冷挤压强化对GH4169合金孔结构室温低循环疲劳寿命影响

对GH4169合金中心孔板材试样进行冷挤压强化,测试了挤压前后GH4169中心孔板材试样在663 MPa/20℃条件下的低循环疲劳寿命;分别采用扫描电镜、X射线衍射残余应力仪、表面轮廓仪分析了疲劳断口、疲劳过程中残余应力场的演化以及表面形貌。结果表明:冷挤压强化后孔结构的疲劳寿命提高为原始试样的2.6倍。冷挤压强化对孔壁的强化效果使得冷挤压试样疲劳源萌生于倒角处单源,而原始试样萌生于孔壁多源。经过50000周次疲劳实验,冷挤压强化残余压应力有所松弛,但进口端与出口端的表面残余应力分别保持了55%和75%。冷挤压后孔壁表面粗糙度R_a由0.354μm减小到0.297μm。

Effect of cold expansion on room-temperature low cycle fatigue life of GH4169 superalloy with hole structure

The fatigue life of GH4169 superalloy plate with central hole was tested at 663 MPa/20 ℃ before and after cold expansion(CE). The fatigue fractures, the evolution of residual stress fields and surface morphology were respectively analyzed by scanning electron microscope, X-ray diffraction residual stress tester and surface profilometer. The results show that CE increases the fatigue life with the hole structure to 2.6 times compared with as-received. As the result of hole wall surface strengthening by CE, the fatigue source of CE specimens is single originated from chamfering, while the original ones are multi-source and sprouted at the hole wall. The CE surface residual stresses relax during 50000 cycles fatigue process, and however, about 55% and 75% compressive residual stresses are still retained at the inlet and outlet ends respectively. Moreover, CE reduces the surface roughness of the hole wall from Ra 0.354 μm to Ra 0.297 μm.