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

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

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

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

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

Continuous monitoring of spray velocity during the cold spray process would be desirable to support quality control, as spray velocity is the key process parameter determining the deposit quality. This study explores the feasibility of utilising Airborne Acoustic Emission (AAE) for real-time monitoring of spray velocity. Six spray tests were conducted, varying pressure and temperature to achieve different velocities. Optical means were used to measure velocity; while, the signal from the AAE was captured during deposition via a microphone. Features demonstrating a strong correlation with velocity were extracted from the acoustic signals. Both rule-based and machine learning models were employed to identify the moments where the nozzle was engaged with the substrate and diagnose the velocity. The results indicate that monitoring the spray velocity of the cold spray process using AAE is feasible. [ABSTRACT FROM AUTHOR]

Cold spray is a dynamic additive manufacturing process which results in a unique microstructure and mechanical properties. This work investigates cold spray deposited material under high strain-rate dynamic loading, and specifically the influence of post-build heat treatment on the material strength when subjected to incipient spallation. As-deposited and heat-treated samples were characterized and subjected to shock loading with a plate impact apparatus; the free-surface velocity was measured during the experiment, and the samples were recovered for postmortem analysis. The test results show that the as-deposited material has little to no strength under high strain-rate tensile loading and breaks into pieces. After a short heat treatment, the material recovers some of its tensile strength (compared to wrought copper) but does not exhibit the expected damage morphology and void distribution. When the heat treatment time is extended to several hours and the temperature is increased, the material exhibits ramp-like shock rise and damage formation that is widely distributed within the sample. This work contributes to a better understanding of the influence of heat treatment on the microstructure and subsequent material strength properties under high strain-rate loading, which is crucial for applications where cold spray is a technique of interest. [ABSTRACT FROM AUTHOR]

This study explores the potential of cold spray technology for repairing high-strength Al7075 alloy components, particularly in the aerospace industry. The gas-atomized powder contains a dendritic cell structure with solutes segregated at the dendritic cell boundaries. Thus, direct aging of atomized powder fails to induce the formation of strengthened precipitates. Therefore, the effect of different powder pre-treatments on the deposition efficiency, microstructure, and aging behavior of the coatings was investigated. Cold spray coatings were deposited using as-received powder, solutionized, and solutionized + aged powders, revealing a significant improvement in thickness for coatings obtained using solutionized (110%) and solutionized + aged (80%) powders compared to the coating from the as-received atomized powder. Further, coatings deposited using as-received, solutionized, and solutionized + aged powders, were aged at 120 °C for various durations and the aging response of different coatings were studied. Microstructural studies revealed that gas-atomized powders exhibited dendritic structures with segregated solutes. Solutionizing eliminated the dendritic features, promoting deposition efficiency upon cold spraying. Aging of the coating from the solutionized powder led to the formation of ultrafine η' precipitates (29 ± 8 nm length, 2 ± 1 nm diameter) at peak-aged condition (after 8 h). These findings demonstrate the effectiveness of powder pre-treatment in tailoring the microstructure and deposition behavior of cold-sprayed Al7075 coatings, offering a promising approach for repair applications. [ABSTRACT FROM AUTHOR]

In this study, the influence of cold‐spray processing on the integration of 1D boron nitride nanotubes (BNNTs) into aluminum (Al) matrix composite deposits is delved into. Successful deposition of Al‐BNNT composite is achieved by pre‐spray dispersion of BNNTs in Al powder via wet mixing aided by ultrasonication. Pure Al powder deposition at 380 °C is limited by nozzle clogging, restricting the deposit thickness to 0.2 mm, while the presence of BNNTs enables longer spraying due to nozzle cleaning and damping by hard BNNTs, allowing thicker Al‐BNNT deposits of about 2 mm. Microstructural analysis reveals severely deformed Al splats decorated with a uniformly distributed network of BNNTs at the intersplat boundaries, reducing the porosity from 8% to 4% and increasing the splat flattening by 40%. Tribological testing demonstrates resistance of BNNTs to normal force, resulting in a 21% improvement in coefficient of friction and a 65% reduction in wear volume in the Al‐BNNT composite. Additionally, incorporating 3 vol.% BNNTs enhances the neutron radiation shielding by 35%. These improvements in the composites are attributed to reduced porosity and the inherent properties of BNNTs, such as high strength, the ability to produce tribofilm lubrication during dry sliding wear, and their high neutron absorption cross‐sectional area. [ABSTRACT FROM AUTHOR]

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

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

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

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

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

A Non-Destructive technique (NDT) based on Active Thermography (AT) is proposed to correlate mechanical properties, process parameters and thermal response for High-Entropy Alloys (HEA) coatings. More in detail, the Pulsed technique is utilised to investigate thermal responses generated by different High-Entropy Alloys (HEA) coatings. In particular, specimens tested in this work are made of several chemical compositions (AlxCoCrCuFeNi and MnCoCrCuFeNi) and are realised by using different Cold Spray temperatures (650°C, 750°C and 850°C), generating coatings with various mechanical properties. This way, results in terms of thermal responses obtained with a Non-Destructive technique are correlated, by means of ANOVA, with the corresponding chemical compositions and process parameters of each specimen. The impact of both roughness and emissivity on the process characterisation was also investigated. [ABSTRACT FROM AUTHOR]

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

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]

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

Fiber-reinforced polymer composites are prominent structural components in various industries such as aerospace, automotive, and wind energy. These materials are considered due to their high strength-to-weight ratio and relative ease of fabrication. However, fiber composites possess low electrical and thermal conductivities and are prone to impact-induced damage. Metallization of fiber-reinforced polymer composites has become an area of interest as a means to prevent abrasive and corrosive damage while also improving other physical properties including thermal and electrical conductivity. The possibility of using cold spray as a novel composite metallization approach has been investigated in this work. The significance of cold spray for metallization is due to relatively low process temperatures which effectively protect the underlaid substrate from potential temperature degradation. As a practical approach to further reduce the possibility of cold spray-induced damage, the present study explores the impact and failure mechanics of metal particles coated with a thin polymeric shell, hence the term polymer-coated metal particle. The thorough model-based analyses presented herein indicate that the so-called polymer-coated metal particles can be cold spray deposited without imposing significant damage to the composite substrate mainly due to the 'cushioning' effect of the thin polymer shell. The results discussed here also provide guidelines for the surface metallization of high-performance fiber-reinforced thermoplastic composites in practice. [ABSTRACT FROM AUTHOR]

In this study, the effect of an in situ shot peening and cold spraying process for depositing niobium using nitrogen gas was studied and compared to that of traditional niobium sprayed using helium gas. The samples were evaluated using Vickers hardness indentation and defect analysis to compare the mechanical properties and microstructure of the shot-peened samples with that of the helium-sprayed samples. During this study, a mathematical model was proposed to effectively predict the amount of shot peening required to achieve a specific increase in sample hardness. A novel means of using two cold spray systems was also proposed to obtain a better level of control during the shot-peening process. It was found during this study that in situ shot peening can be used to increase the as-sprayed hardness and density of nitrogen-sprayed niobium cold spray deposits to levels comparable to niobium cold sprayed using helium gas. This offers a potential means to transition away from the use of helium gas without sacrificing material properties. [ABSTRACT FROM AUTHOR]

PEEK surface copper metallization is widely used in fields such as power, electronics, and new energy. To enhance the mechanical and electrical characteristics of copper coating on PEEK surface further, this study employed a cold spraying deposition technology of graphene-reinforced copper composite coatings. The investigation focused on the properties comparison between composite coatings and pure copper coatings, and systematically studied the influence of nozzle speed within the range of 50–200 mm/s on the structure and properties of composite coatings. Results show that the mechanical and electrical properties of composite coatings are far superior to those of pure copper coatings. And results indicate that at a nozzle speed of 100 mm/s, the composite coating exhibits the densest structure, with a porosity of 0.31% and minimal graphene aggregation, resulting in superior mechanical and electrical properties. Specifically, the friction coefficient is reduced by 46.81% compared to pure copper coating, measuring 0.4046. Additionally, the Vickers hardness of the composite coating reaches 105.96 HV, and its wear rate is 70.59% lower than that of pure copper coating, at 4.32·10−4 mm3/N·m. Furthermore, the conductivity peaks at 1.295·105 S/cm, representing a 38.77%, increase over pure copper coating. [ABSTRACT FROM AUTHOR]

The present study focused on optimizing the cold spray (CS) process parameters for depositing Fe20Cr20Mn20Ni20Co20 (Cantor alloy) coatings using mechanically alloyed (MA) powder. A two-step design of experiments approach was employed, beginning with the initial screening of input variables using the L8 Taguchi method, followed by the refinement of process parameters through the Box–Behnken design of experiments. Key performance indicators included deposition efficiency (DE), coating thickness per pass, and microstructural parameters including porosity, cracks, and interfacial defects/delamination. The study identified process gas temperature as the primary factor influencing both DE and thickness per pass. Higher gas temperature and pressure, combined with increased scanning speed, resulted in higher DE. The DE of the MA Cantor alloy powder peaked at around 14-15%, with a deposit density greater than 99% achieved at the highest process gas temperature and pressure (1000 °C and 60 bar, respectively). The average hardness of the optimal CS coating deposited using MA powder was found to be 679 ± 17 HV0.1, which is approximately 90% greater than the average hardness reported for CS coatings deposited using atomized powder. [ABSTRACT FROM AUTHOR]

This study investigates the feasibility of using cold spray for repair of Inconel 718 (IN718) components. The effect of cold spray parameters on the particle velocity, splat morphology, deposition efficiency (DE), thickness, and porosity was evaluated. Thick coatings of approximately 4 mm were deposited onto ground and polished IN718 substrates using N2 gas heated to 1000 °C with gas pressure of 5 and 7 MPa. The coatings were subjected to standard double aging (DA) and a combination of solutionizing and double aging (STDA) heat treatment. The microstructure, hardness, porosity, tensile strength, and adhesive strength of as-sprayed and heat-treated coatings were evaluated. Additionally, the tensile properties of the coating–substrate combination (sandwich samples) were also evaluated. It was observed that higher gas pressure led to increased particle velocity, decreased porosity, enhanced hardness, and improved adhesion/tensile strength. The splat size increased with higher particle velocity, indicating greater particle deformation. The DE decreased with increase in number of deposited layers and increased with increase in gas pressure. The AS coating microstructure exhibited a deformed powder microstructure having fine dendritic/cellular structure. Following the DA treatment, the dendritic features were preserved, accompanied by the precipitation of γ′, γ′′, and δ phases. After STDA treatment, a homogeneous microstructure with the presence of γ′, γ′′, and Nb and Ti carbides without any δ phase was observed. The most favorable outcomes were achieved with the 7 MPa STDA sample, yielding a minimal porosity level of 0.4 ± 0.1% and a tensile strength of 1325 ± 10 MPa with a failure strain of 6.1 ± 0.6%. The tensile strength of 7 MPa sandwich sample was found better (1049 ± 8.5 MPa) compared to stand-alone coating (965 ± 24 MPa) after DA treatment. [ABSTRACT FROM AUTHOR]

Cold spray is a material deposition technology with a high deposition rate and attractive material properties that has great interest for additive manufacturing (AM). Successfully cold spraying free-form parts that are close to their intended shape, however, requires knowing the fundamental shape of the sprayed track, so that a spray path can be planned that builds up a part from a progressively overlaid sequence of tracks. Several studies have measured track shape using ex situ or quasi-in situ approaches, but an in situ measurement approach has, to the authors' knowledge, not yet been reported. Furthermore, most studies characterize the track cross section as a symmetric Gaussian probability density function (PDF) with fixed shape parameters. The present study implements a novel in situ track shape measurement technique using a custom-built nozzle-tracking laser profilometry system. The shape of the track is recorded throughout the duration of a spray, allowing a comprehensive investigation of how the track shape evolves as the deposit is built up. A skewed track shape is observed—likely due to the side-injection design of the applicator used—and a skewed Gaussian PDF—a more generalized version of the standard Gaussian PDF—is fit to the track profile. The skewed Gaussian fit parameters are studied across two principal nozzle path parameters: nozzle traverse speed and step size. Empirical relationships between the fit parameters and the nozzle path parameters are derived, and a physics-based inverse relationship between nozzle speed and powder mass deposition rate is obtained. One of the fit parameters is shown to be an effective means of monitoring deposition efficiency during spraying. Overall, the approach presents a promising means of measuring track shape, in situ, as well as modeling it using a more general shape function. [ABSTRACT FROM AUTHOR]

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