镍基高温合金单晶叶片中“马赛克”缺陷的形成机理及控制研究

The performance of Ni-based single crystal superalloy blades, utilized as the hot-end part of aero-engines, is one of the key factors to determine the engines’ fuel consumption rate and the thrust-weight ratio. The research on the forming mechanism and control method of metallurgical defects during the directional solidification of single crystal blades is of great significance for improving the new-generation aero-engines’ properties of our country. In this project, a novel metallurgical defect - "Mosaic" defect forming during the directional solidification of Ni-based single crystal superalloy blades is investigated. Through numerical simulation and visualization experiments , the thermodynamic and dynamic reasons for the formation of the "Mosaic" defect and its affecting factors are studied. The theoretical hypotheses of "Remelting Mechanism" and "Microscopic Stress Induction Mechanism" is verified. The formation mechanism model of the "Mosaic" defect is constructed. The influence law of the Re-addition on the "Mosaic" defect formation is achieved. The "Mosaics" defects’ prone with the size of the shroud of single crystal blades is identified. The effect law of the directional solidification parameters on the "Mosaic" defect is revealed. Based on these research results, a technique to control and eliminate the "Mosaic" defects is proposed. This project can enrich the theoretical system of metallurgical defects occurring in single crystal blades, and provide theoretical and technical basis for preparing high-performance single crystal blades and improving the performance of our country’s new-generation aero-engines.

镍基高温合金单晶叶片作为航空发动机中的热端部件，其性能是决定发动机耗油率和推重比的关键因素之一，研究定向凝固过程中单晶叶片冶金缺陷的形成机理和控制方法对提高我国先进航空发动机的性能具有重要的意义。本项目对定向凝固过程镍基高温合金单晶叶片中的一种新型冶金缺陷-“马赛克”缺陷展开研究。通过数值模拟和可视化实验研究“马赛克”缺陷形成的热力学和动力学原因以及影响“马赛克”缺陷产生的因素。验证“重熔机制”和“微观应力诱导机制”的理论假设；构建“马赛克”缺陷形成的机理模型；获得Re元素添加对“马赛克”缺陷形成的影响规律；查清“马赛克”缺陷的形成倾向随单晶叶片缘板尺寸的变化规律；揭示定向凝固参数对“马赛克”缺陷的影响规律；结合相关研究结果，提出控制和消除“马赛克”缺陷的工艺方法。本项目可丰富单晶叶片冶金缺陷的理论体系，为我国高性能单晶叶片的制备和先进航空发动机性能的提高提供理论和技术基础。

单晶涡轮叶片是先进航空发动机的核心热端部件，其质量和成品率低的主要诱因之一是晶粒缺陷问题。研究定向凝固过程中引发晶粒缺陷形成的因素、机理和控制方法是提高其质量和成品率的关键基础问题。本项目针对定向凝固过程中镍基高温合金单晶叶片中的一种新型晶粒缺陷-马赛克缺陷展开系统研究。明确了马赛克缺陷形成的重熔机理，并构建了其机理模型；揭示了Re元素添加对马赛克缺陷形成的影响规律和内在机理；查清了缘板尺寸变化对马赛克缺陷形成的影响规律和机理；探明了抽拉速率对马赛克缺陷的影响规律和内在机理。基于研究结果，提出了控制和消除马赛克缺陷的工艺方法。培养博士研究生3名、硕士研究生1名；在《Materials & Design》《Journal of Alloys and Compounds》等高水平期刊发表研究论文7篇；参加中国高温合金年会等高温合金领域知名会议6次；申请发明专利4项；实现了研究成果在单晶涡轮叶片制备企业的应用，有效指导了单晶叶片工业生产中马赛克缺陷的消除。