Cold spray technology: future of coating deposition processes

Abstract

Cold spray (CS) belongs to a wide family of thermal spray technology with the difference that it is a solid state process in which spray particles are deposited via supersonic velocity impact at a temperature much below the melting point of the spray material. This paper briefly describes the various aspects of this rapidly emerging technology, with almost all the important parameters which affect the deposition behavior along with advantages and limitations; applications and history of emergence of this process is also reviewed. Though this technology emerges three decades ago but still it could not establish itself as viable practical industrial technology. Hence, the efforts, along with funding from public/private sources are required to commercialize this coating process. It is expected that next decade will saw the growth of cold spray as a viable coating process around the globe.

Feasibility of using low pressure cold gas spray for the spraying of thick ceramic hydroxyapatite coatings

“…Two fundamental aspects that distinguish LPCGS from HPCGS are: (a) The utilization of low pressure gas (0.5‐1 MPa instead of 2.5‐3 MPa) and (b) Radial injection of the powder instead of axial injection (in most cases) . In LPCGS process, feedstock particles are drawn in from the powder feeder by Venturi effect, contrary of the particles in HPCGS, which are mixed with the propellant gas in the prechamber zone and then are axially fed into the gas stream . Due to that, LPCGS system was observed to be more suitable than the high pressure, due to the more constant feeding rate.…”

A comparative review on cold gas dynamic spraying processes and technologies

“…Major innovative development began In the 1950s by Rochevill, using a gas flow at a velocity higher than those obtained with the existing methods at that time. The flow of gas through a nozzle called the De Laval Nozzle produces a uniform thin coating [1][2][3].…”

Application of the small punch test to evaluate the integrity of a cold spray titanium coating

“…Traditional repair methods such as welding or hot spraying can lead to a number of deleterious effects on the component being repaired. These include the formation of heat affected zones, residual stresses, oxidation and porosity [1]. Furthermore, the deposition of sufficiently thick coatings is prohibited by thermal stresses generated within the component [2].…”

“…Cold spray is a solid-state material deposition process where micron-sized particles are sprayed onto substrates at temperatures below the melting point of the metallic particles and under supersonic velocities [3]. Particle-substrate and particle-particle bonds are formed via mechanisms pertaining to adiabatic shear instabilities of particles upon impact rather than high temperatures [1,3]. The name of this process is derived from the fact that the feedstock powder material remains solid during the process, which is different from conventional thermal spraying methods, where particles are partially or entirely molten as they impinge on the substrate [3].…”

“…Besides avoiding the aforementioned drawbacks, cold spray is cost effective as it offers short processing times [4]. Detailed explanations of the cold spray process can be found in [1,3].…”