Ni基铸造高温合金焊接热影响区应变时效裂纹形成机制及其原位表征

镍基铸造高温合金具有优异的高温综合性能，被广泛用于航空发动机热端承力部件的制造。热端部件在制造及修复过程中难以避免需要进行焊接。但镍基铸造高温合金焊接性差，特别是采用熔焊方法时，在热影响区容易形成包括应变时效裂纹在内的多种焊接裂纹。为了揭示焊接热影响区应变时效裂纹的形成机制，进而提出有效的控制方法。项目拟采用焊接工艺实验、数值模拟和物理模拟技术相结合的方法对镍基铸造高温合金焊接热影响区敏感组织的来源及其在焊后热处理过程中的组织转变和应力应变演化行为进行研究，揭示应变时效裂纹形成机制；再采用同步辐射X射线成像技术对接头热影响区进行原位热处理观察，表征应变时效裂纹在焊后热处理过程中的萌生与扩展行为，进而优化焊后热处理工艺，达到控制裂纹形成的目的。为航空发动机热端承力部件的高质量焊接制造和修复提供技术支撑。

Nickel-based casting superalloys have excellent high-temperature comprehensive properties and are widely used to manufacture hot-end load-bearing components in aeroengines. During manufacturing and repairing of the hot-end components, welding is an inevitable processing. However, the fusion weldability of nickel-based casting superalloys is poor, a variety of welding defects including strain ageing cracking are easily formed in the heat-affected zone. In order to reveal the strain ageing cracking formation mechanism in the heat-affected zone, and then to propose an effective method to control the cracking. Welding experiment, numerical simulation and physical simulation technologies are intended to employ in the project. The reason for strain ageing cracking sensitive microstructure formation in the heat-affected zone of nickel-based casting superalloy joints will be studied. And the strain ageing cracking sensitive microstructure transformation behavior, the stress and strain evolution behavior during post-weld heat treatment will be discussed. After that the strain ageing cracking formation mechanism will be revealed. The initiation and propagation behavior of strain ageing cracking in the joint heat-affected zone during post-weld heat treatment will be in situ characterized by using synchrotron radiation X-ray imaging technology. And then the post-weld heat treatment procedures will be optimized to control the strain ageing cracking formation. The object of the study is to provide technical support for the high-quality welding manufacturing and repair of the hot end load-bearing components in aero engines.