Effect of substrate roughness and topography on splat formation in suspension plasma spraying

The phenomena during the flattening and solidification phases of melted particles impinging on substrate are difficult to observe in suspension plasma spraying because of the small size of the droplets.If the effect of substrate roughness on splat formation is well-known for particles with size ranging between 20 and 100 µm, it is still an issue for particles with size below five micrometers.

This work seeks a better understanding of the mechanisms controlling the formation of splats resulting from the impacts of sub-micrometer particles. It uses a dimensional approach and compares the impacts of particles 40 µm in diameter at low velocity to the impacts of particles 700 nm in diameter. An experimental test bench permits to study the dynamics (time-variation of temperature, velocity, flattening diameter) of the melted particles flattening on substrates with various surface topographies. This approach is completed by adhesion tests and an examination of splat cross sections.