Characteristics of micro-hole formation during fibre laser drilling of aerospace superalloy

Abstract

High aspect ratio micro-holes are nowadays increasingly used in various applications including aerospace, medical and automotive. This research investigates the characteristic of quasi-CW fibre laser micro-hole drilling (∼100 μm) of nickel superalloy using experimentation and numerical modelling. Micro-holes of diameter around 100 μm was drilled using percussion technique over a 2 mm thick nickel superalloy material. The main investigation focuses on understanding the micro-hole formation during the laser interaction with the material. Finite element modelling tool and high-speed imaging camera had been used to assist in understanding the basic-fundamentals of micro-hole formation during the millisecond laser drilling process. During the micro-hole drilling process, irrespective of the laser parameters, the melt ejections start after around 80 μs, and the total melt ejection duration depends on laser energy and pulse duration. The experimental results showed that it takes 15 ms to drill a micro-hole of diameter around 100 μm using a laser pulse duration of 0.1 ms, laser pulse energy of 1 J and 15 number of percussion pulses.