THERMAL-ANALYSIS AND MEASUREMENTS FOR A MOLTEN-METAL DROP IMPACTING ON A SUBSTRATE - COOLING, SOLIDIFICATION AND HEAT-TRANSFER COEFFICIENT

The behavior of a molten metal droplet impinging, spreading and solidi fying on a solid substrate is relevant to manufacturing processes such as splat cooling and spray deposition. In this study, we have conduct ed experiments aimed at the investigation of the solidification and co oling of a metal droplet after impact. Temperature measurements were c onducted during and after solidification. Some results are presented t o illustrate the effect of superheat and substrate material on the coo ling rate. We have also estimated the thermal contact coefficient betw een splat and substrate by matching for a number of conditions the exp erimental data to predictions of a heat transfer and phase change mode l. The results suggest that this coefficient can decrease by an order of magnitude during solidification for the case of a splat on metal su bstrates. For splats on quartz, where there is good bonding, the therm al contact coefficient appears to stay the same before and after solid ification.