Effects of recast layer on fatigue performance of laser-drilled holes in nickel-based superalloy

The effects of the recast layer on the fatigue performance of laser-drilled holes in Ni-based superalloy were experimentally and computationally investigated. It was found that millisecond-laser drilling leads to a recast layer of about 10μm, whereas no recast layer was observed in the picosecond-laser drilled hole. The recast layer was confirmed to reveal the Niobium segregation, the Laves phase precipitation and small lattice distortions, resulting in low yield stress. In-situ fatigue test results indicated that the recast layer does not show an obvious influence on the fatigue life of the holed structures in the low-cycle fatigue regime. With the help of the developed cyclic plasticity model, computational analysis verified that the recast layer significantly decreased the stress concentrations around the hole root. The shielding effects improved the fatigue performance of the mismatched material system. The investigations confirm that the millisecond-laser-drilled holes can be used in high-performance turbine blades sofar the recast layer does not dominate the fatigue process, which provides new insights into laser manufacturing.