Thermo-Mechanical Analysis on Formation and Strength of Coated Ceramic Film

在本项目中，研究了两种陶瓷涂层方法，以分析其涂层系统中产生的内应力。本文所要分析的涂层过程是爆炸涂层过程和溅射过程，提出了一种计算爆炸涂层过程中非稳态温度场和应力场的解析方法。所提出的程序是通过有限元建模的方法开发的。利用该模型对钢基爆炸涂覆氧化铝的非连续涂层过程进行了数值模拟。通过选择合适的热传递参数组合，模拟了涂层过程中和涂层后的温度随时间的变化。计算结果与实验观测结果基本吻合。应力场的模拟结果表明，X射线分析表明，涂层陶瓷层中产生的残余应力是拉伸的。在射频磁控溅射装置中，在玻璃衬底上沉积了氧化铝和碳化硅薄膜。利用超显微硬度计对溅射膜的硬度进行了测试。结果表明，两种陶瓷薄膜的硬度均随射频输出功率的增加而降低。尝试用分子动力学方法估算溅射薄膜的内应力场。溅射粒子的分子动力学采用硬球模型。根据经验信息，假设溅射粒子团簇随着射频输出功率的增加而增大。利用所提出的分析方法对实验结果进行了定性解释。

In this project, two types of ceramic coating methods were investigated to analyze the internal stress generated in their coating systems. The coating processes to be analyzed in this work were the detonation coating process and the spattering process.An analytical method was proposed to evaluate the unsteady temperature and stress fields during the detonation coating process. The proposed procedure was developed by means of finite element modeling. A simulation using the proposed model was conducted for the detonation coating of alumina on steel as a discontinuous coating process. The temperature variation with respect to time during and after the coating process was simulated by the selection of a suitable combination of heat-transmission parameters. The results almost coincided with the experimental observation. The simulated results for the stress field indicated that the residual stress generated in the coated ceramic layer was tensile, as observed in X-ray analysis.Thin films of alumina and silicon carbide were deposited on the glass substrate in an RF magnetron spattering apparatus. The hardness, as a mechanical property, of the spattered films were evaluated by using an ultra-microscopic hardness testing machine. It was found that the hardness decreased with increasing RF output power in both ceramic films. A molecular dynamics approach was tried to estimate the internal stress field in spattered film. A hard-sphere model was adopted in the molecular dynamics of spattered particles. Based on empirical information, cluster of spattered particles was assumed to be larger with increasing RF output power. The experimental result was explained qualitatively by using the proposed analytical method.