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

Abstract

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.

Keywords

• cold expansion
• gh4169 superalloy
• room-temperature fatigue life
• residual stress