In this work we present the numerical simulation results for the molten nickel and zirconia (YZS) droplets impact on different micro-scale patterned surfaces of silicon. The numerical simulation clearly showed the effect of surface roughness and the solidification on the shape of the final splat, as well as the pore creation beneath the material. The simulations were performed using a computational fluid dynamic software, Simulent Drop, The code uses a three-dimensional finite difference algorithm solving full Navier Stokes Equation with heat transfer and phase change. Volume of fluid (VOF) tracking algorithm is used to track the droplet free surface. Thermal contact resistance at the droplet– substrate interface is also included in the model. Specific attention is paid to the simulation of droplet impact under plasma spraying conditions. The droplet sizes ranged from 15 to 60 microns with the initial velocities of 70-250 m/s. The substrate surface was patterned by a regular array of cubes spaced at 1 µm and 5 µm from each other. The peak to valley height of each cube was between 1 to 3 µm. Different splat morphologies will be compared with those obtained from the experimental results under the same impact and surface conditions.

The current study has been focused on the final morphology of atmospheric plasma sprayed 8% yttria stabilized zirconia single splats. Single splats of two different sizes (-25 µm and +25/-45 µm) of ZrO 2 8Y 2 O 3 powder have been collected on polished stainless steel substrates at three different temperatures (Room, 300°C, and 600°C). The splat morphology and diameter, satellite particles, and splashing behavior were investigated using both scanning electron microscopy and image analysis software. The splat/substrate interface and splat curl up were studied from cross-sections prepared by focused ion beam milling. Results showed primarily pancake morphology and no evidence of delamination along the splat/substrate interface at 300oC substrate temperature and 100 mm spray distance. Overlapped splats showed evidence of melting (microwelding) at the splat boundaries. Splat thickness was measured to be less than 1 µm for all spray conditions. Roughness profiles of the surface of the deposited splats indicated microcracks had formed within the splats. Image analysis results exhibited a higher volume fraction of the splats relative to satellite particles at longer spray distance and higher substrate temperature. The average splat diameter increased as the substrate temperature increased.