A 3D computational model of fluid flow and heat transfer including solidification was developed. The model was used to simulate the impact of nickel particles on a stainless steel substrate in impact conditions measured experimentally (60 11m particles diameter, 73 mls impact velocity, particles 150°C above their melting temperature). We considered two cases where the initial substrate temperature was 29ifC and 400°C. Numerical results were compared with experimental photographs taken at the same conditions. Different splat shapes obtained numerically were comparable with those obtained experimentally. For the substrate initially at 290°C, the final splat had a bulk with fingers around it (star-like shape). Fast growth of solidification was found to be the cause of particle splashing. When the substrate temperature increased to 400°C, the final splat was a flat disk with a round shape. Numerical model showed that the change of splat shape for the two cases was due to a different value of contact resistance at the substrate surface. At a higher substrate temperature, the contact resistance was higher resulting in a lower rate of heat transfer to the substrate and a lower growth of solidification inside the particle. Good qualitative agreement between the results of the numerical model and experimental photographs demonstrated the model to be well suited for studying particle impact in a thermal spray coating process.

Keywords