A contoured nozzle design method for effective cold spray metal coating

In cold spraying, a uniform particle distribution of uniform velocity is desirable to achieve a good quality deposition pattern. Whereas many cold spray facilities use conical convergent-divergent nozzles for accelerating the particles, this paper evaluates a contoured axisymmetric nozzle design to enhance the process efficiency. The performance of a conventional conical cold spray nozzle is compared with that of a new axisymmetric nozzle designed with a smooth throat and contoured for a parallel outflow. The new nozzle profile is obtained by the application of two aerospace design codes based on the Method of Characteristics. A two-way coupled Eulerian-Lagrangian Computational Fluid Dynamics formulation is used, where the continuous phase steady motion is predicted by solving the Reynolds-Averaged Navier-Stokes equations with the Shear Stress Transport k-ω model. A Discrete Phase Model computes the motion of the particles carried by the jet. The numerical predictions show that the new nozzle shape delivers a more radially uniform deposition. A higher particle velocity is also obtained at the same operating conditions used by the industry standard nozzle, which is desirable for good particle bonding to the substrate.