Pulsed gas dynamic spray process

The pulsed gas dynamic spraying (PGDS) process is a patent-pending process originally developed at the University of Ottawa Cold Spray Laboratory (2006). In the PGDS process the feedstock particles are accelerated and heated in a high velocity unsteady flow induced by a series of shock wave generated at a fixed frequency before impacting the substrate to be coated. Similarly to the cold spraying process(often called gas dynamic cold spray), the particles impact the substrate and deform plastically to produce a coating. However, as opposed to cold spray, it is possible to achieve high particle impact temperatures when using PGDS due to the gas compression generating the driving flow.
A such, it is envisioned that this process would allow the particles to be accelerated to high impact
velocities and intermediate impact temperatures, which should lead to a lower critical velocity compared
to CGDS and thus enhance plastic deformation upon impact on the substrate for similar impact velocity.
Soft metals such as Zn, Cu and Al are suited for pulsed gas dynamic spraying, but coating of other hard materials (such WC-Co,AlSi-SiC, NiCrAlY, Ti, etc.) using this process has been reported,.
Unlike thermal spraying techniques, one of the greatest benefits of solid-state technologies is the ability to spray materials at low temperatures, thereby suppressing any detrimental metallurgical transformations or thermal reactions in both deposit and substrate. By avoiding oxidation, grain growth and recrystallization, phase changes, and thermal stresses, this technology is uniquely suitable for depositing a range of temperature-sensitive and advanced materials.
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