Development of a generalized parameter window for cold spray deposition

One-dimensional carbon nanotubes and two-dimensional graphene nanosheets with unique electrical, mechanical and thermal properties are attractive reinforcements for fabricating light weight, high strength and high performance metal-matrix composites. Rapid advances of nanotechnology in recent years enable the development of advanced metal matrix nanocomposites for structural engineering and functional device applications. This review focuses on the recent development in the synthesis, property characterization and application of aluminum, magnesium, and transition metal-based composites reinforced with carbon nanotubes and graphene nanosheets. These include processing strategies of carbonaceous nanomaterials and their composites, mechanical and tribological responses, corrosion, electrical and thermal properties as well as hydrogen storage and electrocatalytic behaviors. The effects of nanomaterial dispersion in the metal matrix and the formation of interfacial precipitates on these properties are also addressed. Particular attention is paid to the fundamentals and the structure–property relationships of such novel nanocomposites.

Recent progress in the development and properties of novel metal matrix nanocomposites reinforced with carbon nanotubes and graphene nanosheets

Adiabatic shear instability based mechanism for particles/substrate bonding in the cold-gas dynamic-spray process

https://bura.brunel.ac.uk/bitstream/2438/13101/1/FullText.pdf

Cold spraying - A materials perspective

In this study, computational fluid dynamics (CFD) and extensive spray tests were performed for detailed analyses of the cold spray process. The modeling of the gas and particle flow field for different nozzle geometries and process parameters in correlation with the results of the experiments reveal that adhesion only occurs when the powder particles exceed a critical impact velocity that is specific to the spray material. For spherical copper powder with low oxygen content, the critical velocity was determined to be about 570 m/s. With nitrogen as the process gas and particle grain sizes from 5–25 µm, deposition efficiencies of more than 70% were achieved. The cold sprayed coatings show negligible porosity and oxygen contents comparable to the initial powder feedstock. Therefore, properties such as the electrical conductivity at room temperature correspond to those of the bulk material. The methods presented here can also be applied to develop strategies for cold spraying of other materials such as zinc, stainless steel, or nickel-based super-alloys.

An analysis of the cold spray process and its coatings

Bonding mechanism in cold gas spraying

In conventional thermal spraying, the spray particles are partially or fully molten when they deposit on the substrate. Cold spraying, in contrast, uses less thermal and more kinetic energy. In this process, solid particles impact on the substrate at high velocities and form excellent coatings. Due to comparatively low temperatures and typically inert process gases, cold spraying is particularly suitable for heat and oxidation sensitive materials. In recent years, modeling and computational methods have been widely used to study this relatively new spraying process, particularly to describe impact conditions of particles, to improve nozzle design, and to provide a better understanding of the thermo-mechanical processes that lead to particle bonding and deposition. This paper summarizes the state of the art in these theoretical studies, alongside a comprehensive description of the process. The paper also discusses the prediction of coating properties in the light of modeling combined with experimental investigations.

/pdf/from-particle-acceleration-to-impact-and-bonding-in-cold-ltb5c2psl2.pdf

From Particle Acceleration to Impact and Bonding in Cold Spraying

Cold spraying has attracted serious attention since unique coating properties can be obtained by the process that are not achievable by conventional thermal spraying This uniqueness is due to the fact that coating deposition takes place without exposing the spray or subtrate material to high temperatures and, in particular, without melting the sprayed particles Thus, oxidation and other undesired reactions can be avoided Spryy particles adhere to the substrate only because of their high kinetic energy on impact For successful bonding, powder particles have to exceed a critical velocity on impact, which is dependent on the properties of the particular spray material This requires new concepts for the description of coating formation but also indicates applications beyond the market for typical thermal spray coatings The present contribution summarizes the current “state of the art” in cold spraying and demonstrates concepts for process optimization

Frank Gärtner

Papers

Bonding mechanism in cold gas spraying

Development of a generalized parameter window for cold spray deposition

Cold spraying - A materials perspective

From Particle Acceleration to Impact and Bonding in Cold Spraying

The cold spray process and its potential for industrial applications