激光喷丸强化镍基合金的高温残余应力松弛模型及疲劳裂纹扩展特性

In this proposal, focus on the anti-fatigue manufacturing technology of the key hot end parts in mechanical engineering, investigation of residual stress relaxation behavior and fatigue crack growth properties subjected to laser peening on nickel-based alloys is carried out at elevated temperature. Microstructure evolution induced by laser peening and the effects on residual stress relaxation behavior at elevated temperature are studied, residual stress relaxation model subjected to laser peening and cyclic loading at the elevated temperature is established, and meanwhile, microstructure strengthening mechanism which improving high-temperature fatigue crack growth behavior is clarified. Numerical analysis platform among laser parameters, compressive residual stress and high-temperature fatigue crack growth is established, and numerical simulation of high-temperature fatigue crack growth behavior under compressive residual stress fields is performed, which can predict the stress intensity factor of crack tip, the fatigue crack growth rate as well as high temperature fatigue life subjected to laser peening. Laser peening and high temperature fatigue crack growth experiments are carried out, relational models between the released residual stress and stress intensity factor of crack tip as well as the fatigue crack growth rate are established. Finally, the evaluation on stability of residual stress and microstructure and standard for life extension technology can be obtained. The research can enrich and develop the basic theory of surface modification technologies, furthermore, promote applications of laser peening technology in the field of anti-fatigue manufacturing engineering.

本项目针对工程领域中关键热端部件的抗高温疲劳制造问题，以典型高温镍基合金为研究对象，开展激光喷丸强化后的高温残余应力松弛行为及其疲劳裂纹扩展特性研究。研究激光喷丸作用下材料微观组织的演变及其对高温残余应力释放行为的影响，建立激光喷丸诱导的残余压应力在高温循环载荷下的松弛模型，阐明改善高温疲劳裂纹扩展特性的微观组织强化机制；建立激光喷丸工艺参数-残余应力分布-高温疲劳裂纹扩展特性集成的数字化分析平台，进行残余压应力场下的高温疲劳裂纹扩展特性数值模拟，实现裂纹尖端应力强度因子、疲劳裂纹扩展速率和高温疲劳寿命的预测；开展激光喷丸强化及其高温疲劳裂纹扩展试验，建立松弛残余压应力与裂纹尖端应力强度因子、疲劳裂纹扩展速率的关系模型，获得应力强化和组织强化效应稳定性的评价方法及抗高温疲劳制造工艺准则。研究成果将丰富和发展表面改性延寿的基础理论，推动激光喷丸技术在抗疲劳制造工程领域的应用。

针对工程领域中关键热端部件的抗高温疲劳制造问题，以典型高温镍基合金IN718为研究对象，开展激光喷丸强化后的高温残余应力松弛行为及其疲劳裂纹扩展特性研究。（1）根据IN718镍基合金的析出强化机制，分析激光喷丸诱导的残余压应力在高温和循环载荷作用下的释放规律；建立高温过程中晶粒尺寸和位错密度的演变模型，从动态再结晶角度，通过分析析出相及位错密度的影响，探讨激光喷丸对IN718镍基合金高温疲劳特性的增益机制；（2）利用ABAQUS-MSC.Fatigue有限元软件编制高温疲劳性能数值分析模块，分析激光喷丸后单联中心孔拉伸试样孔周表层残余应力分布的奇异性，研究不同激光功率密度和服役温度下，试样在疲劳加载过程中的危险节点，探讨不同区域的疲劳损伤对于试样疲劳全寿命的影响程度，以此建立激光喷丸试样疲劳寿命估算模型；（3）开展典型试样激光喷丸强化试验、高温保持试验及常高温疲劳拉伸试验，研究激光喷丸IN718镍基合金在高温服役条件下的残余应力松弛行为和微观组织演变规律，探讨激光喷丸处理及高温服役条件对镍基合金表层塑性形变、残余压应力、表面纳米硬度、晶粒尺寸及位错结构的影响，揭示宏观应力松弛行为与微观组织演变之间的关系，探索喷丸前后试样中晶粒重排与疲劳特性的关系；（4）系统分析激光喷丸强化IN718合金在常温和高温疲劳拉伸过程中的疲劳特性，对疲劳拉伸试样疲劳源萌生区、疲劳裂纹扩展区以及裂纹瞬断区的微观形貌特征等进行定性及定量分析，阐述激光喷丸后合金典型疲劳微观特征在高温下的演变机理，探讨激光喷丸强化对IN718合金高温疲劳裂纹扩展抗力的增益机制。研究成果将丰富和发展表面改性延寿的基础理论，推动激光喷丸技术在抗疲劳制造工程领域的应用。研究发表学术论文16篇，其中SCI收录12篇，EI收录4篇，申请国家发明专利12 件，其中已获批授权11 件，协助培养博士研究生2名，硕士研究生3名。