Cold spray is a solid-state coating deposition technology which has recently been applied as an additive manufacturing process to fabricate individual components and to repair damaged components. In comparison with fusion-based high-temperature additive manufacturing processes, cold spray additive manufacturing (CSAM) has been shown to retain the original properties of the feedstock, to produce oxide-free deposits, and to not adversely influence underlying substrate materials during manufacture. Therefore, CSAM is attracting considerable attention from both scientific and industrial communities. Although CSAM is an emerging additive manufacturing technology, a body of work has been carried out by various research groups and the technology has been applied across a range of manufacturing areas. The purpose of this paper is to systematically summarize and review the CSAM-related work to date.

Cold spray additive manufacturing and repair: Fundamentals and applications

The interior porous defects formed during the layer-by-layer fabrication process have attracted increasing attention for different additive manufacturing (AM) techniques and are regarded as a crucial factor affecting the overall performance. In this work, aiming at the cold spray Ti6Al4V bulk materials, the hot isostatic pressing (HIP) treatment is adopted to reduce the interior defects, adjust the microstructure, and improve the mechanical properties. To characterize the pore morphologies and porosity evolution, the CS Ti6Al4V sample is characterized by optical microscopy and X-ray computed tomography (XCT). The 3D reconstructions by XCT show that the fully dense Ti6Al4V alloy can be obtained through the high temperature diffusion and high pressure compacting of the HIP sample. After the HIP treatment, the severely deformed grains experience an obvious growth with the uniformly distributed β precipitates around equiaxed α grains. The tensile test shows that the strength of CS Ti6Al4V alloys can be largely improved by the enhanced diffusion and resultant metallurgical bonding. With the HIP treatment, the CS samples exhibit highly densified morphology and adjusted microstructure that can benefit the improvement of mechanical properties.

Effect of hot isostatic pressing (HIP) on microstructure and mechanical properties of Ti6Al4V alloy fabricated by cold spray additive manufacturing

The aim of this study is to promote significant bond strength with laser surface texturing tools for different coating deposited by spray processes. Pulsed nanosecond laser has been used to improve the ultimate adhesion strength of thermal spray coating designed for specific applications, and the full potential of this technology must be further explored. This technology proposes several benefits such as free of grit-particle inclusions, limited affected zone and the interface contact quality. The most important improvement is the coating anchoring in the substrate by laser patterned surface. Adhesion bond strength has been improved and evaluated with the contact area. Fracture mechanic analysis has been studied and it showed that the pattern morphology has an impact on crack propagation. A mixed-mode failure has been defined and chosen to explain adhesion strength improvements for the different applications. Laser surface texturing was performed on light metal alloys substrates before cold spraying of light metal alloys powder, wire-arc metallization and atmospheric plasma spraying of thermal barrier coating without bond coat. This study has highlighted laser potential to enhance adhesion bond strength in the dry deposition field.

Laser surface texturing to enhance adhesion bond strength of spray coatings – Cold spraying, wire-arc spraying, and atmospheric plasma spraying

Supersonic cold spraying is an emerging technique for rapid deposition of films of materials including micrometer-size and sub-micrometer metal particles, nanoscale ceramic particles, clays, polymers, hybrid materials composed of polymers and particulates, reduced graphene oxide (rGO), and metal-organic frameworks. In this method, particles are accelerated to a high velocity and then impact a substrate at near ambient temperature, where dissipation of their kinetic energy produces strong adhesion. Here, recent progress in fundamentals and applications of cold spraying is reviewed. High-velocity impact with the substrate results in significant deformation, which not only produces adhesion, but can change the particles' internal structure. Cold-sprayed coatings can also exhibit micro- and nanotextured morphologies not achievable by other means. Suspending micro- or nanoparticles in a liquid and cold-spraying the suspension produces fine atomization and even deposition of materials that could not otherwise be processed. The scalability and low cost of this method and its compatibility with roll-to-roll processing make it promising for many applications, including ultrathin flexible materials, solar cells, touch-screen panels, nanotextured surfaces for enhanced heat transfer, thermal and electrical insulation films, transparent conductive films, materials for energy storage (e.g., Li-ion battery electrodes), heaters, sensors, photoelectrodes for water splitting, water purification membranes, and self-cleaning films.

Supersonic Cold Spraying for Energy and Environmental Applications: One-Step Scalable Coating Technology for Advanced Micro- and Nanotextured Materials.

Cold spray (CS) is a new solid state coating technique that has attracted considerable attention as it is quite suitable for mass production of metallic materials or metal matrix composites. More r...

‘Cold spray +’ as a new hybrid additive manufacturing technology: a literature review

Today, cold gas dynamic spray (CGDS) technology has thrived with considerable capabilities for manufacturing various technological depositions. The deposition conditions have been developed through many years and that have led to produce ample experimental data which is available in the literature. But, recent research and development activities also reveal innovative findings regarding various deposition conditions. This paper contains a review of experimental deposition procedures for the cold spray additive manufacturing. Details of processing conditions are reported and classified into various categories of baseline working conditions, specific processing including deposition of nanotechnological components, composites-based structures and hybrid coating with substrate deposition. Available substrate treatments and their contributions on the deposition capability were also included. A large collection of experimental data from the literature is addressed in the Section 7.

Cold gas dynamic spray technology: A comprehensive review of processing conditions for various technological developments till to date

Coating characteristics are highly dependent on substrate preparation and spray parameters. Hence, the surface must be adapted mechanically and physicochemically to favor coating–substrate adhesion. Conventional surface preparation methods such as grit blasting are limited by surface embrittlement and produce large plastic deformations throughout the surface, resulting in compressive stress and potential cracks. Among all such methods, laser patterning is suitable to prepare the surface of sensitive materials. No embedded grit particles can be observed, and high-quality coatings are obtained. Finally, laser surface patterning adapts the impacted surface, creating large anchoring area. Optimized surface topographies can then be elaborated according to the material as well as the application. The objective of this study is to compare the adhesive bond strength between two surface preparation methods, namely grit blasting and laser surface patterning, for two material couples used in aerospace applications: 2017 aluminum alloy and AISI 304L stainless steel coated with NiAl and YSZ, respectively. Laser patterning significantly increases adherence values for similar contact area due to mixed-mode (cohesive and adhesive) failure. The coating is locked in the pattern.

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Laser Patterning Pretreatment before Thermal Spraying: A Technique to Adapt and Control the Surface Topography to Thermomechanical Loading and Materials

Robin Kromer

Papers

Cold gas dynamic spray technology: A comprehensive review of processing conditions for various technological developments till to date

Laser Patterning Pretreatment before Thermal Spraying: A Technique to Adapt and Control the Surface Topography to Thermomechanical Loading and Materials