等离子喷涂-物理气相沉积7YSZ热障涂层沉积机理及其CMAS腐蚀失效机制

doi:10.15541/jim20140397

摘要/Abstract

摘要：

采用等离子喷涂-物理气相沉积(PS-PVD)以团聚烧结的ZrO₂-7wt%Y₂O₃(7YSZ)为原料, 在850℃基体温度下制备了具有柱状结构的热障涂层, 并通过场发射-扫描电镜(FE-SEM)分析了柱状涂层的显微结构。此外, 基于原子聚集理论研究了PS-PVD中7YSZ气相分子在基体上的形核与生长过程, 并分析了高温基体下7YSZ柱状涂层的沉积机理。另外, 在1200℃下考察了7YSZ柱状涂层的CaO-MgO-Al₂O₃-SiO₂(CMAS)腐蚀性能并探讨了其失效机制。结果表明, 在高温下7YSZ气相分子首先吸附在基体上, 通过扩散迁移形成分子团并吸附在基体表面上, 然后分子团再与其它吸附分子碰撞结合形成临界晶核, 临界晶核捕获其它吸附分子进一步长大形成晶核小岛, 此后依次经过岛状、联并、沟道、连续这四个阶段最终形成柱状涂层。高温下 CMAS熔融并在毛细管力的作用下沿着柱状涂层孔隙往深度方向渗透并与涂层发生热化学反应使涂层热物性能发生变化, 最终在热化学与热机械的相互作用下使涂层内产生平行于表面的横向裂纹, 并层离失效。

关键词: 等离子喷涂-物理气相沉积, 沉积机理, CMAS腐蚀, 腐蚀机制

Abstract:

Using agglomerated and sintered ZrO₂-7wt%Y₂O₃(7YSZ) powders as raw materials, columnar thermal barrier coatings (TBCs) were prepared by plasma spray-physical vapor deposition (PS-PVD) at substrate temperature of 850 ℃. The microstructures of columnar coating were analyzed by field emission-scanning electron microscope (FE-SEM). Based on the theory of atoms together, the formation and growth process of 7YSZ nucleus were investigated and the deposition mechanism of columnar coating was also analyzed. Besides, under the temperature of 1200 ℃, the CMAS (CaO-MgO-Al₂O₃-SiO₂) corrosion of columnar 7YSZ coating was examined and its failure mechanism was also discussed. During the deposition process of columnar 7YSZ coating, the 7YSZ gas molecules were firstly absorbed on substrate, then through diffusion and migration, the critical nucleus formed rapidly. Besides, the critical nucleus further grew up forming crystal island by absorbing other molecules. Then after following four steps of island formation, union formation, channel formation and continuation, the columnar coating formed eventually. When above melting temperature, the CMAS could penetrate into porous columnar coating by capillary force and react with the 7YSZ coating. Finally, the cracks appeared in the coating due to thermochemical and thermomechanical interaction.

Key words: plasma spray-physical vapor deposition, deposition mechanism, CMAS corrosion, corrosion mechanism

中图分类号:

TQ174

张小锋, 周克崧, 宋进兵, 邓春明, 牛少鹏, 邓子谦. 等离子喷涂-物理气相沉积7YSZ热障涂层沉积机理及
其CMAS腐蚀失效机制[J]. 无机材料学报, 2015, 30(3): 287-293.

ZHANG Xiao-Feng, ZHOU Ke-Song, SONG Jin-Bing, DENG Chun-Ming, NIU Shao-Peng, DENG Zi-Qian. Deposition and CMAS Corrosion Mechanism of 7YSZ Thermal Barrier Coatings Prepared by Plasma Spray-Physical Vapor Deposition[J]. Journal of Inorganic Materials, 2015, 30(3): 287-293.

图/表 8

表1 PS-PVD喷涂7YSZ热障涂层参数

Table 1 Coating parameters of 7YSZ thermal barrier prepared by PS-PVD

Materials	Power /kW	Ar /slpm	N₂ /slpm	Feed rate /(g?min^-1)	Carrier Gas Ar /nlpm	Stand-off distance/mm	Pre-heating temperature/℃	Chamber pressure /Pa
7YSZ	127	35	60	2×9	16	950	850	150

表2 X射线荧光分析获得的蛭石成分

Table 2 Compositions of vermiculite obtained by XRF

Oxides	CaO	MgO	Al₂O₃	SiO₂	Rest (Fe₂O₃, Na₂O, K₂O, etc)
Weight /wt%	2	21	17	42	18

图1 蛭石矿物的DSC-TG分析

Fig. 1 DSC-TG analysis of Vermiculite

图2 PS-PVD 制备的7YSZ涂层微观结构

Fig. 2 Microstructures of 7YSZ coating prepared by PS-PVD (a) Cross-section view; (b) Surface; (c) Bottom view of cross-section area (1) and (d) Top view of cross-section area (2) in (a)

图3 晶核形成与生长的物理过程

Fig. 3 Physical process of nucleus formation and grown (a) Molecule diffusion; (b) Molecule group; (c) Critical nucleus; (d) Stable nucleus; (e) Island phase; (f) Union phase; (g) Channel phase

图4 结构区域模型原理图[23-24]

Fig. 4 Schematic diagram of microstructure model[23-24]

图5 CMAS腐蚀前后7YSZ热障涂层的结构变化及元素分布

Fig. 5 Corrosion of columnar 7YSZ coating (a) Before corrosion; (b) After corrosion at 1200℃ for 24 h; (c) Enlarged coating tip in Fig. b, and (d) EDS spectra of Si in Fig. b

图6 柱状结构7YSZ涂层CMAS腐蚀失效示意图

Fig. 6 Schematic diagram of CMAS corrosion of 7YSZ coating (a) Crack delamination; (b) Mechanism of crack propagation

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