Ni−Al−Co−Cr−B体系TLP连接的扩散动力学及金属间化合物溶解机理研究

The welding joint of Ni-based single crystal superalloy is the key point to restrict the service performance and service life of aero-engine turbine blades. The brittle intermetallics are often observed in the joints bonded by transitional liquid phase (TLP), which seriously affects the mechanical properties of superalloys. The dissolution mechanism of intermetallics in the process of solid phase homogenization of TLP bonding should be revealed, which is beneficial to the fundamental control of intermetallic compounds. Therefore, this project will choose Ni-Al-Co-Cr-B system as the research object. The following studies will be carried out: (1) the diffusion coefficient matrix of Ni-Al-Co-Cr-B alloy will be measured in high throughput by combining the multi-element diffusion joint technique and numerical regression method, and then the atomic mobility database of the system will be obtained. (2) Based on thermal and kinetic database, the diffusion path and component distribution of each element in the process of solid phase homogenization of TLP bonding will be simulated by DICTRA software, and the diffusion mechanism of element will be clarified. (3) The dissolution rate and influencing factors of all kinds of intermetallics in solid phase homogenization will be studied. The dissolution mechanism of intermetallics will be revealed by theoretical simulation and experimental results. The completion of this project will provide guidance for the design of interlayer alloy of TLP bonding and the optimization of bonding process.

镍基单晶高温合金焊接接头是制约航空发动机涡轮叶片服役性能和使用寿命的关键点，采用过渡液相（TLP）连接的镍基单晶高温合金接头处容易出现脆性金属间化合物残留的问题，严重影响高温合金的力学性能。揭示TLP连接固相均匀化过程中金属间化合物的溶解机制，有利于从根本上控制金属间化合物。因此，本项目拟选择Ni−Al−Co−Cr−B体系为研究对象，开展如下研究：（1）结合多元扩散节技术和数值回归方法高通量测定Ni−Al−Co−Cr−B合金的互扩散系数矩阵，进而获取该体系的原子移动性数据库；（2）基于热、动力学数据库，利用DICTRA软件模拟TLP连接固相均匀化过程中各元素的扩散路径和成分分布，阐明元素扩散机制；（3）研究固相均匀化阶段各类金属间化合物的溶解速率及影响因素，结合理论模拟和实验结果，揭示金属间化合物的溶解机理。本项目的完成将为镍基单晶高温合金TLP连接中间层合金设计和连接工艺的优化提供指导。

本项目针对镍基单晶高温合金接头处容易出现脆性金属间化合物残留而引起高温合金的力学性能下降的问题，提出选择Ni−Al−Co−Cr体系为研究对象，开展互扩散研究，并探索高熵合金作为镍基合金中间层的可行性。本项目重要研究成果如下：1）结合多元扩散节技术和数值回归方法高通量测定了γ和γ’相Ni−Al−Co−Cr合金的互扩散系数矩阵，并直接从成分距离曲线获取了该体系的原子移动性数据库，探讨了合金元素、温度、物相对于扩散系数的影响；2）选用Co-Cr-Fe-Ni高熵合金作为中间层合金，研究了其与Ni−Al−Co−Cr合金的相互扩散行为，Co-Cr-Fe-Ni高熵合金与γNi−Al−Co−Cr合金扩散后形成了固溶体，并且高熵加速了Al的扩散，减缓了Co的扩散；3）探索了Ni−Al−Co−Cr合金分别与低熵、中熵和高熵合金的扩散行为，揭示了熵、合金元素对互扩散系数的影响机制，阐明了元素的扩散机制。本研究将为镍基单晶高温合金焊接中间层合金的设计和连接工艺的优化提供理论和实践指导。