Chinese Journal of Material Research 2016 , 30 (8): 627-633 https://doi.org/10.11901/1005.3093.2015.313

Orginal Article

Yb/Y双掺杂氧化锆在熔盐腐蚀环境中的元素扩散和相变机理研究*

徐俊¹, 陈宏飞¹, 杨光¹, 罗宏杰¹, 高彦峰¹^,²

1. 上海大学材料科学与工程学院上海 200444
2. 中国科学院上海硅酸盐研究所上海 200072

Elements Diffusion and Phase Transitions in Yb/Y Co-doped Zirconia Ceramic under Molten-salt Corrosive Environment

XU Jun¹, CHEN Hongfei¹^,^**, YANG Guang¹, LUO Hongjie¹, GAO Yanfeng¹^,²^,^**

1. College of Materials Science and Engineering, Shanghai University, Shanghai 200444, China
2. Shanghai Institute of Ceramics, Chinese Academy of Science, Shanghai 200072, China

文献标识码: 分类号 TB304 文章编号 1005-3093(2016)08-0627-07

收稿日期: 2015-05-28

网络出版日期: 2016-09-28

基金资助: * 国家自然科学基金51402183和上海市科委基础研究重大项目12DJ1400403资助

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摘要

高温腐蚀性环境是发动机热端部件热障涂层出现机械应力失配和氧化锆晶型变化从而发生失效的主要原因之一。本文通过共沉淀-煅烧法制备了Yb/Y双掺杂氧化锆粉体, 压片烧结后进行高温熔盐(CaO-MgO-Al₂O₃-SiO₂, CMAS)腐蚀实验, 利用XRD、SEM及EDS等表征手段对腐蚀过程中元素的扩散和物相、形貌的变化进行研究。结果表明, 氧化锆晶格中的Yb在腐蚀过程中先于其他元素与CMAS反应而流失(从氧化锆晶格扩散至腐蚀剂中), 但Yb的流失能减缓Y元素的偏析, 从而稳定亚稳四方相氧化锆( $t ′$ -ZrO₂); Yb的最优掺杂量为5%, 此时腐蚀反应产生的单斜相氧化锆(m相)的含量最少。

关键词： 材料失效与保护 ; 热障涂层 ; Yb/Y双掺杂氧化锆 ; 熔盐腐蚀 ; 扩散 ; 结晶相转变

Abstract

Ingeneral,high-temperature salt-corrosion may usually induce mechanical stresses and phase transformation within ZrO₂,as the main componentof thermal barrier coatings (TBCs), therewith further cause the failure of TBCsfor hot section components of gas turbine. Yb/Y co-doped zirconia (YbYSZ) powder was synthesized by a coprecipitation-calcination method, thenYbYSZ ceramic pallets were obtained by cold pressing and subsequent sintering at high temperature. The corrosion behavior of thepallets coated with a film of powder mixture CaO-MgO-Al₂O₃-SiO₂ (CMAS) was examined in air at 1250℃ for different time intervals. The elemental diffusion and phase transformationwith YbYSZ after high-temperature corrosion wereinvestigated by XRD, SEM and EDS. The results showed that among othersthe elementYbin YbYSZ reacted preferenyially with CMAS and dissolved into the molten saltCMAS. The loss of Yb could suppressed the segragation of Y from the rest YbYSZ.Consequently, it stabilized the metastable tetragonal phase (t'-zirconia). The optimal dose of Yb is 5 mass% for the minimal yield of monoclinic ZrO₂ in the YbYSZ after corrosion test.

Keywords： materials failure and protection ; thermal barrier coating ; Yb/Y co-doped zirconia ; molten-salt corrosion ; diffusion ; phase transition

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徐俊, 陈宏飞, 杨光, 罗宏杰, 高彦峰. Yb/Y双掺杂氧化锆在熔盐腐蚀环境中的元素扩散和相变机理研究*[J]. , 2016, 30(8): 627-633 https://doi.org/10.11901/1005.3093.2015.313

XU Jun, CHEN Hongfei, YANG Guang, LUO Hongjie, GAO Yanfeng. Elements Diffusion and Phase Transitions in Yb/Y Co-doped Zirconia Ceramic under Molten-salt Corrosive Environment[J]. Chinese Journal of Material Research, 2016, 30(8): 627-633 https://doi.org/10.11901/1005.3093.2015.313

用于涡轮发动机热端部件表面的热障涂层(TBCs)在服役过程中直接与高温燃气接触, 因此空气中的沙粒、尘土等在高温的作用下会沉积在热障涂层表面, 从而影响涂层的性能^[1-3]。早在20世纪90年代, Kim^[12]、Stott^[1]、Borom^[13]等就在沙特阿拉伯、中东和波斯湾等沙漠地区的飞机发动机叶片上发现了玻璃状沉积物, 揭示了这种腐蚀失效现象的存在。据研究, 这些随助燃空气进入发动机的物质的主要成分为CaO-MgO-Al₂O₃-SiO₂(CMAS)^[4]。随着涡轮发动机工作温度的提高(>1200℃), CMAS对热障涂层的腐蚀问题愈发严重, 大幅降低了涂层的服役寿命^[5], 主要因为CMAS在960℃时开始软化并在1240℃左右熔化为高温熔盐^{[6, 7]}, 这种玻璃态的高温熔盐会沿着涂层中的孔隙和裂纹渗入到涂层内部。Krama等详细阐述了CMAS与电子束物理气相沉积(EB-PVD)制备的热障涂层的热化学作用以及柱状晶陶瓷的形貌与结构演变^[4]。对于目前商用的氧化钇稳定的氧化锆(YSZ)涂层, 渗入到涂层中的CMAS会通过热化学和热机械作用使涂层失效^[8-11]。其中, 热机械破坏源于渗透进入涂层内部的CMAS与涂层之间的热膨胀系数不匹配从而产生热应力导致涂层产生横向微裂纹; 热化学作用体现为腐蚀过程中熔盐与涂层材料发生反应, 破坏了氧化锆的相稳定性, 导致四方相氧化锆( $\begin{matrix} \overset{′}{t} \end{matrix}$ -ZrO₂)发生相变, 相变过程中产生的体积收缩使涂层开裂。Chen、Evans等^[14]进一步提出了YSZ层在CMAS作用下的分层破坏机制。包括Mark、Habibi、何箐^{[11, 15, 16]}在内的国内外专家通过研究认为在高温下CMAS中的SiO₂会与YSZ中的Y发生化学反应, 反应方程式为:

$\begin{matrix} 2 Y_{2} O_{3} + 3 Si O_{2} \to Y_{4} (Si O_{4})_{3} \end{matrix}$

由于上述反应的发生导致YSZ晶体中的Y持续向腐蚀剂中扩散, 造成晶体中Y的偏析, 生成了高Y的立方相(c相)氧化锆和低Y的单斜相(m相)氧化锆。相变的产生伴随着体积的收缩, 而体积收缩最终会导致YSZ热障涂层剥落失效。因此, 如何提高热障涂层, 尤其是YSZ涂层的耐CMAS腐蚀性能成为一个亟需解决的课题。

Zacate^[17]等研究证实掺入氧化锆中的稀土元素与氧空位形成缔合缺陷, 二者之间存在缺陷缔合能, 缺陷缔合能的存在使得稀土元素与氧化锆晶体的结合力增强。本文通过向7YSZ中掺稀土元素Yb从而引入缔合缺陷, 一方面Yb、Y与氧缺陷之间的缺陷缔合能够使晶体更加稳定, 掺杂元素不易从晶体中流失; 另一方面即使由于长时间服役存在掺杂元素流失的情况, 缺陷缔合能较小^[17]的Yb更易流失从而确保Y保留在氧化锆晶体中。即本文的重点在于利用Yb掺杂YSZ来达到减缓Y的流失, 从而减少m相产生, 达到稳定 $\begin{matrix} \overset{′}{t} \end{matrix}$ 相的目的。此外, 本研究的另一个目标是通过考察稀土元素双掺氧化锆材料耐CMAS腐蚀过程中元素含量和物相的变化来探索腐蚀反应中稀土元素的扩散规律以及7YSZ的相变机理。

1 实验方法

1.1 粉体制备

将Y₂O₃与Yb₂O₃按化学计量比称量后, 加入稀释的浓硝酸中溶解。Y₂O₃的量保持7%(质量分数)不变, Yb₂O₃则按实验设计分别加入1%、3%、5%、7%, 稀土氧化物的溶解速度因元素不同而有较大差异, 为加速溶解, 将其置于~80℃水浴中加热并持续搅拌, 直至溶液澄清, 即得到稀土硝酸盐溶液。与此同时, 将按化学计量比称量好的ZrOCl₂8H₂O溶于去离子水后与上述稀土硝酸盐溶液混合并持续搅拌。然后向混合溶液中滴入氨水至过量。滴定过程中会伴随白色胶体状沉淀的产生。当pH=10~11时沉淀物的量达到最大值。此时停止滴定, 将沉淀物离心分离, 烘干之后沉淀物在1200℃下煅烧2 h后得到所需双掺氧化锆粉体。粉体经充分研磨之后加入浓度为10%的PVA作为粘结剂, 然后在5 MPa下压成直径为11 mm的圆片。将圆片置于炉中1500℃烧结10 h, 随炉冷却取出备用。

1.2 腐蚀实验

本文中采用的CMAS组分构成主要参考Borom^[13]等人的研究结果, 该结果显示在中东地区沙漠环境中考核后涡轮叶片上残余腐蚀剂CMAS的成分为33CaO-9MgO-13AlO_1.5-45SiO₂(C_0.33M_0.09A_0.13S_0.45), 由于我国在西部地区, 尤其是新疆也存在相似的沙漠环境, 所以CMAS组成参考上述配比。按此摩尔比称取相应质量的CaCO₃、MgO、SiO₂和Al₂O₃, 配料完成后放入研钵充分研磨备用。

研磨好的CMAS在模具中按压得到薄片, 将薄片放置在陶瓷片表面, 置于炉中在1250℃下分别热处理1 h、2 h和5 h。

1.3 表征和测试

采用日本理学D/Max2200VPC衍射仪对试样进行物相分析。测试中使用Cu Kα射线(λ=1.5418)作为X射线发射靶源, 使用的加速电压和电流分别为40 kV和40 mA, 扫描范围为10-90°, 扫描速度为8°/min。

采用S-4800场发射扫描电子显微镜(SEM)来观察材料的显微组织。测试时工作模式为高真空, 加速电压30 kV。并通过SEM自带的EDS来表征所选区域内的元素含量。

2 结果与讨论

2.1 腐蚀时间对CMAS腐蚀深度的影响

CMAS的软化温度是960℃, 因此在实验温度为1250℃时CMAS以熔融的玻璃态形式存在。由于CMAS的量影响腐蚀速度, 在前期实验过程中, 当使用少量CMAS(0.05 g/cm²)进行腐蚀实验时, 无法有效检测到反应的产物以及反应的过程; 当使用较大量CMAS(0.5 g/cm²)腐蚀时则在短时间内就能将样品穿透(~30 min), 也无法进行有效观测。因此, 本研究选择的CMAS量为0.2 g/cm², 通过控制CMAS的加入量使样品的失效演变过程能在有限的实验时间内被有效观测。在整个软化熔融过程中CMAS片的致密度逐渐升高, 然后以流体的形式将陶瓷片浸润。图1为3%Yb掺杂的YSZ(YbYSZ)在1250℃分别腐蚀1 h、2 h、5 h的截面SEM图, 从图中可以看出整个腐蚀过程中微观结构的演变。当腐蚀时间为1 h时, 如图1A所示, 整个CMAS熔盐紧密地附着在陶瓷片基体上, 由于CMAS与YbYSZ陶瓷间的热膨胀系数不匹配, 导致在冷却过程中形成体积收缩, 原本半径与陶瓷片相同大小的CMAS薄片由于体积收缩在陶瓷片边缘留下空缺, A图右上角即是CMAS体积收缩造成的空缺。CMAS的体积收缩给YbYSZ陶瓷片带来指向圆心的切应力。CMAS熔盐由于毛细管力的作用沿着陶瓷片的气孔和缝隙渗透进入陶瓷片内部。在图1A中, 由于CMAS还未渗透到基体内部, 因此热匹配失效带来的只是表面CMAS薄片的半径变小。当腐蚀时间达到2 h(如图1B所示), CMAS在YbYSZ中的渗透深度为1.25 mm左右, 由于熔盐所引起的化学反应, 在渗透区域内形成了因腐蚀而产生的缝隙(关于腐蚀反应将在下一节中详细叙述)。当腐蚀时间延长至5 h时, 腐蚀反应持续进行, 渗透区域深度扩至2 mm左右, 腐蚀区域内原有缝隙相互联结, 形成横向贯穿型大孔洞。

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图1 3%Yb掺杂YSZ在1250℃不同腐蚀时间的SEM图

Fig.1 SEM images of 3%Yb doped YSZ corroded in molten CMAS at 1250℃ for: (A) 1 h; (B) 2 h; (C) 5 h

2.2 腐蚀过程中YbYSZ的截面形貌演变与化学反应

CMAS对YbYSZ陶瓷的作用除2.1讨论的热应力效应影响之外, 另一个比较重要的效应为腐蚀过程中的化学反应作用, 即CMAS与YbYSZ之间发生了化学反应, 生成了新的物相。从图2中能直观地观察到CMAS腐蚀YbYSZ晶体的过程。

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图2 YbYSZ被CMAS在1250℃腐蚀2 h后的SEM图, B图为A图的局部放大

Fig.2 (A) SEM image of YbYSZ corroded by CMAS for 2 hours at 1250℃, (B) high magnification image of local area in images A

图2为YbYSZ被CMAS在1250℃腐蚀2 h后的SEM图(截面), 其中, A图中窄条状C区域为CMAS。CMAS腐蚀YbYSZ中各区域元素含量如表1所示。从表中所列的元素含量可以看出, C区域主要组成是CMAS, 而D区域为YbYSZ。

表1 CMAS腐蚀YbYSZ中各区域元素含量

Table1 Elements contentsdetermined by EDS in the regions C and D of YbYSZ corroded by CMAS (%, atom fraction)

Elements content	Region C	Region D
O	65.89	72.80
Zr	1.36	23.82
Y	0.69	2.49
Yb	0	0.34
Ca	11.70	0.30
Mg	2.59	0.12
Al	4.15	0.08
Si	13.60	0.06

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这些窄条状分布的CMAS腐蚀剂将大颗粒割裂, 颗粒边界的地方由于接触到的腐蚀剂最多, 因此被分割成很多小块。小块的YbYSZ晶体被CMAS包裹溶解, $\begin{matrix} \overset{′}{t} \end{matrix}$ 相YbYSZ溶于熔体中并沉淀出球状单斜氧化锆。图2中B图为A图中晶粒边界处的局部放大图。从B图中能够观察到大的晶粒最终都被腐蚀成小球状。整个腐蚀过程示意图如图3所示。

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图3 CMAS在1250℃腐蚀YbYSZ陶瓷的过程示意图

Fig.3 Diagrammatic drawing of corrosion process of YbYSZ ceramic in molten CMAS at 1250℃

将陶瓷片表层的刮下来进行X射线衍射分析, 将得到X射线图谱进行一定的平滑处理后能够得到腐蚀反应产物的物相图谱(图4)。

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图4 YbYSZ腐蚀产物XRD图

Fig.4 XRD pattern of corrosive product of YbYSZ ceramic

图4中MAlSiO主要由两种成分组成: Mg₃Al₂Si₃O₁₂和Ca₃Al₂Si₃O₁₂, 为单斜相, 是CMAS高温下反应生成的化合物, MZrO的成分较为复杂, 主要包括Ca_0.15Zr_0.85O_0.18、Zr_0.866Ca_0.134O_1.7和Al_0.5Zr_0.48O_0.174等, 物相为Ca、Al元素掺杂ZrO₂后形成的单斜相的氧化物, 所以图中MZrO的部分衍射峰和单斜相ZrO₂重叠, 这些产物是CMAS与YbYSZ反应后生成的产物。再结合EDS的元素分析可以确认: ZrO₂与CMAS中的Ca、Mg、Al、Si均发生了反应。反应之后YbYSZ产物的物相主要是四方相的氧化锆。同时图4中还能观察到有少量单斜相(m相)的存在, 这主要是因为如下反应造成了Yb和Y的流失, 从而使部分的四方相氧化锆转变成了单斜相:

$\begin{matrix} 2 Y b_{2} O_{3} + 3 Si O_{2} \to Y b_{4} (Si O_{4})_{3} \end{matrix}$

$\begin{matrix} 2 Y_{2} O_{3} + 3 Si O_{2} \to Y_{4} (Si O_{4})_{3} \end{matrix}$

2.3 腐蚀过程中的元素扩散和物相变化

去除表层未反应的CMAS和部分腐蚀产物(约从表面往下1 mm)之后, 对剩余陶瓷基体进行分析可得到受腐蚀影响的陶瓷层的元素含量的变化和物相变化。图5显示不同腐蚀时间条件下样品中元素含量的变化和相同腐蚀时间下不同Yb掺杂量的YbYSZ晶体中各元素含量的变化。从图5a各元素相对含量随腐蚀时间变化曲线可以看出, 随着腐蚀时间的增加, Y、Yb均有不同程度的流失, 而Yb的流失量相对较高, 造成Zr的相对含量反而有所增加, 腐蚀5 h后Yb的量几乎到零。Y也存在一定的流失, 但总体上Y的相对含量还是能够维持在10%左右。图5b为各元素相对含量与Yb掺杂量之间的关系。从图中可以看出: CMAS腐蚀反应之后每组不同Yb掺杂的样品中Yb的量均小于腐蚀前掺杂的量, 即Yb在腐蚀的过程中发生流失。整个过程中Y的含量并未出现明显的减少, 反而有增加的趋势, 这主要是因为Zr的量在减少, 使得Zr+Y+Yb总量减少的同时Y的相对含量增加。如上分析可知: Yb的掺杂起到了以Yb的流失来稳定氧化锆晶格中Y的作用。具体表现为Y/Zr的量在腐蚀的过程中逐渐增加。

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图5 (a)3%Yb掺杂YSZ分别腐蚀1 h、2 h、5 h后各元素含量变化; (b)不同Yb掺杂量的YSZ腐蚀5 h后各元素含量的变化

Fig.5 Elements contents of (a) YSZ doped with 3%Yb after corrosion for different time (1 h, 2 h, 5 h); (b) various YbYSZ after 5 hours' corrosion

如图6所示, 经过1250℃2 h的CMAS腐蚀之后, 未掺杂第二种稀土元素Yb的YSZ有明显的m相存在, 随着Yb元素掺入量的增加, m相的峰越来越不明显, 说明Yb的掺入能进一步稳定四方相的结构。而如图7所示: 随着腐蚀时间的增加, m相的衍射峰变得更加尖锐, 衍射峰强度增加(28.2°处, ( $\begin{matrix} \overset{̅}{1} 11 \end{matrix}$ )晶面), 表明m相的结晶性随着腐蚀时间的增加越来越好。为了研究m相的相对含量变化过程, 本文采用X射线衍射峰相对强度值估算法来估算, 计算公式如下:

$\begin{matrix} m (%) = \frac{I_{m} (\overset{̅}{1} 11) + I_{m} (111)}{I_{t} (101) + I_{m} (\overset{̅}{1} 11) + I_{m} (111)} \times 100 % \end{matrix}$

其中, $\begin{matrix} I_{m} (\overset{̅}{1} 11) \end{matrix}$ 、 $\begin{matrix} I_{m} (111) \end{matrix}$ 和 $\begin{matrix} I_{t} (101) \end{matrix}$ 分别代表单斜相氧化锆 $\begin{matrix} (\overset{̅}{1} 11) \end{matrix}$ 和(111)衍射峰的相对强度和四方相氧化锆(101)衍射峰的相对强度值。通过计算可以得到m相含量与稀土掺杂元素含量及腐蚀时间的关系, 如图8所示。

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图6 不同掺杂浓度YbYSZ在1250℃腐蚀2 h后的XRD图

Fig.6 XRD patterns ofvarious doped YbYSZ corroded for 2 hours at 1250℃

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图7 3%YbYSZ在1250℃腐蚀不同时间的XRD图

Fig.7 XRD patterns of 3%YbYSZ corroded for different time at 1250℃

图8所示为当掺杂量分别为0、1%、3%、5%、7%, 腐蚀温度为1250℃时不同腐蚀时间(1 h、2 h、5 h)后的m相含量的变化。由图可知随着腐蚀时间的增加m相的含量持续增加。而随着掺杂浓度的增加, m相含量呈现先降低后升高的趋势。当Yb的掺杂量为5%时m相的含量达到最低。即Yb的最优掺杂量为5%。此外, 根据图5b中所示Y/Zr比随Yb的掺杂量持续升高, 由于当Yb的含量超过某一值之后晶体的对称性下降^[18], $\begin{matrix} \overset{′}{t} \end{matrix}$ -ZrO₂的含量减少从而导致了m相的相对含量增加。

Yb含量的减少主要是由于Yb与晶格中氧空位的缔结能比Y低^[19], 两者在晶格中所处环境相同, 因此, Yb比Y更容易与CMAS中的SiO₂反应。从图5a可以看出, Y/Zr随着腐蚀的进行呈下降趋势, 因此Y比Zr更容易与CMAS反应, 这是由于Zr与O之间的结合能相比Y以及Yb更高。所以Y、Yb、Zr三元素与CMAS的反应难易程度依次为Zr>Y>Yb。在腐蚀反应过程初期, Yb/Y与Zr/O之间形成的键合增加了体系中Yb、Y与SiO₂反应的难度, 因此Yb/Y双掺杂的ZrO₂比单纯的Y掺杂的ZrO₂更加稳定, m相更少(图6), 随着腐蚀的进行, Yb流失, 与SiO₂反应, 在这个过程中抑制了Y的流失, 从而起到了稳定 $\begin{matrix} \overset{′}{t} \end{matrix}$ 相的作用。

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图8 m相氧化锆相对含量与稀土掺杂元素含量及时间的关系图

Fig.8 Relative contents of m-zirconia vs. Yb-doping contents and corrosive time

3 结论

1. CMAS腐蚀YbYSZ的过程是一个渗透-分解-溶解-再沉淀的过程。这个过程首先是CMAS对YbYSZ的物理渗透, 接着大的YbYSZ晶体被CMAS分解成若干小的晶体, 小晶体被CMAS包裹溶解, 冷却之后再结晶会有m相的氧化锆小球析出。

2. 采用缺陷缔结能比Y小的Yb掺杂YSZ, 在与CMAS腐蚀反应过程中, 通过掺杂元素Yb的损耗可减少稳定剂Y的流失, 从而抑制晶体中m相的产生, 达到维持 $\begin{matrix} \overset{′}{t} \end{matrix}$ -ZrO₂相稳定性的目的。Yb的掺杂量为5%时, YbYSZ经1250℃不同时间的CMAS腐蚀后, m相的含量增加最少。

The authors have declared that no competing interests exist.

参考文献

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被引期刊影响因子

[1]	Borom M. P., C. A. Johnson, L. A. Peluso, Role of environment deposits and operating surface temperature in spallation of air plasma sprayed thermal barrier coatings, Surface and Coatings Technology, 86, 116(1996) DOI URL [本文引用: 2] 摘要 Spallation of air plasma sprayed (APS) thermal barrier coatings (TBCs) was investigated on power generation combustors, military turboshaft engines, and commercial turboprop engines. In each case, irrespective of operating conditions or geographic location, spallation was linked to the presence and infiltration of high temperature molten phases of similar composition. Electron microprobe analysis found that, from all the possible oxides available in the external environment, only CaO, MgO, Al 2 O 3 and SiO 2 (CMAS) are incorporated in the molten phase that infiltrates the TBC microstructure. Fe and Ni oxides from metallic components and zirconia and yttria from the TBC were also found in varying amounts in the molten phase. The melting and recrystallization behavior of CMAS deposits was carefully defined by differential thermal analysis.
[2]	Mercer C., A delamination mechanism for thermal barrier coatings subject to calcium-magnesium-alumino-silicate (CMAS) infiltration. Acta Materialia, 53(4), 1029(2005) DOI Magsci 摘要 <h2 class="secHeading" id="section_abstract">Abstract</h2><p id="">When a turbine airfoil attains temperatures that allow calcium–magnesium–alumino-silicate (CMAS) infiltration into the thermal barrier coating (TBC), a new mechanism of in-service spalling may be activated. The mechanism is associated with cold shock of the infiltrated layer during shut down. It has been identified by inspecting an airfoil removed from service. The identification has been based on observations of sub-surface delaminations within infiltrated regions of the TBC. Three important aspects of the mechanism are as follows. (a) The sub-surface delaminations always initiate at surface-connected vertical separations. (b) They are fully-infiltrated with CMAS. (c) They are strictly mode I. A thermal shock analysis has been invoked to identify a critical infiltration thickness, above which delaminations are possible. The analysis also defines a characteristic depth beneath the surface at which the delaminations are most likely. The observations made on the airfoils are consistent with these two dimensions. A second mechanism has been explored as the potential cause of large spalled regions also observed on the airfoils. But it has not been possible to verify the mechanism using the current observations.</p>
[3]	Krämer S., Mechanisms of cracking and delamination within thick thermal barrier systems in aero-engines subject to calcium-magnesium-alumino-silicate (CMAS) penetration, Materials Science and Engineering: A, 490(1), 26(2008) DOI URL [本文引用: 1] 摘要 An analysis has been conducted that characterizes the susceptibility to delamination of thermal barrier coated (TBC) hot-section aero-turbine components when penetrated by calcium-magnesium-alumino-silicate (CMAS). The assessment has been conducted on stationary components (especially shrouds) with relatively thick TBCs after removal from aero-engines. In those segments that experience the highest temperatures, the CMAS melts, penetrates to a depth about half the coating thickness, and infiltrates all open areas. Therein the TBC develops channel cracks and sub-surface delaminations, as well as spalls. Estimates of the residual stress gradients made on cross-sections (by using the Raman peak shift) indicate tension at the surface, becoming compressive below. By invoking mechanics relevant to the thermo-elastic stresses upon cooling, as well as the propagation of channel cracks and delaminations, a scenario has been presented that rationalizes these experimental findings. Self-consistent estimates of the stress and temperature gradients are presented as well as predictions of channel cracking and delamination upon cooling.
[4]	Krämer S., Thermochemical interaction of thermal barrier coatings with molten CaO-MgO-Al₂O₃-SiO₂ (CMAS) deposits, Journal of the American Ceramic Society, 89(10), 167(2006) DOI URL [本文引用: 2] 摘要 Thermal barrier coatings (TBCs) are increasingly susceptible to degradation by molten calcium-magnesium alumino silicate (CMAS) deposits in advanced engines that operate at higher temperatures and in environments laden with siliceous debris. This paper investigates the thermochemical aspects of the degradation phenomena using a model CMAS composition and ZrO 2 -7.6%YO 1.5 (7YSZ) grown by vapor deposition on alumina substrates. The changes in microstructure and chemistry are characterized after isothermal treatments of 4 h at 1200掳-1400掳C. It is found that CMAS rapidly penetrates the open structure of the coating as soon as melting occurs, whereupon the original 7YSZ dissolves in the CMAS and reprecipitates with a different morphology and composition that depends on the local melt chemistry. The attack is minimal in the bulk of the coating but severe near the surface and the interface with the substrate, which is also partially dissolved by the melt. The phase evolution is discussed in terms of available thermodynamic information.
[5]	Li L., N. Hitchman, J. Knapp, Failure of Thermal Barrier Coatings Subjected to CMAS Attack, Journal of Thermal Spray Technology, 19(1-2), 148(2009) URL [本文引用: 1] 摘要 This edition of the Progress in Ceramic Technology series compiles articles published on thermal barrier coatings (TBCs) by The American Ceramic Society (ACerS). It collects in one resource the current research papers on materials-related aspects of thermal barrier coatings and associated technologies. Logically organized and carefully selected, the papers in this edition divide into six categories: Applications Material Improvements and Novel Compositions Developments in Processing Mechanical Properties Thermal Properties Citations follow each title in the table of contents, making this a key resource for professionals and academia.
[6]	Guo X., Crystallization and microstructure of CaO-MgO-Al₂O₃-SiO₂ glass-ceramics containing complex nucleation agents, Journal of Non-Crystalline Solids, 405, 63(2014) DOI URL [本文引用: 1] 摘要 The CaO–MgO–Al 2 O 3 –SiO 2 (CMAS) glass–ceramics containing binary complex nucleation agents were prepared by body crystallization process, and the effects of complex nucleation agents on the crystallization and microstructure of CMAS glass–ceramics were investigated by differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The complex nucleation agents consist of constant fluorine (8.002wt.% CaF 2 ) and different oxides (3.002wt.% TiO 2 , ZrO 2 , or P 2 O 5 ). Compared with the CMAS glass with only CaF 2 , the respective addition of oxides promotes the crystallization of CMAS glass, especially TiO 2 or P 2 O 5 . The addition of TiO 2 or ZrO 2 has no obvious effect on the compositions of main crystalline phases, while P 2 O 5 results in the precipitation of pyroxene phase instead of diopside phase, with the existence of more small crystals. The CMAS glass–ceramic containing CaF 2 02+02TiO 2 or CaF 2 02+02P 2 O 5 achieves full body crystallization with high crystallization ratio, and has high hardness, good chemical resistance and water absorption.
[7]	Wiesner, V. L. and N.P. Bansal, Crystallization kinetics of calcium-magnesium aluminosilicate (CMAS) glass, Surface and Coatings Technology, 259, 608(2014) DOI URL Magsci [本文引用: 1] 摘要 The crystallization kinetics of a calcium-magnesium aluminosilicate (CMAS) glass with composition relevant for aerospace applications, like air-breathing engines, were evaluated using differential thermal analysis (DTA) in powder and bulk forms. Activation energy and frequency factor values for crystallization of the glass were evaluated. X-ray diffraction (XRD) was used to investigate the onset of crystallization and the phases that developed after heat treating bulk glass at temperatures ranging from 690 degrees C to 960 degrees C for various times. Samples annealed at temperatures below 900 degrees C remained amorphous, while specimens heat treated at and above 900 degrees C exhibited crystallinity originating at the surface. The crystalline phases were identified as wollastonite (CaSiO3) and aluminum diopside (Ca(Mg,Al)(Si,Al)(2)O-6). Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were employed to examine the microstructure and chemical compositions of crystalline phases formed after heat treatment Published by Elsevier B.V.
[8]	Grant K. M., CMAS degradation of environmental barrier coatings, Surface and Coatings Technology, 202(4-7), 653(2007) DOI URL [本文引用: 1] 摘要 Environmental barrier coatings (EBCs) based on Ba 1026102 x Sr x Al 2 Si 2 O 8 (BSAS) have demonstrated potential for the protection of Si-based ceramic matrix composites (CMCs) against moisture-induced degradation in gas turbines. However, EBCs are susceptible to attack by calcium–magnesium alumino-silicate (CMAS) melts produced when siliceous debris is ingested with the intake air and deposits on component surfaces. The mechanism involves the dissolution of BSAS into CMAS and re-precipitation as a modified Celsian phase incorporating Ca, as well as secondary crystalline silicates that may degrade the durability and efficiency of the EBC. The process is aggravated by grain boundary penetration of CMAS into the polycrystalline BSAS. The mechanisms and their potential implications for durability are discussed.
[9]	Peng H., Degradation of EB-PVD thermal barrier coatings caused by CMAS deposits, Progress in Natural Science: Materials International, 22(5), 461(2012) DOI URL 摘要 In aero-turbine engines,thermal barrier coatings(TBCs) must be capable to withstand harsh environments,such as high-temperature oxidation and hot-corrosion.Recently,a new failure mode of TBCs caused by calcium-magnesium-alumina-silicate(CMAS) glass has attracted increasing attention.In this paper,yttria stabilized zirconia(YSZ) TBCs produced by electron beam physical vapor deposition(EB-PVD) were exposed to CMAS deposits at 1250℃.The microstructure evolution and failure mechanism of the coatings were investigated.It has been shown that CMAS glass penetrated into the YSZ ceramic layer along the inter-columnar gaps and interacted with YSZ.As a result,an interaction zone of about 20μm thickness,which was the mixture of CMAS and YSZ with equiaxial structure,was formed in the YSZ surface layer after 4h heat-treatment at 1250℃.Meanwhile,yttria in YSZ layer as a stabilizer was dissolved in CMAS glass and caused accelerated monoclinic phase transformation.After 8h heat-treatment,degradation of YSZ TBC occurred by delamination cracking of YSZ layer,which is quite different from the traditional failure caused by interfacial cracking at the YSZ/metallic bond coat.Physical models have been built to describe the failure mechanism of EB-PVD TBCs attacked by CMAS deposits.
[10]	Drexler J. M., Air-plasma-sprayed thermal barrier coatings that are resistant to high-temperature attack by glassy deposits, Acta Materialia, 58(20), 6835(2010) DOI Magsci 摘要 <h2 class="secHeading" id="section_abstract">Abstract</h2><p id="sp005">Thermal barrier coatings (TBCs) used in gas-turbine engines afford higher operating temperatures, resulting in enhanced efficiencies and performance. However, at these high operating temperatures, environmentally ingested airborne sand/ash particles melt on the hot TBC surfaces and form calcium–magnesium–aluminosilicate (CMAS) glass deposits. The molten CMAS glass penetrates the TBCs, leading to loss of strain tolerance and TBC failure. Here we demonstrate the use of the commercial manufacturing method of air-plasma-spray (APS) to fabricate CMAS-resistant yttria-stabilized zirconia (YSZ)-based TBCs containing Al and Ti in solid solution. Results from thermal stability studies of these new TBCs and CMAS/TBC interaction experiments are presented, together with a discussion of the CMAS mitigation mechanisms. The ubiquity of airborne sand/ash particles and the ever-increasing demand for higher operating temperatures in future high efficiency/performance gas-turbine engines will necessitate CMAS resistance in all hot-section components of those engines. In this context the versatility, ease of processing, and low cost offered by the APS method has broad implications for the design and fabrication of next-generation CMAS-resistant TBCs for future engines.</p>
[11]	HE Qing, LIU Xinji, LIU Bo, Influence of CMAS infiltration on microstructure of plasma-sprayed YSZ thermal barrier coating, China Surface Engineering, 25(4), 42(2012) [本文引用: 2] (何箐, 刘新基, 柳波, CMAS 渗入对等离子喷涂 YSZ 热障涂层形貌的影响, 中国表面工程, 25(4), 42(2012)) URL [本文引用: 2] 摘要研究了等离子喷涂不同结构YSZ涂层在CMAS渗入作用下的形貌演变规律。对带有模拟CMAS沉积物的YSZ涂层进行高温热处理试验,并在低CMAS输送量条件下对YSZ涂层进行冲刷试验,试验后涂层均出现了严重的层间剥离失效。通过试验前后涂层的截面形貌及Raman光谱分析,结果表明:涂层的显微形貌变化主要表现在高温下熔融态CMAS沿涂层表面微裂纹和孔隙渗入内部,引起YSZ陶瓷层孔隙收缩、表层致密化,同时在涂层表面粘附的CMAS耦合作用下,YSZ涂层表层中产生大量横向微裂纹和明显分层;另外,YSZ涂层表层在CMAS中溶解并导致YSZ加速相变失稳也是影响涂层形貌变化和过快失效的因素之一。CMAS沉积层厚度增加时,同等条件下CMAS对涂层失效的影响会加剧。
[12]	Kim J., Deposition of volcanic materials in the hot sections of two gas turbine engines, Journal of Engineering for Gas Turbines and Power, 115(3), 641(1993) [本文引用: 1]
[13]	Stott F., R. Taylor, D. de Wet, The effects of molten silicate deposits on the stability of thermal barrier coatings for turbine applications at very high temperatures, Proceedings of Advanced Materials, 3(A93-53376 23-23), 92(1992) [本文引用: 2]
[14]	Chen X., On the propagation and coalescence of delamination cracks in compressed coatings: with application to thermal barrier systems, Acta Materialia, 51(7), 2017(2003) DOI Magsci [本文引用: 1] 摘要 <h2 class="secHeading" id="section_abstract">Abstract</h2><p id="">Coatings subject to residual compression eventually fail by buckle-driven delamination. The phenomenon is most vivid in thermal barrier coatings (TBCs) used in gas turbines. The failure evolution commences with the formation of a large number of small cracks at geometric imperfections near the interface. These cracks spread upon thermal exposure, particularly upon thermal cycling, because of the formation of a thermally grown oxide (TGO) beneath the TBC, which introduces normal and shear stress near the interface. Experimental observations indicate that some of these cracks coalesce to form large-scale delaminations susceptible to buckling. The mechanics governing crack coalescence and the consequent failure are addressed in the present analysis.</p><p id="">A model is introduced that simulates stresses induced in the TBC by spatial variations in TGO growth. Energy release rates for cracks evolving in this stress field are determined. Two related scenarios are considered, which differ in the way the TGO shape evolves. In both, contact between the crack faces and the consequent wedging action is responsible for ultimate coalescence. The wedging force induces a mode I stress intensity that becomes infinite as the cracks coalesce. The consequence is that, for some TGO shapes, the energy release rate is always non-zero, with a minimum at a characteristic crack length. This minimum establishes a criterion for crack coalescence and failure.</p><p id="">Based on these insights, finite element simulations have been used to predict cyclic crack growth rates in a TBC system that correlate well with experimental observations.</p>
[15]	Majewski M. S., Stress measurements via photoluminescence piezospectroscopy on engine run thermal barrier coatings, Surface and Coatings Technology, 206(11-12), 2751(2012) DOI URL [本文引用: 1] 摘要 Optical measurements of stress in a thermally grown oxide (TGO) layer that has formed between a metallic bond coat and thermal barrier coating (TBC) have been previously demonstrated and shown useful in understanding aspects of TBC failure. These measurements have promise for nondestructive evaluation of coated turbine components. However, engine-run turbine parts collect significant surface contamination consisting of calcium-magnesium-alumina-silicate (CMAS). The deposited CMAS both blocks optical measurement of stress in the TGO and produces false stress signals. A recently developed laser ablation technique has enabled contaminant removal with minimal TBC damage. The locally cleaned engine run parts can then have their TGO stresses optically determined. In the present paper, it is shown that sporadic signals from contamination are still present due to CMAS infiltration into the TBC and due to local regions that cannot be cleaned without damaging the TBC. Methods for separating the contamination signal from the TBC signals are presented as needed for successful use of optical stress measurement on engine run turbine components. The stress measurements censored for false signals are compared to other destructive approaches and the methods are shown to provide robust nondestructive evaluation of the coating stress.
[16]	Habibi M. H., L. Wang, S. M. Guo, Evolution of hot corrosion resistance of YSZ, Gd₂Zr₂O₇, and Gd₂Zr₂O₇+YSZ composite thermal barrier coatings in Na₂SO₄+V₂O₅ at 1050℃, Journal of the European Ceramic Society, 32(8), 1635(2012) DOI Magsci [本文引用: 1] 摘要 This paper compares the hot corrosion performance of yttria stabilized zirconia (YSZ), Gd2Zr2O7, and YSZ + Gd2Zr2O7 composite coatings in the presence of molten mixture of Na2SO4 + V2O5 at 1050 degrees C. These YSZ and rare earth zirconate coatings were prepared by atmospheric plasma spray (APS). Chemical interaction is found to be the major corrosive mechanism for the deterioration of these coatings. Characterizations using X-ray diffraction (XRD) and scanning electron microscope (SEM) indicate that in the case of YSZ, the reaction between NaVO3 and Y2O3 produces YVO4 and leads to the transformation of tetragonal ZrO2 to monoclinic ZrO2. For the Gd2Zr2O7 + YSZ composite coating, by the formation of GdVO4, the amount of YVO4 formed on the YSZ + Gd2Zr2O7 composite coating is significantly reduced. Molten salt also reacts with Gd2Zr2O7 to form GdVO4. Under a temperature of 1050 degrees C, Gd2Zr2O7 based coatings are more stable, both thermally and chemically, than YSZ, and exhibit a better hot corrosion resistance. (C) 2012 Elsevier Ltd. All rights reserved.
[17]	Zacate M. O., Defect cluster formation in M₂O₃-doped cubic ZrO₂, Solid State Ionics, 128(1), 243(2000) DOI URL [本文引用: 2] 摘要 Atomistic simulation calculations based on energy minimization techniques have been used to study the energetics associated with M 2 O 3 solution in ZrO 2 . Results predict that the binding energy of an oxygen vacancy to one or two substitutional cations is a strong function of dopant cation radius. Oxygen vacancies occupy sites that are first neighbour with respect to small dopants whereas oxygen vacancies are located in second neighbour sites with respect to large dopants. The crossover occurs at approximately Sc 3+ , which also exhibits the smallest binding energy. This behaviour is a consequence of long-range relaxation of the oxygen sublattice. The model is validated by comparing predicted lattice parameters of M 2 O 3 :ZrO 2 solid solutions with experimental data.
[18]	LIU Huaifei, Preparation and properties of zirconia based thermal barrier coatings co-doped with two rare earth oxides, PhD dissertation, Central South University (2011) [本文引用: 1] (刘怀菲, 二元稀土氧化物复合稳定氧化锆热障涂层材料的制备及性能研究, 博士学位论文, 中南大学(2011)) DOI URL [本文引用: 1] 摘要传统6～8wt.%Y203-Zr02 (YSZ)热障涂层的相变和烧结(1200℃),限制了其在更高温度的使用。因此,为满足高推重比航空发动机对热障涂层材料的性能要求,研制在1200℃以上具有相稳定性、抗烧结和低热导率的新型热障涂层材料具有极其重要的意义。采用化学共沉淀-煅烧法制备了(La2O3, Y2O3)-ZrO2 (LaYSZ)、(Yb2O3, Y2O3)-ZrO2 (YbYSZ)、(Sc2O3, Y2O3)-ZrO2 (ScYSZ)三种体系稀土氧化物复合稳定氧化锆陶瓷材料,并对其高温相稳定性和热物理性能进行了研究,分析和讨论这三种体系作为高温热障涂层材料应用的可能性；揭示二元稀土氧化物稳定氧化锆的晶体学特征、稳定剂含量对相稳定性的影响规律以及多元体系的相变机理；采用等离子喷涂(APS)技术制备了ScYSZ体系热障涂层,分析了涂层的相稳定性、相变动力学特征以及掺杂原子特征(化合价、原子量、离子半径)对热导率的影响机制,并对涂层在高温氧化、腐蚀、热冲击环境下的组织结构演变和失效机理进行了研究,为新型热障涂层材料的开发和应用提供理论依据。较系统地研究了LaYSZ, YbYSZ, ScYSZ体系陶瓷粉末的相稳定性和热物理性能。与YSZ陶瓷材料相比,1.OLaYSZ在1400℃具有较好的相稳定性,且La2O3的加入能有效抑制陶瓷坯体烧结。3.5YbYSZ、(5.3～7.1) ScYSZ在1400℃、1500℃均具有较好的相稳定性、抗烧结性以及较低的热导率,其中ScYSZ体系中非平衡四方相(t')的稳定区域较大,且Sc2O3的加入对抑制烧结和降低热导率效果最为显著。因此,三种体系中,ScYSZ体系为TBCs材料最佳选择。三种多元体系陶瓷粉末的晶体学特征表明稳定剂含量与热处理温度是决定t'相稳定性的重要因素。建立了多元体系四方度(c/(?)a)与稳定剂含量的定量关系,三种体系的四方度均随稳定剂含量的增加而线性减小。高稳定剂区域易于t'相和立方相(c)稳定,而低稳定剂区域易于平衡四方相(t)和单斜相(m)形成。ScYSZ体系粉末的相变动力学特征表明t'相向t相和c相的转变是与温度和时间密切相关的扩散型相变,其相变速率取决于掺杂原子的扩散速率。高温热处理过程中掺杂原子扩散引起的稳定剂分布不均是导致t'相稳定性降低的直接原因。采用Avrami方程建立了ScYSZ陶瓷粉末和涂层相变量与时间的关系。热处理温度越高,涂层的相变孕育期愈小；对于同种成分材料,在相同的热处理条件下,涂层的相变孕育期明显大于粉末的相变孕育期,表明涂层微观组织结构、应力、缺陷、晶格畸变等对相变有着重要的影响。6.4Sc0.5YSZ和7.1Sc0.53YSZ涂层分别在1400℃热处理550h和1500℃热处理300h均未发生相变。6.4Sc0.5YSZ和7.1Sc0.53YSZ具有优良的高温相稳定性。根据声子导热机制和缺陷化学原理,分析了掺杂原子特征及掺杂量对热导率的影响机制。对于低价阳离子掺杂稳定氧化锆体系,氧空位和置换原子缺陷均可加强声子散射,降低声子平均自由程,从而降低热导率。ScYSZ体系中Sc与Zr较大的原子量和离子半径差异对降低热导率贡献较大；增加ScYSZ体系中Sc2O3的含量使氧空位数量增多也可有效降低热导率。涂层中相组成、晶界、裂纹和孔隙对热导率有着重要影响。与8YSZ涂层相比,ScYSZ涂层的高相稳定性和抗烧结性是其具有低热导率的重要原因。研究了ScYSZ(TC)/NiCoCrAlTaY (BC)双层结构热障涂层在高温氧化、腐蚀和冷热循环载荷条件下的失效机理。高温氧化试验结果表明BC层的氧化导致TC/BC界面形成热生长氧化物(TGO)层,TGO层的生长应力以及TGO与TC, BC热膨胀系数不匹配产生的热应力是导致涂层氧化失效的主要原因。TGO层的生长应力主要是由大体积氧化物(Cr,Al)2O3+(Co,Ni)(Cr,Al)2O4+NiO(CSN)的形成和生长而产生的；当TC/BC界面有连续TGO层生成时,TGO与TC、BC的热失配而产生的热应力开始作用。采用ANSYS软件对TC/TGO/BC涂层及界面的热应力分布进行了模拟,结果表明热失配导致TGO层产生较大的径向压应力,从而对涂层造成压缩性破坏。TC/TGO界面压应力值最大且白试样中心向边缘逐渐减小。随着氧化时间的增加,涂层最终以TC层中心鼓起和剥离的方式失效,剥离面为TC/TGO界面。涂层高温腐蚀和热震试验结果表明,与传统的YSZ涂层相比较,ScYSZ涂层具有更好的抗V、S腐蚀能力及抗热震性能,但在腐蚀剂作用下,粘结层的氧化速率被大大提高；在长期冷热循环载荷条件下,TC/BC界面有较大厚度的TGO层生成,粘结层的氧化是导致涂层热震失效的主要原因。因此,较理想的涂层是在满足抗热震的条件下,应尽量提高涂层的致密度以及厚度。 ScYSZ体系热障涂层在1400℃和1500℃具有稳定相组织结构,较YSZ具有更优异的抗烧结性、抗热震性、耐熔盐腐蚀性能以及更低的热导率,在作为超高温(≥1400℃)热防护涂层方面具有极大的应用前景。
[19]	Mohan P., et al, Degradation of yttria stablized zirconia thermal barrier coatings by molten CMAS(CaO-MgO-Al₂O₃-SiO₂) deposits in Materials Science Forum. Trans. Tech. Publ., (2008) DOI URL [本文引用: 1] 摘要 In advanced gas turbine engines that operate in a dust-laden environment causing ingestion of siliceous debris into engines, thermal barrier coatings (TBCs) are highly susceptible to degradation by molten CMAS (calcium-magnesium alumino silicate) deposits. In this study, the degradation mechanisms other than the commonly reported thermomechanical damage are investigated with an emphasis on the thermochemical aspects of molten CMAS induced degradation of TBCs. Free-standing yttria stabilized zirconia (8YSZ) TBC specimens in contact with a model CMAS composition were subjected to isothermal heat treatment in air at temperatures ranging from 1200°C to 1350°C. Phase transformations and microstructural development were examined by using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Starting at 1250°C, the molten CMAS readily infiltrated and dissolved the YSZ coating followed by reprecipitation of zirconia with a different morphology and composition that depends on the local melt chemistry. Significant amount of Y2O3 depleted monoclinic ZrO2 phase evolved from CMAS melt that dissolved 02-ZrO2 was evident. Thus the mechanism of dissolution and reprecipitation due to molten CMAS damage resulted in destabilization of the YSZ with disruptive phase transformation (t’ f + m).

C. A. Johnson, L. A. Peluso, Role of environment deposits and operating surface temperature in spallation of air plasma sprayed thermal barrier coatings,

1996

... 用于涡轮发动机热端部件表面的热障涂层(TBCs)在服役过程中直接与高温燃气接触, 因此空气中的沙粒、尘土等在高温的作用下会沉积在热障涂层表面, 从而影响涂层的性能^[1-3].早在20世纪90年代, Kim^[12]、Stott^[1]、Borom^[13]等就在沙特阿拉伯、中东和波斯湾等沙漠地区的飞机发动机叶片上发现了玻璃状沉积物, 揭示了这种腐蚀失效现象的存在.据研究, 这些随助燃空气进入发动机的物质的主要成分为CaO-MgO-Al₂O₃-SiO₂(CMAS)^[4].随着涡轮发动机工作温度的提高(>1200℃), CMAS对热障涂层的腐蚀问题愈发严重, 大幅降低了涂层的服役寿命^[5], 主要因为CMAS在960℃时开始软化并在1240℃左右熔化为高温熔盐^{[6, 7]}, 这种玻璃态的高温熔盐会沿着涂层中的孔隙和裂纹渗入到涂层内部.Krama等详细阐述了CMAS与电子束物理气相沉积(EB-PVD)制备的热障涂层的热化学作用以及柱状晶陶瓷的形貌与结构演变^[4].对于目前商用的氧化钇稳定的氧化锆(YSZ)涂层, 渗入到涂层中的CMAS会通过热化学和热机械作用使涂层失效^[8-11].其中, 热机械破坏源于渗透进入涂层内部的CMAS与涂层之间的热膨胀系数不匹配从而产生热应力导致涂层产生横向微裂纹; 热化学作用体现为腐蚀过程中熔盐与涂层材料发生反应, 破坏了氧化锆的相稳定性, 导致四方相氧化锆(

\begin{matrix} \overset{′}{t} \end{matrix}

-ZrO₂)发生相变, 相变过程中产生的体积收缩使涂层开裂.Chen、Evans等^[14]进一步提出了YSZ层在CMAS作用下的分层破坏机制.包括Mark、Habibi、何箐^{[11, 15, 16]}在内的国内外专家通过研究认为在高温下CMAS中的SiO₂会与YSZ中的Y发生化学反应, 反应方程式为: ...

... [1]、Borom^[13]等就在沙特阿拉伯、中东和波斯湾等沙漠地区的飞机发动机叶片上发现了玻璃状沉积物, 揭示了这种腐蚀失效现象的存在.据研究, 这些随助燃空气进入发动机的物质的主要成分为CaO-MgO-Al₂O₃-SiO₂(CMAS)^[4].随着涡轮发动机工作温度的提高(>1200℃), CMAS对热障涂层的腐蚀问题愈发严重, 大幅降低了涂层的服役寿命^[5], 主要因为CMAS在960℃时开始软化并在1240℃左右熔化为高温熔盐^{[6, 7]}, 这种玻璃态的高温熔盐会沿着涂层中的孔隙和裂纹渗入到涂层内部.Krama等详细阐述了CMAS与电子束物理气相沉积(EB-PVD)制备的热障涂层的热化学作用以及柱状晶陶瓷的形貌与结构演变^[4].对于目前商用的氧化钇稳定的氧化锆(YSZ)涂层, 渗入到涂层中的CMAS会通过热化学和热机械作用使涂层失效^[8-11].其中, 热机械破坏源于渗透进入涂层内部的CMAS与涂层之间的热膨胀系数不匹配从而产生热应力导致涂层产生横向微裂纹; 热化学作用体现为腐蚀过程中熔盐与涂层材料发生反应, 破坏了氧化锆的相稳定性, 导致四方相氧化锆(

\begin{matrix} \overset{′}{t} \end{matrix}

A delamination mechanism for thermal barrier coatings subject to calcium-magnesium-alumino-silicate (CMAS) infiltration.

2005

Mechanisms of cracking and delamination within thick thermal barrier systems in aero-engines subject to calcium-magnesium-alumino-silicate (CMAS) penetration,

2008

\begin{matrix} \overset{′}{t} \end{matrix}

Thermochemical interaction of thermal barrier coatings with molten CaO-MgO-Al₂O₃-SiO₂ (CMAS) deposits,

2006

\begin{matrix} \overset{′}{t} \end{matrix}

... [4].对于目前商用的氧化钇稳定的氧化锆(YSZ)涂层, 渗入到涂层中的CMAS会通过热化学和热机械作用使涂层失效^[8-11].其中, 热机械破坏源于渗透进入涂层内部的CMAS与涂层之间的热膨胀系数不匹配从而产生热应力导致涂层产生横向微裂纹; 热化学作用体现为腐蚀过程中熔盐与涂层材料发生反应, 破坏了氧化锆的相稳定性, 导致四方相氧化锆(

\begin{matrix} \overset{′}{t} \end{matrix}

N. Hitchman, J. Knapp, Failure of Thermal Barrier Coatings Subjected to CMAS Attack,

2009

\begin{matrix} \overset{′}{t} \end{matrix}

Crystallization and microstructure of CaO-MgO-Al₂O₃-SiO₂ glass-ceramics containing complex nucleation agents, Journal of

2014

\begin{matrix} \overset{′}{t} \end{matrix}

N.P. Bansal, Crystallization kinetics of calcium-magnesium aluminosilicate (CMAS) glass,

2014

\begin{matrix} \overset{′}{t} \end{matrix}

CMAS degradation of environmental barrier coatings,

2007

\begin{matrix} \overset{′}{t} \end{matrix}

Degradation of EB-PVD thermal barrier coatings caused by CMAS deposits,

2012

Air-plasma-sprayed thermal barrier coatings that are resistant to high-temperature attack by glassy deposits,

2010

CMAS 渗入对等离子喷涂 YSZ 热障涂层形貌的影响,

2012

\begin{matrix} \overset{′}{t} \end{matrix}

... [11, 15, 16]在内的国内外专家通过研究认为在高温下CMAS中的SiO₂会与YSZ中的Y发生化学反应, 反应方程式为: ...

CMAS 渗入对等离子喷涂 YSZ 热障涂层形貌的影响,

2012

\begin{matrix} \overset{′}{t} \end{matrix}

... [11, 15, 16]在内的国内外专家通过研究认为在高温下CMAS中的SiO₂会与YSZ中的Y发生化学反应, 反应方程式为: ...

Deposition of volcanic materials in the hot sections of two gas turbine engines,

1993

\begin{matrix} \overset{′}{t} \end{matrix}

R. Taylor, D. de Wet, The effects of molten silicate deposits on the stability of thermal barrier coatings for turbine applications at very high temperatures,

1992

\begin{matrix} \overset{′}{t} \end{matrix}

... 本文中采用的CMAS组分构成主要参考Borom^[13]等人的研究结果, 该结果显示在中东地区沙漠环境中考核后涡轮叶片上残余腐蚀剂CMAS的成分为33CaO-9MgO-13AlO_1.5-45SiO₂(C_0.33M_0.09A_0.13S_0.45), 由于我国在西部地区, 尤其是新疆也存在相似的沙漠环境, 所以CMAS组成参考上述配比.按此摩尔比称取相应质量的CaCO₃、MgO、SiO₂和Al₂O₃, 配料完成后放入研钵充分研磨备用. ...

On the propagation and coalescence of delamination cracks in compressed coatings: with application to thermal barrier systems,

2003

\begin{matrix} \overset{′}{t} \end{matrix}

Stress measurements via photoluminescence piezospectroscopy on engine run thermal barrier coatings,

2012

\begin{matrix} \overset{′}{t} \end{matrix}

L. Wang, S. M. Guo, Evolution of hot corrosion resistance of YSZ, Gd₂Zr₂O₇, and Gd₂Zr₂O₇+YSZ composite thermal barrier coatings in Na₂SO₄+V₂O₅ at 1050℃,

2012

\begin{matrix} \overset{′}{t} \end{matrix}

Defect cluster formation in M₂O₃-doped cubic ZrO₂,

2000

... Zacate^[17]等研究证实掺入氧化锆中的稀土元素与氧空位形成缔合缺陷, 二者之间存在缺陷缔合能, 缺陷缔合能的存在使得稀土元素与氧化锆晶体的结合力增强.本文通过向7YSZ中掺稀土元素Yb从而引入缔合缺陷, 一方面Yb、Y与氧缺陷之间的缺陷缔合能够使晶体更加稳定, 掺杂元素不易从晶体中流失; 另一方面即使由于长时间服役存在掺杂元素流失的情况, 缺陷缔合能较小^[17]的Yb更易流失从而确保Y保留在氧化锆晶体中.即本文的重点在于利用Yb掺杂YSZ来达到减缓Y的流失, 从而减少m相产生, 达到稳定

\begin{matrix} \overset{′}{t} \end{matrix}

相的目的.此外, 本研究的另一个目标是通过考察稀土元素双掺氧化锆材料耐CMAS腐蚀过程中元素含量和物相的变化来探索腐蚀反应中稀土元素的扩散规律以及7YSZ的相变机理. ...

... [17]的Yb更易流失从而确保Y保留在氧化锆晶体中.即本文的重点在于利用Yb掺杂YSZ来达到减缓Y的流失, 从而减少m相产生, 达到稳定

\begin{matrix} \overset{′}{t} \end{matrix}

2011

... 图8所示为当掺杂量分别为0、1%、3%、5%、7%, 腐蚀温度为1250℃时不同腐蚀时间(1 h、2 h、5 h)后的m相含量的变化.由图可知随着腐蚀时间的增加m相的含量持续增加.而随着掺杂浓度的增加, m相含量呈现先降低后升高的趋势.当Yb的掺杂量为5%时m相的含量达到最低.即Yb的最优掺杂量为5%.此外, 根据图5b中所示Y/Zr比随Yb的掺杂量持续升高, 由于当Yb的含量超过某一值之后晶体的对称性下降^[18],

\begin{matrix} \overset{′}{t} \end{matrix}

-ZrO₂的含量减少从而导致了m相的相对含量增加. ...

2011

\begin{matrix} \overset{′}{t} \end{matrix}

-ZrO₂的含量减少从而导致了m相的相对含量增加. ...

2008

... Yb含量的减少主要是由于Yb与晶格中氧空位的缔结能比Y低^[19], 两者在晶格中所处环境相同, 因此, Yb比Y更容易与CMAS中的SiO₂反应.从图5a可以看出, Y/Zr随着腐蚀的进行呈下降趋势, 因此Y比Zr更容易与CMAS反应, 这是由于Zr与O之间的结合能相比Y以及Yb更高.所以Y、Yb、Zr三元素与CMAS的反应难易程度依次为Zr>Y>Yb.在腐蚀反应过程初期, Yb/Y与Zr/O之间形成的键合增加了体系中Yb、Y与SiO₂反应的难度, 因此Yb/Y双掺杂的ZrO₂比单纯的Y掺杂的ZrO₂更加稳定, m相更少(图6), 随着腐蚀的进行, Yb流失, 与SiO₂反应, 在这个过程中抑制了Y的流失, 从而起到了稳定

\begin{matrix} \overset{′}{t} \end{matrix}

相的作用. ...

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Yb/Y双掺杂氧化锆在熔盐腐蚀环境中的元素扩散和相变机理研究*

Elements Diffusion and Phase Transitions in Yb/Y Co-doped Zirconia Ceramic under Molten-salt Corrosive Environment

1 实验方法

1.1 粉体制备

1.2 腐蚀实验

1.3 表征和测试

2 结果与讨论

2.1 腐蚀时间对CMAS腐蚀深度的影响

2.2 腐蚀过程中YbYSZ的截面形貌演变与化学反应

2.3 腐蚀过程中的元素扩散和物相变化

3 结论

参考文献 文献选项 原文顺序 文献年度倒序 文中引用次数倒序 被引期刊影响因子

参考文献

原文顺序

文献年度倒序

文中引用次数倒序

被引期刊影响因子