Effect of Solidification and Wetting on Flattening Behavior of Thermal Sprayd Particles.

点击翻译按钮获取中文摘要

In this research, the effects of both solidification in the splat and wetting at splat/substrate interface on the flattening of the thermal sprayd particle were investigated. In the first year, 1) investigation of the effects of both thermal conductivity of the substrate and dynamic wetting on the flattening, 2) trial of the model experiment, were carried out. Keeping the wetting condition at interface constant, change in flattening behavior of particle on each Au coated substrate was studied, as a result a tendency was confirmed that the larger thermal conductivity of the substrate was the higher the transition temperature was. This means that the initial solidification plays a significant role to the splashing. Keeping the initial solidification condition constant, flattening behavior of the particle on AISI304 substrate with various metal PVD films was studied, as a result it was confirmed that the more active the film metal was the higher the transition temperature was. This sugges … More ts a tendency difficult to splash for excellent wetting condition.In the second year, 1) more precise observation of the flattening behavior of droplet in model experiment, 2) trial of in situ observation of flattening of the sprayd particle, was conducted. As the setting of the trigger for the particle's arrival on the substrate was considerably difficult, in situ observation of the solidification and flattening in the rear surface of the splat was postponed to the future study. From the comparison in the flattening ratio between experimentally obtained in this study and each theoretical formulae, remarkable discrepancy between these was recognized even in the most advanced Rangel's analysis. More improvement is needed in the analyzes. It was confirmed that the splash-type splat spread with quite high acceleration from the in situ observation of the flattening behavior of the droplet, and the splash splat was characterized as the quite porous structure in the rear surface. It was clarified from these facts that the splashing was formed by jetting away of the low viscous fluid flow from collision center to periphery. The reason for the drastic change in the splat pattern near the transition temperature has to be investigated in more detail in the future study. Less