Effects of laser shock processing on fatigue property of GH742 Ni-based superalloy

Laser shock processing/peening (LSP) was carried out on a Ni-based superalloy GH742. The effect of LSP on fatigue property of the alloy was examined by axial fatigue and vibration fatigue tests, respectively. The residual stress in the specimens before and after LSP treatment was measured on a moiré interferometry system and fatigue fracture surface was observed by SEM. Comparing with the non LSP treated specimens, the results show that LSP can increase axial fatigue life of Ni-based superalloy (GH742) to about 3.6 times, and the vibration fatigue life to 2.4 times. The depth of compressive residual stress is up to 1.0 mm and the maximum value of compressive residual stress reaches -1180 MPa for the specimen after LSP treatment. It is believed that the high compressive residual stress formed in the specimen after LSP is responsible for the improvement of fatigue property of the Gh742 alloy.