Strengthening effect of laser peening on fatigue performance and life extension of laser cladded IN718 nickel-based alloy parts

Strengthening effects of laser peening (LP) on fatigue life extension of IN718 nickel-based alloy parts repaired by laser cladding (LC) were investigated. Special attention was paid on the microhardness, residual stress, microstructures and fatigue performance. The results show that LP increases the microhardness and compressive residual stress of LCed samples and the induced severe plastic deformation closes the metallurgical defect. In addition, LP changes the microstructure of LCed parts, transforms a large number of columnar dendritic structures into cellular dendritic structures. The grains in the subsurface were refined and a high-density dislocation structure is produced as well. As a result, while compared with the matrix sample, the fatigue life of LPed sample with laser power density of 11.30 GW/cm2 is increased by 54.9 %. Finally, synergistic strengthening mechanism of LP on LCed IN718 nickel-based alloy parts through defective pore closure effect, high-amplitude residual stress, and microstructure evolution was revealed.