CMAS组分对EB-PVD热障涂层微结构退化的影响

Effect of CMAS Composition on the Microstructural Degradation of EB-PVD Thermal Barrier Coatings

该文对典型Ca/Si原子比为0.33、0.73、1.78的CMAS(主要组分为CaO-MgO-Al2O3-SiO2)腐蚀的氧化钇稳定的氧化锆(YSZ)热障涂层(TBCs)的微观结构特征进行了详细的对比研究.研究发现:当Ca/Si原子比为0.33时,沿着整个被腐蚀的YSZ涂层会有ZrSiO4形成,YSZ陶瓷层上部区域原始的“羽毛状”柱状晶转变成相互连接的颗粒状结构,陶瓷层中部和下部区域仍为柱状晶结构,在颗粒状晶粒间隙和柱状晶晶粒间隙都有CMAS渗入.当Ca/Si原子比增加到0.73时,YSZ上部柱状晶退化成晶粒,下部柱状晶“羽毛状”结构退化,柱状晶上有明显的腐蚀坑,整个YSZ晶粒之间充满了非晶态的CMAS,而且在YSZ的顶部有部分m-ZrO2出现,在YSZ/Al2O3界面处还有硅酸锆(ZrSiO4)、钙长石(CaAl2Si2O8)和尖晶石(MgAl2O4)形成.当Ca/Si原子比增加到1.78时,柱状晶转变成等轴晶,非晶的CMAS和MgAl2O4填充在晶粒间隙,并伴随有t-ZrO2到m-ZrO2的相转变.结果表明,Ca/Si原子比含量高的CMAS对YSZ涂层具有更大的破坏性.

The microstructural characteristics of Y2O3 stabilized ZrO2(YSZ)thermal barrier coatings(TBCs)corroded by calcium oxide,magnesium oxide,alumina oxide,silicon oxide(CMAS)with the typical Ca/Si atomic ratios of 0.33,0.73,1.78,are comparatively studied in detail.We find that ZrSiO4 forms along the entire corroded YSZ coating with the CMAS of Ca/Si=0.33 and the original feather-like columns in the upper section of the coating transform into some interconnected fine grains with amorphous CMAS infiltrating into the intercolumnar gaps.As the Ca/Si atomic ratio increases to 0.73,the amorphous CMAS is filled with the intergrain gaps of the entire layer of the YSZ coating.The upper columns of YSZ degenerate into grains,while feathery-like structure of columnar grains disappears at the lower section of the YSZ with significant voids development in the columnar grains.ZrSiO4,CaAl2Si2O8 and MgAl2O4 are detected at the YSZ/Al2O3 interface.With increasing the Ca/Si atomic ratio in the CMAS to 1.78,the columnar grain structure transforms into more equiaxed grains and the intergrain gaps are filled with amorphous CMAS and MgAl2O4 along with the t-ZrO2 to m-ZrO2 phase transformation.These results indicate that the CMAS with a high content of the Ca/Si atomic ratio is more destructive to the YSZ coating.