Substrate Roughness and Thickness Effects on Cold Spray Nanocrystalline Al-Mg Coatings

Cold spraying is a solid-state powder deposition process with several unique characteristics, allowing production of coatings or bulk components from a wide range of materials. The process has attracted much attention from academia and industry over the past two decades.The technical interest in cold spraying is twofold: first as a coating process for applications in surface technology, and second as a solid-state additive manufacturing process, offering an alternative to selective laser melting or electron beam melting methods. Moreover, cold spraying can be used to study materials behaviour under extremely high strain rates, high pressures and high cooling rates. The cold spraying process is thus considered to be relevant for various industrial applications, as well as for fundamental studies in materials science.This article aims to provide an overview of the cold spray process, the current understanding of the deposition mechanisms, and the related models and experiments, from a materials science perspective. IntroductionCold spraying (CS) is a solid-state material deposition technique, where micron-sized particles of a powder bond to a substrate as a result of high-velocity impact and the associated severe plastic deformation. Acceleration of particles to high velocities is obtained via expansion of a pressurised and (ironically) 'hot' gas through a diverging-converging nozzle.Despite heating the process gas -which is to provide higher acceleration of the gas and also to facilitate particle deformation through thermal softening -the feedstock remains in the solid state throughout the entire process; hence the name 'cold' spraying. This is to underline the contrast to conventional thermal spraying where particles are completely or partially molten upon impact onto the substrate. Alternative terminology includes cold gas spray, micro cold spray, cold gas dynamic spray, kinetic spray, supersonic particle deposition and metal powder application (MPA), all of which refer to the same principle of solid-state powder deposition as described above. CS is used for coating and repair. It is also used for additive manufacturing (AM) at relatively high deposition rates as compared to the methods based on selective laser or electron beam melting. The main advantage of CS is that it alleviates the problems associated with high temperature processing of materials, such as oxidation and unfavourable structural changes. It is possibly the only continuous method to produce bulk components of metastable materials that are available only in the powder form, e.g. as obtained from mechanical attrition or gas atomisation. The aim of the present paper is to provide an overview of CS from a materials perspective, particularly for a broader audience in materials research, e.g. with interest in dynamic phenomena, plasticity and phase transformations. In terms of application and properties, CS is perhaps best to be compared to thermal spraying processes, as in [24,25]. In view of relevant physical phenomena, however, CS is mos...

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“…it can lead to higher deposition efficiency of the first layer [168]. However, it may not necessarily result in increased bond strength [169].…”

mentioning

confidence: 99%

Cold spraying – A materials perspective

et al. 2016

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“…This happens because the particles deform more severely on a rough surface than on a smooth surface. In addition, these coatings show greater adhesion on blasted substrates 3,22,47,48 .…”

Section: Substrate Preparationmentioning

confidence: 96%

“…Before spraying, the preparation of the substrate is mainly done in two ways: abrading using silicon carbide papers (SiC) which provides a roughness around 0.5 μm, or blasting, which is the most widely used method, in which Al 2 O 3 particles are blasted on the substrate surface, what may produce a surface roughness up to 5 μm 47 . To prepare the surface by blasting procedure, it is important to define the following parameters / conditions: the type of particle used, its size and shape, gas pressure, angle, and time of blasting, as these characteristics can determine how rough the surface may be 31,48 . In general, Al 2 O 3 particles of granular shape and size of less than 100 μm are used.…”

Section: Substrate Preparationmentioning

confidence: 99%

“…This is a great advantage as it prevents exposure of the clean surface to the environment for a long time, preventing the formation of oxides or deposition of dirt on the surface. Studies report that when CGS coatings are deposited on rougher surfaces, the deposition efficiency of the material increases 3, 31,47,48 . This happens because the particles deform more severely on a rough surface than on a smooth surface.…”

Section: Substrate Preparationmentioning

confidence: 99%

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Cold gas spray coatings: basic principles corrosion protection and applications

et al. 2017

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ABSTRACT:In this review, the beginnings and evolution of the cold gas spray (CGS) technique are described, followed by the main fundamental aspects of the technique together with a description of the several spraying systems up to date. Sequentially, the main spray parameters and their influence on the properties of the coatings are reported. Afterwards, the most important methodologies for preparing the feedstock powders to be sprayed, the effect of the powder composition, microstructure, particle size and shape on the properties of the coatings are discussed. The nature of the spray gun and nozzle, and the substrate pre-treatments were also discussed. With regard to microstructure and properties, the chemical and physical characterization of the coatings and the performance in protecting the substrates against corrosion together with some mechanical properties are presented and compared. The lacking systematic studies about the great part of investigated systems is the main drawback to compare the published results. Closing this review, the main applications, and the potentialities of the CGS coatings are evidenced.

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“…These jets during cold spray may lead to the production of mechanical interlocking or mechanical bonding. In order to enhance and increase mechanical interlocking some surface preparation can be performed on the substrate, such as grit blasting [44]. Figure 2.12 illustrates mechanical bonding and formation of jets around a Cu particle on a Cu substrate [40].…”

Section: Particle Deformation and Bonding Mechanismmentioning

confidence: 99%

Influence of Alumina Addition to Aluminum Fins for Compact Heat Exchangers Produced by Cold Spray Additive Manufacturing

et al. 2015

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Aluminum and aluminum-alumina powder mixtures were used to produce pyramidal fin arrays on aluminum substrates using cold spray as an additive manufacturing process. Using aluminum-alumina mixtures instead of pure aluminum powder could be seen as a costeffective measure, preventing nozzle clogging. The fin geometries that were produced were observed using a 3D digital microscope to determine the flow passages width and fins geometric details. Heat transfer and pressure tests were carried out using different ranges of appropriate Reynolds numbers for the sought commercial application to compare each fin array and determine the effect of alumina content. It was found that the presence of alumina reduces the fins' performance when compared to pure aluminum but that they still outperform traditional fins. Numerical simulations were performed and were used to explain

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Substrate Roughness and Thickness Effects on Cold Spray Nanocrystalline Al-Mg Coatings

Cited by 90 publications

References 22 publications

Cold spraying – A materials perspective

Cold spraying – A materials perspective

Cold gas spray coatings: basic principles corrosion protection and applications

Influence of Alumina Addition to Aluminum Fins for Compact Heat Exchangers Produced by Cold Spray Additive Manufacturing

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