Numerical simulation and experimental analysis on femtosecond ablation of K24 superalloy

To explore the interaction mechanism between femtosecond laser and K24 Nickel-based superalloy, Planck equation and Fresnel's formula are employed to derivate variation curve of pulse width dependent reflectivity and absorption coefficient of K24 superalloy. Linear hypothesis taken from solid mechanics is utilized to derivate lattice heat capacity and electronic specific heat coefficient of K24 superalloy. Temperature variation of electron and lattice during single pulse femtosecond laser ablation process is theoretically described by a simplified one dimensional two temperature model and finite difference method. Theoretical single pulse femtosecond laser ablation depth is calculated referring to vaporization temperature of K24 superalloy. Corresponding experiments are carried out to verify the accuracy of simulation results using low pulse frequency. Orthogonal experiments are carried out to investigate the influence rules of several technological parameters on the morphology features of micro holes. Results show that the scanning velocity is of the most significant effect, followed by feed distance, while scanning time and average power have relatively small effects on morphology of micro holes. This work provides theoretical and experimental foundation for the application of femtosecond laser drilling of superalloy.