Papers by Author: L. Yang

Abstract: During plasma spray forming, the forming quality is directly influenced by the flattening behavior of the droplet impacted onto the substrate, which is determined by the flattening configuration and solidification state of the droplet. In this study, according to the rule of Reynolds number and Peclet number, the flattening behavior of big-size molten droplet impacted onto the substrate with low-speed were experimentally simulated during flattening. The droplets of Sn30Pb70, Zn and ZA12 impacting onto the stainless steel substrate with different velocity were investigated. Splashing degree was introduced to evaluate the flattening profiles of the splats. The relationships between the splashing degree and the impact velocity, Reynolds number and Weber number of the droplet were established. Experimental results show that the flattening and diffusion are impeded by the dynamic viscosity and surface tension of the droplets, and the impeding effects are more remarkable when the impact velocity is lower. The research has a significant ap

Abstract: The quality of coatings is directly influenced by the flattening and solidification of many individual molten droplets in plasma spray forming, so many properties such as thermal, electrical, mechanical etc are strongly linked to the real contact between the “piled-up” splats. The research on the transient temperature of impacting droplets and the heat transfer between droplets and substrate plays an important role in improving the quality of coatings. Because of complexity and high cost of temperature measurement systems for molten droplet during flattening in plasma spray forming at present, this paper presents a new kind of simulation measurement system for transient temperature of spray droplets when impacting on substrate based on LabVIEW, which could display the real-time changes of the temperature by waveform graph. Finally, the experiments were carried out on Pb-Sn alloy molten droplets to reveal the close connection between the impacting droplets temperature changes and the coatings quality, and the heat transfer between droplets and substrate was discussed.

Abstract: The main factors that influence the deposition efficiency and forming quality are the state of in-flight particles, which are directly effected by process parameter during plasma spray forming. In this study, plasma spraying of ZrO2 powder was employed according to the method of orthogonal experiments, and the relationship between spray parameters and characteristics of in-flight particles, which were monitored by an optical monitoring system of CCD camera, were investigated. Radial basis function (RBF) neural network model had been designed to forecast the temperature and velocity of in-flight particles, and optimized spray parameter. The comparison of the simulations with the experimental results shows the validity of the model.