. Considering that the selected conditions were suboptimal for the deposition of copper particles, no surface damage was caused as no penetration of the copper particles into the polymer substrate occurred. The results show that increasing the copper content in the powder mixtures significantly improved the resulting coating uniformity and the retained copper content. In addition, the coating deposited by spraying the powder mixture with a higher copper content of 75 vol.% and using the longer nozzle yielded the highest cohesion strength. To further improve coatings cohesion, two post-spray processing methods of furnace heating and hot pressing were used, and the effect of each process on coatings properties was investigated.Please confirm if the author names are presented accurately and in the correct sequence (given name, middle name/initial, family name). Given name: [Kintak Raymond] Last name [Yu]. Also, kindly confirm the details in the metadata are correct.The author names are now correct: Kintak Raymond given name and Yu last name All other details are corrects [ABSTRACT FROM AUTHOR]

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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 modeling additively manufactured geometry; however, such a data-driven modeling 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 modeling of an overlapping-track profile using a Gaussian Process Regression model. The proposed Gaussian Process modeling 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 could provide better predictive performance than the Gaussian superposing model alone and the 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. [ABSTRACT FROM AUTHOR]

In this study, the role of feedstock powder in influencing the characteristics of cold spray deposition is explored. Four distinct types of Cu feedstock powders, derived through electrolysis and employing varied gas atomization methods, are applied to a Cu substrate via low-pressure cold spray coating. We investigated the impact of feedstock powder on the resultant coatings' microstructure and mechanical properties. A comprehensive statistical model is developed, considering the cold spray parameters, weight change, coating thickness, and discerning their significance and interactions. Optimal conditions for carrier gas temperature and pressure are identified at approximately 400 °C and 1.99 MPa, respectively, consistent across all Cu powders. Velocity analysis reveals particle velocities ranging from 373 to 564 m/s under these optimal conditions. Coatings deposited using satellite-free gas-atomized powder, characterized by enhanced sphericity, exhibit superior characteristics, including minimal porosity (0.66 ± 0.35%), high flattening ratio (3.57 ± 1.51), elevated microhardness (107 ± 3 HV) and high bonding strength (20.7 ± 2.3 MPa). In contrast, coatings deposited with gas-atomized powder featuring microsatellite particles and electrolytic powder with irregular shapes display distinct properties. The observed trends are attributed to lower oxygen content and reduced oxide levels near the surface of the more spherical, satellite-free powder. This powder also demonstrates heightened plastic deformation during deposition. The increased peening effect of satellite-free gas-atomized powder during cold spray results in elevated dynamic recrystallization near the substrate surface, leading to smaller grains at the interface. Microstructural evolution analysis, utilizing electron backscatter diffraction, further elucidates the heterogeneous deformation and grain refinement occurring in Cu splats during cold spray coating. [ABSTRACT FROM AUTHOR]

High-performance polymers such as poly(ether ether ketone) (PEEK) are appealing as composite components for a wide variety of industrial and medical applications due to their excellent thermomechanical properties. However, conventional PEEK metallization methods can often lead to poor quality control, low deposition rate, and high cost. Cold spray is a promising potential alternative to produce polymer–metal composites rapidly and inexpensively due to its relatively mild operating conditions and high throughput. In this study, we investigated the deposition characteristics of metal–polymer composite feedstock, composed of PEEK powder and copper flake in varying ratios, onto a PEEK substrate. Copper-PEEK powder blends were prepared by both hand-mixing and cryogenic milling (cryomilling), which predominantly creates composite particles with micron-scale copper domains coating PEEK particle surfaces. This process non-monotonically affects the relative dominance and length scales of the multiple contributing deposition mechanisms present in mixed-material cold spray. In low-pressure cold spray, deposits showed significant changes in deposition efficiency and composition as a result of milling, with improvements in these characteristics most dramatic at lower Cu fractions. Deposits of a cryomilled blend of nominally 30 vol.% copper in PEEK exhibited minimal porosity under scanning electron microscopy, complete retention of powder composition, and the highest deposition efficiency among all samples tested. Notably, neither neat PEEK nor neat Cu meaningfully deposited at the same mild conditions as this 30 vol.% Cu blend, indicating a synergistic departure from linear mixing rules driven by the relative balance of local deposition interactions (e.g., hard–soft, soft–soft, etc.). Intentional powder and process design toward optimizing this balance may facilitate cold spray metallization applications. [ABSTRACT FROM AUTHOR]

Polymers have proven to be challenging to cold spray, particularly with high efficiency and quality when using inexpensive nitrogen (N2) and air propellants. Helium (He), when used as a process propellant, can improve spray deposit properties but is often undesirable due to its limited availability and high cost. In this study, additives of multiple particle sizes and materials were mixed with polymer powder in an effort to improve the performance of polymer sprays using mainly N2 as a process propellant. The effects of hard-phase additives on deposit microstructure were investigated by precise ion beam polishing of deposit cross sections and subsequent electron microscope imaging. Additional metrics including the density and post-spray composition of deposits were investigated to quantify the peening effect and the amount of embedded additive. Additives, regardless of size, were observed to embed in the spray deposits. Additionally, hard-phase additives demonstrated nozzle cleaning properties that continually remove polymer fouling on the nozzle walls. Inversely, sprays with polymer powder and no additives tended to clog the nozzle throat and diverging section because of continual fouling. [ABSTRACT FROM AUTHOR]

Cold spray (CS) is a solid-state process for depositing thick layers of material via the successive high-velocity impact of powder particles onto a solid surface, which leads to high rates of deformation, interparticle bonding, and coating build-up. Although CS is finding commercial utilization in non-load-bearing repair and coating applications, clear nondestructive characterization procedures are necessary to realize its potential in load-bearing structural applications. In this study, the viability of electrical conductivity and through thickness ultrasound wave velocity measurement methods was studied to serve as a means for nondestructive quantitative measurement for quality control in CS and potentially other additive manufacturing (AM) methods. Eddy current, ultrasound, porosity, hardness, and uniaxial tensile strength tests were conducted on CS deposited layers of aluminum alloy 6061 and copper on aluminum alloy 6061 and commercially pure copper substrates, respectively. CS gas dynamic parameters were intentionally and systematically varied to result in corresponding discrete differences in mechanical properties of deposits. Ultrasound measurements of longitudinal wave velocity and eddy current electrical conductivity measurements showed good correlation with process conditions, microstructural characterization results, and destructive mechanical tests (hardness, tensile). The results of this work show that ultrasound wave velocity and electrical conductivity correlate well with increased particle impact velocity in CS deposited aluminum and copper blocks, which evidently show an incremental decrease in porosity, increase in hardness, and increase in tensile strength. The outlined ultrasound and eddy current nondestructive testing methods present effective means for quantitative assessment of cold spray deposited structures while intact with the substrate. [ABSTRACT FROM AUTHOR]

The use of process–microstructure–property relationships for cold spray can significantly reduce application development cost and time compared to legacy trial and error strategies. However, due to the heterogeneous microstructure of a cold spray deposit, with (prior) particle boundaries outlining consolidated splats (deformed particles) in the as-spray condition, the use of automated analysis methods is challenging. In this work, we demonstrate the utility of quantitative data developed from a convolutional neural network (CNN) for feature extraction of cold spray microstructures. Specifically, the power of CNN is harnessed to automatically segment the deformed particles, which is hardly accessible at scale with traditional image processing techniques. Deposits produced with various processing conditions are evaluated with metallography. Parameters related to particle morphology such as flattening ratio are also quantified and correlated to strength. [ABSTRACT FROM AUTHOR]

A previous study on the pull-off testing of metallized carbon fiber-reinforced polymers (CFRPs) via cold spray showed that better adhesion strengths could be obtained when features such as carbon fibers or surfacing elements were present, by providing potential mechanical interlocking features. In this work, a first approach to determining the effect of the fiber orientation on the deposition and bonding of the metallic coating to the thermoplastic composite substrate is explored. Pure Sn powder was cold sprayed onto two thermoplastic Polyether–Ether–Ketone (PEEK) CFRP substrates, containing carbon fibers with different orientations: one had fibers in the plane of the substrate (unidirectional tape), while the other had fibers mostly perpendicular to the substrate (ZRT film). Characterization of the coatings was performed via scanning electron microscopy (SEM) and confocal microscopy, and some aspects of mechanical testing (namely wear and scratch testing) were carried out to assess the effect of the substrate on the properties of the coatings. A slight improvement of the coating deposition was observed on the sample with the ZRT film, and this was associated with deeper penetration of tin into the substrate, around the carbon fibers, for improved mechanical interlocking. Wear testing did not seem to reveal any differences between both samples. Finally, scratch adhesion tests were performed to qualitatively assess the bonding mechanism at the coating-substrate interface, and while adhesive failure seems to be the main failure mechanism, the coating of the Z sample seems to co-deform with the substrate during testing, which could highlight better adhesion strength. [ABSTRACT FROM AUTHOR]

The promising structural properties of fiber-reinforced polymer composites make them widely popular in the energy, automotive, defense, and aerospace industries. One of the most challenging limitations associated with the application of composites is their maintenance and repair. In this study, a polymer cold spray approach is introduced as an efficient alternative for the structural repair of fiber-reinforced polymer composites, without the use of additional repair media. Damage in the form of circular tapered holes is created in glass fiber-reinforced polymer (GFRP) composite substrates using conventional drilling. This damage is repaired by cold spray with thermoplastic (nylon 6) and thermosetting (polyester epoxy resin) materials. The fundamental adhesion mechanisms near the repair surface are investigated through microstructural observations and highlight the role of adiabatic shear instability due to the occurrence of severe plastic deformation in the particle impact zone. Microstructural examinations also suggest that no significant fiber damage or surface degradation occurs due to the repair by cold spray. Mechanical tests performed on neat, damaged, and repaired composites reveal the partial recovery of structural performance and load-bearing capacity after cold spray repair. Additionally, the cold spray-repaired GFRP samples are compared with conventional epoxy resin repair methods. Results obtained in this work highlight cold spray as a promising and rapid technique for the on-site repair of composite structures with minimal pre-/post-processing requirements. [ABSTRACT FROM AUTHOR]

Cold spraying (CS) of high-strength materials, e.g., Inconel®625 is still challenging due to the limited material deformability and thus high critical velocities for achieving bonding. Further fine-tuning and optimization of cold spray process parameters are required, to reach higher particle impact velocities and temperatures, while avoiding nozzle clogging. Only then, sufficiently high amounts of well-bonded particle–substrate and particle–particle interfaces can be achieved, assuring high cohesive strength and minimum amounts of porosities. In this study, Inconel®625 powder was cold sprayed on carbon steel substrates, using N2 as propellant gas under different spray parameter sets and different powder sizes for a systematic evaluation. Coating microstructure, porosity, electrical conductivity, hardness, cohesive strength, and residual stress were characterized in as-sprayed condition. Increasing the process gas temperature or pressure leads to low coating porosity of less than 1% and higher electrical conductivity. The as-sprayed coatings show microstructures with highly deformed particles. X-ray diffraction reveals that powder and deposits are present as γ-solid-solution phase without any precipitations. The deposits show high microhardness and compressive residual stresses, which is attributed to work hardening and peening effects. The optimized deposits reach almost bulk material properties and are thus well suited for industrial applications. [ABSTRACT FROM AUTHOR]

Cold spraying has great potential for additive manufacturing, especially of oxidation-sensitive metals, because the material is not melted and significantly higher deposition rates can be achieved than with conventional additive manufacturing processes such as selective laser melting or direct metal deposition. Titanium is regarded as a high-performance engineering material due to its unique combination of properties, including good corrosion resistance, biocompatibility and high strength at comparatively low density. However, due to its high price, it appears reasonable for many applications to use material compounds in which titanium is only used on the surface of the workpiece, while less expensive materials such as aluminum are used for the remaining volume. In the present work, cold sprayed pure titanium coatings were deposited on Al substrates and then formed to defined 3-dimensional final contours by die forging and rotary swaging. Different porosities were selectively set in order to evaluate their influence on the coating adhesion and cohesion in the forming process. Pre-consolidation of the coatings and the use of Al/Ti interlayers proved to be promising strategies. [ABSTRACT FROM AUTHOR]

Cold spraying has emerged as a promising technique for the repair of metallic components. Manipulating the cold spray gun by industrial robots, referred to as robot-guided cold spraying, enables flexible and controlled material deposition. This work proposes a concept for automated planning of robotic cold spray paths and trajectories, enabling effective and efficient material deposition at specified repair locations. The concept incorporates predefined cold spray parameterizations and boundary conditions to provide the best possible material deposition for the individual repair application. The concept begins with the extraction of the volume to be filled. This volume is then sliced into suitable adaptively curved layers and converted into point clouds for path planning. Subsequently, the cold spray path is converted into a trajectory by adding a calculated spray velocity profile to produce the required locally varying layer thicknesses. In addition, simulation of the material deposition and a kinematic analysis of the simulated trajectory are performed. These are utilized as performance indicators for assessing deposit quality and material efficiency, enabling the validation and improvement of the parameterized trajectory. Finally, the implementation of the entire concept is demonstrated by representative use cases. The results demonstrate successful automated path and trajectory planning by the proposed concept, contributing to the overall goal of automated repair of damaged components by cold spraying. [ABSTRACT FROM AUTHOR]

In the cold spray additive manufacturing (CSAM) process, layer-by-layer stacking is an efficient method to achieve materials additive manufacturing (AM). Unlike other AM processes, such as selective laser cladding, which can quickly achieve trajectory planning by using commercial software, there is currently no general methodology for spray trajectory planning in the CSAM process. Accurate and fast generation of trajectories for each layer of the manufactured workpiece is a challenge. When a component with multiple features is manufactured, the spray paths between features cannot be created easily due to the "one-stroke" character. That is, the powder feeding cannot be interrupted during the entire spraying process. This means that for the deposition of multi-featured components, the planning of the path of the nozzle transfer from one feature to another is a challenge. If the transfer path goes directly across the area of the deposited feature, it can significantly change the shape of the deposit and cause undesired deposition results. Additionally, the spray gun or the substrate held by the robot usually needs to be deflected by a certain angle to compensate for the loss of deposit along the edges. An accurate and efficient spray trajectory planning is the most critical part of the CSAM process. Thus, this article proposes a general manufacturing methodology for complex structural components in the CSAM process. The simulation and experimental results revealed that the methodology can efficiently generate the necessary spray trajectory to fabricate the desired deposit. It makes CSAM truly possible in the manufacture of workpieces with complex geometries. [ABSTRACT FROM AUTHOR]

In this study, the effect of particle size on the microstructure and mechanical properties of cold-sprayed nickel coatings was investigated using three particle size ranges of pure nickel powders. The experimental results show that the mechanical properties of the coating fabricated by the fine powder with a D50 of 25 μm are lower (microhardness and tensile strength of 257.5 HV0.1 and 126 MPa, respectively) compared to those from the coarser particle sizes (D50 = 45 μm and 67 μm) because of the higher yield strength of powder, which makes it difficult to generate sufficient plastic deformation during the spraying process. The powder with the largest particle size, D50 of 67 μm, has a low impact velocity, which does not allow for a high-quality coating due to less plastic deformation, and the porosity is higher up to 0.7%. When the mean particle size of the powder is 45 μm, the coating shows the highest degree of densification, the porosity is 0.4%, and the mechanical properties of the coating are better with the microhardness and tensile strength of 289.2 HV0.1 and 208 MPa, respectively. [ABSTRACT FROM AUTHOR]

The residual stress state in cold spray coatings, which is typically compressive in nature, can be crucial for the coating integrity at high levels or for thick coatings. As an alternative, the analysis using the curvature measurement was applied in this study. The stress measurement during cold spray deposition was made by using an in situ coating property sensor (ICP sensor), which is relatively widely used in thermal spray and enables a fast comparison of several process parameters. The results were then compared to post-deposition curvature measurements. It could be revealed that the usage of a very slow robot traverse speed can lead to tensile residual stresses in cold-sprayed coatings. This finding was explained by the high local temperature during deposition and the formation of tensile stresses during cooling of the deposited material to the average substrate temperature. The increase in the powder feed rate can increase this effect. Preheating did not influence the final stress state. An analytical model is presented which can at least semi-quantitatively explain the observed findings. As an outcome of the research work, it is now possible to adjust the residual stress state in cold spray coatings from tensile to compressive and vice versa with the opportunity of a zero stress state. [ABSTRACT FROM AUTHOR]

Al-x%Al2O3 composite protective coatings were prepared on the surface of LA43M Mg-Li alloy substrate by cold-spraying technology. The microstructure, corrosion resistance, tribological properties of the coatings were investigated in detail. The results showed that the addition of hard Al2O3 particles was conducive to the deposition of Al-based coating, and the bonding mode between Al-x%Al2O3 coating and substrate was metallurgical bonding and mechanical interlocking. Moreover, the addition of Al2O3 particles was beneficial for increasing the density of the coating, and significantly improving the corrosion resistance, hardness and tribological properties of composite coatings. Respecting the corrosion resistance of Al-x%Al2O3 composite coatings, the electrode potential of coatings increased significantly and stabilized to about − 1.0 V when the additive amount of Al2O3 increased to 10-25%, while the corrosion current density decreased to about 10-8 A/cm2, which was four orders of magnitude lower than that of LA43M Mg-Li alloy substrate. On the other hand, the tribological properties of Al- x%Al2O3 composite coatings were improved with the additive amount of Al2O3 phase increased. When the additive amount of Al2O3 increased to 15-25%, the coefficient of friction was stable at about 0.45 and the wear rate decreased. [ABSTRACT FROM AUTHOR]

High-strength bolt attachment parts of steel bridges are prone to corrosion at an early stage, and blast nozzles and power tools cannot be inserted due to the structural shape during repairs, and there are many cases where rust remains partially. To solve such a problem, the Cold Spray technology, which uses a powder that mixes zinc and alumina, exhibits corrosion resistance by depositing a film even if rust remains. In this paper, first the anticorrosion mechanism on the residual rust was examined by focusing on the permeation prevention of the corrosion factor of the Cold Spray anticorrosion film and the adhesion of the residual rust boundary. Findings indicate that the Cold Spray anticorrosion film exhibits a porosity approximately one-tenth that of films engendered via the thermal spraying method, thereby constituting a denser film with heightened environmental barrier attributes. The firm adherence of the Cold Spray anticorrosion film to the residual rust interface is explained by differences in hardness between Cold Spray, residual rust, and zinc. Furthermore, the physical characteristics of zinc undergo modifications influenced by the temperature environment during construction, imparting a plasticity to zinc on uneven rust surfaces. [ABSTRACT FROM AUTHOR]

In this work, the effect of double-aging (DA) heat treatment on the microstructure and the tribological behaviour of cold-sprayed Inconel 718 (IN718) coating was studied and compared with hot-rolled IN718. After double-aging, the dendrite structure of the as-sprayed coating was modified and secondary phases such as γʹ, γʺ, and δ phases were formed. The microhardness of the coating improved after double-aging and was higher than the double-aged IN718 due to the leftover microstrain in the coating. Sliding wear tests were carried out at room temperature (RT) and 600 °C using a ball-on-disc tribometer with alumina balls. The double-aged coating had improved wear resistance than the as-sprayed coating and the double-aged substrate at room temperature. At 600 °C, the wear rate of the hot-rolled IN718 was marginally lower than the as-sprayed coating due to the formation of a comparatively thick mechanically mixed layer (MML) reinforced with Al2O3 which was more protective in nature. The double-aging treatment improved the wear resistance of the coating significantly at 600 °C and its wear rate was comparable to that of the double-aged substrate. The substrate and the coating undergo a combination of abrasive and tribo-oxidative wear at RT. At 600 °C, the wear mechanism involves a combination of oxidative and abrasive modes. Raman analysis revealed that the oxide formed on the wear track consisted of NiO and Fe3O4 at RT, and the glaze layer formed during high-temperature wear consisted of a mixture of the NiFexCr2-xO4 spinel and Fe3O4. [ABSTRACT FROM AUTHOR]

In an effort to improve the fretting corrosion resistance of cold spray (CS) additively manufactured 316L stainless steel (SS), friction stir processing (FSP) was applied as a post-processing surface modification technique. The change in wear-corrosion synergy and degradation was evaluated by assessing changes in mechanical, chemical, and elemental responses. It was found that the improvement in hardness and reduction in porosity induced by FSP improved the stiffness of the surface, resulting in a nearly full-stick fretting regime. Due to the influence of fretting corrosion, high amounts of Ni were present within the fretting wear track, decreasing the surface's propensity for accelerated corrosion. The fretting wear mechanism for the CS FSP specimen was abrasion-dominant, whereas the CS specimen mainly consisted of surface fracturing and some abrasion. Other material factors such as surface strengthening, microstructural refinement, and changes in the atomic phase enabled by FSP also contributed to the improvement in fretting corrosion resistance. Collectively, this work shows that FSP post-treatment is a viable technique to improve the fretting corrosion degradation resistance of additively manufactured CS 316L SS components. [ABSTRACT FROM AUTHOR]

Due to its low heat input to the temperature-sensitive substrates, cold spray (CS) is regarded as a promising coating technique for achieving polymer surface metallization. In previous studies, the performance (e.g., electrical conductivity, adhesive strength, tribological properties, etc.) of the metalized Al coatings on the polyether ether ketone (PEEK) is rather poor. Therefore, in this paper, irregular Al2O3 particles were strategically added to the feedstock in different proportions (0, 10, 20, 30, 40 wt.%) to achieve better coating performance. The influence of Al2O3 percentage on coating microstructure, microhardness, adhesion strength, electrical conductivity, and wear resistance was comprehensively investigated. The results revealed that adding an appropriate proportion of irregular Al2O3 particles to feedstock can effectively improve the electrical conductivity, adhesion strength, and wear resistance of the coating. The highest electrical conductivity (18.9 MS/m) and adhesion strength (6.4 MPa) were achieved for 20 wt.% Al2O3, and the lowest wear rate (i.e., half that of pure Al coating) was achieved for 30 wt.% Al2O3 content in the feedstock. These attributes were mainly related to enhanced cohesion between Al-Al splats, the 'anchor effect' of Al2O3 particles at the coating/substrate interface, and the excellent load-bearing capacity of Al2O3 particles, respectively. [ABSTRACT FROM AUTHOR]

This paper investigates customized AA5083 and Al-Mg binary powders produced by gas atomization and assesses cold spray (CS) deposition of these materials with the evaluation of interface quality, deposition efficiency, porosity, and microhardness. While there has been extensive research progress on CS deposition of AA2024, AA6061, and AA7075, less attention has been given to CS 5xxx-series (Al-Mg) aluminum alloys. For the development and investigation of CS Al-Mg series alloys, AA5083 and customized Al-Mg binary powders were fabricated using a close-coupled inert gas atomizer, and those powders were sprayed using a high-pressure cold spray system to produce CS Al-Mg deposits. The microstructural characteristics of the powders, such as lattice constant and the formation of intermetallic networks, were affected by the Mg content of as-atomized powders. Selected CS parameters were able to produce highly dense CS deposits over a range of 1.7-5 wt.% Mg. The Mg content of as-atomized powders also influenced the hardness of the deposits and the DE while having no effect on porosity. The influence of Mg content on powder properties, CS process, and CS Al-Mg deposits has been discussed. [ABSTRACT FROM AUTHOR]

The inter-particle bonding (IPB) mechanism of cold-sprayed titanium alloy during heat treatment (HT) is not clear. The interfacial microstructure and bonding characteristics at the interface of cold-sprayed Ti6Al4V after HT were studied at the micro- and nano-scale. As a result, the nanocrystallization at IPB during cold spray (CS) cannot cause obvious metallurgical bonding between Ti6Al4V particles. The average Young's modulus of CS Ti6Al4V is 57% higher than that of powder, but the average Young's modulus of HT sample decreases by 16%. The internal stress and dislocation distribution of interfacial microstructure can lead to various microstructure features and non-uniform rates of microstructure growth at deformed transition layer and IPB during HT. The nanograins at the IPB grow into micron-equiaxed grains. On the contrary, the micron martensitic laths at deformed transition layer adjacent to IPB show the characteristics of equiaxed nanograins transformation under the action of grain boundary bulges induced by dislocation entanglement. [ABSTRACT FROM AUTHOR]

Hybrid bond layers (BLs) were designed, fabricated, and evaluated for cold spray metallization of CFRP. The bond layers consisted of metal mesh embedded in a polymer film adhesive co-cured to the CFRP. Efforts were devoted to identifying the critical opening ratio—i.e., the ratio of mesh opening size to powder diameter, for deposition of an adherent coating. Analysis of powder deposited at mesh openings show a transition from erosion (at a mesh opening ratio of 6.4) to mechanical interlocking and formation of a continuous coating with decreasing opening ratio. Selection of opening ratio yielded either (a) a grid of consolidated thin-walled deposits atop mesh wires separated by microchannel openings, or (b) densified coatings of cold-sprayed Ti. The effective opening ratio increased with increasing diameter ratio—i.e., the ratio of wire diameter to powder size, a consequence of eroded wire peripheries at shallow impact angles. These findings inform the design of future hybrid BLs, in concert with the selection of powder size, for cold spray metallization of CFRP. [ABSTRACT FROM AUTHOR]

Residual stress is an important factor that affects the properties of cold spray coatings. The study performed 2D single-, 3D single-, and 3D multiple-particle finite element simulations based on the Eulerian method, and hole drilling measurements to study residual stress in cold-sprayed copper coatings. The study examined how the basic modeling parameters affect residual stress in the 2D system. It found that the mesh size, substrate dimension, and simulation duration change the residual stress; while material failure does not have much effect because failure is localized. It also found that thermal softening, which occurs when the initial temperature and/or plastic deformation increase, helps to reduce the residual stress. In addition, the residual stress along the axisymmetric axis of the particle changes from being compressive at first to being compressive-tensile-compressive along the through-depth thickness direction with the interfacial stress being tensile that mainly originates from friction shear of the interfacial layers. For the 3D single-particle simulations, the average residual stress to the through-depth thickness shows tension to compression transition and is similar to the 2D cases. For the 3D multiple-particle simulations, the residual stresses in the coatings/substrate are all compressive because of the repeated and strong impact of the particles, which agree with the experimental measurements. The study also found that the compressive stresses decrease when the coating thickness increases because of more plastic deformation-induced thermal softening. This paper clarifies the effects of Eulerian-based finite element parameters on simulating residual stress in cold spray and will serve as a valuable reference for future studies. [ABSTRACT FROM AUTHOR]

The present study investigates the application of friction stir processing (FSP) on the degradation (wear, corrosion, and wear-corrosion synergism) response of cold spray additive manufactured (CSAM) 316L SS components. All tribological-based tests were conducted using a reciprocating ball-on-flat configuration in 3.5 wt% NaCl solution. Each degradation response was then correlated with the atomic, microstructural, and mechanical characteristics of the pre-and-post-FSP surfaces. In pure wear conditions, the austenitic phase transformation induced by FSP treatment decreased the frictional response and slightly increased the wear rate compared to the unprocessed CSAM substrate. In pure corrosion conditions, the densified surface enabled by FSP resulted in improved electrochemical resistance and a lessened corrosion rate. In wear-corrosion synergism conditions, the influence of FSP decreased the cumulative wear loss and wear-corrosion synergism of the CSAM substrate. It is believed that the combination of phase change, surface densification, and microstructural refinement induced by FSP are responsible for the improved wear-corrosion resistance. Based on these findings, it can be suggested that FSP is indeed a useful technique to improve the wear, corrosion, and wear-corrosion characteristics of CSAM 316L SS. [ABSTRACT FROM AUTHOR]

In high-pressure cold spray, it has been demonstrated that the enthalpy of the particle carrier gas has a significant effect on the propellant gas conditions and resulting particle impact velocities and temperatures. Through modeling and experimentation, this study demonstrates that in low-pressure cold spray, the enthalpy of the particle carrier gas has a minimal effect on the particle velocity; therefore, particle temperature can be controlled independently from particle velocity. This is a unique feature of downstream injection and a valuable tool when dealing with temperature sensitive substrates and particles. In this study, particle preheating was used to inject pure aluminum particles up to temperatures of 500 °C, about 80% of their melting temperature. This particle preheating was accomplished without clogging because of a novel particle preheater which eliminated the particles exposure to hot metal surfaces. It was found that even after substantial spray time, there was no evidence of wear or clogging. The preheating resulted in a DE increase of 3.6 times when compared to the injection of room temperature particles. [ABSTRACT FROM AUTHOR]

This study presents a bibliometric analysis of cold spray research publications from the Scopus database from 1994 to 2022 period. This study aimed to: (a) examine the evolution and dissemination of cold spray research; (b) identify the key topics discussed in cold spray research; and (c) identify the research power of this research area and its collaborations. The study retrieved 1944 documents for further analysis using various tools based on the keywords used in the article title that are related to cold spray. This study employed Microsoft Excel for frequency analysis, VOSviewer for data visualization, and Harzing's Publish or Perish for citation metrics and analysis. Standard bibliometric indicators such as the growth of publications, authorship patterns, collaboration, and prolific authors, country contribution, most active institutions, and most cited articles are used to report the findings of this study. According to our study, there has been a steady increase in publications on cold spray research for almost three (3) decades. The results of the bibliometric analysis illustrate the positive trend in cold spray research around the world, highlighting the advancement of cold spray technology, applications, and fabrications. Indirectly, it would also affect manufacturers all over the world since the promising results of research into cold spray would eventually lead to a rise in demand for cold spray. The study contributes significantly to expanding the accessibility and global reach of cold sprays. [ABSTRACT FROM AUTHOR]