等离子喷涂Al_2O_3熔滴铺展形貌分析

Spreading morphology analysis of plasma spray Al_2O_3 droplet

研究碰撞速度、粒径、前铺展层、雷诺数、粗糙度以及接触热阻等因素对熔滴铺展形貌的影响规律,建立了Al_2O_3熔滴铺展过程的数学模型。通过FLUENT进行数值模拟,采用专用装置收集粒子,通过SEM分析涂层形貌,结合计算结果分析各因素对铺展形貌的影响。结果显示:随熔滴直径和速度增大,铺展的边缘出现断裂,形成飞溅。前层铺展的凸起阻碍后面的熔滴铺展。随雷诺数增大,熔滴形貌从不飞溅过渡到飞溅。当oh>0.2时,熔滴飞溅的临界值为Re>470±10;当oh<0.2时,熔滴飞溅的临界值为We>1.35×10~4±100。接触热阻增大,飞溅现象显著。基体表面粗糙度增大,铺展程度降低。

The effects of droplet speed, particle size, previous spreading layer, Reynolds number, roughness and thermal contact resistance on the spreading morphology were analyzed. Mathematical model of A1203 droplet spreading process was set up, and numerical simulation was carried on through FLUENT software. The isolated plant was adopted to collect the particles, and the coating morphology was analyzed through SEM. Combined with the calculation results, the effect of various parameters on spreading morphdogy was studied. The results show that the edges of the spreading form splash with the increase of droplet diameter and velocity. The previous droplet spreading hinders the subsequent droplet from spreading. Droplet morphologies become splash with the increase of Reynolds number. When oh〉 0.2, the critical value for splash is Re〉470±10. When oh〈0.2, the critical value for splash is We〉 1.35×10^4±100. Splash strengthens with the increase of thermal contact resistance. Spreading reduces along with the increase of the substrate surface roughness.