Powder stream characteristics in cold spray nozzles

Abstract

Abstract. The exponential increase of industrial demand in the past two decades has led scientists to the development of alternative technologies for the fast manufacturing of engineering components, aside from standard and time consuming techniques such as casting or forging.Cold Spray (CS) is a newly developed manufacturing technique, based upon the deposition of metal powder on a substrate due to high energy particles impacts. In this process, the powder is accelerated up to considerable speed in a converging-diverging nozzle, typically using air, nitrogen or helium as a carrier gas. Recent developments have demonstrated significant process capabilities, from the building of mould-free 3D shapes made of various metals, to low porosity and corrosion resistant titanium coatings.In the CS process, the particle stream characteristics during the acceleration process is important in relation to the final geometry of the coating. Experimental studies have shown the tendency of particles to spread over the nozzle acceleration channel, resulting in a wide exit stream and in the difficulty of producing narrow tracks. This paper presents an investigation on the powder stream characteristics in CS supersonic nozzles. The powder insertion location was varied within the carrier gas flow, along with the geometry of the powder injector, in order to identify their relation 2 with particles trajectories. Computational Fluid Dynamic (CFD) results by Fluent v6.3.26 are presented, along with experimental observations. Different configurations were tested and modelled, giving deposited track geometries of copper and tin ranging from 1mm to 8mm in width on metal and polymer substrates.

Hladna metalizacija

“…Razvijeno je mnogo različitih postupaka nanošenja prevlaka, a jednu veliku grupu čine postupci metalizacije. Hladna metalizacija (Cold Spaying) je postupak metalizacije koji se konstantno razvija i predstavlja jedan od postupaka budućnosti [3]. U poslednjih nekoliko godina, zbog velike potražnje za proizvodnjom metalnih prevlaka u različitim industrijskim postrojenjima, postupci metalizacije i njihove tehnologije evoluirali su od začetaka (gasnoplamena metalizacija, elektrolučna metalizacija žicom itd.…”

“…Kod tradicionalnih postupaka metalizacije dodatni materijal je zagrejan do visokih temperatura, pa prevlake mogu da sadrže visok procentualni udeo oksida, što ograničava dalju širu upotrebu ovih postupaka. Ova ograničenja moguće je prevazići pomoću postupka hladne metalizacije, koji je razvijen relativno skoro [3][4][5]. Hladna metalizacija (Cold Spraying) u literaturi se može naći i pod drugim nizivima kao npr.…”

Computational Simulation on a Coaxial Substream Powder Feeding Laval Nozzle of Cold Spraying

“…It is worth noting that all particles are assumed to be injected in X direction. Actually, the particles have a random injection direction at the Pressure Outlet1 [14,15]. As in conventional nozzle, most of the particles always travel through the highest gas velocity area in the nozzle.…”

A comparative review on cold gas dynamic spraying processes and technologies

“…Studying of relevant literature has shown that CGDS provides the deposition dynamics that could not be achieved literally by conventional spraying techniques such as plasma spray, wire arc, high-velocity oxy-fuel (HVOF) and wire flame which associate with phase properties changes and high temperatures. These associated limitations can easily be overcome by newly developed technology namely cold spraying coating technology [1,[11][12][13]. Cold spraying processes offers several advantages both in the processing itself and in the deposition result.…”