喷枪扫描速度对等离子喷涂Mo/8YSZ梯度热障涂层温度场的影响规律研究

Effects of Scanning Speed of Spraying Gun on Temperature Field of Mo/8YSZ Gradient Thermal Barrier Coatings by Plasma Spraying

目的突破新型动力热障涂层高温环境易剥落的技术瓶颈,揭示等离子喷涂过程中,喷枪扫描速度对梯度热障涂层温度分布的影响规律。方法利用ANSYS有限元仿真模拟软件,建立了等离子喷涂Mo/8YSZ梯度热障涂层温度场的仿真模型,模型中考虑了材料热物性参数随温度的变化情况及材料的相变潜热。结果当喷枪扫描速度由550mm/s增加至1000mm/s时,喷枪与基体或已沉积涂层间交互作用的时间缩短,在喷涂构件自身热传导及喷涂构件与外界环境对流换热等综合因素作用下,致使喷涂作业结束时,喷涂构件的最高温度由475℃降低至371℃,涂层厚度方向的最大温度梯度由2.15×10^7℃/m降低至2.05×10^7℃/m。由于喷涂构件的温度、温度梯度及等离子射流热源用于粉末粒子直接温升的比例均与材料的热物性参数密切相关,致使在喷涂作业结束时,喷涂构件各部分最高温度及涂层厚度方向的最大温度梯度均呈现陶瓷层最高、过渡层次之、粘结层最低的分布规律。由于等离子喷涂过程中,先沉积的涂层对后沉积的涂层存在一个预热作用,故伴随着涂层厚度的增加,喷涂构件的最高温度增加。结论在等离子喷涂过程中,通过增大喷枪扫描速度,可在牺牲涂层最高温度的条件下,降低喷涂构件的最大温度梯度。热障涂层采用梯度结构,可实现涂层厚度方向材料热物性参数的连续梯度变化,进而实现对喷涂构件空间温度分布的有效调控。

The paper aims to break through the technical bottleneck of the new dynamic thermal barrier coatings which is easy to peel off at high temperature,and reveal the rule on influences of scanning speed of plasma spraying gun on temperature distribution of gradient thermal barrier coatings.A temperature field simulation model of Mo/8YSZ gradient thermal barrier coatings by plasma spraying was established by using ANSYS finite element simulation software,and the variation of thermal property parameters with temperature and latent heat of the material were considered in this model.When the scanning speed of the spraying gun was increased from 550 mm/s to 1000 mm/s,the time of interaction between the gun and the substrate or the deposited coatings was shortened.Under the combined effects of thermal conduction of spraying component and convection heat transfer between spraying component and external environment,the highest temperature of spraying component was decreased from 475 ℃ to 371 ℃,and the maximum temperature gradient in the direction of thickness of coatings was decreased from 2.15×10^7 ℃/m to 2.05×10^7 ℃/m.Due to temperature,temperature gradient and plasma spraying component jet heat source used for powder particles directly in proportion to the temperature rise were closely related to the thermal and physical parameters of the material,at the end of spraying,the maximum temperature of each part of the spraying component and the maximum temperature gradient in the thickness direction of coatings presented the distribution law of the highest ceramic layer,the transition layer and the lowest bonding layer.In the process of plasma spraying,the coating deposited first had a preheating effect on the coating deposited later.Therefore,the maximum temperature of spraying component was increased with the increase of coating thickness.Therefore,by improving the spray gun scanning speed in the process of plasma spraying,the highest temperature of coatings can be sacrificed to reduce the maximum temperature gradient.At the same time, the gradient structure of thermal barrier coatings can realize continuous gradient change of material thermal property parameters in the direction of coating thickness,and then effectively control the temperature distribution of spraying component space.