Molecular dynamics investigation of femtosecond laser ablation of Inconel 718 alloy

In this work, the expansion, spallation, pressure wave propagation, and structural evolution during femtosecond laser ablation of Inconel 718 alloy were investigated using molecular dynamics simulation. The results found that femtosecond laser ablation achieves deeper energy penetration than continuous laser, facilitating finer processing. Under the irradiation of femtosecond laser, the crystal structures of the target are gradually transformed from a long-range ordered structure to an amorphous structure, accompanied by the generation of stacking faults composed of BCC crystal structures. In addition, the effect of laser parameters is also examined. It is found that the expansion of the heat affected region with increasing laser fluences is one of the reasons for inducing compressive pressure generation. The transmission of the pressure wave is independent of the pulse durations, but the surface temperature rise of the target is closely related to the pulse durations. As pulse durations decrease, the surface ablation becomes more intense, which can be attributed to a higher temperature rise at the surface of the target rather than a greater tensile pressure. Thus, femtosecond laser ablation effect is caused by the combined impact of pressure wave and temperature. This work lays a theoretical foundation for exploring the dynamic thermodynamic mechanism phenomena and crystal structures evolution of high temperature alloy materials processed by femtosecond laser.