镍基单晶高温合金的激光冲击强化模型及中温疲劳性能调控机理研究

Ni-based single crystal superalloy for aero engine turbine blade tenon structure usually works under the condition of medium temperature, and it is very easy to fatigue ineffective due to high centrifugal loads. Because of the relaxation of residual stress and instability of microstructure induced by thermal loads, traditional surface strengthening technologies have been unable to meet the extension requirement of fatigue life. The present project aims to establish a laser shock processing model of anisotropic materials and provide a new method of high thermal stability for controlling the medium temperature fatigue properties of Ni-based single crystal superalloy. With focus on the modification of surface integrity caused by laser shock processing, the coupling mechanism of laser shock induced dynamic plastic deformation and microstructure evolution will be investigated and the effect of cold hardening rate on residual stress and microstructure suffered from thermal loads will be uncovered. The laser shock processing model of single crystal alloy can be established and the effect of optimized laser shock processing technology on high-cycle fatigue behavior at elevated temperature will be expounded. This project will reveal the strengthening mechanism of single crystal alloy and improve the application theory system of laser shock processing, providing the research foundation for developing advanced surface strengthening technology for aero engine hot end component materials.

航空发动机涡轮叶片榫头结构的镍基单晶高温合金材料在中温工况承受超高的离心载荷且极易诱发高周疲劳损伤，然而热载荷引发的应力松弛与组织失稳等问题导致传统表面强化技术无法满足疲劳延寿需求。本项目通过建立各向异性材料的激光冲击强化模型，提出调控镍基单晶高温合金中温疲劳性能的高热稳定性激光冲击新方法。对激光冲击强化效果在各向异性单晶合金不同表面完整性参量上的体现进行表征，探讨激光冲击诱导动态塑性变形与微观组织演变的耦合机制，深入研究冷作硬化率对热载荷作用下残余应力与显微组织的影响规律；明确不同晶体学取向的特定强化工艺并建立单晶合金的激光冲击强化模型，阐明激光冲击处理后镍基单晶高温合金材料的中温高周疲劳断裂机制与性能调控原理。本项目将揭示激光冲击对于单晶合金的强化机理，完善激光冲击强化应用理论体系，为发展面向航空发动机热端部件材料的先进表面强化技术奠定研究基础。

航空构件的长寿命与高可靠性制造是直接影响我国国防事业发展的“卡脖子”瓶颈之一，美国在十年前便将激光冲击表面处理技术列为四代机发动机延寿关键技术，而我国脉冲激光强化的相关探索仅停留在实验室水平。美国公开了少量针对叶片等零部件进行激光冲击处理的专利，但具体应用理论与方法仍为绝密技术资料。本项目提出调控镍基高温合金服役性能的激光冲击新工艺与新方法，对激光冲击强化效果在高温合金表面形貌、残余应力等不同表面完整性参量上的体现进行了表征，探讨了激光冲击诱导动态塑性变形与微观组织演变的耦合机制，阐明了激光冲击处理后高温合金材料的性能调控原理。本项目针对航空曲面构件激光冲击处理的应用障碍，开展了曲面结构“形-性”协同激光表面加工的理论和方法研究。具体探索了曲面构件不等强度/高强度激光表面强化的新方法。基于激光参数及吸收层等调控等离子体冲击强度的物理机制，形成了“不等强度”与“高强度”激光冲击新技术。本项目成果揭示了激光冲击对于高温合金的强化机理，提高了曲面构件激光表面加工的工业应用水平，为发展面向航空发动机热端部件材料及其实际构件的先进表面强化技术奠定了研究基础。