Abstract
Plasma spraying using liquid precursors makes it possible to produce finely-structured coatings with a broad range of microstructures and properties. Nonetheless, issues with coating reproducibility and control of deposition efficiency continue to be a concern. With conventional dc plasma torches that inject liquid feedstock transversely into the plasma stream, coating quality depends on transient interactions between the liquid and plasma jet. Numerical models may assist in understanding these interactions provided they are able to predict droplet fragmentation, which determines the trajectories of droplets and their behavior in the plasma flow. Although various models for droplet fragmentation have been proposed in the literature, they include parameters and constants that need to be validated for plasma spraying conditions. This study simulates liquid material injection and break-up in the plasma jet using an enhanced Taylor analogy break-up (TAB) model. Model constants are adapted to plasma spray conditions by observation of liquid behavior in the plasma flow, which is accomplished by means of a shadowgraph system using pulsed backlight illumination.
