Low-Pressure Cold Spray Deposition Window Derived from a One-Dimensional Analytical Model

Low-pressure cold spray (LPCS) coating deposition requires the consideration of multiple parameters to define spraying conditions. The use of a parameter window provides an integral approach to achieving this goal. In this work, an LPCS deposition window for zinc powders was obtained through the development of a one-dimensional analytical model of fluid and particle interaction. The model considers powder particle injection downstream of the nozzle and follows the particle from injection to impact. The model equations relate the particle velocity (v(p)) to the process parameters, such as the gas pressure ( P-0) and temperature ( T-0), particle size ( d(p)) and stand-off distance (SoD). The values of the particle velocity ( v(p)) at the nozzle exit and during the "free-jet", as well as the drag coefficient (C-d), were calculated using experimental spraying conditions for Cu and Al that have previously been documented in LPCS studies. The model's accuracy and applicability to other materials were confirmed upon comparing the results with those in the aforementioned studies. Moreover, the definition of the model equations allowed for the identification of three new parameters: (gamma) the maximum ideal particle velocity, (beta) the capacity to accelerate the powder particle inside the nozzle and (alpha) the deceleration of the particle in the free-jet zone. These parameters have not previously been published and allow for comparative evaluation between LPCS processes.