Investigation of dynamic wetting behavior in flattening of thermal sprayed particles and dominating relation between wetting and initial solidification

热喷涂颗粒扁平化过程中动态润湿行为的研究以及润湿与初始凝固之间的主导关系

• 批准号: 10650707
• 负责人: FUKUMOTO Masahiro
• 金额: $ 2.18万
• 依托单位: Toyohashi University of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10650707/
• 关键词: Thermal Spraying; Thermal Sprayed Particle; Substrate Temperature; Splashing; Flattening; Solidification; Surface Tension; Transition Temperature; Dynamic Wetting

Effects of both solidification and interface wetting on the flattering behavior of thermal sprayed particles are quite essential under the conditions of the particles relating factors kept constant. Dominating relation between wetting and initial solidification, however, has not been fully understood yet. As the flattering behavior of the thermal sprayed particles can be considered to be dynamic wetting phenomenon, dynamic wetting behavior in flattening of the thermal sprayed particles and dominating relation between wetting and initial solidification were investigated in this research.In the first year, several kinds of particles were plasma sprayed on the metallic flat substrate surface held at various temperatures, and the effects of both solidification and wetting at particles/substrate interface on the flattening behavior of the particles were investigated. The relation between transition temperature and thermal conductivity of the particles had the strong linearity, and the worse … More was the static wettability at interface, the steeper was the gradient of the line. This indicates that even in the ceramic particle, the rapid solidification at the bottom part of the splat occur when the substrate temperature is close to the transition temperature. However, as the splashing was observed in the material combinations of poor wetting, it was indicated that the most dominating factor on the flattening was wetting. Free falling experiments of the molten metal droplets was also conducted as a simulation of the thermal spraying. From the results, it was estimated that the unique porous microstructure on the bottom surface of the droplet was formed by the taking in a gas physically.In the second year, effect of dynamic wetting on the flattening behavior of the thermal sprayed particles and the dominating relation between wetting and initial solidification were investigated. The central disk part in the splash splat expanded gradually according to the increasing of the substrate temperature, and wholly scattered splat could be often observed when the wetting was bad. From these results, it may be concluded that the wetting seemed to be the most dominating factor in the flattening of the thermal sprayed particle on the substrate. The rapid initial solidification at the bottom part of the splat was thought to affect on the flattening of the particle when the wetting reached to some critical condition.In-flight measurement if the velocity and temperature of the particle was also conducted and transition temperature of the splat was measured. The transition temperature increased with increasing the velocity, temperature and diameter of the particles. Splashing parameter : K=WeィイD10.5ィエD1ReィイD10.25ィエD1 is usually used as a determinant of the splashing. The transition temperature increased with increasing Splashing parameter based on the measured data of the particle. However, from the relation with the transition temperature, it was found that only splashing parameter could not determine the transition phenomenon. Then, Flattening K value : Kf=0.5aィイD11.25ィエD1ReィイD1-0.3ィエD1K was defined and introduced in this study. It was concluded that The splashing seemed to occur when the Kf value of the splat reached to some critical values.From the free fallen experiment under low pressure, it is revealed that the atmosphere itself has an inhibitive action to the wetting at the droplet/substrate interface. From the comparison between the splat on the naked substrate and that on the gold coated substrate, it was found that the wetting at splat/substrate interface was improved through the morphological change of the substrate surface according to the increasing of the substrate temperature. From the observation results of the high-speed video, it was found that the flattening velocity of the splash splat is extremely higher than that of the disk splat. The Higher flowing of the splat seems to be caused by the ultra rapid cooling at the bottom part of the splat. Less

在颗粒相关因素一定的情况下，凝固和界面润湿对热喷涂颗粒的扁平化行为的影响是十分重要的。然而，润湿和初始固化之间的主导关系尚未完全理解。由于热喷涂颗粒的扁平化行为可以看作是动态润湿现象，因此本文研究了热喷涂颗粒扁平化过程中的动态润湿行为以及润湿与初始凝固之间的主要关系。研究了颗粒/基体界面的凝固和润湿对颗粒扁平化行为的影响。相变温度与导热系数的关系呈较强的线性关系， ...更多信息 为界面静态润湿性，线的梯度越陡。这表明，即使在陶瓷颗粒中，当衬底温度接近转变温度时，也会在飞溅的底部发生快速凝固。而在润湿性差的材料组合中，则出现了飞溅现象，说明润湿性是影响压扁的主要因素。作为热喷涂的模拟，还进行了熔融金属液滴的自由下落实验。结果表明，熔滴底面的多孔结构是由物理吸湿作用形成的。第二年，研究了动态润湿对热喷涂颗粒扁平化行为的影响以及润湿与初始凝固之间的主导关系。随着基体温度的升高，飞溅区中心圆盘部分逐渐扩大，润湿性较差时，飞溅区常为整体分散状。从这些结果可以得出结论，润湿似乎是最主要的因素在平坦的热喷涂颗粒在基板上。研究认为，当润湿达到某一临界条件时，片状物底部的快速初始凝固会影响颗粒的扁平化，并对颗粒的速度和温度进行了飞行测量，测量了片状物的转变温度。转变温度随颗粒粒径、速度和温度的增加而升高。飞溅参数：K=We φ D10.5 φ D1 Re φ D10.25 φ D1通常用作飞溅的决定因素。根据颗粒的测量数据，转变温度随着飞溅参数的增加而增加。然而，从与转变温度的关系中发现，仅飞溅参数不能决定转变现象。在此基础上，定义并引入了展平K值：Kf=0.5a ~ 11.25 a ~ 11.25 d ~ 1.25 d ~ 1.2.25 d ~ 1.25 d ~ 1.1.25结果表明，当飞溅的Kf值达到某一临界值时，飞溅似乎发生了，低压下的自由落体实验表明，大气本身对液滴/基体界面的润湿有抑制作用。通过比较裸基片和镀金基片上的溅射，发现随着基片温度的升高，溅射/基片界面的润湿性通过基片表面形貌的改变而得到改善。从高速视频的观察结果，发现飞溅的扁平化速度远高于圆盘飞溅的扁平化速度。飞溅的较高流动似乎是由飞溅底部的超快速冷却引起的。少

项目成果

西岡映二: "速度および温度実測データに基づく溶射粒子偏平挙動の把握"溶接学会論文集 掲載決定. 18(印刷中). (2000)

Eiji Nishioka：“根据速度和温度测量数据了解喷涂颗粒的扁平行为”，发表于《日本焊接学会会刊》18（出版中）。

Masahiro Fukumoto: "Effect of substrate temperature on flattening and solidification of freely fallen metal droplet"Quarterly J. of the Japan Welding Society. Vol.17-No.2. 243-250 (1999)

Masahiro Fukumoto：“基材温度对自由落体金属熔滴的扁平化和凝固的影响”日本焊接学会季刊。

田中康徳: "セラミックス溶射粒子の偏平挙動における支配因子の特定"溶接学会論文集. 17. 259-265 (1999)

Yasunori Tanaka：“陶瓷喷涂颗粒压平行为的控制因素的识别”日本焊接学会会议记录 17. 259-265 (1999)。

Yasunori Tanaka: "Investigation of dominating factors on flattening behavior of plasma sprayed ceramic particles"Surface & Coatings Technology. Vol.12-121. 124-130 (1999)

Yasunori Tanaka：“等离子喷涂陶瓷颗粒扁平化行为的主导因素的研究”表面

田中康徳: "セラミックス溶射粒子の偏平挙動における支配因子の特定"溶接学会論文集. 17-2. 259-265 (1999)

Yasunori Tanaka：“陶瓷喷涂颗粒压扁行为的控制因素的识别”日本焊接学会会议记录 17-2（1999）。