【作者】 马骏；

【导师】 张华堂；

【作者基本信息】 清华大学 ， 材料科学与工程， 2007， 硕士

【摘要】 ZrO2热障涂层是航空工业中广为应用的重要涂层之一,等离子喷涂是制备热障涂层的主要方法。本文以等离子喷涂ZrO2热障涂层为对象,研究了电弧超声激励的引入对其性能的优化与稳定作用。通过测定分析不加电弧超声与加入不同参数的电弧超声制备的涂层的结构和性能,分析了电弧超声对涂层性能的影响规律,并初步探讨了电弧超声的激发和作用机理。根据热障涂层的特点,选择涂层厚度、拉伸结合强度、热震性能、微观形貌作为涂层性能检测的指标。围绕涂层的性能评价,将电弧超声激励系统以及喷涂系统、超声信号检测系统联系起来进行试验方案的设计,由此获取详实、综合的试验结果。本文研究了电弧超声频率、激励电流对涂层性能的影响。与不加电弧超声相比,加入电弧超声后的涂层在相同喷涂条件下,厚度明显增加;涂层的拉伸结合强度值普遍提高,最多提高了20%以上,并且数据离散程度减小;涂层的抗热震性能显著提高,最多提高了50%以上;涂层均匀致密,孔隙率降低,裂纹减少。研究表明,在50kHz与80kHz电弧超声频率、10A左右激励电流下,涂层性能改善作用最为明显。综合分析涂层性能测试结果发现,由电弧激发的超声提高了等离子喷涂过程中粉末的加热效率,并且作用于涂层的沉积过程,改变了涂层中的残余应力,从而提高了涂层的性能。运用超声信号检测系统对电弧超声等离子喷涂过程中的超声声压进行检测,结果说明电弧超声对等离子喷涂过程中的能量传递有改善作用。本文的研究结果对电弧超声激励在等离子喷涂热障涂层中的深入、广泛应用具有重要价值。更多还原

【Abstract】 ZrO₂ thermal barrier coatings （TBCs） are important in aero-industry applications. Plasma spaying is a main method to form TCBs. Based on the plasma spraying process of TBCs, the effect and optimization of qualities of TBC in plasma spraying by arc-ultrasonic was investigated. Compared with the coatings without ultrasonic, the microstructure and performance of the coatings under ultrasonic were studied to find the effect of arc-ultrasonic. The exciting mechanism and effect of ultrasonic in the plasma spraying process were discussed briefly in this paper.According to the characteristics of TCBs, the thickness of the coating, the adhesive strength of the coating, the thermal shock performance and the microstructure were chosen to be the standards of the coating quality test and evaluation. Experiments were devised by using the plasma spraying system, the arc-ultrasonic exciting system and the signal examining system so as to get comprehensive and integrated results.The influences of arc-ultrasonic frequency and current on the qualities of TBC were investigated. Compared with the coatings without ultrasonic, the thickness of coatings with arc-ultrasonic increases prominently under the same condition of spraying. The adhesive strength of most of the coatings increases and the most prominent ones can increase by more than 20%. The data of adhesive strength are much more concentrative. All TBCs specimens with different arc-ultrasonic frequency have better performance in the thermal shock test. And coatings on some specimens with certain frequency can bear about 50% more thermal cycles than coatings without arc-ultrasonic. The porosity and cracks of ZrO₂ coating decrease when arc-ultrasonic is induced and the porosity and cracks are uniformly distributed. The coatings become more compact under arc-ultrasonic. The frequency parameters of 50kHz and 80kHz and the current parameter of 10A are the most effective to the improvement of the TBC qualities.Based on the tests of the TBC qualities, the exciting mechanism was probed into. The excited ultrasonic improves the heating efficiency of powder and changes the distribution and property of residual stress in the coatings. So the performances of coatings are improved. The signal examining system was used to test the ultrasonic pressure in the plasma spraying process. The result shows that the transfer of energy in the process meliorates under the effect of arc-ultrasonic.The result of the dissertation is valuable to the practical use of the plasma spraying by arc-ultrasonic.更多还原