Experimental investigation and parametric optimisation of the hole-circularity and recast layer during the laser trepan drilling

Abstract

ABSTRACT Re-solidified layer of molten metal during laser trepan drilling of Inconel-718 is a serious concern. Re-solidification affects the dimensional stability and geometrical features. Many scientific efforts have been reported for understanding and minimising the re-solidification layer (recast layer) thickness in laser cutting and percussion drilling operations. However till date, limited scientific work has been reported concerning recast layer formation during the laser trepanning of Inconel-718. In the present work, a methodology has been proposed for reducing the recast layer formation during the laser trepanning of Inconel-718. For understanding and achieving minimum recast layer thickness with better circularity, series of laser trepanning experiments have been performed on a thin sheet of Inconel-718. Recast layer thickness and hole- circularity are measured for each laser trepan drilled hole followed by the development of mathematical models using response surface methodology. The developed mathematical models are optimised with the help of multi-objective genetic algorithm to ascertain the optimum trepan drilling parameters. The obtained values of optimum parameters are validated by conducting more experiments. From validation experiments, it has been found that the obtained range of input parameters is significant, and the heat affected zone can be controlled using the proposed methodology.