A study on magnetic field assisted laser percussion drilling and its effect on surface integrity

Abstract

Purpose: of this paper is to reduce the taper angle and surface roughness of the laser drilled hole on Aluminium alloy with the assistance of magnetic field. At lower laser powers, able to achieve higher material removal rate in drilling with reduced taper angle and roughness. Design/methodology/approach: Aluminium alloy is a highly reflective material, while laser drilling it ejects plumes, which makes the drilling unreliable. The plume generated due to this action causes deteriorating effects over the work piece as such affecting surface textures. Removal of plume is the major consideration in laser machining process, especially in laser assisted drilling. The plume is a form of cluster of ions having charges in it. Due to the magnetic field input, the ions line the path along the lines of force of magnets. Thus, the ion cloud can be cleared at the localized plane, where the subsequent laser drilling going to be happens, leads to reduced plume thereby reduces the taper angle and surface roughness. Findings: The defect of percussion laser drilling that is barrelling effect in the drilled hole was reduced with the assistance of magnetic field setup. For the laser energy of 90 mJ, the magnetic assisted laser drilling shows better improvement in the material removal rate of 64.5%, the profile error (spatter height) was reduced to 45% and the taper angle of the drilled hole also reduced by 16.3%. The results confirmed the fact that, the Lorentz force confined the plume particle to be raised upwards and circulated outwards to the sidewall from the centre of the laser beam. This expansion of laser induced plasma plume, improved the material removal rate of the hole. Research limitations/implications: Laser drilling was carried out by a constant magnetic field and the parameters like material removal rate, taper angle, profile error, surface roughness were studied. In the future work, these parameters were studied with the application of varying magnetic field. Practical implications: As a result of the work, laser drilling was carried out on turbine blades or complex shapes for retention properties, with reduced taper hole and surface roughness, thereby improving the efficiency of the systems. Originality/value: The novelty of the work is providing magnetic flux for the laser drilling process, which improves the process parameters. The incorporation of magnetic field to the laser drill needs a cost less setup, which can ensure reliable improvement in the material removal rate, reduction in taper angle and profile error.