热障涂层陶瓷材料的研究现状与展望 李志明,钱士强,王伟 (上海工程技术大学材料工程学院,上海201620) [摘要] 目前主要研究的热障涂层陶瓷材料分为氧化物稳定的Zr02、钙钛矿结构ABO3陶瓷、焦绿石或萤石结构A2B207陶瓷、磁铁铅矿结构MMeAl11O19陶瓷及其他先进陶瓷材料5大类。概述了各类材料的研究进展,对热障涂层陶瓷材料今后的发展方向进行了探讨,认为氧化物稳定的Zr0:在热障涂层中的应用地位必将被使用温度更高的新型陶瓷材料所替代。 [关键词] 热障涂层;稳定Zr02; A2B207陶瓷;MMeAl11O19陶瓷;抗高温;隔热 [中图分类号] TG174.45 [文献标识码]A [文章编号]1001 - 1560( 2011) 01 - 0038 - 04 O前言 目前,高温合金材料已无法满足现代涡轮发动机对高进口温度的要求[1],金属部件(如燃烧室内壁、涡轮叶片等)上需制备热障涂层,以承受更高的温度,同时提高发动机的使用寿命和效率[2]。 热障涂层具有隔热、抗高温氧化和耐腐蚀等作用,其典型结构为双层系统,由表层的陶瓷热障层和中间的金属粘结层构成。在热障涂层中实际起隔热作用的是陶瓷热障层,它能有效减少向金属基体的热传导,保护关键零部件。合适的热障涂层陶瓷材料应满足高熔点、低热导率、热膨胀系数与金属基体较匹配、低烧结速率、良好的高温化学稳定性、与金属层结合力高、在室温与工作温度之间无相变等要求[3]。 氧化物稳定的Zr02是目前应用最为广泛的热障涂层陶瓷材料,钙钛矿结构的ABO3陶瓷和焦绿石或萤石结构的A2B207陶瓷也不断受到关注;此外,新型磁铁铅矿结构的MMeAl11O19陶瓷及其他先进陶瓷材料也开始得到重视。如下综述了目前国内外热障涂层陶瓷材料的研究现状,介绍了最新的先进热障涂层陶瓷材料并探讨了其今后的发展趋势。 15类热障陶瓷涂料研究近况 1.1 氧化物稳定的Zr02 氧化物稳定Zr02具有较低的热导率、较高的热膨胀系数和良好的高温性能[4],很长一段时期内充当着主要的热障涂层陶瓷材料。用于稳定Zr02的氧化物种类繁多,二价稳定剂有Ca0和MgO[5]等,三价稳定剂有Y203[6],Sm203[7],Nd203[8],Er203[9]等,四价稳定剂有Ce02 [10],Hf02[11]等。其中,Y203是Zr02最常用的稳定剂,完全致密质量分数为7%的Y203 - Zr02陶瓷的热导率室温时为3.0 W/(m·℃),在 氧化物稳定的Zr02可以满足 的温度[15]。为此,需寻求新的陶瓷材料应用于热障涂层,氧化物稳定的2r02热障陶瓷材料面临严峻的挑战。 1.2钙钛矿结构AB03陶瓷 钙钛矿结构的ABO3陶瓷中,早期有SrZr03 [ 另外,还有一类新开发用于热障涂层中的钙钛矿陶瓷是BaLn2Ti3010(Ln为La,Sm,Nd,Pr中的一种或多种组合),为层状钙钛矿结构,热导率低并具有良好的烧结阻力。采用BaC03,Ti02,La203在 1.3焦绿石或萤石结构A2B207陶瓷 A2B207(A为稀土元素,B为Zr,Hf,Ce等元素)陶瓷材料具有比Zr02材料更低的热导率,相当的热膨胀系数及良好的高温相稳定性能,被认为是最有希望替代Zr02的材料体系。目前,对该材料体系的研究主要集中在La2Zr0207[23],Gd2Zr207[24],Nd2Zr207[25],La2 Ce207[26,27], Eu2Zr207[26],DY2Zr207[28], Sm2Zr207[29]等的热物理性能方面。其中,La2Zr0207的研究相对较多[30,31],其晶格内部由Zr06八面体构成大的网状结构,la3+填充在由六个Zr06构成的八面体孔隙中,在满足电中性的条件下,LA3+和Zr4+可以被具有相近离子半径的其他离子替代。La2Zr207作为热障涂层陶瓷材料应用的主要不足之处是其热膨胀系数较低[30],制备成涂层时在高温热循环下易剥落。由于Ce02具有较大的热膨胀系数(1.3×10 1.4磁铁铅矿结构MMeAL11019陶瓷 磁铁铅矿结构的六铝酸盐MMeAL11019(M为La,Nd,Sr等元素,Me为碱土金属元素等)陶瓷显微结构由随机排列的片层组成,是较晚开发的用于高温下能保持长期良好的结构和热稳定性的热障涂层,具有远低于Zr02基热障涂层材料的烧结速率[34],存在较多的微孔,有良好的热绝缘效果。用于热障涂层的MMeAL11019陶瓷,研究相对较早、较多的是镁基六铝酸镧(MMeAL11019,简称LMA),等离子喷涂制备的LMA热障涂层完全可以替代氧化物稳定的Zr02而应用于使用温度更高的热障涂层[34,35]。近年来,MMeAL11019陶瓷用于热障涂层越来越受到关注。采用固相反应法合成了LMA陶瓷,对其LMA热障涂层进行了激光重熔处理研究[36,37]。采用固相法制备了可应用于大气等离子喷涂的镁基六铝酸镧喷涂粉末,在 1.5其他热障涂层陶瓷材料 除上述已成体系的热障涂层陶瓷材料外,还开发了其他具有热障涂层应用前景的陶瓷材料。钇铝石榴石(Y3Al5012,简称YAG)也是一种良好的热障涂层材料,属石榴石结构,其从室温至熔点( 2 5类热障涂层陶瓷材料的研究展望 氧化物稳定的ZrO2因有限的高温服役能力而无法满足新一代涡轮发动机的需要。随着对钙钛矿结构的AB03陶瓷、焦绿石或萤石结构的A2B207陶瓷、磁铁铅矿结构的MMeAL11019陶瓷及其他先进陶瓷材料研究的深入,这些新型的热障材料将有可能替代氧化物稳定的Zr02应用于热障涂层系统中并带动高温部件系统一次新的飞跃。然而,目前存在的问题还很多,如新型热障涂层陶瓷材料研究不够成熟、其与金属粘结层及金属基体的匹配问题尚无充分的研究数据等。因此,大量的相关研究亟待进行,其重点有以下几方面: (1)对于氧化物稳定的Zr02,粉体的制备技术和理论研究已较成熟,今后主要是对涂层制备工艺的优化以及涂层结构设计等的创新研究; (2)探索新型热障涂层陶瓷材料高纯度粉体的最佳制备工艺,研究各新型材料的热导率、热膨胀系数等随温度的变化规律,优化对应材料的涂层制备技术,以获得高性能的新型热障涂层; (3)根据新型热障涂层陶瓷材料与氧化物稳定Zr02材料的热物理性能,开展双层陶瓷层、多层陶瓷层或者设计梯度涂层结构的研究,减少涂层系统在高温下的热失配,提高涂层服役寿命; (4)系统研究不同新型热障涂层陶瓷材料与金属粘结层的结合问题及新型陶瓷热障涂层高温工况下有别于传统YSZ涂层的失效行为; (5)采用高能束表面处理技术(如激光重熔等)对新型热障涂层进行表面修饰,以优化涂层的组织结构,提高涂层高温性能; (6)结合计算机软件对新型陶瓷热障涂层隔热性能、应力状态、热循环寿命、失效机理等进行模拟计算,推动新型热障涂层陶瓷材料的实际应用。 [参考文献] [1]Perepezko J H.The Hotter the Engine,the Better[J]. 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