Quality Evaluation of Micro-Holes Processed by Efficient One-Step Femtosecond Laser Helical Drilling Method in Nickel-Based Superalloy

This research work details the main factors affecting the orifice and profile morphology of micro-holes processed by the one-step femtosecond laser helical drilling method. Cylindrical holes or even inverted cone holes can be obtained with the appropriate deflection angle and translation distance. The orifice morphology of the micro-hole is mainly influenced by the rotation speed of the Dove prism installed inside the hollow motor, laser output power, and laser repetition frequency. A higher instantaneous power density can improve the outlet morphology and produce sharper cutting edges and thinner recast layers, although it may increase the splashing around the inlet to some extent. Subsequent to the experiment, it was determined that in order to enhance the quality of the holes, it was necessary to select a higher laser power and a lower repetition frequency, such as 10 W and 100 kHz, according to the experiments. A recast layer thickness of less than 5 µm and a surface roughness value of less than 0.8 µm were obtained within 3–5 s processing time, which can satisfy the requirements for aircraft application of efficiency and quality.