EB-PVD制备热障涂层完整介绍

EB -PVD 及其制备功能涂层的研究进展EB -PV D Technology and Development in Preparing Protectio n Coatings滕　敏,孙　跃,赫晓东,李明伟(哈尔滨工业大学复合材料与结构研究所,哈尔滨150080)TENG Min ,SUN Yue ,HE Xiao -dong ,LI M ing -w ei(Center for Composite m aterials ,H arbin Institute of Technology ,H arbin 150080,China )摘要:介绍了电子束物理气相沉积(EB -P VD )设备的结构、工艺技术特点等,重点介绍了EB -P VD 技术在制备各种防护涂层方面所取得的成果及研究进展。

关键词:电子束物理气相沉积;涂层;热防护文献标识码:A 文章编号:1001-4381(2007)Suppl -0131-05A bstract :T he equipment config uration ,process and technolog ical cha racteristics of electro n beam physical v apor depo sition (EB -PVD )a re introduced in this paper .Applied achievements and develop -m ent in various protectio n co atings prepared by EB -PVD are recom mended .Key words :EB -PVD ;co ating ;thermal pro tection 随着现代工业的发展,对各种机械设备零件表面性能的要求也越来越高,在高速、高温重载、磨损、腐蚀介质等条件下工作零件,常常因其表面局部损坏而使整个零件失效报废。

北京航空材料研究院硕士学位论文EB-PVD氧化锆纳米结构热障涂层研究姓名：***申请学位级别：硕士专业：材料物理与化学指导教师：***20061220２）在气冷条件相当的情况下，压气机室进气口温度一样，有热障涂层的发动机热端部件其基体承受的温度较低。

有研究表明，降低温度能大大提高材料的疲劳寿命，故而提高发动机部件的使用寿命｛９］；３）当气冷条件相当，基体合金工作温度一样的情况下，由于使用热障涂层的发动机可以承受更高温度的燃烧气体，因此可以提高发动机的推力，增加推重比。

图Ｌ２热障涂层技术为航空发动机带来的综合效益示意１８１总之，热障涂层技术是发展高推重比航空发动机的关键技术之一，在目前及今后～个阶段，在先进航空发动机叶片上使用热障涂层技术是一个被普遍接受的共识。

１．２热障涂层体系热障涂层的基本思路是在合金基体上涂覆或沉积陶瓷涂层以达到隔热的作用，但是由于陶瓷和基体合金晶格不匹配，且热膨胀系数差别较大，涂层和基体的连接不会太好，伴随着热循环过程中产生的应力，容易造成涂层的失效。

因此，在基体和陶瓷层之间还应有一层粘结层来增强涂层的结合力，缓解涂层使用过程中的热应力。

基体、粘结层和陶瓷层构成了一个复杂的材料体系。

该材料体系中各部分的作用可如图１．３表示：基体合金主要是承载，需具备良好的高温力学性能；粘结层用于过渡合金基体和陶瓷层，减小两者热性能参数的不匹配，且在热循环过程中能够在其表面生成一溥层热生长氧化物层（Ｔｈｅｒｍａｌｇｏｗｎｏｘｉｄｅ，简称ＴＧＯ），阻止氧离子和腐蚀介质的扩散，保护基体合金，减少高温氧化和腐蚀；陶瓷层用来隔热，当带有热障涂层的热端部件（如发动机动叶）达到稳态传热时，在热障涂层两端能够产生一个温降，从而降低基体高温合金表面的温度Ｉ８１。

图１．３经典热障涂层体系及各部分作用［８Ｉ１．２．１粘结层粘结层位于陶瓷层和基体之间，对热障涂层体系的性能有着十分重要的影响。

由于ＹＳＺ陶瓷层在高温下是氧离子导体，对氧离子的扩散没有阻隔作用【１０１，因此粘结层需具备优良的抗高温氧化性能，氧化膜的生长动力学常数应较低。

2023 年第 43 卷航　空　材　料　学　报2023，Vol. 43第 4 期第 17 – 24 页JOURNAL OF AERONAUTICAL MATERIALS No.4 pp.17 – 24铂铝黏结层体系EB-PVD热障涂层的热循环行为贺文燮1, 甄 真2, 王 鑫2, 彭 超2, 牟仁德2,何利民2, 黄光宏2, 许振华2*（1．贵阳航发精密铸造有限公司 ，贵阳 550014；2．中国航发北京航空材料研究院 航空材料先进腐蚀与防护航空科技重点实验室，北京 100095）摘要：在镍基单晶高温合金基体上采用化学气相沉积法制备铂铝金属黏结层，并采用电子束物理气相沉积制备氧化钇部分稳定化的氧化锆（YSZ）陶瓷面层。

研究了黏结层相组成对热障涂层循环氧化行为的影响，借助扫描电子显微镜（SEM）、X射线能谱分析（EDS）和X-射线衍射分析（XRD）等方法分析涂层的相结构、显微组织和化学成分。

结果表明：黏结层主要成分包括Ni、Al、Pt、Co和Cr 元素并由β-（Ni,Pt）Al相和PtAl2相组成；经热循环测试后，涂层在热生长氧化物（TGO）和黏结层内部及其界面可能出现剥离；随着热暴露时间的延长，TGO层处的残余应力总体上呈现出逐渐减小的演变趋势；控制铂铝黏结层前驱体活性、Pt/Al元素含量、抑制脆性PtAl2相生成、改善TGO层/黏结层界面韧性和降低TGO层应力应变水平可有效延长铂铝黏结层体系热障涂层的热循环寿命。

关键词：热障涂层；热循环；相结构；界面；失效doi：10.11868/j.issn.1005-5053.2023.000058中图分类号：TG174.4 文献标识码：A 文章编号：1005-5053(2023)04-0017-08Thermal cycling behavior of EB-PVD TBCs with Pt modifiedaluminide bond coatHE Wenxie1, ZHEN Zhen2, WANG Xin2, PENG Chao2, MU Rende2,HE Limin2, HUANG Guanghong2, XU Zhenhua2*（1. Guiyang AECC Power Precision Casting Co., LTD, Guiyang 550014, China；2. Aviation Key Laboratory of Science and Technology on advanced Corrosion and Protection for Aviation Material，AECC Beijing Institute of Aeronautical Materials，Beijing 100095, China）Abstract:The（Ni, Pt）Al bond coats were prepared on the surface of nickel base single crystal superalloy by chemical vapor deposition（CVD）, and then YSZ ceramic coats were directly deposited on the surface of bond coats by electron beam physical vapor deposition（EB-PVD）.The influence of phase constituent of bond coat on the cyclic oxidation behavior of （Ni, Pt）Al/YSZ thermal barrier coatings was investigated in detail. The phase structure, morphology and chemical composition of the coatings were analyzed. The experimental results show that the bond coat is mainly composed of β-（Ni,Pt）Al and PtAl2 phases and the contents of the as-deposited bond coat are primarily including Ni, Al, Pt, Co and Cr elements. The spallation location of the TBCs probably occurs at the interface of TGO layer and bond coat, inside of TGO layer and within the bond coat. After thermal cycling test, it is found that the spallation may occur in the interior and interface of TGO and adhesive layer. With the extension of thermal exposure time, the residual stress located at the TGO layer decreases gradually in total. Therefore, controlling the precursor activity, Pt/Al element content, inhibiting the formation of brittle PtAl2 phase, improving the interfacial toughness of TGO layer/bonding layer, and reducing the stress-strain level of TGO layer are important ways to extend the thermal cycling life of（Ni, Pt）Al/YSZ thermal barrier coatings. Key words: thermal barrier coatings；thermal cycling；phase structure；interface；failure热障涂层技术是一种将耐高温、高隔热陶瓷材料沉积在合金基体表面的高温防护技术，其可以有效降低热端部件表面温度，提高基体材料耐高温氧化腐蚀性能，提升发动机的推重比和热效率，延长高温高应力状态下热端部件的使用寿命[1-2]。

采用EB-PVD技术制备两种多分层热障涂层的研究刘亮;张华芳;高巍;雷新更;崔向中;郑玉峰【期刊名称】《材料导报》【年(卷),期】2012(026)020【摘要】基于电子束物理气相沉积(EB-PVD)技术,设计并分别采用离子束辅助沉积法和低转速法制备了两种具有分层结构的热障涂层(TBCs),对陶瓷层引入层状结构后的组织结构与性能进行了研究.结果表明,层状结构的引入带来大量平行于沉积面的分层界面和相邻分层间的密度调制变化.层状结构TBCs的占优取向由(100)逐渐变化到(111),但仍都形成了不可转变的四方相(t(’))结构.依据分层结构本身的差异和分层界面所处位置的不同,低转速分层试样具有更好的抗氧化性能,但离子辅助分层试样具有明显更长的热循环寿命.【总页数】4页(P21-24)【作者】刘亮;张华芳;高巍;雷新更;崔向中;郑玉峰【作者单位】哈尔滨工程大学生物医用材料与工程研究中心,哈尔滨150001;中航工业北京航空制造工程研究所高能束流加工技术重点实验室,北京100024;中航工业北京航空制造工程研究所高能束流加工技术重点实验室,北京100024;中航工业北京航空制造工程研究所高能束流加工技术重点实验室,北京100024;中航工业北京航空制造工程研究所高能束流加工技术重点实验室,北京100024;中航工业北京航空制造工程研究所高能束流加工技术重点实验室,北京100024;哈尔滨工程大学生物医用材料与工程研究中心,哈尔滨150001;北京大学工学院,北京100871【正文语种】中文【中图分类】TG174.453【相关文献】1.EB-PVD热障涂层皱曲问题研究进展 [J], 何伶荣;张坤;陈光南2.钛合金基体EB-PVD热障涂层的制备与初步研究 [J], 何博;李飞;周洪;姚振中;孙宝德3.EB-PVD方法制备热障涂层热循环性能研究 [J], 姚振中;武洪臣;冯建基;雷新更4.力学载荷条件下EB-PVD热障涂层损伤行为研究 [J], 牟仁德;王占考;陆峰;舒焕烜5.EB-PVD热障涂层粘结层/TGO界面性能的研究进展 [J], 刘林涛;张勇;吕海兵;何飞因版权原因，仅展示原文概要，查看原文内容请购买。

专利名称：一种利用EB-PVD技术制备的高熵氧化物超高温热障涂层及其方法
专利类型：发明专利
发明人：赵晓峰,张显程,郭芳威,石俊秒,范晓慧,杨凯,王卫泽,陆体文,刘利强,孙子豪
申请号：CN202111182239.1
申请日：20211011
公开号：CN114000107A
公开日：
20220201
专利内容由知识产权出版社提供
摘要：本发明提供一种利用EB‑PVD技术制备的高熵氧化物超高温热障涂层及其方法，该方法包括以下步骤：1)分别称取ZrO2、Y2O3、Ta2O5、Nb2O5和Yb2O3；2)将原料进行湿法球磨，烘干，第一次烧结，造粒；3)经冷等静压制成陶瓷胚体，第二次烧结，得到陶瓷靶材；4)提供一种合金基体，进行磨抛处理，喷砂粗化，清洗，利用APS技术在表面制备NiCoCrAlY粘结层；5)将合金基体装入高温合金夹具，将陶瓷靶材放入电子束物理气相沉积设备中，用高能电子束熔化靶材使得蒸发的靶材原子沉积到粘结层表面，即得。

根据本发明制备的热障涂层能够在1600℃高温下仍保持四方相，可应用于下一代航空发动机热障涂层材料。

申请人：上海交通大学,华东理工大学,中国科学院上海硅酸盐研究所
地址：200240 上海市闵行区东川路800号
国籍：CN
代理机构：上海智信专利代理有限公司
代理人：余永莉
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电子束物理气相沉积(EB-PVD)技术制备热障涂层技术黄升摘要：本文介绍电子束物理气相沉积（EB-PVD）制备热障涂层技术，结合发展历程综述其技术原理、设备构造及工艺特点。

关键词：电子束物理气相沉积（EB-PVD）热障涂层1 引言当今航空涡扇发动机正朝高流量比、高推重比和高涡轮进口温度方向发展，这就使得发动机叶片所承受温度不断升高，据报道目前商用飞机燃气温度达1500 °C、军用飞机燃气温度高达1700 °C[1]。

而当前所使用镍基高温合金最高工作温度只能达到1200 °C，并几乎已达到其使用温度上限，提升空间极其有限。

面对发动机使用的高温障碍，降低发动机叶片温度就成了极其关键的任务。

热障涂层就是一种降温的有效途径（见图1），自20世纪70年代初问世以来[2]，受到广泛重视并迅速发展成为高温涂层研究的热点[3-8]。

图1 涡轮叶片承温能力所谓热障涂层（Thermal Barrier Coatings, TBCs）是指由金属缓冲层或者黏结层和耐热性好、隔热性好的陶瓷热保护功能层组成的层合型金属陶瓷复合涂层系统[9]。

一般由具有一定厚度和耐久性的陶瓷涂层、金属粘结层和承受机械载荷的合金组成。

目前根据不同设计要求热障涂层具有如图2所示双层、多层、梯度系统三种结构形式。

图2 热障涂层结构示意图而电子束物理气相沉积（Electron bean-physical vapor deposition EB-PVD）制备热障涂层（TBCs）是在20世纪80年代开发，近年来不断发展成熟起来的新技术，其使用高能电子束加热并汽化陶瓷源，陶瓷蒸汽以原子形式沉积到基体上而形成涂层。

EB-PVD法制备的TBCs涂层表面光洁，有良好的动力学性能；涂层/基体的界面以冶金结合为主，结合力强，稳定性好。

特别是其制备涂层组织为垂直基体表面柱状晶结构，具有很高的应变容限，较热喷涂制备涂层热循环寿命提升巨大。

Surface and Coatings Technology 168(2003)23–290257-8972/03/$-see front matter ᮊ2002Elsevier Science B.V .All rights reserved.doi:10.1016/S0257-8972(02)00925-8Effect of thermal exposure on the microstructure and properties ofEB-PVD gradient thermal barrier coatingsHongbo Guo *,Shengkai Gong ,Khiam Aik Khor ,Huibin Xu a,b ,a c aSchool of Materials Science and Engineering,Beijing University of Aeronautics and Astronautics,Xueyuan Road 37,Beijing,PR ChinaaInstitut fur Werkstoffe und Verfahren der Energietechnik 1,Forschungszentrum Julich GmbH,52425Julich,Germanyb¨¨School of Mechanical Production Engineering,Nanyang Technological University,Nanyang Avenue 639798,Singapore,SingaporecReceived 11June 2002;accepted in revised form 10December 2002AbstractThe effects of thermal exposure on the microstructure,properties and failure of electron beam physical vapor deposited Al O –23yttria stabilized zirconia (YSZ )gradient thermal barrier coatings (GTBCs )were studied.The GTBCs,with lifetimes of more than 500h for 1-h cycles and 13h for 0.25-h cycles at 11008C,exhibited a better thermal shock resistance than two-layered-TBCs consisting of a NiCoCrAlY bond coat and a YSZ topcoat.The GTBCs also showed a relatively low oxidation rate under cyclic exposure,due to the formation of a pre-deposited Al O film on the bond coat.The oxidation of the bond coat is dominated 23by the selective oxidation of aluminum.The values of hardness and modulus for the Al O –YSZ graded layer are in the range 23of 2.0–3and 170–230GPa,respectively,whereas after 500h exposure a considerable reduction in the mechanical properties occurred in a rich Al O area of the graded layer.Micro-cracks initiated and propagated in the rich Al O area,and finally 2323resulted in the spallation failure of the coating.The thermal conductivity of a GTBC was found to be 1.7W y mK,which was marginally lower than that of the two-layered-TBC at 2.2W y mK.However,the value of thermal conductivity increased up to 2.0W y mK after 500h exposure.ᮊ2002Elsevier Science B.V .All rights reserved.Keywords:EB-PVD;Gradient thermal barrier coating;Failure mechanism;Thermal cycling;Mechanical property;Thermal conductivity1.IntroductionThermal barrier coatings (TBCs )are used in and being developed for the hot section parts of gas turbines.Typical TBCs consists of a PtAl diffusion or an MCrAlY overlay bond coat and a ceramic topcoat of partially yttria stabilized zirconia (P-YSZ )deposited by electron beam physical vapor deposition (EB-PVD )or by plasma spraying.The EB-PVD process offers the advantage of superior strain and thermal shock tolerant behavior of TBCs due to their columnar microstructure.Strain tol-erant microstructure that has allowed TBCs to be suc-cessfully operated on highly stressed turbine components without spalling.However,for the traditional two-lay-ered-TBCs the interface between the metallic bond coat and the P-YSZ topcoat is the weakest link in this system.During high temperature thermal exposure,a*Corresponding author.Tel.:q 49-2461-613520;fax:q 49-2461-612455.E-mail address:h.guo@fz-juelich.de (H.Guo ).thermally grown oxide (TGO )layer forms on the bond coat.Different thermo-mechanical properties between the TGO layer and bond coat and YSZ topcoat,together with the applied temperature gradients,usually results in high thermal stresses concentration at the bond coat y TGO or TGO y YSZ topcoat interface that can be large enough to initiate interface cracks.With cyclic thermal exposure,these cracks propagate and finally lead to spallation failure of the EB-PVD TBCs w 1–4x .A gradient thermal barrier coating (GTBC )with a compositionally graded structure of NiCoCrAlY q Al O y Al O y Al O q YSZ provides a more gradual 232323transition in properties from metallic bond coat to ceramic YSZ topcoat,compared with the sudden change of properties in a two-layered-TBC system w 5–8x .It has been investigated by finite element method that interface stress concentration is reduced greatly in the GTBC relative to the two-layered-TBC,due to the Al O –YSZ 23graded layer w 9x .Previous studies have also shown that the Al O –YSZ graded layer plays an important role in2324H.Guo et al./Surface and Coatings Technology 168(2003)23–29Fig.1.Schematic diagram showing the locations of indentation test on the cross-section surface of GTBC.Table 1Cycling lifetimes of TBCs Type of Thermal cycling lifetime (h )exposure GTBCs Two-layered-TBCs 1h 7132900.25h164.5improving the resistance of coating to cyclic oxidation and high temperature hot-corrosion w 8,10x .Presumably,the graded layer is a crucial location in determining the lifetime and failure mechanisms of the GTBC.The present studies focus on the effects of thermal exposure on the microstructure and thermo-mechanical properties (modulus,microhardness and thermal conduc-tivity )of the Al O –YSZ graded layer,and to under-23standing the failure mechanism of the GTBC thereby.2.ExperimentalA four-electron-gun EB-PVD equipment with three water-cooled copper crucibles was used to prepare the GTBC.A directionally solidified nickel-base superalloy DZ24was chosen to be the substrate materials,on which a bond coat with an approximate composition of Ni–22Co–22.5Cr–8.56Al–0.95Y (wt.%)was first deposited by EB-PVD.Then,a tablet of Al–Al O –23ZrO –8wt.%Y O pressed from mixed powders was 223evaporated and deposited onto the bond coat by EB-PVD.And finally,the GTBCs were finished with a deposition of the YSZ topcoat.Detailed procedures about the fabrication of the GTBC have been discussed elsewhere w 6,9x .For comparison,typical two-layered-TBCs,consisting of a NiCoCrAlY bond coat and a YSZ topcoat,were produced also by EB-PVD.Before the deposition of the YSZ topcoat,the bond coat was pre-treated in vacuum at 11008C,and then surface strength-ened by shot-peening.The coated specimens were exposed to laboratory air at 11008C under cyclic conditions.The cyclic exposures were performed in a vertical tube furnace that permitted rapid specimen heating and cooling.The exposures were conducted in two ways as follows:1-h cycle:heat to 11008C in 5min,hold at 11008C for 1h,cool to 208C in 5min by forced air cooling;0.25-h cycle:heat to 11008C in 5min,hold at 11008C for 0.25h,quench in iced water.During 1-h cycles the specimens were weighed by a TG 328A thermal analytical balance with a precision of 10g.To perform the microstructural characterization y 5of coatings using scanning electron microscope (JEOL JSM-5410)with energy disperse spectrum,the speci-mens were cut,ground,finely polished and then etched in a solution of FeCl and alcohol,and finally coated 3with a conductive carbon film.Transmission electron microscope (TEM,JEOL JEM-2010)was also used for the microstructural observation on the interface of the GTBC.Phase analysis using a Shimadzu X-ray diffrac-tometer with Cu K a radiation generated at 50kV and 20mA was carried out to determine the phases of GTBC.Before the test,the YSZ topcoat was removed carefully by grinding with fine emery paper.The hardness and the modulus of GTBCs were deter-mined locally by nano-indentation.The actual test was conducted on a fine polished cross-section surface using a XP nano-indenter.In this case,the indents were produced at a load of 100mN along a line across the thickness of the coating.Fig.1is a schematic illustration of the indentation location on the cross-section surface.The thermal diffusivity (k )was measured on standard TBC specimens using a laser flash method (TC-3000)at room temperature.All the measurements were per-formed in an argon atmosphere.The accuracy of the thermal diffusivity measurement was within "5%.The specific heat (c )was measured using a standard differ-ential scanning calorimeter (STA 449C,NETZSCH ),with alumina as the reference material.The thermal conductivity is then given by l s k r c ,where r is the Archimedes immersion density.3.Results3.1.Cyclic oxidation of GTBCsThe duration times to failure for the cyclic exposures are listed in Table 1.The GTBC exhibited lifetimes of more than 500and 13h for the 1-h cycles and the 0.25-h cycles,respectively,whereas the lifetime of the two-layered-TBC was no longer than 350and 6h for the cycles,respectively.This indicates that the thermal shock resistance of the GTBC is far superior to that of the two-layered-TBC.Fig.2compares the kinetics of a GTBC specimen and a two-layered-TBC specimen during 1-h cycles at 11008C.Both the GTBC and the two-layered-TBC had25H.Guo et al./Surface and Coatings Technology 168(2003)23–29Fig.2.Kinetics of GTBC and two-layered-TBC during 1-h cycles at 11008C.Fig.3.XRD patterns of Al O –YSZ graded layer of GTBC:(a )as-23deposited,and after (b )100and (c )5001-h cycles at 11008C.Fig.4.(a )Cross-section micrograph of an as-deposited GTBC,and (b )higher magnification of (a ).a weight gain of approximately 0.6mg y cm after 300h 2exposure,indicating a low oxidation rate.After approx-imately 350h exposure,the two-layered-TBC showed a slight increase in weight,but following a further another 100h exposure,the coating showed an abrupt loss in weight,resulting from spallation failure of the YSZ topcoat.In contrast,the abrupt loss in weight for the GTBC did not occur until after approximately 600h exposure,indicating the GTBC improved the lifetime by up to 200h.3.2.Microstructural evolution and characterization Fig.3compares XRD patterns of the as-deposited GTBC and the GTBC after the 1-h cycles at 11008C,when the YSZ topcoat had been removed.Analysis shows that a -Al O phase and t-ZrO phase are main 232constituents in the as-deposited coating,indicating that the graded layer consisted of the two-phases.In addition,some g q g9phases,coming from the bond coat,can be also detected.In contrast,after 100and 500cycles,the fraction of the a -Al O phase shows a dramatic increase,23due to the oxidation of NiCoCrAlY bond coat.It is noteworthy that other oxide phases and spinels,such as NiO,Cr O and NiAlO ,can not be detected in the 232coatings,suggesting that selective oxidation of Al ele-ment from the bond coat occurred during the thermal exposure.Fig.4a shows a micrograph of the as-deposited GTBC,where an Al O –YSZ graded layer of 8m m 23thickness (middle )is bound intimately to a NiCoCrAlY bond coat (left ),followed by an YSZ topcoat (right )with a typical columnar microstructure.Fig.4b shows a higher magnification micrograph of the graded layer.One can see that a black Al O thin film of less than 123m m thickness formed on the surface of the bond coat,and the Al O –YSZ composite layer,with a graded and 23laminated microstructure,become darker and darker in color as the concentration of Al O component increases23gradually towards the bond coat.Fig.5shows a bright-field image of the two-phase ZrO q Al O area of the 223graded layer.It can be observed that the Al O phase,23in the form of spherical particles,is dispersed in the matrix of ZrO .Previous studies have also shown that 2a graded porous microstructure formed in the graded layer,due to a ‘shadow effect ’during the deposition of the mixtures of Al O and YSZ w 11x .23After 5001-h cycles,the GTBC remains bonded closely to the superalloy substrate,and no cracks can be found in the coating,as shown in Fig.6.In the26H.Guo et al./Surface and Coatings Technology168(2003)23–29Fig.5.TEM bright-field image of Al O–YSZ graded layer of as-23depositedGTBCs.Fig.7.Cross-section of GTBC after6001-h cycles at11008C.Fig.6.Cross-section micrograph of GTBC after500h exposure dur-ing1-hcycles.Fig.8.XRD pattern from the top surface of the YSZ-spalled MCrAlY bond coat surface of the GTBC during1-h cycles.meantime,a black layer of approximately5m m thick-ness developed on the bond coat.The EDX result proved that the black zone mainly consists of the Al O phase23and small amount of YSZ phase.It is clear that the richAl O layer increased dramatically in thickness com-23pared with the pre-deposited Al O thin film.The growth23of an Al O rich layer may be due to the formation of 23Al O by the selective oxidation of Al in the bond coat 23w6x and the outward diffusion of the Al O phase in the23graded layer.Fig.7presents a cross-section of the microstructureof the GTBC after6001-h cycles.The Al O–YSZ23 graded layer close to the YSZ topcoat remains largely intact.However,many cracks initiated and propagated in the Al O rich area of the graded layer.It can be 23inferred that spallation of the YSZ topcoat will soonoccur by cracking at the Al O rich area,after further23cyclic exposure.Fig.8shows an XRD pattern obtained from the top surface of the YSZ-spalled bond coat surface.g q g9 phases are the main constituents of the coating,which came from the NiCoCrAlY bond coat.In addition,somea-Al O phase and t-ZrO phase,resulting from the 232Al O–YSZ graded layer,can be also detected.This 23confirms the inference that the GTBC cracked at the Al O y YSZ graded layer interface.23Fig.9a and b show morphological and cross-section micrographs of the GTBC after600.25-h cycles,respec-tively.Although the YSZ topcoat remains bonded to the substrate,many cracks developed parallel to each other in the coating,as shown in Fig.9a.In the meantime, micro-cracks also initiated and developed along the uneven bond coat y graded layer interface,resulting from the severe deformation of the coating during the cyclic exposure(Fig.9b).Additionally,several micro-cracks occurred in the graded layer normal to the interface. Presumably,spallation failure of the GTBC occurred by the detachment of the graded layer from the bond coat.3.3.Thermo-mechanical propertiesThe measured hardness and modulus distribution ofthe Al O–YSZ graded layer are shown in Fig.10a and 23b,respectively.The values of hardness and modulus for the as-deposited graded layer are in a range of2.0–327H.Guo et al./Surface and Coatings Technology 168(2003)23–29Fig.9.(a )Morphology and (b )cross-section micrograph of GTBCs after 600.25-h cycles.(1)bond coat;(2)Al O –YSZ graded layer;23(3)YSZtopcoat.Fig.10.(a )The hardness and (b )the modulus distribution of Al O –23YSZ graded layer inGTBCs.Fig.11.Thermal conductivities of EB-PVD TBCs at room tempera-ture:as-deposited two-layered-TBC (1),as-deposited GTBC (2),and GTBC after 50(3),300(4)and 500(5)1-h cycles at 11008C,respectively.and 170–230GPa,respectively.The hardness of the graded layer is increasing gradually towards that of the YSZ topcoat,resulting from both the density increase and the micro-porosity decrease in the graded layer towards the YSZ topcoat w 6,7x .After 250h,the hardness of the layer decreased marginally,but the modulus was much lower than the as-deposited one.After 500h exposure,a considerable reduction in both the hardness and modulus occurred in the Al O rich area of the 23layer.This means that the thermal exposures have had a significant effect on the mechanical properties of the Al O rich area of the Al O –YSZ graded layer.2323Fig.11presents the measured thermal conductivity at room temperature for the EB-PVD TBCs with a ceramic topcoat of approximately 120m m thickness.The value of thermal conductivity for the two-layered-TBC is approximately 2.2W y mK,which is a little different from values reported in Refs.w 12–14x .A thermal conductivity for the as-deposited GTBC was found to be 1.7W y mK.However,the thermal conductivity increased up to 2.0W y mK after 500h exposure.It can be deduced that the thermal exposures contributed increase thermal conductivity of GTBCs.4.DiscussionThe above results show that the GTBC showed a lower oxidation rate than the two-layered-TBC.Asmentioned in the experimental details,the NiCoCrAlY coating of the two-layered-TBC was pre-treated in vac-uum before the deposition of the YSZ ceramic coating.As a result,a pre-oxide layer formed on the surface of28H.Guo et al./Surface and Coatings Technology168(2003)23–29the metallic coating,which consisted of Al O and some23Ni y Co rich oxides(e.g.spinel)w15x.Although the pre-oxide layer can effectively prevent the two-layered-TBC from further oxidation during thermal exposure,the spinels may be responsible for the premature spallation of YSZ topcoat during the thermal cyclic oxidation w16–18x.For the GTBC,the pre-deposited Al O film on the23bond coat also plays an important role in improving the oxidation resistance of the coating.During thermal exposure,the growth mechanism of the oxide layer of a GTBC is dominated by the inward diffusion of oxygen, because the inward diffusion rate of oxygen is much faster than the outward diffusion rate of the metallic atoms in the bond coat w10x.Failure of the EB-PVD two-layered-TBC often occurred by cracking within or near the TGO,which is caused in most cases by thermal stresses,resulting from the growth of the TGO and the thermal mismatch between the TGO and the bond coat and the YSZtopcoat.The Al O–YSZ GTBC with a NiCoCrAlY y23NiCoCrAlY–Al O y Al O–YSZ graded structure pro-2323vides a gradual transition in properties from the metallic bond coat to the ceramic topcoat,in contrast to the sudden change of the two-layered-TBC properties.Thus, a sharp stress concentration arising from thermal mis-match can be avoided at the bond coat y YSZ topcoat interface.Further more,the thickness of the pre-depos-ited Al O film on the bond coat can be accurately 23controlled during the EB-PVD process and consequently, the thermal stress resulting from the volume expansion of the TGO can be minimized.As a result,the GTBC shows a better resistance to thermal shock than the two-layered-TBC,resulting in a significant improvement in thermal cycling lifetime.Previous studies have also shown that a maximumresidual stress develops in the Al O rich area of the23graded layer w9x,which can be enough to initiate micro-cracks in this area.Due to the initiation of micro-cracks, the thermal stress can be relaxed greatly.However,these micro-cracks led to the significant reduction in mechan-ical properties of the graded layer.With the additional contribution of the cyclic stress,these micro-cracks propagated,and finally resulted in the failure of theGTBC by cracking at the rich Al O area of the Al O–2323 YSZ graded layer.Thus,the graded layer became the crucial location in determining the lifetime of a GTBC. The microstructure of TBCs is well known to influ-ence substantially the thermal conductivity w12,19x.The EB-PVD process provides the TBCs with a strain tolerant columnar microstructure that has allowed TBCs to be successfully operated on highly stressed turbine components without spalling.In addition to the excellent strain tolerance,EB-PVD technologies result in an excellent surface finish w20x and good erosion resistance w21x,but this is at the expense of the thermal insulation capability because the thermal conductivity may be twice that of the best plasma sprayed TBCs w13,20,22x.Thus the challenge is to lower the thermal conductivity of EB-PVD TBCs to match that of plasma sprayed ceramics.There are three obvious ways to attempt to low the thermal conductivity of TBCs.These are:(1) to make the TBCs of many thin alternating layers to creat a significant interface resistance;(2)to increase and control porosity;and(3)to decrease the inherent thermal conductivity of the TBC by increasing atomic scale disorder w13x.In the present study,the EB-PVD two-layered-TBC has a thermal conductivity of approximately2.2W y mK that is slightly higher than those reported in Refs.w12–14x,which may be caused by different deposition techniques.For example,the thermal conductivity has been observed to vary with the coating thickness w22x. In contrast to the two-layered-TBC,the GTBC reduced the thermal conductivity by up to20%.This appreciable reduction in thermal conductivity can be mainly due to the two microstructural characteristics of the GTBC. One is the formation of a micro-porous and laminated microstructure in the Al O–YSZ layer of the coating.23It is concluded that a laminated ceramic coating offers a most promising route to lower the thermal conductivity by modifying both phonon and photon transport within the coatings,while a porous microstructure acts to scatter phonons which also serves to reduce the thermal con-ductivity w23x.The other one is the increased vacanciescontent of the ZrO lattice which is caused by an anion2deficiency due to the introduction of cations fromAl O and Y O w7x.Tamari et al.w24x believe that the 2323vacancies appearing in the ZrO lattice,which are caused2by the introduction of some cations with a valence distinct from that of zirconium into this lattice,can reduce the thermal conductivity of EB-PVD ceramic coatings by20–30%.It should be noted that the GTBCs after thermal cycling testing exihibited a little higher thermal conduc-tivity than those before testing.The increase of GTBCs in the thermal conductivity can be considered as the result of the change in the microstructure of the coatings after thermal exposure,including the micro-poroisty, crack density,laminated microstructure and vancancy concentration.5.ConclusionsThe effects of cyclic exposure on the microstructure, thermal-mechanical properties and failure of EB-PVDgraded Al O–YSZ thermal barriers coating have been 23studied.Some conclusions can be drawn as follows:1.The GTBC,with lifetimes of more than500h for1-h cycles and13h for0.25-h cycles at11008C, exhibit a better thermal shock resistance than a two-layered-TBC.29 H.Guo et al./Surface and Coatings Technology168(2003)23–292.The pre-deposited Al O film in a GTBC can improve23the oxidation rate of the NiCoCrAlY bond coat,andthe growth of the oxide layer is dominated by the selective oxidation of Al.3.Cyclic exposure resulted in a significant reduction ofthe Al O rich area of the Al O–YSZ graded layer 2323in mechanical properties,and micro-cracks initiatedand propagated in the rich Al O area,and finally23resulted in the failure of the GTBC by cracking at this location.4.The thermal conductivity of the GTBC is found to be1.70W y mK,which is marginally lower than that of the two-layered-TBC at2.2W y mK.However,the values of thermal conductivity increased up to2.0 W y mK after5001-h cycles,possibly resulting from a change in the grain boundaries,micro-porosity, laminated microstructure and vacancies of the coating.AcknowledgmentsThis research is sponsored by National Natural Sci-ence Foundation of China(NSFC)and Aviation Science Foundation of China(ASFC).Referencesw1x D.R.Mumm,A.G.Evans,I.T.Spitsberg,Acta Mater.49(2001) 2329.w2x Y.H.Sohn,J.H.Kim,E.H.Jordan,M.Gell,Surf.Coat.Technol.146–147(2001)70.w3x K.Kokini,J.Dejonge,S.Rangaraj,B.Beardsley,Surf.Coat.Technol.154(2002)223.w4x V.Krishnakumar,E.Gell,E.Jordan,Surf.Coat.Technol.133–134(2000)28.w5x B.A.Movchan,G.S.Marinski,Surf.Coat.Technol.100–101 (1998)309.w6x H.B.Xu,H.B.Guo,F.S.Liu,S.K.Gong,Surf.Coat.Technol.130(2000)133.w7x H.B.Guo,H.B.Xu,X.F.Bi,S.K.Gong,Mater.Sci.Eng.A 325(2002)389.w8x H.B.Guo,S.K.Gong, C.G.Zhou,H.B.Xu,Surf.Coat.Technol.148(2002)110.w9x H.B.Guo,S.K.Gong,H.B.Xu,Mater.Sci.Eng.A325(2002) 261.w10x H.B.Guo,H.B.Xu,S.K.Gong,J.Mater.Sci.37(24)(2002) 5333.w11x H.B.Guo,X.F.Bi,H.B.Xu,S.K.Gong,Scripta Mater.44 (2001)683.w12x K.An,K.S.Ravichandran,R.E.Dutton,S.L.Semiatin,J.Am.Ceram.Soc.82(2)(1999)399.w13x J.R.Nicholls,wson,D.S.Rickerby,P.Morrel,Advanced proceeding of TBCs for reduced thermal conductivity,NATO Workshop on Thermal Barrier Coatings,Aalborg,Denmark, AGARD-R-823,1998,paper6.w14x R.B.Dinwiddie,S.C.Beecher,W.D.Porter,B.A.Nagaraj,The Effect of Thermal Aging on the Thermal Conductivity of Plasma-Sprayed and EB-PVD Thermal Barrier Coatings, ASME96-GT-982,1996,p.107.w15x X.F.Bi,H.B.Xu,S.K.Gong,Surf.Coat.Technol.130(2000) 122.w16x E.Y.Lee,R.R.Biederman,R.D.Sisson Jr.,Mater.Sci.Eng.A 121(1989)467.w17x E.A.G.Shillington,D.R.Clarke,Acta Mater.47(1999)1297. w18x L.Pawlowski,P.Fauchais,Int.Metall.Rev.271(1992)31. w19x R.E.Taylor,X.Wang,X.Xu,Surf.Coat.Technol.120–121 (1999)89.w20x P.Morrel,D.S.Rickerby,Advantages y disadvantages of various TBC system as perceived by the engine manufacturer,NATO Workshop on Thermal Barrier Coatings,Aalborg,Denmark, AGARD-R-823,1998,paper20.w21x J.R.Nicholls,Y.Jaslier,D.S.Rickerby,Erosion and foreign object damage of thermal barrier coatings,Fourth International Symposium,On High Temperature Corrosion,Les Embiez, France,May1996.w22x wson,J.R.Nicholls,D.S.Rickerby,The effect of coating thickness on the thermal conductivity of CVD and PVD coatings,Fourth International Conference,On Advanced in Surface Engineering,Newcastle,UK,1996.w23x J.R.Nicholls,wson,A.Johnstone,D.S.Rickerby,Surf.Coat.Technol.151–152(2002)383.w24x Y.A.Tamarin, E.B.Kachanov,S.V.Zherzdev,Mater.Sci.Forum251(1997)949.。

电子束物理气相沉积(EB-PVD)技术制备热障涂层技术黄升摘要：本文介绍电子束物理气相沉积（EB-PVD）制备热障涂层技术，结合发展历程综述其技术原理、设备构造及工艺特点。

关键词：电子束物理气相沉积（EB-PVD）热障涂层1 引言当今航空涡扇发动机正朝高流量比、高推重比和高涡轮进口温度方向发展，这就使得发动机叶片所承受温度不断升高，据报道目前商用飞机燃气温度达1500 °C、军用飞机燃气温度高达1700 °C[1]。

而当前所使用镍基高温合金最高工作温度只能达到1200 °C，并几乎已达到其使用温度上限，提升空间极其有限。

面对发动机使用的高温障碍，降低发动机叶片温度就成了极其关键的任务。

热障涂层就是一种降温的有效途径（见图1），自20世纪70年代初问世以来[2]，受到广泛重视并迅速发展成为高温涂层研究的热点[3-8]。

图1 涡轮叶片承温能力所谓热障涂层（Thermal Barrier Coatings, TBCs）是指由金属缓冲层或者黏结层和耐热性好、隔热性好的陶瓷热保护功能层组成的层合型金属陶瓷复合涂层系统[9]。

一般由具有一定厚度和耐久性的陶瓷涂层、金属粘结层和承受机械载荷的合金组成。

目前根据不同设计要求热障涂层具有如图2所示双层、多层、梯度系统三种结构形式。

图2 热障涂层结构示意图而电子束物理气相沉积（Electron bean-physical vapor deposition EB-PVD）制备热障涂层（TBCs）是在20世纪80年代开发，近年来不断发展成熟起来的新技术，其使用高能电子束加热并汽化陶瓷源，陶瓷蒸汽以原子形式沉积到基体上而形成涂层。

EB-PVD法制备的TBCs涂层表面光洁，有良好的动力学性能；涂层/基体的界面以冶金结合为主，结合力强，稳定性好。

特别是其制备涂层组织为垂直基体表面柱状晶结构，具有很高的应变容限，较热喷涂制备涂层热循环寿命提升巨大。