热循环条件下NiCrAlYSi/YSZ热障涂层层间损伤及元素扩散行为研究

Behavior of Interlayer Damage and Elements Diffusion of NiCrAlYSi/YSZ Thermal Barrier Coatings under Thermal Cyclic

采用真空电弧镀设备制备热障涂层(TBCs)中的NiCrAlYSi金属粘结层,采用电子束物理气相沉积工艺(EB-PVD)制备YSZ陶瓷层,利用带能谱仪的扫描电子显微镜对沉积态和热循环损伤后的热障涂层试样的形貌、组织结构以及元素成分进行分析,研究热障涂层从热循环初期到失效的过程中层间损伤及元素扩散行为。结果表明,随着热循环时间的延长,NiCrAlYSi/YSZ涂层先后经历快速氧化和氧化速率很低的阶段,1100h后由于陶瓷层脱落,粘结层继续氧化导致涂层增重突然增大。热循环初期,Zr、O向内扩散,Ni、Cr、Al向外扩散,TGO层中的Al元素供应充足,主要发生Al的选择性氧化;1100h后,TGO层中Al元素供应不足,Cr、Ni开始氧化,生成Al1.92Cr0.08O3和镍铝氧化物。这种不均匀的氧化使局部涂层体积膨胀,裂纹萌生于TGO层,随着裂纹的增殖、生长,最终贯穿等轴晶区和TGO层,导致热障涂层失效。

The NiCrAlYSi bonding layer was prepared by vacuum arc plating.The YSZ ceramic layer was prepared by electron beam physical vapor deposition(EB-PVD).Microstructure,crack morphology and elemental composition of the as-deposited coatings and TBCs after thermal cyclic were analyzed by using SEM with energy dispersive spectrometer.The behavior of interlayer damage and elements diffusion of TBCs from early stage of thermal cycling to failure process were investigated.The results show that,with the increase of the thermal cycling time,NiCrAlYSi/YSZ TBCs experienced rapid oxidation and low oxidation rate stages.After 1100 h,the ceramic layer fell off and the bond coat continued to oxidize,resulting in a sudden increase in coatings weight.At the beginning of the thermal cyclic,Al,Ni,and Cr in bond coat diffused outwards,while O and Zr diffused inwards from the ceramic layer.Al in the TGO layer is sufficient and the selective oxidation of Al mainly occurred.After 1100 h,Al in the TGO layer was insufficient,Cr and Ni began to oxidize,forming Al1.92Cr0.08O3 and nickel aluminum oxide.The uneven oxidation resulted in the local volume expansion in the coatings and the cracks initiated in the TGO layer.With the proliferation and growth of cracks,the cracks eventually penetrated the equiaxed crystal region and TGO layer,leading to the failure of TBC.s.