A model of the shock-wave induced spray process (SISP) and the criteria for bonding are used to predict whether particles traveling within the unsteady flow regime will adhere to the substrate upon impact. The results are then used to predict if a coating can be formed under specific spraying conditions. Having been validated based on particle velocity measurements, the model is used to investigate the effect of varying spray parameters, such as powder and gas initial temperature, gas heater length, and spray frequency.

In this study, a downstream injection cold spray nozzle is modeled numerically under various loadings. Instead of micron-sized particles, liquid feedstock as a carrier of nanoparticle suspension is fed into the nozzle through a port located 6 mm downstream of the nozzle throat at the diverging section. Water is used as the liquid carrier with a droplet size distribution of 5-100 µm and liquid-to-gas ratio ranging from 5 to 15%. The radial injection of droplets is simulated by Lagrangian particle tracking which includes the effects of heating and evaporation. The effect of the feedstock on downstream flow is analyzed and the optimum solid-to-liquid fraction in the suspension is determined.

Computational Fluid Dynamics (CFD) is used to model the Shock-wave Induced Spray Process (SISP). SISP utilizes the kinetic and thermal energy induced by a moving shock-wave to accelerate and heat powder particles, similar to Cold Gas-Dynamic Spraying (CGDS), where the particles impact the substrate and deform plastically to produce a coating. Individual powder particles reach the substrate at different velocities and temperatures depending on their location within the unsteady flow regime. The critical velocity correlated to particle impact temperature and a CFD model are used to predict whether a particle traveling within this unsteady flow regime will bond to the substrate upon impact or bounce off. This information is then used to predict if a coating can be formed under a specific set of spray conditions.

The Shock-wave Induced Spray Process (SISP) is a method of applying coatings of various metallic-based materials onto a wide range of different substrates. It utilizes the kinetic and thermal energy induced by a moving shock-wave to accelerate and heat powder particles. A transient axisymmetric model for the process is developed using Fluent. The model is validated with reference to a simplified one-dimensional approximation of the flow field. Values of pressure, axial velocity, Mach number, as well as static and total temperature are carefully examined. It is found that a zone develops in the flow that experiences elevated levels of temperature and velocity simultaneously. This is the main distinction between SISP and traditional CGDS processes. The effects of varying supply pressure and temperature on these flow variables are investigated in detail. Additionally, the effect of changing the driving gas type is investigated using air and helium as examples.

A computational fluid dynamic (CFD) model of the cold gas dynamic spray process is presented. The gas dynamic flow field and particle trajectories within an oval shaped supersonic nozzle as well as in the immediate surroundings of the nozzle exit, before and after the impact with the target plane, are simulated. Predicted nozzle wall pressure values compare well with experiment. In addition, predicted particle velocity results at the nozzle exit are in qualitative agreement with those obtained using a side-scatter laser Doppler anemometer (LDA.) Details of the pattern of particle release into the surroundings are visualized in a convenient manner.