陶瓷层与界面孔隙率对热障涂层寿命及其失效机制的影响

Effect of porosity of ceramic-coats and interface on lifetime and failure mechanism of thermal barrier coating

以NiCoCrAlY作为粘结层、8wt%Y2O3稳定的ZrO2(8YSZ)为陶瓷层,利用等离子喷涂(PS)技术制备2种在陶瓷层及陶瓷层/粘结层界面处具有不同孔隙率的热障涂层(TBCs),研究TBCs的热循环寿命差异,分析不同孔隙率TBCs的失效机制。结合有限元模拟计算了TBCs应力分布,分析了高孔隙率TBCs中重复平行裂纹形成的原因及2种TBCs剥落的失效模式。利用光学显微镜(OM)、SEM和EDX分析TBCs的断面微观结构及元素分布。结果显示:高孔隙率TBCs比致密TBCs的寿命增加了1倍。高孔隙率TBCs在陶瓷层及界面处存在更多的孔隙和微裂纹,释放了TBCs中积累的应变能,同时氧化铝层中出现的重复平行裂纹能进一步减小了陶瓷层与粘结层之间的应力,进而延长了高孔隙率TBCs的寿命。为制备长寿命TBCs奠定结构设计基础。

Two kinds of thermal barrier coatings（TBCs）with different porosities at ceramic-coat and ceramic-coat/bond-coat interface by plasma spraying（PS）technology with NiCoCrAlY as bond-coat and 8wt% Y2O3 stabilized ZrO2（8YSZ）as ceramic-coat.The difference of thermal cyclic lifetime of TBCs were studied,and the failure mechanism of TBCs with different porosities was analyzed.The distribution of stress in TBCs was calculated with finite element simulation,and the formation reason of the repeated parallel cracks in the porous TBCs and the failure mode of the two TBCs peeling were also analyzed.The cross-section microstructures and element distribution of TBCs were analyzed by using optical microscope（OM）,SEM and EDX.The results show that the porous TBCs have a double longer lifetime than the dense TBCs.For the porous TBCs,as a consequence of the more pores and microcracks in ceramic-coats and interface to release the accumulated strain energy within the TBCs.At this time,the repeated parallel cracks in alumina layer further decrease the stress between ceramic-coats and bond-coats,which can prolong the lifetime of porous TBCs.Foundation for the structure design of the longer lifetime TBCs was laid.