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 solidifying on a solid substrate is relevant to manufacturing processes such as splat cooling and spray deposition. In this study, we have conducted experiments aimed at the investigation of the solidification and cooling of a metal droplet after impact. Temperature measurements were conducted during and after solidification. Some results are presented to illustrate the effect of superheat and substrate material on the cooling rate. We have also estimated the thermal contact coefficient between splat and substrate by matching for a number of conditions the experimental data to predictions of a heat transfer and phase change model. The results suggest that this coefficient can decrease by an order of magnitude during solidification for the case of a splat on metal substrates. For splats on quartz, where there is good bonding, the thermal contact coefficient appears to stay the same before and after solidification.