单面沉积热障涂层失效模式的研究

用电子束物理气相沉积方法(EB-PVD)制备了双层结构热障涂层,对其在热循环过程中的组织结构变化与失效模式用扫描电镜(SEM)与交流阻抗法进行了测试分析.结果表明,与双面沉积热障涂层的失效模式不同,单面沉积热障涂层的剥落发生在陶瓷层内,而不是发生在热氧化生长层内.应力分析表明,双面沉积的热障涂层在热循环过程中主要受到由于热不匹配所产生的平行于样品表面的剪切力的作用,而单面沉积的热障涂层则不仅受到剪切力的作用,而且还将受到沿样品法线方向应力的作用,从而导致在陶瓷层内产生开裂.用交流阻抗法可以有效地表征上述横向裂纹的萌生及其扩展.

FAILURE MECHANISM OF ONE SIDE COATED THERMAL BARRIER COATING

Two layered structure thermal barrier coatings were prepared by electron beam physical vapor deposition.The changes on microstructure and the failure mode of the specimen during thermal cyclic oxidation were analyzed by scanning electron microscopy(SEM) and impedance spectroscopy(IS).It is shown that the spallation of one side coated TBCs occurred mainly in YSZ top coat,instead of in thermally grown oxide(TGO) layer as often observed in double sides coated TBCs.Stress analysis indicates that during thermal cycling,double sides coated TBCs are mainly subjected to the thermal mismatched shear stress parallel to the sample surface,but one side coated TBCs are subjected not only to the shear stress,but also to the stress along the normal direction,and finally crack inside the YSZ.IS method can characterize the initiation and expansion of the transversal crack in the TBCs.