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IN-SITU MEASUREMENT AND SIMULATION FOR DEFORMATION AND SOLIDIFICATION PHENOMENA OF SUPER-COOLED SINGLE DROPLET UNDER PLASMA SPRAY CONDITIONS (2002)

等离子喷涂条件下过冷单液滴变形和凝固现象的原位测量与模拟（2002）

基本信息

批准号：
12305048
负责人：
YOSHIDA Toyonobu
金额：
$ 30.18万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

The principal findings can be summarized as follows:1.To date, many modeling efforts related to the deformation and solidification processes of a droplet impacting on the substrate under plasma spraying conditions have been reported. However, no modeling effort has dealt with the super-cooling effects on the deformation and solidification processes, though much evidence of super-cooling effects has been reported. In this research, we could show the first results derived from our recent modeling efforts for the case of Al_2O_3 droplets, which clearly show the strong effects of the super-cooling conditions on the deformation and solidification processes. For example, we successfully predicted a significant decrease in deformation degree -defined as the ratio of droplet to splat diameters -to less than 2.0, and also a faster solidification front velocity of up to 5 m/s. Although the small deformation degree is caused by the larger value of viscosity under super-cooled conditions, the rapi … More d solidification is eventually caused by the super-cooling. The model did not predict a dendritic growth, but it clearly suggested that plasma sprayed particles are not all but may be actually in super-cooled state, and any modeling efforts should include the super-cooling effects.2.We developed an in-situ measurement system for precise 1:1 correlation between splat morphology and temperature history during impinging on the substrate under plasma spraying conditions with sampling the events successively under controlled atmosphere. In order to reveal the effectiveness of the system, deformation and solidification process of yttria-stabilized zirconia powder sprayed by hybrid plasma was measured successively at a horizontally moving substrate heated up to 700 K by a radiation-plate. The temperature was measured by 700 and 1000 nm emissions from a droplet, and the droplet size was evaluated ex-situ precisely based on the three dimensional morphology of the splat. The system made it possible to sample about 10 single particles successively within 10 second, and correlate precisely the relations between the size, temperature and impacting velocity of each droplet, and deformation-solidification process and morphology of the splats. The most striking finding is that a part of the droplets may be actually in super-cooled condition before impinging, but a drastic difference was not found in deformation process. In addition, as secondary results, we could evaluate the viscosity of YSZ and the thermal resistance between the splat and the substrate.From the above, it can be seen that considerable progress was made towards the overall goal of this project, and the results obtained so far clearly demonstrate the feasibility of this approach. Less

主要研究结果如下：1.迄今为止，已经有许多关于等离子喷涂条件下熔滴撞击基体的变形和凝固过程的模拟研究。然而，没有模拟的努力已经处理过冷效应的变形和凝固过程中，虽然过冷效应的证据已经报道。在这项研究中，我们可以显示的第一个结果来自我们最近的模拟工作的情况下，Al_2O_3液滴，这清楚地显示了强大的影响过冷条件的变形和凝固过程。例如，我们成功地预测了变形程度（定义为液滴与飞溅直径之比）的显著降低，小于2.0，以及高达5 m/s的更快的凝固前沿速度。虽然过冷条件下的粘度值较大，导致变形程度较小，但过冷条件下的快速变形， ...更多信息 D凝固最终由过冷引起。该模型没有预测枝晶的生长，但它清楚地表明，等离子喷涂颗粒并不都是，但实际上可能是在过冷状态，任何建模工作都应该包括过冷效应。2.我们开发了一个原位测量系统的精确的1：1之间的相关性飞溅的形态和温度的历史在等离子喷涂条件下在基板上的冲击在受控气氛下连续采样的事件。为了揭示该系统的有效性，在水平移动的基底上，通过辐射板加热至700 K，连续测量了混合等离子体喷涂氧化钇稳定氧化锆粉末的变形和凝固过程。通过来自液滴的700和1000 nm发射测量温度，并且基于溅射的三维形态精确地非原位评估液滴尺寸。该系统可在10秒内连续采集10个左右的单颗粒样品，并精确地关联了每个液滴的尺寸、温度和撞击速度与变形凝固过程和液滴形貌之间的关系。最显著的发现是，一部分液滴在撞击前可能处于过冷状态，但在变形过程中没有发现明显的差异。此外，作为次要结果，我们可以评估YSZ的粘度和溅射物与衬底之间的热阻。从上面可以看出，朝着这个项目的总体目标取得了相当大的进展，到目前为止所获得的结果清楚地证明了这种方法的可行性。少