Cold spray (CS) is a solid-state process for depositing metal powder, accelerated by a high-velocity gas such that it bonds to the substrate metal through kinetic impact energy. Although the technology is finding applications in non-load bearing repair and coating applications, work is needed in the quality control procedures for CS for its use in load bearing structural applications. in this study, the viability of electrical conductivity and through thickness ultrasound wave velocity measurement methods are studied to serve as a means for nondestructive quantitative measurement methods 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 copper and aluminum samples that were manufactured using CS. Ultrasound measurements of longitudinal wave velocity and eddy current electrical conductivity measurements showed good correlation with process conditions that were varied to control particle velocity to intentionally produce samples with varying deposition quality. Influence of process conditions on particle velocity was confirmed via particle image velocimetry. Porosity, hardness, and tensile test results were further correlated to ultrasound wave velocity and electrical conductivity measurements. The results of this work show that nondestructive testing methods can be effectively used to quantitatively assess the cold spray products for quality control purposes.

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. Further fine tuning and optimization of cold spray process parameters is required, to reach higher particle impact velocities as well as 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 N 2 as propellant gas under different refined spray parameter sets and 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 and well bonded internal boundaries. X-ray diffraction reveals that powder and deposits are present as γ- solid-solution phase without any precipitations. By work hardening and peening effects, the deposits show high microhardness and compressive residual stresses. With close to bulk material properties, the optimized deposits should fulfill criteria for industrial applications.

In the current work, a NiCrAlY and Fe-based alloy are HVOF-sprayed due to the combination of high coating density and customizable coating properties. The oxygen to fuel gas ratio was varied to modify coating defects in a targeted manner. The results demonstrate material dependent defect mechanisms. Further investigations regarded residual stresses, hardness, and electrical conductivity. In particular, the thermal diffusivity proved to be very promising. Moreover, the coatings were compared with previous work on arc-sprayed coatings of similar chemical composition regarding insulation capability.

In the current work, typical thermal-sprayed copper-based alloys are investigated to reduce the spread of pathogenic germs in broiler farming. Compressed air and nitrogen are used as process gas, while the coating torches and the alloys were varied. The results demonstrate a significant reduction in pathogenic load due to the coatings. This accounts especially for the bacterial strain E.ceocurm, which is the predominant bacteria in broiler farming. Further investigations regarded the microstructure and the electrical conductivity of the coatings.

Tin was successfully cold sprayed onto carbon fiber reinforced polymers (CFRPs) in previous studies at McGill University and a “crack-filling” mechanism was described as the mechanism that allowed deposition of the metal onto the composite counterpart. By adding other metal powders (aluminum, copper, zinc), it was possible to improve the deposition efficiency (DE) of the tin on the CFRP, as well as improve the electrical conductivity of the coating (notably with copper). While the effect of mixing powders with tin, and more notably the effect of the secondary component (SC) properties on the deposition improvement, were more thoroughly addressed in following studies, the question of the properties of these coatings remained. With the perspective of providing a metallic coating to a relatively poorly conductive composite substrate, this study aims to explore the electrical conductivity and the coating strength of cold sprayed tin with other SCs onto CFRPs. An extensive study on fractured surfaces highlighted the importance of the CFRP surface finish, and it was observed that the coating strengths improved with decreasing DE of pure tin.

In the current work, a typical NiCrAlY alloy and, moreover, amorphous Fe-based alloys are arc-sprayed for the desired application in cryogenic environments. Nitrogen is used as process gas, while the stand-off distance and number of passes were varied. The results demonstrate coatings with low, but varying porosity and oxide content and mostly high electrical conductivity. Especially the amorphous Fe-based coatings reveal homogeneous coating structures and promising properties. Further investigations regarded the deposition efficiency, tensile adhesive strength, hardness, durability under cryogenic conditions and the thermal diffusivity.

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

Unlike their metal counterparts, composite structures do not readily conduct away the electrical currents generated by lightning strikes. Cost reduction and expected production growth of the next middle range airplanes require automated manufacturing process of polymer components. The development of an automated technology to metallize polymer based composite for lightning strike protection is the aim of the CO3 project (EU Grant agreement: ID831979). In this study, thermal and electrical conductivities of composites were achieved by cold spray deposition of Cu or Al coatings. Critical points to be addressed were substrate erosion during cold spray, lack of polymer-metal adhesion and poor deposition efficiency. Several strategies were tested: i) a thin polymer film was cocured at the substrate surface before cold spraying, to enable implantation of metallic particles in the film, helping coating build-up and protecting the fibers of the composite. ii) Cold spraying a mix of metal and polymer powders to improve coating adhesion and prevent fiber damage. iii) Supercritical Nitrogen Deposition technology, prior to cold spray, to mechanically anchor metallic particles into the polymer. Subsequent cold spraying of purely metallic coatings was more efficient and showed better adhesion. All coatings were tested in terms of adhesion strength and electrical conductivity.

Stabilized bismuth oxide with fluorite structure is considered a promising electrolyte material for intermediate temperature solid-oxide fuel cells (SOFCs) due to its high oxygen ion conductivity. The ternary system, Bi2O3-Er2O3-WO3, is of particular interest because it is ionically conductive as well as thermally stable. This study investigates the quality of Bi2O3-Er2O3-WO3 (EWSB) electrolyte produced by plasma spraying. The phase structure and cross-sectional microstructure of plasma-sprayed EWSB were characterized by XRD and SEM. The as-sprayed EWSB was found to have a dense microstructure with well bonded lamellae. XRD analysis showed the formation of EWSB with δ-phase and a trace of β-phase, while the β-phase disappeared after annealing at 750°C for 10h. Electrical property tests revealed that the plasma-sprayed electrolyte also had excellent ionic conductivity (0.26 S cm-1 at 750 °C), making it a strong candidate for use in SOFCs at intermediate temperatures.

This study investigates the effect of deposition temperature and particle size on lanthanum strontium chromite (LSC) deposits produced by atmospheric plasma spraying. The results show that dense deposits with lamellar interface bonding can be achieved at temperatures above the critical bonding temperature and that particle size has a significant effect on chromium vaporization losses. The loss of chromium may be responsible for the low electrical conductivity of LSC deposits produced from small powders, which suggests that conductivity can be controlled with appropriate process adjustments.

Polymer metallization using cold spray method, due to low process temperature, is a potential candidate to form electrically conducting polymers as well as composites and improve the mechanical properties of their surface (abrasion, corrosion, etc.). Low Pressure Cold Sprayed copper coatings on PEEK (Poly-Ether-Ether-Ketone) based composites reinforced by carbon fibers have been investigated. Cold Spraying involves high erosion on composite materials due to solid state and high velocity particles thus a new way has been developed. Based on the elastic behaviors of organic materials, pure PEEK matrix has been added on the composite surface to behave as an interfacial layer between the composite and the coating. Optimization of the LPCS parameters has then been carried out using a careful choice of powder size distribution in order to avoid substrate destruction, erosion and delamination of the coating. Consequently, dense thick copper coatings have been obtained and analyzed in terms of microstructure implementing SEM observations. Finally, electric measurements have been performed in order to check the efficient metallization of the composites. A new way for metallic coating on organic composites using Low Pressure Cold Spraying is then demonstrated.

Metallic coatings can be produced easily with thermal spray and cold gas spray processes. However, when coating thicknesses below 50 μm are required for economical or technological reasons, the use of these well-established processes becomes more challenging. The company OBZ Innovation GmbH has developed spray processes that can produce metallic coatings with thicknesses of less than 20 μm. Such coatings are of interest for applications such as cold gas sprayed silver coatings with high purity and good electrical conductivity. Thinner sprayed coatings of such valuable materials have economic advantages, and the process may be competitive with commonly used thin film coating methods.

In current process techniques to manufacture sliding bearings, bronze components are soldered to the respective parts, which is cost and energy intensive. Apart from that, so far most bearing materials still contain lead, which in new applications is omitted by EU law to avoid associated health risks. The present study aims to offer solutions for both by using cold gas spraying as additive manufacturing technique for processing bearings directly onto steel parts and by applying that to new lead-free bronze alloys. A lead-free bronze alloy was processed as powders by gas atomization and classified to optimum sizes for cold spraying. During cold spraying, the process gas pressures and temperatures as well as the substrate temperature were varied with the aim to study influences by impact conditions and effective surface temperature on particle deformation and bonding. Respective coatings show low porosity, high hardness and high electrical conductivities. With properties similar to that of bulk cast material respectively manufactured parts should meet the requirements for new bearing applications.

Cold-sprayed copper coatings tend to be brittle and their electrical conductivity is inferior to that of the bulk material. In order to solve these problems, conventionally, it has been attempted to recover the metallic structure by heat treatment. This study, however, focuses on the effects of phosphorus and tin with the aim of improving cold spray copper coatings by optimizing the impurity content of Cu powder. It is shown that, by adjusting the content of P and Sn, dense copper coatings can be obtained with high ductility and electrical conductivity equal to that of the bulk material.

In this work, copper and PEEK powder mixtures are cold sprayed onto carbon fiber-reinforced polymer (CFRP) substrates with the aim of producing a well-adhered conductive layer. The composite coatings were optimized through the study of the deposited mass and its dependence on process parameters and Cu powder morphology. A morphological model based on Cu phase data was developed to better understand coating microstructures. Coatings synthesized from irregular Cu particles were found to be electrically conductive, while those containing spherical Cu particles were insulating. These phenomena are explained using the developed simulation tools coupled with the investigation of coating build-up and microstructure.

Interparticle bonding is considered the most important factor in cold sprayed coatings, determining mechanical properties as well as physical and chemical behaviors. In this study, a Cu feedstock with low oxygen content is deposited with relatively high spray pressure and temperature in order to improve interparticle bonding and obtain a coating cohesive strength. Mechanical bonding between deposited particles is deduced from fracture morphology and the deformation behavior of Cu particles is simulated by finite element analysis.

Carbon fibre reinforced polymers (CFRPs) are more and more used in a wide range of industries, especially in the aerospace industry, but their low electrical conductivity has limited their application. During the past few years, metallization of CFRP has attracted increasing interest. To make the polymer composites electrically conductive, a conductive media must be either embedded into or coated onto the composites. Cold spray is one coating approach to achieve this. In this work, metallic powders were cold sprayed onto the CFRPs used in aircraft by using two different cold spray systems. The coatings as well as the coating/substrate interfaces were characterized and the deposition mechanism onto the CFRP substrate was determined.

The influence of flame spraying parameters on coating microstructure and electrical conductivity of aluminum- 12silicon coatings deposited on polyurethane substrates was studied. In order to evaluate the effect of the spray parameters on temperature distribution and its corresponding effect on coating characteristics, an analytical model based on a Green’s function approach was employed. It was found that the addition of air to the flame decreased the temperature within the substrate. Dynamic mechanical analysis (DMA) of the PU substrate revealed that the PU softened as the temperature increased. Therefore, by increasing the pressure of the air injected into the flame spray torch from 35 kPa to 69 kPa, the particles impacted a stiffer substrate. This led to increased deformation of the particles into splats upon impact, improved interlocking, and the overall coating had lower porosity and lower electrical resistance. The results obtained indicated that coating properties are sensitive to both thermal spraying parameters and temperature distribution within the substrate when depositing on elastomeric materials. The effect of torch stand-off distance on coating properties was also evaluated. It was found that higher air pressure can cool the substrate and, therefore, allow for a decrease of the stand-off distance. As a result of shorter stand-off distances, a coating with lower porosity and electrical resistance was deposited.

LSCF(La 0.6 Sr 0.4 Co 0.2 Fe0 .8 O 3 ) with a perovskite structure has been widely studied as cathode materials for intermediate solid oxide fuel cell(SOFC). It has well-known excellent electrode performance due to its high ionic and electronic conductivity. However, application of LSCF cathode is likely to be limited by the surface catalytic properties and long term stability. Sr and Co may segregate from LSCF under cathode polarization, leading to increased resistance of the cathode. Oxygen hyper-stoichiometric La 2 NiO 4+δ with a K 2 NiF 4 structure possesses a higher catalytic properties, ionic conductivity and stability compared to LSCF cathode. However, the electrical conductivity of the La 2 NiO 4+δ (76 S cm –1 at 800 °C ) in the IT range are lower than 100 S/cm, which is regarded as the minimum requirement in electrical conductivity for an SOFC cathode. Taking account of both the advantages and disadvantages of the two different cathode materials, and good chemical compatibility of those two cathode materials, it is possible to prepare a composite cathode by infiltrating a thin film of La 2 NiO 4+ä on the porous LSCF to enhance the LSCF cathode performance. Therefore, in this study, the LSCF cathode was deposited by atmospheric plasma spray. The porous LSCF cathode was infiltrated by La 2 NiO 4+δ . The microstructure was characterized by SEM and TEM. The effect of infiltration on the polarization of LSCF cathode was investigated.

The paper discusses a possibility of metallization of polymers using low pressure cold spray (Dymet 413). The bonding mechanism of the coating is discussed as well as the influence of the number of spraying passes on coating microstructure. Two commercial powder were used (i) tin; and (ii) aluminum to obtain coatings on PA6 polymer substrate. The substrate topography was modified with sandblasting. The adhesion strength, residual stresses, electrical resistivity, and microstructure were determined and characterized. Finally the comparison with other metallization methods was made and the application of cold spray for producing local conductive paths was assessed.