In the present work, we have examined the role of active elements in controlling the extent of splashing of plasma sprayed splats. Splats of Copper (Cu) and Copper alloyed with Al, Zr were deposited by plasma spray or as free-falling droplet. The splat formation and splat-substrate interfaces were characterised using SEM and FIB. It was found that the presence of Zr, either in the splat material or the substrate, enhanced disk splat formation in free falling droplets. Similarly, the presence of aluminium in plasma sprayed Cu- 10%Al increased the portion of favourable disk-shaped splats compared to pure copper. It was also found that the disk-shaped splat proportion of Cu-10%Al at room temperature is nearly identical to that of Cu splat at 300ºC, indicating that the addition of Al in the alloy leads to the improvement of splat formation, correlating with the improvement in the interface bonding with the substrate.

For years, special attention has been paid to study and to develop innovative copper alloys and composites, with improved mechanical behaviour in respect to pure copper and preserving its excellent electrical and thermal properties. In this work different copper/alumina blends have been prepared and then deposited by cold spray at different gas carrier temperatures. The deposition efficiency and the content of embedded alumina have been determined by means of image analysis using SPIP software. Optimized deposition temperature results 450°C: the coatings exhibit compact, pore-free microstructure and very low oxidation. Microhardness and friction coefficient have been evaluated of both pure copper and composite coatings. An increase of microhardness from 65HV 0.015 to 150HV 0.5 has been observed while a progressive reduction of friction coefficient as a function of alumina content has been reported. Further characterizations to determine thermal and electrical properties of copper/alumina composites are in progress.

In this work, effect of substrate roughness on the deposition behavior of the particles through kinetic spray technology is studied. Finite element analysis program, ABAQUS 6.7-2 was used to estimate the results. Particle impact on the planar and roughened substrates were analyzed and compared. Interface temperature, contact area and contact time were found to be higher for the particle impact on roughened surfaces than that of the planar one for constant spray condition. These factors are significant for bonding mechanism. Experiments were performed on the polished and grit blasted surfaces in order to compare the results. The deposition efficiency and the bond strength values were used to evaluate the effect of surface roughness.

Surface preparation is very important for reliable adhesive bonding of cold sprayed coatings to the substrate. In this work, the grit blasting of low-carbon A516 steel substrates with Al2O3 particles was studied and the roughness parameters Ra and Rt of the grit blasted surfaces were then measured. The influence of alumina grit size on the roughening of the A516 steel substrate, and the resulting effect on the roughness of the Cu coating – steel interface were studied. The results showed that variations of the grit blast size had significantly affected the resultant surface roughness of the substrate. The adhesive strength of the formed copper coatings on A516 steel substrates depends on the surface roughness and hardness of the base material. The adhesive strength about 110-200MPa was achieved. The specific features of the Cu coating-A516 steel interface topography were examined and discussed.

Pure copper thick deposits were vacuum plasma sprayed in such a way that several porosity levels were obtained. Mechanical compressive tests permitted to assess the mechanical behavior of these materials and to study the associated pore microstructural changes. A linear porosity level decrease was observed during the first stages of the compressive squeezing, until the stress reached a specific value corresponding to a transition between pore contraction and copper splats deformation. Stereological measurements showed that the pore squeezing was isotropic.

In this work, the benefits of the Protal process were investigated, comparing adhesion and morphology of different APS thermal spray copper coatings onto an aluminum base substrate. The Protal process operates simultaneously an atmospheric thermal spray torch and a Q-switched laser (Nd:YAG) to perform surface preparation and coating deposition in a single operation. In that case, substrates are coated rough from the machine shop, i.e. without any prior surface preparation. Results obtained in this way were compared with results obtained using a classical procedure, Le, degreasing followed by sandblasting prior to coating deposition.

The low-pressure cold spray (LPCS) technique could be an attractive method for copper metallization of ceramic substrates to power module applications due to its one-step quick and low-temperature process. However, manufacturing pure copper coating on a ceramic substrate by LPCS is still challenging due to its low deposition efficiency and poor adhesion strength. Our previous study successfully demonstrated the possibility of obtaining a zirconia substrate's metallization by using a feedstock powder mixture of copper and aluminum. However, the copper content in the coating was not high enough for power module applications. Therefore, in this study, we aim to improve the copper content in the coating layer composed of the composite powder deposited by LPCS on alumina and zirconia substrates. The influence of the gas pressure and standoff distance on the copper content and coating thickness are evaluated. The coating build-up with a high copper content and thickness is highly dependent on the kinetic energy of particles, enhanced by high gas pressure and short stand-off distance.

Metal surface characteristics play a significant role in interacting with their biological environment. Copper surfaces have been identified for their antimicrobial properties. Improvement of antibacterial and antiviral performances can be tailored by surface microstructure modification. Severe plastic deformation is an effective surface modification procedure to improve the mechanical performance of metal surfaces. This technique can be adapted to obtain surface grain refinement and induce surface roughness. In this work, cold spray shot peening is used to modify copper substrate surfaces and study the effects on their antibacterial properties. To modify the grain structure of copper, different shot-peening parameters were examined. The surface roughness and microstructure were investigated by employing optical and scanning electron microscopy. The bactericidal activity of copper substrates after shot peening treatment is discussed and a comparison between the bacterial load on treated (shot-peened surface and cold sprayed copper coating) and untreated surfaces (as-received) is provided. Testing of the surfaces after their exposure to the biological environment demonstrated improved microbial inactivation performances for surfaces that had undergone grain refinement without exceeding a certain roughness value.

Pratt & Whitney's upper stage rocket engine development program, designated "RL60", has incorporated cold-sprayed copper to improve the design and function of this new engine. Combustion chamber designs contain two stainless steel manifolds connected by a series of copper tubes. The manifold where the hydrogen fuel exits is located near the injector face. The combustion gases from the injector would cause over-heating of this manifold. Thick copper application was needed to actively cool this manifold by conducting the cold temperatures from the hydrogen fuel inside the copper tubes. Plating copper greater than 0.050-inch thick resulted in poor adhesion following a subsequent braze cycle and required 2 weeks to plate. Cold sprayed copper was attempted which has surpassed plated copper in its ability to adhere through this braze cycle and can be applied in a few hours. In addition, the hazardous chemicals associated with copper plating have now been eliminated.

For thermal sprayed coatings, compactness of their constituent particles is required in many applications, e.g. to obtain impermeable anticorrosion coating in marine use. We investigated key factors to improve compactibility of deposited particles in HVOF sprayed coatings by condition measurements of spray particles. The results revealed that plastic deformability of the sprayed particles as well as their molten fraction was important to obtain the dense VHOF coatings.

During the last decades, the application of copper alloys has become very prominent in engineering. Judging from the properties of bulk materials or galvanic copper coatings, a thermal sprayed coating shows significant disadvantages. The reason for this effect is the build up of a thermal sprayed coating by individual droplets. The main aim of this work is to improve the properties of the twin wire arc sprayed copper alloys, thereby expanding the application of these kind of coatings to the areas where galvanic copper plating technique are mainly used. A copper-cobalt-beryllium alloy has been investigated and the possibility of its application in the twin wire arc process evaluated. The arc sprayed coatings were classified based on the properties of bulk material. The improvement of properties like hardness is based on an investigation of several spraying parameters of the arc spray process. To achieve a maximum value of thermal or electrical conductivity, minimum porosity of the coatings was the aim. Furthermore, a post heat treatment of the sprayed coatings, with the aim of reducing residual tensile stresses within the coating and to improve the wear resistance by means of hardening effects, was carried out. The investigations involved metallographic examination of the coatings using optical microscopy and scanning electron microscopy. Phase composition and residual stresses were detected by X-ray diffraction analysis. Microhardness was measured in the as sprayed as well as in the heat treated state.

Al 2 O 3 and Cr 2 O 3 coatings were deposited by atmospheric plasma spraying. The tribological properties of coatings against copper alloy were evaluated with a block-on-ring configuration under dry friction conditions at room temperature. Microstructure of powders and coatings were observed using scanning electron microscopy (SEM) and optical microscope (OM). Some thermo-physical properties of coatings were measured. Results showed that the Cr 2 O 3 coating exhibits cracking failure in the sliding condition with a normal load of 500N and a sliding velocity of 0.84 m/s. This failure of the plasma sprayed Cr 2 O 3 coating is explained in terms of its low thermal conductivity.

Cold sprayed copper coatings have been widely studied but the effect of substrate properties and spraying conditions on the bond strength still needs further investigations. Using nanoindentation, it is possible to compare the effect of spray parameters on the change in hardness of the coating due to the difference in size distribution of the powder. Deposition of 2 copper powders on aluminium and Ta6V substrates has been done at different stagnation temperatures and pressures using nitrogen as process gas. Hardness profiles show how the speed of the particles induces shot peening effects on the surface. The interaction between the hot gas jet and the surface may modify the hardness profiles. The effect on the substrate hardness has also been investigated.

Thick pure tungsten coatings were deposited on molybdenum and copper substrate by vacuum plasma spray for different purpose. The microstructures of tungsten coatings were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of preheating temperature of the substrate and introduction of gradient bond layer on the adhesive strength of the coating was investigated. High heat load was tested by high power electron beam bombardment only for tungsten coating on copper. All the results show that the properties of tungsten coating were strongly influenced by different processes, and the density of the coatings is close to 95% of theory density.

In this paper, copper coatings were deposited on a metallic substrate by means of multi-function micro-plasma spraying under different processing parameters. The microstructure and phase structure of copper coatings were investigated using a scanning electron microscope and X-ray diffraction, bonding strength were tested by an electron tensile tester, droplet impinging and flattening on a flat substrate surface and the residual stress after solidification were studied numerically. The experimental results show that the density of copper coatings was improved with increasing plasma power and operating gas flow, and this copper coating possessed high adhesion strength and low residual stress, still without obvious oxidation. This spraying system extends the application field of tradition plasma spray. Through changing the processing parameters, materials with different melting points, even as low as copper can be produced.

Viruses and microbial pathogens can survive for hours on fabrics. This paper reports that copper-doping of natural and synthetic fabrics inactivates, within minutes, a human COVID surrogate pathogen. The fabric is embedded with copper particles by twin-wire arc thermal spray. The long-lasting fabric surface simultaneously provides good breathability, it is scalable and cost-effective. Virucidal activity is not affected by repeated washing of the fabric. Importantly, copper-embedded material will provide effective protection against all classes of pathogens, regardless of their mutation rates and infection strategies. It also can provide protection against all classes of pathogens, regardless of their mutation rates in industrial and residential filters.

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.

In order to improve the wear resistance and service life of the copper, the composite coating consisting of a Ni-base self-fluxing alloy (NiCrWB+50%Al 2 O 3 ) and WC (WC-12%Co) alloy were sprayed on a copper substrate using High Velocity Air Fuel(HVAF). The coating could meet the operating requirements including high hardness, good wear resistance and low cost. The Ni-base composite coating was analyzed by means of optical microscopy, scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results indicated that the structure of coating was composed of melted particles and partly unmelted round particles of Ni-base alloy, and WC particle. Only a small proportion of the Al 2 O 3 particles were retained in the coating. The phases in the coating consisted of γ-Ni, WC and a little Ni 3 B. Amorphous structures appeared and some Al 2 O 3 phase existed. The adhesion strength between coating and copper substrate was more than 50MPa. Wear results showed that the Ni-base composite coating exhibited better wear resistance than the coating with no WC particles.

Copper ion was added in liquid feedstock to deposit ion doping TiO 2 photocatalytic coatings through liquid flame spraying. The coating microstructure was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The photocatalytic performance of coatings was examined by photodegradation of acetaldehyde. XRD analysis shows that the crystalline structure of coatings is not significantly influenced by the metal ion doping. The photocatalytic activity of the TiO 2 coatings is enhanced by the copper ion doping. It is found that a high concentration of ion doping decreases the activity. XPS analysis shows that the adsorbed oxygen concentration is increased with the increase of Cu 2+ dopant concentration and decreases with the further increase of dopant concentration. The enhancement of photocatalytic activity can be attributed to the adsorption ability of oxygen and other reactants on the surface of doping TiO 2 coatings.

Among the different wires used in arc spraying, copper is a material of choice in some applications. Its malleability is used to allow an easy machining procedure after spraying. This article focuses on the limitations of the oxidation of copper during arc spraying and its influence on coating process and properties. The aim of this series of experiments was to improve coating properties of copper sprayed with the electrical wire arc spraying process by substituting compressed air with nitrogen. These experiments show that coating properties, as well as electric wire arc spraying process, are strongly influenced by the gas employed as the atomising element.