Femtosecond laser helical drilling of nickel-base single-crystal super-alloy: Effect of machining parameters on geometrical characteristics of micro-holes

Abstract

Laser micro-hole processing has been widely used in industry. Many laser processing parameters can affect the processing results. The relationship between the geometrical shapes of micro-holes and the laser processing parameters has not been determined accurately. In this paper, experiments on the femtosecond laser drilling of the nickel-base single-crystal super-alloy (DD6) materials were conducted to determine the relationship between the parameters, such as the laser single-pulse energy, rotation rate, and downward focus rate, and the geometrical characteristics of the micro-holes, such as the diameter, and roundness. A group of orthogonal experiments were conducted to determine the effects of the comprehensive influencing factors on the geometrical characteristics of the micro-holes. After the experiments were conducted and analysed, the experimental results were modelled by a backpropagation neural network, and the mapping relationship between the laser parameters and the geometrical morphologies of the micro-holes was constructed. The model established by the backpropagation neural network could obtain accurate prediction results, and the predictions of the diameters of the micro-holes were better than those of the roundness.

Numerical Simulation and Validation of Multiscale 3D Laser Spiral Machining of Microholes

“…At the University of Stuttgart, Germany, physical experiments on annular drilling were conducted based on a four-light wedge rotation system, demonstrating that the quality achieved by annular drilling was significantly improved compared to that by percussion drilling [24]. Yin et al [25] found that femtosecond laser spiral machining can better handle high depth-to-diameter ratio holes, but the relationship between the geometric evolution process of small hole formation and the main processing parameters during spiral hole making is unclear. Moreover, there is a lack of model guidance for the optimization of processing parameters.…”

Optimization of femtosecond laser drilling process for DD6 single crystal alloy

“…The effect of current femtosecond laser parameters on single-crystal high-temperature alloys has been studied by scholars to some extent. It has been shown that the diameter increases with increasing single pulse energy in the range of 80 µJ to 130 µJ [12]. The entrance and exit diameters and roundness tend to be stable, while the taper exhibits a slight variation.…”