Cold Spray Research Articles

Emerging trends in large format additive manufacturing processes and hybrid techniques

AbstractLarge format additive manufacturing (LFAM) technologies are rapidly growing with significant potential for application in multiple technological sectors like aerospace, tooling, automotive, marine, construction, and energy. LFAM processes offer significant advantages including reduced lead time, cost, and material waste, which are further amplified due to the increased volume of the components. This review paper focuses on LFAM technologies with the highest technology readiness level, i.e., metal Directed Energy Deposition (DED), polymer extrusion, and solid-state deposition (i.e. cold spray additive manufacturing (CSAM)). Common system setups, the maximum deposition rate, and the range of processable materials, along with the achievable mechanical properties and geometrical characteristics, are outlined for each technology, both in individual and hybrid manufacturing formats. The main technological challenges are gathered and discussed to highlight the areas that require further development. Finally, the current industrial applications for LFAM technologies and the expected future developments are outlined. This review provides an overview of LFAM technologies’ current status and discusses their potential in improving the manufacturing of complex and large geometries, with a significant reduction in material and energy consumption, while ensuring high-quality and high-performance components.

Tribological behavior of Ni-based composite coatings produced by cold spray

The current experiment examined the friction and wear characteristics of Ni-based composite coatings developed by cold spray route. In the developed coatings, fixed concentration of MoS2 (10 wt. %) and varying concentrations of Ag (5, 10, and 15 wt. %) were incorporated to evaluate the lubricating potential of reinforcing elements. The specimens were slid in various working regimes of loads (6, 11, 16, & 21 N) and at a fixed sliding speed of 0.3 m/s under room temperature (RT). According to the investigation, all participating composite coatings have revealed a lower coefficient of friction (COF) and wear rate as the testing load increased from 6 to 16 N, beyond which a reverse trend was recorded till 21 N. However, composite coating with 10 wt. % Ag has shown excellent tribological properties in terms of the lowest COF (0.29) as well as wear rate (4.0 × 10−5 mm3/Nm) at 16 N and 0.3 m/s. The superior tribological characteristics of the aforesaid coating have been explained and well connected to the synergistic effect of solid lubricants (Ag and MoS2) as well as the optimal weight percent of Ag in the creation of tribo layer on the wear track.

Effect of Nonessential Alloying Elements and Solution pH on Corrosion Behavior of Al-Mg Alloys Fabricated by Cold Spray Deposition

This paper highlights the difference in corrosion behavior of cold spray (CS) deposited AA5083 and Al-5.0 wt% Mg alloys with an emphasis on the effect of nonessential alloying elements and solution pH. CS process is an emerging technology for repairing damaged structures via solid-state deposition. While recent works have focused on CS Al alloys, less attention has been paid to CS Al binary alloys in comparison to Al engineering alloys, which have important implications for the integrity of structural components repaired by the CS process. Herein, the microstructure of CS AA5083 and Al-5.0 wt% Mg binary alloy was analyzed using various microstructure characterization techniques. Corrosion behavior was assessed using electrochemical and immersion tests in 0.6 M NaCl (pH 8.3 and 11.5) solution. Intermetallic phases, such as Fe- and Si-containing phases, in CS AA5083 decreased corrosion resistance by increasing cathodic kinetics in a near-neutral solution. In addition, immersion tests demonstrated lower corrosion resistance in CS AA5083 than in CS Al-5.0 wt% Mg, whereas an alkaline environment showed the presence of a secondary passive layer on CS AA5083, providing higher corrosion resistance compared to CS Al-5.0 wt% Mg.

Tailoring the tribological properties of Cu composite coatings via integrating strengthening W particles and lubricant graphene

In this study, by integrating the strengthening strategy with solid lubricant modification, we fabricated Cu composite coatings that incorporate both strengthening W particles and lubricative graphene nanoplatelets (GNPs) through cold spraying. Experimental findings demonstrate that the Cu-W-GNPs coating achieves a remarkably low coefficient of friction (COF) of 0.16 and a wear rate of only 1.9 × 10−5 mm3/N·m. This synergy effectively prevents the formation of a brittle nanostructured tribolayer and dynamically recrystallized structures, fostering a more resilient subsurface layer, which results in decreased COF and wear rate. This study not only underscores significant tribological improvements offered by the Cu-W-GNPs composite coating but also provides a sophisticated strategy for developing innovative metal/solid lubricant coatings with enhanced low-friction and wear-resistant properties.

Evaluating the damage tolerant behavior of cold spray repaired aluminum alloys

Cold spray presents a promising solution for repair of damaged material within high-value components. However, before employing cold spray for component repair, it is crucial to assess its damage tolerance and durability. This study focuses on evaluating the fatigue behavior of helium-sprayed AA6061 applied to an A356-T6 cast substrate compared to the same specimen geometry made entirely of the A356-T6 material. Fatigue testing was conducted using a marker band schedule to analyze fatigue crack growth rates in the cold spray and substrate materials. To complement the fatigue testing, experimental uncertainties and variabilities were incorporated into a crack growth model using a Monte Carlo approach to probabilistically assess reliability. The results indicate that the AA6061 cold spray material exhibited faster crack growth, resulting in a ∼25% lower life compared to the baseline A356-T6 material. Given the cost effectiveness of the cold spray repair process, it appears to be a viable approach, with the caveats that the residual life is expected to be less than the pristine substrate material and the cold spray interface is prone to delamination during crack impingement.

Effect of continuous and random multi-particle impaction on the aluminum coating and copper substrate in cold spraying

In this study, the process of multi-particle cold spraying has been numerically simulated and compared with the actual cold spraying results. The results show that in the continuous multi-particle models, the maximum depths of compressive residual stress reached 4.90 μm, 3.99 μm, 4.78 μm, and 5.19 μm for each increment in particle number. The penetration depth of residual stress increases then decreases, due to two opposite factors effects on the penetration depth of residual stress. the maximum compressive residual stresses on the substrate are 438.14 MPa, 293.57 MPa, 286.19 MPa, and 279.30 MPa respectively, declining as the number of impacting particles grows. With the subsequent deposition of particles, the further deformation of the substrate causes the stress on the side to gradually homogenize, and the peak value decreases. Surface stress of the workpiece alleviates after multiple Al particles impact Cu substrate. In all random multi-particle models of different gas pressure, the residual stress begins to disappear at about 100 μm from the surface, and basically disappear at about 300 μm. As the collision speed of particles increases, the substrate deformation increases, but the growth rate of deformation decreases. The influence of coating thickness on the substrate deformation gradually decreases with the increase of coating thickness.

Preparation of high-tensile-ductility and high-conductivity alumina dispersion-strengthened copper via a cold spray additive manufacturing-friction stir processing composite process

The solid-state forming capabilities of cold spray additive manufacturing (CSAM) offer a new method for creating nano-reinforced materials. However, the interface of the deposits often fails to form strong metallurgical bonds, leading to mechanical defects that weaken the material. This study investigates the preparation of highly plastic nano-alumina dispersion-strengthened copper by combining CSAM with friction stir processing (FSP), both solid-state techniques. The results show that FSP treatment fuses the interfaces of the deposited particles, transforming the microstructure from multi-scale, elongated grains to a uniform ultrafine-grained (UFG) structure. The average grain size reduces from 3.1 μm to 0.86 μm, and the proportion of high-angle grain boundaries increases from 42.5 % to 85.2 %. This treatment significantly enhances both mechanical and electrical properties. The ultimate tensile strength increases from 210 MPa to 450 MPa, elongation at break improves from 1 % to 35 %, and electrical conductivity rises from 70 % IACS to 81 % IACS. These findings demonstrate the potential of the combined CSAM-FSP approach for producing high-performance nano-alumina dispersion-strengthened copper with superior mechanical and electrical properties.

Atomistic simulation on the deposition behavior of cold spray

Cold spray is an effective method for surface coating, which has been applied in various engineering areas. However, it is difficult to directly observe the dynamic deformation process in experiments. This paper applies the molecular dynamics simulation to model the deposition of a monocrystalline Cu particle onto a Cu substrate and, subsequently, carries out a systematic study on the deposition mechanism and microstructure evolution. The results indicate that the deposition process consists of an impact stage and a relaxation stage. It is mainly the high speed collision and the friction following the collision that lead to particle deposition, which, under different circumstances, can be defined as surface deposition or penetration deposition. Two methods, namely, drastic shear deformation and cooling in the relaxation stage, can help form nanocrystallines. Jetting and melting are not the necessary factors for the deposition of nano-sized particles. The formation of dislocation lines is influenced by impact velocities. At lower impact velocities, the dislocation lines are mainly distributed near the contact surface. However, when the impact velocity is higher, dislocation lines are almost uniformly distributed in the particle.

Coating of Refractory Surfaces with Fine TiO2 Particles via Gas-Dynamic Cold Spraying

Refractory materials are used worldwide in process equipment. However, gaseous and liquid process products penetrate the surface layer and deep into the volume of refractories, destroying rather expensive constructions that are complicated to repair. To address this challenge, there is a need to develop protective coatings for refractory materials that can limit the penetration of working media and extend their operational lifespan. In this work, the application of gas-dynamic cold spraying (CGDS) to produce a coating on the refractory materials using fine titanium dioxide (TiO2) particles is explored. These particles are accelerated within a nitrogen flow, passing through a Laval nozzle, and then sprayed onto a fireclay surface. The mechanisms of particle deposition and layer formation on porous surfaces through experiments and numerical simulations were investigated. The geometry of a typical refractory pore was determined, which was then incorporated into computational fluid dynamics (CFD) simulations to model the cold spraying process of porous substrates. As a result, the influence of the particle size on its velocity and angle of penetration into pores was established. Experimental findings demonstrate the effective closure of pores and the formation of a particle layer on the refractory surface. Furthermore, the nanoindentation tests for the refractory samples showcase capabilities for checking coating thickness for porous materials.

Mechanical Processing with Solid-State of Supercapacitor Materials: A Review of High Energy Milling and High Velocity Particle Methods

Supercapacitors have emerged as a crucial energy storage technology, bridging the gap between traditional capacitors and batteries. The performance of supercapacitors is heavily dependent on the properties of the electrode materials used. Mechanical processing methods, particularly High Energy Milling (HEM) and High-Velocity Particle (HVP) methods have shown great promise in enhancing the physical and electrochemical properties of supercapacitor materials. This review explores the fundamental principles, mechanisms, and recent advancements in HEM and HVP techniques for the synthesis and modification of supercapacitor materials. High energy milling, including ballmill and attritor milling, facilitates particle size reduction, increased surface area, and the creation of nanostructures, leading to improved capacitance and energy density. High velocity particle methods, such as cold spraying and thermal spraying, enable the deposition of uniform and dense coatings, enhancing conductivity and stability. The review also discusses the impact of process parameters on material properties, the challenges faced in scaling up these techniques, and the potential future directions for research. By providing a comprehensive overview of these mechanical processing methods, this paper aims to highlight their significance and potential in advancing supercapacitor technology.

Multi-layer formation by oxidation and solid-state crystallization of cold sprayed amorphous coatings during dry sliding wear

Amorphous alloy coatings, known for the exceptional wear resistance, have emerged as a key solution for enhancing the wear performance of magnesium alloys under harsh environments. In this study, Fe-based amorphous alloy coatings were deposited on magnesium alloy by cold spraying technology, and the influence of microstructural evolution on the wear performance of coatings under dry sliding wear conditions was discussed. The results showed that a dense adherent oxide layer with a thickness of ∼700 nm comprising nanograins of less than 8 nm was formed at the outmost surface, which played a role of self-lubricating. Underneath, a 1 μm thick nanocrystalline-amorphous layer with nanograins of ∼20 nm dispersed in the amorphous alloy matrix was formed through in-situ crystallization induced by flash temperature. This composite structure prevented the formation of shear bands in amorphous alloys and enhanced the durability. Therefore, the transition from abrasive wear to adhesive wear was a consequence of the microstructural evolution from a dual-phase composite layer to a self-lubricating oxide layer.

Effect of powder feeding rate and size on critical velocity and mechanical properties of cold sprayed Al2O3/2024 deposit

The particle acceleration behavior and deposition mechanism of cold spraying aluminum matrix composites (Al2O3/2024) are complicated by the addition of ceramic particles. The effects of different feeding rates and particle diameters on critical velocity and mechanical properties were studied by numerical simulation and experiment. The results indicate that as the powder feeding rate increases, the impact velocity of gas and particles gradually decreases, and the temperature of gas and particles increases, resulting in an increase in the difference between particle impact velocity and critical velocity. The highest tensile strength of the deposit is achieved at a powder feeding rate of 1 r/min, which is 343 MPa. As the powder feeding rate increases, the performance of the deposits decreases, but it significantly saves time and cost. As the particle diameter increases, the impact temperature first increases and then decreases, resulting in the critical velocity first decreasing and then increasing, and the mechanical performance first increasing and then decreasing. To some extent, the best performance of the deposit is achieved when the size of the metal particle is close to that of the ceramic particle.

DEPOSITION BEHAVIOR OF WC-17Co COLD-SPRAYED COMPOSITE COATING ON HYDRO TURBINE STEELS

Cold spraying is a promising technique for depositing wear-resistant coatings on components like hydroturbine steels. This paper highlights the feasibility of hard WC-17Co coating on 13Cr4Ni hydroturbine steel. The coating was deposited at 25, 30, and 40 bar at 800∘C and 50 bar at 900∘C. Further, different characterization techniques (SEM, XRD) were used to analyze the developed coatings. The Vicker hardness testing was employed to determine the hardness of the coated sample. It was observed that WC-17Co coatings deposited at 40 bar and 800∘C offered a maximum hardness of up to 275 Hv, which is an excellent quality for anti-wear applications in hydro turbine blades.

Optimization of particle acceleration parameters of special cold spray nozzles via neural network and genetic algorithm

Optimization of particle acceleration parameters of special cold spray nozzles via neural network and genetic algorithm

Efficacy of topical local anesthetic, topical cooling spray, and audiovisual distraction on relief of needle-related pain during blood collection: A randomized controlled trial.

Venipuncture is one of the most common invasive procedures in healthcare, often resulting in the experience of pain. While audiovisual distraction, topical anesthesia and cold spray application have been reported as methods to reduce pain, there is a lack of studies that focus on comparing their efficacy and safety. We aimed to compare the efficacy and safety of pain reduction during venipuncture using audiovisual distraction, topical anesthesia and cold spray application. A randomized controlled study was conducted at Walailak University (Nakhon Si Thammarat, Thailand) from April 2023 to July 2023. Eligible adult participants voluntarily enrolled in the study and were randomly assigned to 1 of 4 groups: group 1 (control), group 2 (topical anesthetic), group 3 (cooling spray), and group 4 (audiovisual distraction). Pain scores and satisfaction levels were assessed following the venipuncture procedure on the upper extremities. Forty-seven participants were included in the final analysis. The participants had a mean age of 42.3 years (standard deviation (±SD): 13.1), with the majority being female (66.0%). The participants in the intervention groups reported lower pain scores than those in group 1. The mean differences were 2.67 points in group 2 (95% confidence interval (95% CI): 1.49-3.84; p < 0.001), 1.56 points in group 3 (95% CI: 0.15-2.98; p = 0.077), and 1.67 points in group 4 (95% CI: 0.37-2.96; p = 0.042). However, the pain reduction did not reach statistical significance when comparing these 3 interventions. All groups reported a median satisfaction level of 3, with no significant difference among them (H(3) = 6.050, p = 0.109). Pain reduction interventions, including topical anesthetic, cooling spray and audiovisual distraction, are effective methods for alleviating pain during venipuncture. Participants who received a topical anesthetic reported the lowest pain scores and highest levels of satisfaction.

Microstructure and wear resistance of cold sprayed CoCrFeNi HEA coatings: Influence of powder particle size and spraying temperature

This study focuses on the successful fabrication of three distinct types of CoCrFeNi high entropy alloy (HEA) coatings through cold spray (CS) technology, with an emphasis on analyzing the impact of varying crucial CS parameters (spraying temperature and the range of powder particle size), on the coating's microstructure and tribological properties. Contrasted with conventional thermal spraying techniques, lower operational temperature in CS safeguards the materials from undergoing oxidation or phase transitions that are typically induced by high-temperature conditions. Additionally, the high-velocity impact of particles onto the substrate within CS process triggers plastic deformation, resulting in the creation of coatings that are characterized by heightened hardness, and greater density. Such coatings exhibit significantly enhanced performance and durability. The cocktail effect observed in CoCrFeNi HEA is reflected in a suite of exceptional properties that markedly surpass those exhibited by traditional alloys. Chiefly, this phenomenon is manifested through the alloy's exceptionally high hardness and dense structure, positioning CoCrFeNi HEA as a promising candidate for applications in high-wear scenarios. Experimental outcomes indicate that when smaller powder particles and higher spraying temperatures are employed, the porosity of CSed CoCrFeNi HEA coatings was observed to decrease by nearly an order of magnitude, concomitant with a 22.46% enhancement in microhardness. This improvement in microhardness translates into a significant reduction of over 72% in the wear rate, underscoring the positive correlation between enhanced microstructural integrity and wear resistance properties. By meticulously tuning spraying temperature and powder particle size, the resulting microstructure can be rendered increasingly dense and refined.

A REVIEW ON THE MECHANICAL AND TRIBOLOGICAL PROPERTIES OF THERMALLY SPRAYED HYDROXYAPATITE COATINGS FOR BIOMEDICAL IMPLANT MATERIALS

In recent years, many different biomedical implants have been created for prolonged usage within the human body. The number of these implants has been steadily expanding. It is a common practice to use metallic bioimplants as substitutes when attempting to replace human body components in an anatomically acceptable manner. But the metallic bioimplant was mostly made biocompatible by putting a biocompatible coating on its surface and then using the right surface modification techniques. This was the primary method by which the biocompatibility of the bioimplant was achieved. Thermal spraying is a method that is frequently employed in surface modification treatments to modify metallic bioimplants. These methods can be found in the medical field. This is due to the adaptability of the thermal spraying method. Because of their capacity to respond and adapt to physiochemical circumstances, coatings that are based on hydroxyapatite (HAp) are the most popular type to be used in thermal spraying. This is due to the fact that HAp is a naturally occurring mineral. On the other hand, the majority of the HAp coatings are unsuccessful as a result of the coating’s weak mechanical qualities and insufficient adhesive strength. Supplying the coating in question with reinforcement in the form of hard particles and doing so in the appropriate proportions makes it feasible to alter the qualities of HAp-based coatings to fulfill a variety of requirements. This can be accomplished by providing the coating with reinforcement. The purpose of this inquiry was to deconstruct and analyze a variety of thermally sprayed (TS) coatings. These coatings were used to adhere HAp-based coatings on bioimplants. In addition, a detailed discussion is offered on how the reinforcements have an effect on the mechanical and biocompatible qualities of the coatings. In addition, we have discussed the difficulties associated with TS HAp coatings and their potential uses in the manufacturing of 3D biomedical implants through the utilization of cold spray (CS).

Solid State Additive Manufacturing of Thermoset Composites.

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

Effect of Microstructure on Energy Release Characteristics of Al/Ni Energetic Structural Material Prepared by Cold Spraying.

Al/Ni energetic structural material with both high strength structural properties and high energy release functional properties can undergo a strong exothermic reaction under heating or impact loading conditions. In order to investigate the influence of microstructure on the mechanical properties and energy release characteristics of the Al/Ni energetic structural material, the materials with different Ni contents were prepared by cold spraying. With the increase of Ni particles, the microstructure inside the energetic structural material gradually changes from a continuous network structure of Al to a continuous network structure of Ni. The contact between Ni particles will make the stress transfer more uniform during the compression process of the energetic structural material, which enhances their strength. The results of heat-induced exothermic and shock-induced energy release show that the Al/Ni energetic structural material exhibits the best exothermic performance when Ni particles are uniformly dispersed and there are enough Al and Ni to make the material completely transform into the AlNi phase. The increase in the contact interface between Al and Ni particles facilitates the occurrence of a solid/solid reaction exothermic reaction between Al and Ni as well as the diffusion of Ni into the Al melt to generate the AlNi phase. The formation of the Ni continuous phase will lead to a reduction in the contact interface between Al and Ni, as well as an increase in porosity, which will result in a decrease in the amount of heat released during the diffusion reaction. This study will provide insights into the preparation of an Al/Ni energetic structural material with excellent properties.

Peridynamics simulation of microparticle impact: Deformation, jetting, and the influence of surface oxide layer

Over the past decade, cold spraying (CS) has become a significant additive manufacturing technology for creating metallic structures and repairing damaged components. This study uses a novel peridynamic model to investigate the behavior of 12 μm copper particles impacting a copper substrate during CS deposition. The model examines deformation behavior, material jetting, and the effect of a native particle oxide layer. Two oxide thicknesses, 6 nm and 30 nm, were considered. The 6 nm oxide, typical for gas-atomized copper powders, had a negligible effect on deformation, while the 30 nm oxide showed a notable influence. For the 30 nm oxide, the experimentally observed coefficient of restitution (COR) deviated from theoretical predictions in the velocity range of 400–600 m/s due to cracking and fracturing of the oxide layer at higher impact velocities, reducing particle rebound velocity without sufficient metal-to-metal contact for permanent bonding. Permanent adhesion requires significant oxide fragmentation and separation. The study also identified threshold velocities for material jetting from the substrate and particle, showing that oxide presence delays particle jetting by impeding plastic deformation at the edges. Quantifying the oxide volume at the particle-substrate interface clarifies the effect of jetting on COR and bonding strength. The analysis includes effects of deflected jets at extremely high velocities (e.g., 870 m/s), compared with existing literature. Overall, the results demonstrate the efficacy of the peridynamics-based simulation in accurately representing material behavior during high-velocity impacts, effectively predicting oxide breakup, detachment, and removal in CS, and their effects on deposition characteristics.