Verification of Dominant Factors for Splatting and Solidification of Plasma Sprayd Particles.

通过在AISI 304不锈钢基体上喷涂几种金属粉末材料，系统地研究了等离子喷涂粒子撞击平坦基体表面时飞溅和凝固的主要因素，得到的结果如下：1）Ni、Cr、Cu、Fe和Mo粉末在不锈钢基体上的溅射过程中，在300 K的基体温度下出现了典型的溅射现象，随着基体温度的升高，溅射形貌发生了剧烈的变化，从有溅射到无溅射;观察了另一方面，在Al、Ti和Zr的情况下，这些未被识别。从飞溅物底面的观察结果和粉末材料潜热的比较来看，撞击后飞溅物的初始快速凝固似乎是飞溅的显著原因之一。从粉体材料的表面张力与转变温度的关系可知，粉体材料的表面张力是影响飞溅的主要因素之一。用简单的飞溅和凝固模型估算了撞击粉末的初始凝固速率，飞溅的发生与凝固速率和粉末材料表面张力的关系有很好的对应关系。5）对于凝固和凝固的间隔，当凝固更容易发生时，两者似乎同时发生，6）HVOF喷涂粒子的溅射斑图随基体温度的升高而发生转变，这与粒子的速度无关。

The dominant factors for splatting and solidification of the plasma sprayd particles impinging on the flat substrate surface were systematically investigated by spraying the several metal powder materials on the AISI304 stainless steel substrate.The results obtained are summarized as follows :1)In the splatting of Ni, Cr, Cu, Fe and Mo powder on stainless steel substrate, typical splashing at the substrate temperature of 300K and a drastic fraction change of the splat pattern, from the form with splashing to the one without splashing with the substrate temperature, were observed. On the other hand, those were not recognized in the case of Al, Ti and Zr. It seems that splatting strongly depends on thje powder material.2)From the observation result of the bottom surface of the splat and the comparison of the latent heats of the powder materials, initial rapid solidification of the splat just after the impingement seems to be one of the remarkable reasonsfor the splashing.3)It revealed that the surface tension of the powder material was one of the dominant factors for the splashing from the relation between surface tension and transition temperature of the powder.4)The initial solidification rates of the powder impinged were estimated by the simple splat and solidification model, and the incident of the splashing corresponded well to the relation between solidification rate and surface tension of the powder material.5)As for the intervals between solidification and flattenning, it seems that both occur simultaneously when the solidification tends to occur easier, while the flattenning occurs preferentially followed by the solidification when the solidification rate is lower.6)Particle's velocity is not suspected to be responsible for the transition behavior in the splat pattern of the sprayd particle, for the transition behavior of the splat pattern attendant to the substrate temperature increasing was observed in HVOF sprayd particles.