纳米复合多层涂层界面结构辐照效应研究

The development of protection coatings for the fuel assembly protection is the key technology for the safety of nuclear power plant. It also affects the development and broader application of nuclear actor. Nitrides nano-composite multilayered coatings, which possess thermal stability, excellent oxidation resistance, and irradiation resistance, are promising candidates for fuel assembly protection. However, researches on the irradiation damage mechanism are rare, especially the effects of multi-type interfaces on the irradiation behavior. This project will focus on following three issues in nano-composite multilayered coatings after irradiation to study the strengthening effects of multi-interfaces on the irradiation resistance. The three issues are the microstructure evolution, the radiation effects of the interfaces, and the degradation mechanism of mechanical properties. Firstly, CrN/TiSiN coatings with different fractions of each interface type will be synthesized and the ion irradiation experiment will be conducted to reveal the microstructure evolution. Secondly, the quantitative research of irradiation damage and mechanical property degradation in CrN/TiSiN coatings will be carried out to explore the influence rule of different interfaces on the irradiation toleration and the mechanism of irradiation damage. Finally, the atomic distribution around the interface will be observed before and after irradiation to reveal the intrinsic mechanism for effects of different interfaces on the mechanical properties degradation. The research results will provide scientific basis for the design of new radiation-resistance materials and the high temperature protection of metal fuel assembly.

燃料组件保护涂层开发是核电安全关键技术之一，影响核电系统开发与扩大应用。耐高温抗氧化氮化物纳米复合多层涂层具有优异抗辐照性能，是保护涂层备选材料，但其辐照损伤机制研究缺乏，特别是多类型界面辐照效应。本项目将聚焦纳米复合多层涂层辐照的三个基本问题：涂层结构损伤形式、不同界面辐照效应和涂层辐照性能退化机理，以认识纳米复合多层涂层中多类型界面抗辐照强化内在机理。首先，制备具有多类型界面的TiSiN/CrN纳米晶复合多层涂层，调制各种界面比例，开展不同温度与剂量辐照实验，表征涂层辐照微观结构演化；其次，定量研究不同界面比例涂层结构损伤与力学性能退化，揭示不同类型界面对抗辐照性能影响规律以及辐照后力学性能退化，并验证规律的高温适用性；最后，获取辐照损伤前后原子在界面附近分布的高分辨像，揭示多类型界面对涂层抗辐照性能影响的内在机制。研究结果可为新型抗辐照材料设计和金属燃料组件高温保护提供科学依据。

铅冷快堆是第四代安全堆型之一，其发展主要制约因素之一为堆内核心零部件结构材料辐照失效及其防护，氮化物陶瓷特别是纳米复合多层涂层由于其出色化学惰性、耐磨性以及抗辐照性能，被认为是堆内结构材料潜在防护材料之一。以CrN/TiSiN纳米复合多层涂层为研究对象，探究其多类型界面堆内复杂环境下的演化与作用机制，具有重要科学意义。采用多弧离子技术优化制备CrN/TiSiN纳米复合多层涂层，通过调控Si含量与偏压，实现涂层纳米晶界面、纳米晶/非晶界面与层界面密度调节，在界面强化作用下，涂层硬度高达29GPa，涂层划痕下结合力超过110 N；采用He+离子辐照实验对不同CrN/TiSiN涂层进行辐照，其主要损伤形式为表层CrN非晶化与层界面中氦泡聚集，由此导致涂层分别出现软化与硬化现象，多层涂层相对于单层涂层具有较小非晶层与力学性能变化，晶粒细化带来纳米晶界面与纳米晶/非晶界面密度升高，涂层辐照损伤减小，可见，纳米晶界面、纳米晶/非晶界面与层界面对于均能通过促进辐照缺陷湮灭融合，减缓辐照损伤程度；但界面强化效应存在临界值，当纳米晶晶粒尺寸小于9 nm后，涂层抗辐照性能下降；此外，项目发现，多层涂层外延生长所形成共格界面能有效提升He+扩散，减缓氦泡聚集现象；多类型界面不但能有效增加涂层力学性能与抗辐照性能，同时有利于提升涂层抗腐蚀性能。铅铋腐蚀研究显示，细化晶粒与多层复合能有效提升涂层抗腐蚀性能。辐照后涂层电化学腐蚀实验表明，多层涂层相对单层涂层具有更大的电化学电阻值，更小腐蚀电流，同时细化晶粒也能有效提升涂层抗腐蚀性能； 辐照产生的无序金属离子与高能态缺陷能促进涂层钝化，提升涂层抗腐蚀性能。辐照研究结果揭示多类型界面在辐照与腐蚀条件下的作用，深化了人们对纳米复合多层材料的辐照、腐蚀效应的理解，对第四代核电结构材料防护的发展具有重要意义。