高熔点强化元素弥散载入对粉末高温合金与单晶高温合金钎焊接头的强化机理研究

An advanced technology for joining P/M superalloy and single crystal superalloy is urgently needed for fabricating a high-strength bladed disk (or blisk) in the new aircraft engine and the joints must meet the use of harsh conditions such as long time, high temperature and high pressure service requirements. Due to the special structure of blisk, there is no mature method that can achieve its preparation. In several promising joining methods, brazing is one of the most potential to achieve. However, if the conventional brazing fillers and processing parameters are used, excessive low melting point compounds will be formed in the dissimilar superalloy joint, which greatly deteriorates the joint property. According to the above mentioned issues, high melting point strengthening elements are added dispersedly in the P/M superalloy/single crystal superalloy joint and their contents are adjusted to achieve the goal of increasing the joint strength. Moreover, combination of brazing and heat treatment after brazing process will make the fully diffusion of the melting point depressant element B, and further improves the joint property. Therefore, the following points are the main interests: composition design of the new NiCoCr-B brazing fillers; addition method of high melting point strengthening elements; optimization of brazing and post-brazing heat treatment variables; interface metallurgy behavior and joint strengthen mechanism. In summary, under the premise of that the brazing temperature is lower than the solution temperatures of the two parent alloys, high melting point strengthening elements are added to the joint and reach the role of increasing the strength and toughness. The research will not only be useful in putting the P/M superalloy and single crystal superalloy joints into the engineering application in aviation area, but also be theoretically valuable in joining those dissimilar materials in a wide range.

新型航空发动机整体叶盘研制过程中，需将单晶叶片和粉末涡轮盘进行连接，接头需满足长时、高温、高压等苛刻环境下使用要求。由于整体叶盘结构特殊，目前尚无成熟焊接方法能够实现其制备，在现有几种有希望连接该结构的方法中，钎焊是最有潜力实现的。但是，常规钎料及工艺获得的接头中，常因存在过多的较低熔点物相而削弱了接头性能。本项目针对上述需求，从钎料成分设计入手，在接头中弥散载入高熔点强化元素并调控其含量来达到提高接头强度目的；同时，配合钎焊+焊后扩散处理组合工艺使得接头中降熔元素B充分扩散，进一步改善接头性能。研究内容包括：NiCoCr-B系钎料成分设计、高熔点强化元素载入方法研究、钎焊组合工艺优化、界面冶金行为及接头强化机理研究。本项目在保证钎焊温度低于母材固溶处理温度的前提下，将高熔点强化元素均匀添加入接头中，达到接头增强增韧的作用，在工艺方法上实现创新，研究结果为整体叶盘上的实际应用提供技术储备。

新型航空发动机整体叶盘研制过程中，需将单晶叶片和粉末涡轮盘进行连接，接头需满足长时、高温、高压等苛刻环境下的使用要求。由于整体叶盘结构特殊，目前尚无成熟焊接方法能够实现其制备，在现有几种有希望连接该结构的方法中，钎焊是最有潜力实现的。但是，常规钎料及工艺获得的接头中，常因存在过多的较低熔点物相而削弱了接头性能。本项目针对上述需求，完成了NiCoCr-B系钎料的成分设计、高熔点强化元素W、Mo、Ta、Re等强化元素载入方法研究、钎焊+焊后热处理工艺优化研究、界面冶金行为及接头强化机理等研究内容。在本项目研究技术上，还通过对钎焊接头施加小压力方法实现了不对接头进行焊后扩散热处理就能获得高性能水平接头新焊接工艺，并揭示了接头连接机理，为整体叶盘的制备提供了新的研究思路。通过本项目的研究，获得的FGH96/DD6钎焊接头室温强度达到1187MPa，已经达到了与DD6母材室温强度相同水平；750℃强度达到851MPa，达到了DD6母材指标强度的85%左右。另外，还探索研究了这两种材料的局部加热扩散焊方法，获得了高性能水平接头，接头750℃性能达到了母材的90%以上，为整体叶片的研制提供了新的技术思路。此外，建立了高熔点强化元素扩散及分布于接头性能关系的模型，钎料熔化—凝固过程物理模型等，揭示了FGH96/DD6接头界面冶金行为及强化机理，为后续完善焊接工艺提供了技术依据。