ZrB2-SiC基超高温陶瓷复合涂层的制备及机理研究

Faced with extremely complex high-temperature environments, high temperature protective properties of high-temperature structural ceramics are important problem for many industrial fields. Currently, the research on high-temperature protective properties of high temperature ceramic mostly depends on the improvement and optimization of materials itself, but it has some limitations. Preparation of ultra-high temperature coating on the surface of ceramic brings a new idea for improving high temperature protective properties. In this study, ZrB2-SiC matrix coating on the surface of ZrC ultra high temperature composite ceramic is prepared by reactive plasma spray and laser technique using Zr-Si-B4C SHS system. During reactive plasma spraying, ZrB2-SiC matrix coating with good interface bonding can be realized by good chemical compatibility between ZrB2-SiC droplet and ZrC and process optimization of spraying. Reaction formation mechanism of ZrB2 and SiC during spraying is studied, and fusion process and interface bonding mechanism between coating and substrate is analyzed. Favorable microstructure and densification of the coating can be achieved by adjusting laser parameters. The relation between laser remelting parameters and microstructure of coating is investigated, and the response behavior between coating and laser is revealed. Based on the project, high-temperature applications of ZrC will be promoted.

面对极其复杂的高温环境，使高温结构陶瓷保持良好的高温防护性能是众多工业领域亟待解决的重要问题。目前针对高温陶瓷高温防护性能问题的研究大多依赖于材料的改进与优化，存在一定的局限性。在陶瓷表面制备超高温涂层进行表面改性，为提高其高温防护性能带来了全新的思路。本项目选用Zr-Si-B4C的SHS体系，采用反应等离子喷涂和激光技术，在ZrC超高温复相陶瓷表面制备ZrB2-SiC基超高温复合涂层。反应等离子喷涂时，利用喷涂产物ZrB2-SiC熔滴和ZrC良好的化学相容性，并通过喷涂工艺优化，制备出界面结合良好的ZrB2-SiC基涂层，研究喷涂过程中ZrB2、SiC反应形成机理，分析涂层与基体间熔合过程和界面结合机制。通过调控激光参数，获得有利的涂层组织结构，实现涂层的致密化，研究激光重熔参数与涂层组织结构的联系，揭示涂层与激光间的响应行为和规律。本项目研究成果为推动ZrC在高温领域的应用奠定基础。

在极其复杂的高温环境下，结构陶瓷存在严重的氧化问题。本项目突破常规的材料改进与优化手段，采用等离子喷涂技术结合团聚粉末制备方法以及激光技术在ZrC-SiC结构陶瓷表面成功地制备了ZrB2-SiC-ZrC超高温陶瓷涂层，实现了陶瓷材料的表面改性，为解决结构陶瓷的高温防护性能提供了全新的思路。本项目从ZrC陶瓷的本质属性出发，基于热膨胀系数相似原则，选用ZrB2-SiC-ZrC超高温陶瓷作为高温防护涂层，通过DSC分析与等离子淬熄试验结合起来，揭示了团聚颗粒经ZrH1.66、Zr3O、ZrC、ZrB2、Zr2Si、ZrSi、ZrB2、SiC和ZrC物质转变合成ZrB2、SiC和ZrC的反应过程与机理。采用ZrB2-SiC-ZrC材料预先反应热压烧结合成再喷涂和ZrB2-SiC-ZrC复合涂层的反应等离子喷涂两种制备方法，通过喷涂电流、喷涂距离和送粉气流量等特征参数，获得了等离子喷涂ZrB2-SiC-ZrC涂层的组织变化和界面结合规律。等离子射流中粉末不同的熔化能量、撞击速度和停留时间使喷涂涂层表现出纳米或无定形结构的平滑盘状组织和粗糙的堆积组织。涂层与基体形成机械结合。利用激光重熔技术，调整激光功率、激光光斑直径、扫描速度等工艺参数，研究了重熔处理后涂层微观组织的变化特征和界面结合，实现了对等离子喷涂ZrB2-SiC-ZrC涂层的微观组织控制。不同的温度条件、不同的冷却速度使激光重熔涂层具有明显的区域特征，包含细晶粒区，枝状组织区，喷涂态组织区以及边缘氧化区。重熔层与基体界面结合良好。