High-temperature fatigue cracking mechanism and microstructure evolution of aero-engine K4169 superalloy in service process  

航空发动机用K4169高温合金的高温疲劳开裂机制及其在服役过程中的显微组织演变

作　　者：Song-jun WANG Jian-jun HE Zhi-hui GONG Wei-ping LI Jun-gang YANG Ya-jun SHAO Yu-hui CAI Yue-xin DU Cheng-wei YANG 王嵩钧;何建军;龚志辉;李伟平;杨俊刚;邵雅君;蔡宇晖;杜悦欣;杨铖伟(长沙理工大学能源与动力工程学院,长沙410114;湖南大学机械与运载工程学院,长沙410082;中国航发南方工业有限公司,株洲412002)

机构地区：[1]School of Energy and Power Engineering,Changsha University of Science and Technology,Changsha 410114,China [2]College of Mechanical and Vehicle Engineering,Hunan University,Changsha 410082,China [3]AECC South Industry Co.,Ltd.,Zhuzhou 412002,China

出　　处：《Transactions of Nonferrous Metals Society of China》2025年第2期499-510,共12页中国有色金属学报(英文版)

基　　金：National Natural Science Foundation of China (No. 51975200);Hunan Provincial Innovation Foundation for Postgraduate,China (No. QL20220201)。

摘　　要：By using fatigue crack propagation testing and microstructural characterization,the crack fracture and propagation mechanisms of K4169 superalloy under various loads were investigated.The results demonstrate that the grain sizes of K4169 superalloy significantly increase,and the precipitation of the needle-likeδphase and the Laves phase is observed.Voids and microcracks form at location of Laves phase enrichment,creating conditions for crack propagation.By the a−N(a is the crack length,and N is the number of cycles)relationship curve,the change in the fatigue crack growth rate with the increasing number of cycles progresses through three separate stages.The fracture process of K4169 superalloy under low-stress cyclic loading(3 kN)exhibits the ductile fracture.Subsequently,the fracture process starts to change from the ductile fracture to the brittle fracture as the stress increases to 4.5 kN.In the microstructures of fractures in both stress states,intergranular propagation is the mechanism responsible for crack propagation.Moreover,the Laves phase exists near the fracture crack,which is in line with the post-service structural phenomenon.通过疲劳裂纹扩展试验及显微组织表征研究了K4169高温合金在不同载荷下的裂纹断裂和裂纹扩展机理。研究结果表明,K4169高温合金在服役后晶粒尺寸明显增大,存在针状δ相和Laves相析出现象,在Laves相富集处萌生出孔洞与微裂纹,为裂纹的扩展创造了条件。a-N (a为裂纹长度,N为循环次数)关系曲线显示,随着循环次数的增加,疲劳裂纹扩展率的变化经历了3个不同的阶段。在低应力循环载荷(3 kN)下,K4169高温合金的断裂机制为韧性断裂。当应力增加到4.5 kN时,其断裂机制开始从韧性断裂转变为脆性断裂。在这两种应力状态下,显微组织中的裂纹扩展机制均为沿晶裂纹扩展,同时还发现在断裂裂纹处存在Laves相,与服役后合金的组织现象相吻合。

关 键 词：K4169 superalloy high-temperature fatigue MICROSTRUCTURE crack propagation AERO-ENGINE 

分 类 号：V231.95[航空宇航科学与技术—航空宇航推进理论与工程] V252[一般工业技术—材料科学与工程] TG132.3[航空宇航科学与技术—航空宇航制造工程]