Laser shock peening is considered to be one of the most effective means to improve the fatigue life of engine blades, which can improve the oxidation resistance, fatigue resistance and corrosion resistance of metal materials. Nickel-based single crystal superalloy is widely used in the manufacture of aeroengine and gas turbine blades because of its excellent high temperature strength, oxidation resistance and corrosion resistance. However, as engine blades work at high temperature, high pressure and high speed for a long time, the surface of the blades is prone to fatigue cracks, leading to high-cycle fatigue fracture of engine blades. The purpose of this work is to solve the problem of surface damage caused by nickel-based single crystal superalloy engine blades in use, and to explore the mechanism of laser shock peening of nickel-based single crystal superalloy SRR99. The samples of nickel-based single crystal superalloy were treated with one, two and three times shot peening respectively by 8 J high power short pulse laser. The spot size was 3 mm, the binding rate was 50% and the pulse width was 15 ns. The surface morphology and roughness, microhardness and residual stress of single crystal superalloy peened by laser shock were measured by white light interferometer, microhardness tester and X-ray analyzer. The effects of laser shock peening on surface morphology, roughness, microhardness and residual stress of nickel base single crystal superalloy were analyzed. The microstructure, dislocation structure and phase composition of the single crystal superalloy were observed by scanning electron microscope, transmission electron microscope and X-ray diffractometer. The surface microstructure and phase composition of the single crystal superalloy peened by laser shock were discussed, and the plastic deformation mechanism of the single crystal superalloy peened by laser shock was analyzed. After 1, 2, and 3 laser shocks, the surface of single crystal superalloy samples had serious plastic deformation. With the increase of the impact times, the pits on the surface of single crystal alloy were gradually deepened, and the surface roughness increased from 0.107 μm to 1.566, 1.868, 2.265 μm. The microhardness was increased by 15.3%, 25.8% and 32.1% respectively, and the surface residual compressive stress was increased to −790, −870, −917 MPa. After shot peening, a distorted layer was formed on the surface of the sample, and the area value and volume fraction of γ' phase increased. No phase transformation occurred, but the crystal lattice distortion occurred in the two phases, and the change of lattice constant and crystal plane spacing lead to the mismatch of the two phases. The higher the impact times, the greater the mismatch degree of the two phases, the stronger the dislocation structure of the strengthened γ' phase and γ channel on the surface of the sample, the stronger the dislocation interaction at the γ/γ' interface. And a lot of dislocation entanglement is accumulated. In addition, through the cross dislocation slip band of the γ' phase and γ' phase, the formation of a dense dislocation network inhibits the dislocation movement and improves the plastic deformation resistance of single crystal superalloy. It also produces obvious work hardening effect, which is the main deformation mechanism of nickel base single crystal superalloy SRR99 laser shock peening. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.
