The Effects of Laser Shock Peening on Fatigue Life in Ni-Based Superalloy

Abstract

The goal of this work was to determine effects of laser shock peening (LSP) on the fatigue life of the nickel-based superalloy, as well as the mechanism including the residual stress-depth profile (both depth of compression and magnitude) and the microstructure. The vibration fatigue performance of the standard test coupons made by Ni-based superalloy K417 with and without laser shock peening is researched. The residual stress distribution and microscopic structure after LSP are tested and analyzed by X-ray diffraction, SEM and TEM. The results indicated that the compress residual stress is up to 1.0mm in the test coupons after LSP, and the maximum residual compressive stress is about 660MPa under the surface. At the same time, the high pressure shock wave caused by laser propagate into the material which formed high density dislocation in the surface of the samples, and the γ' is divided leading to increase the sub-grain. Because of the deep residual compressive stress, high density dislocation and much more sub-grains, the vibration fatigue strength is improved about 180MPa by LSP. It is very instructive in the structure design and applying LSP to Ni-based superalloy.

Effects of laser peening on fretting wear behaviour of alloy 718 fretted against two different counterbody materials

“…Laser peening has been shown to improve hardness and fatigue strength in a number of metallic materials including nickel based superalloys. [19][20][21][22] Laser peening does not change the surface finish much, which is more important for the improvement of fatigue properties. 23 The studies on laser peened nickel-based superalloys either focus on improvement of the fatigue resistance or thermal stability of the induced compressive residual stress.…”