From Surface Modification to Additive Manufacturing of Components by Solid-State Cold Spray Technology

Dear Colleagues,

In additive manufacturing processes, sources such as electron beams or lasers with high energy are utilized for selectively melting down the powder bed, in which the resulted solidified metal can form the solid component. The most well known metal additive manufacturing methods include selective laser sintering, selective laser melting and electron beam melting. However, as high energy sources are used in these methods, disadvantages such as undesirable phase transformations, and residual stress caused by high processing temperatures, are inevitable. Likewise, most common additive manufacturing processes have been typically utilized to produce complicated Ti, Fe, or Ni-based alloy/super alloy components. Nonetheless, because of melting, these processes are not appropriate processes for producing the components made of non-ferrous alloys like Mg alloys, high-strength Cu, or Al-based alloys. Thus, another additive manufacturing technique is needed to produce the parts made of such non-ferrous materials. Cold spray is a newly developed technology that is able to produce the components via solid-state deposition of powder particles. Compared to traditional deposition processes which use high temperatures (such as prevalent additive manufacturing methods and traditional thermal spray processes), in the cold spray technique, the deposition process typically uses the kinetic energy of the powder particles, before impinging, in place of the thermal energy. The feedstock powder utilized in the CS process keeps its solid state throughout the whole deposition process. The deposition is attained via mechanical interlocking and local metallurgical bonding, which are formed by severe local plastic deformations at particle–substrate interfaces and also at the inter-particle boundaries. As mentioned, the relatively low temperature in the cold spray process averts the common defects occurring in the deposition processes that include high temperatures, like phase transformation, oxidation, residual thermal stress (tensile), grain growth, etc.

The abovementioned remarkable advantages make cold spray technology an effective method for producing coatings with a wide range of materials; they can comprise most metals and their alloys, nanostructured metals, and MMCs. In addition, there is no limitation in the growth of thickness in the cold spray coating process. Hence, besides the application of solid-state cold spray processes for the coating of surfaces and the repairing of structures, they can be employed in with faster build rates (minutes) compared to selective laser melting and electron beam melting processes.  

The objective of this Special Issue is to present the latest experimental and theoretical developments in this field, through original research and short communication papers, and review articles from academia and industry around the world.

In particular, the topics of interest include, but are not limited to:

• 3D printed/additively manufactured coatings and repair of structurally critical components using cold spray technology.
• Cold spray additive manufacturing of high entropy alloys, Ti, Al, Fe, Ni based alloys and super alloys, refractory metals, etc.
• Improvement of corrosion, wear and high temperature oxidation resistances of additively manufactured cold sprayed components/deposits using post-cold spray treatments.
• Modification of mechanical properties of additively manufactured cold sprayed components using post-cold spray treatments.
• Application of additively manufactured cold sprayed components/deposits for biomedical applications.
• Hybrid additive manufacturing: the combination of cold spray processes and common additive manufacturing methods.

Dr. Mohammadreza Daroonparvar
Guest Editor

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