Session BB2.5

3:30 PM BB2.5
EXPERIMENTAL INVESTIGATION OF DROPLET SPREADING ON SUBSTRATE DURING PLASMA THERMAL SPRAY. X.Y.Jiang, S.Sampath and G-X. Wang, Center for the Thermal Spray Research, Department of Materials science and Engineering, State University of New York at Stony Brook Stony Brook, NY.

Spreading of molten ceramic or metallic droplets is the first step of coating build-up on the substrate in thermal spray. The comprehensive understanding of the spreading and solidification process is important for the controlling of coating microstructure and, therefore the coating properties. In this experimental study, the spreading behavior of Molybdenum and PSZ ZrO2 droplets are investigated. The morphologies of the splats, ranging from star-like with severe splashing to regular disk-like shape are found to be sensitive to the process conditions such as plasma parameter, distance between the nozzle and the substrate, particle size, substrate materials and temperature. The formation mechanism of different splat morphologies and the droplets splashing pattern is suggested in relation to the process parameters. The flattening ratio and the thickness of the disk-like splats are measured quantitatively and compared with the values predicted by existing models. The interaction between the splat and the substrate is discussed based on the observation splat morphologies and heat transfer modeling.
* This work was supported by the MRSEC Program of the National Science Foundation under Award Number DMR-9632570