Spreading and Solidification of Hollow Molten Droplet under Its Impact onto Substrate: Computer Simulation and Experiment

摘要

The peculiarities of plasma treatment of agglomerated (spray dry) YSZ powder and subsequent plasma spraying of produced HOSP powder (consisting of the hollow spherical particles) are analyzed. Formation of splats of hollow YSZ droplets deserves a special attention within thermal spraying. In this case, immediately prior to particle—substrate collision, we have a droplet that consists of a liquid shell enclosing a gas cavity heated to a temperature close to the melt temperature. The paper presented includes the results of computer simulation and model experiments carried out under full control of the key physical parameters: temperature, velocity, external diameter of droplet, thickness of its shell, and temperature of polished substrate. It was shown that formation of splats of hollow droplets proceeds in a manner more stable compared to the case of “dense” molten particles obtained from fused and crushed compacts, and this provides superior coating-substrate interface.