High temperature oxidation resistance and thermal growth oxides formation and growth mechanism of double-layer thermal barrier coatings
High temperature oxidation resistance and thermal growth oxides formation and growth mechanism of double-layer thermal barrier coatings
复制标题
双层热障涂层的高温抗氧化与热生长氧化物形成及生长机理
DOI：
10.1016/j.jallcom.2019.05.052
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发表时间：
2019
影响因子：
6.2
通讯作者：
Liu Li
中科院分区：
文献类型：
--
作者：
Wang Ran;Dong Tian-shun;Di Yue-lan;Wang Hai-dou;Li Guo-lu;Liu Li
为了揭示高温氧化过程中双层热障涂层中热生长氧化物（TGO）的形成和生长机理，并进一步阐明锆酸镧（LZ）作为最外层陶瓷涂层提高双层热障涂层高温抗氧化性能的机理，采用空气等离子喷涂法制备了两种热障涂层，其陶瓷涂层分别为单层YSZ和双层LZ/8YSZ。随后，将两种tbc在1100 ℃下氧化，对比研究了TGO在高温氧化过程中的微观结构和生长行为。结果表明：两种tbc在氧化初期增重速度较快，氧化时间超过100 h后增重速度明显减慢；但在整个高温氧化过程中，双层TBCs的氧化增重明显慢于单层TBCs。在高温氧化过程中，TGO在双层tbc中生长较慢。经过相同时间的氧化处理，与单层tbc相比，双层TGO的形貌更薄、更致密，孔洞的形成时间也有所延迟，且未出现明显的裂纹。随着氧化时间的延长，氧化石墨烯中依次形成Al2O3、尖晶石氧化物和络合物。尖晶石氧化物和络合物统称为SC，是tbc高温氧化过程中裂纹形核和扩展的关键物质。由于LZ陶瓷涂层具有较好的隔离外界氧的能力，双层tbc结合涂层中元素的扩散动力学发生了变化。在氧化初期，Al3+、Ni3+、Co3+、Cr3+金属阳离子的氧化延迟。因此，SC的组建被推迟。在氧化后期，随着Al2O3的逐渐生长和增厚，O2−很难通过Al2O3保护屏障扩散到TGO与键合涂层之间的界面，这也阻碍了SC的生长，因此双层tbc的耐高温氧化性能优于单层tbc。
In order to reveal the formation and growth mechanism of thermal growth oxides (TGO) in double-layer thermal barrier coatings (TBCs) during high temperature oxidation, and to further clarify the mechanism of lanthanum zirconate (LZ) as the outermost ceramic coating to improve the high temperature oxidation resistance of double-layer TBCs, two kinds of TBCs were prepared by air plasma spraying, whose ceramic coating were single-layer YSZ and double-layer LZ/8YSZ, respectively. Subsequently, the two TBCs were oxidized at 1100 °C, whereupon the microstructure and growth behavior of TGO during high temperature oxidation were studied comparatively. The results show that the weight gain of the two TBCs were faster in the early stage of oxidation, and obviously slowed down when the oxidation time exceeded 100 h. But for the whole process of high temperature oxidation, the oxidation weight gain of double-layer TBCs was obviously slower than that of single-layer TBCs. In the process of high temperature oxidation, TGO growth in double-layer TBCs was slower. After oxidation for the same time, not only the morphology of TGO in double-layer TBCs was thinner and more compact, but also the formation time of holes was delayed than in single-layer TBCs, besides, no obvious cracks appeared. With oxidation time extending, Al2O3, spinel oxides and complex compounds formed in TGO successively. Spinel oxides and complex compounds were collectively called SC, which was critical for cracks nucleation and propagation during high temperature oxidation of TBCs. Due to better ability to isolate external oxygen of LZ ceramic coating, the diffusion kinetics of elements in bonding coating of double-layer TBCs was changed. In the early stage of oxidation, the oxidation of Al3+, Ni3+, Co3+, Cr3+metal cations was delayed. Accordingly, the formation of SC was postponed. In later stage of oxidation, with the gradual growth and thickening of Al2O3, it is difficult for O2−to diffuse to the interface between TGO and bonding coating through Al2O3protective barrier, which also prevents the growth of SC. Consequently, the high temperature oxidation resistance of double-layer TBCs is superior to single-layer TBCs.