A perspective review on the bonding mechanisms in cold gas dynamic spray

Abstract

The Cold Gas Dynamic Spray technology, generally referred as Cold Spray, is a relatively new additive manufacturing technique able to produce fully dense coatings through the deposition of particles on a substrate. Fine powders are accelerated to high velocity and projected onto a substrate, upon impact with the target surface, conversion of kinetic energy to plastic deformation occurs and the solid particles deform and bond together. During the cold spray deposition process, the particles remain in a solid state during the deposition, resulting in high-quality coatings with low residual stresses and oxide inclusions. The relative lower process temperatures allow the cold spray to manufacture coatings on high temperature-sensitive materials. It could also be a valid method for deposition of a wide variety of materials, from metallic alloys up to ceramics and composites. Depending on the materials employed as substrate and coating, different bonding mechanisms can occur during the deposition. The present review aims to summarise the main bonding theories proposed up to now for the cold spray, focusing on both the particle deformation behaviour during the contact with the surface and the interfacial bonding mechanisms. The available theories for different substrate/coating configurations will be discussed and compared. The effects of deposition parameters, the substrate's surface and microstructure of feedstock powders on the bonding mechanism will also be discussed.

Characterization of Cold-Spray Coatings on Fiber-Reinforced Polymers through Nanoindentation Tests

“…To date, a lot of adapted techniques have been developed for coating deposition and surface metallization, such as vapour-phase deposition, thermal-spray deposition, electrodeposition, electroforming and electroless plating. Unfortunately, the abovementioned technologies suffer from a series of disadvantages: long production cycle and high cost of the mould for electroforming, distortion of the substrate surface resulting from the molten particles, and high-temperature flames in thermal spraying (TS) [6][7][8]. Compared to these techniques, cold-spray (CS) deposition provides intriguing advantages when spraying metallic particles on polymeric or FRPs substrates [9]: the deposition is made possible only by a mechanical interlocking mechanism, and no chemical reactions are required [10].…”

Physically Based Finite Element Modeling Method to Predict Metallic Bonding in Cold Spray

“…The critical velocity could be an indication of the onset of metallurgical bonding in CS, although adhesion solely attributed to mechanical anchoring also requires a critical velocity to be reached ( Ref 2,[38][39][40]. The critical velocity is dependent on the particle and substrate material properties, particle size, substrate and particle impact temperatures, and oxide or hydroxide layer thickness on both particle and substrate ( Ref 19,38,41,42).…”

Manufacturing and metallization of hybrid thermoplastic-thermoset matrix composites

“…The process of metallizing the polymer based substrate contains two primary stages i.e. (1) the first layer formation which involves particle to substrate impingement and, (2) buildup of the coating which also involves particle to particle impact [23]. During the first stage of metallic deposition, thermal softening of polymer matrix occurs owing to the metallic particle impact and subsequent kinetic energy dissipation.…”