铅基反应堆泵叶轮用玻璃陶瓷梯度涂层中热应力的形成机制

The lead-based reactor was selected by the IAEA as one candidate for the 4th generation nuclear power reactors due to its good neutronics and heat transfer characteristics. Glass ceramics have high temperature stability, excellent corrosion resistance and wear resistance, and have great application potential for the coating materials of the pump impeller. However, the single glass-ceramic coating has poor thermal expansion coefficient matching with the metal matrix, which causes the coating to fall off. It is one of the key factors restricting the application of the glass-ceramic coating. This project intends to use the design idea of gradient glass-ceramic coating to alleviate the thermal stress between the glass ceramic coating and the pump impeller. The gradient inner layer is composed of Li2O-ZnO-Al2O3-SiO2 glass ceramic whose thermal expansion matches well with the metal matrix. The gradient outer layer is composed of CaO-MgO-Al2O3-SiO2 glass ceramic with excellent erosion resistance in liquid lead bismuth alloy. And the middle layers consists of gradient components of two different glass ceramics. Through the combination of thermal shock test, fusion high-energy neutron radiography, microstructure analysis and finite element simulation, the distribution of cracks in the gradients glass-ceramic will be systematically studied, and the influence of crystal phase content on the stress distribution in gradient glass-ceramic coatings will also be discussed. According to explain the formation mechanism and control strategy of thermal stress in gradient glass-ceramic coating, it will provide theoretical guidance for the design of glass-ceramic coating used on the pump impeller of lead-based reactor.

铅基反应堆因具有良好的中子学和传热特性被国际原子能机构选作第Ⅳ代核电反应堆候选方案。玻璃陶瓷具有高温稳定性好、抗腐蚀性和耐磨性优良等特点，在铅基堆泵叶轮涂层材料领域极具应用潜力。而单一的玻璃陶瓷涂层与金属基体的热膨胀系数匹配性差，导致涂层脱落失效是制约玻璃陶瓷涂层应用的关键问题之一。本项目拟采用玻璃陶瓷梯度涂层的思路缓解玻璃陶瓷涂层与泵叶轮的热应力。梯度内层由热膨胀系数和金属匹配的Li2O-ZnO-Al2O3-SiO2玻璃陶瓷构成，梯度外层由抗铅铋冲刷腐蚀性能优异的CaO-MgO-Al2O3-SiO2玻璃陶瓷构成，中间层由两种不同组分玻璃陶瓷梯度构成。通过热震实验、高能中子照相技术、微观组织分析和有限元模拟相结合的方法，系统研究玻璃陶瓷梯度涂层中的裂纹分布规律，探讨析晶相含量对涂层中应力分布的影响规律，阐明玻璃陶瓷梯度涂层中热应力的形成机制，为铅基堆泵叶轮用玻璃陶瓷涂层的研发提供理论指导。

铅基反应堆因具有良好的中子学和传热特性被国际原子能机构选作第Ⅳ代核电反应堆候选方案。作为核反应堆的“心脏”，核主泵服役条件苛刻，开发与泵叶轮金属材料基体匹配性好、结合力强，并抗铅铋腐蚀的涂层具有重要的科学意义。本项目开展了铅基反应堆泵叶轮用玻璃陶瓷梯度涂层制备及热应力形成机制研究，主要结果如下：（1）完成单层CaO-MgO-Al2O3-SiO2（CMAS）玻璃陶瓷涂层的制备，腐蚀实验结果表明CMAS具有较好的抗铅铋腐蚀性能；（2）制备了Li2O-ZnO -SiO2 /CaO-MgO-Al2O3-SiO2（LZS/CMAS）玻璃陶瓷梯度涂层，相较于单层CMAS涂层，梯度涂层抗热震性能大为提高，热震后涂层内析晶相含量增加；（3）对LZS和CMAS玻璃陶瓷的热物性参数进行了测量，析晶相含量的增加会使玻璃陶瓷的弹性模量、热导率、热膨胀系数有一定程度的升高，而泊松比和比热容出现一定程度的下降；（4）对LZS/CMAS玻璃陶瓷梯度涂层开展了热应力模拟分析，结果表明涂层的成分分布指数、梯度层数、层厚以及析晶相含量变化均会对梯度涂层内热应力的形成产生重要的影响，尤其是析晶相含量的增加会在一定程度上缓解涂层与基体之间的热应力。本项目研究成果可为我国铅基反应堆核主泵部件涂层材料研发提供技术支持和理论依据。