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在大气环境中,测试7YSZ热障涂层抗1 000℃高温氧化性能,以模拟发动机叶片的巡航飞行高温氧化过程。采用交流阻抗技术并结合扫描电镜及X射线衍射系统研究了高温氧化过程中TGO层生长与YSZ层微结构演变。结果表明:随着氧化时间的增加,TGO层厚度增加符合抛物线规律,在中频阶段的阻抗谱响应愈加显著。YSZ熔融颗粒在较低测试温度下表现为容抗特征,随测试温度升高逐步表现为感抗特征。阻抗谱分析显示YSZ晶粒的电阻及电容随氧化时间增加,均呈一定幅度波动变化,高温氧化对熔融颗粒本身的电学特征影响不明显;随着氧化时间的增加,YSZ晶界电阻值不断增加,电容值不断下降,表明YSZ内微裂纹发生了生长和扩展,最终导致YSZ层的剥落失效。
In the atmospheric environment, 7YSZ thermal barrier coatings were tested for their resistance to 1 000 ℃ high temperature oxidation to simulate the high temperature oxidation process of cruise flight of engine blades. The growth of TGO layer and the microstructure evolution of YSZ layer during high temperature oxidation were studied by AC impedance technique combined with scanning electron microscopy and X-ray diffraction. The results show that with the increase of oxidation time, the thickness of TGO increases in accordance with the law of parabola, and the impedance spectroscopy response becomes more significant in the mid-frequency stage. The YSZ melted particles behave as a capacitive reactance at lower test temperatures and progressively exhibit an inductive reactance with increasing test temperature. Impedance spectroscopy analysis showed that the resistance and capacitance of YSZ grains fluctuated with a certain amplitude when the oxidation time was increased. The effect of high temperature oxidation on the electrical characteristics of the melted particles was not obvious. With the increase of oxidation time, the grain boundary resistance of YSZ increased continuously , The declining capacitance value indicates that the micro-cracks in YSZ have grown and expanded, finally resulting in the peeling failure of the YSZ layer.