ACCURACY AND SURFACE INTEGRITY ANALYSIS OF MICRO HOLES DRILLED ON HASTELLOY-X ALLOY USING A LASER SOURCE WITH OPTIMIZATION

Abstract

Hastelloy-X is a nickel-based superalloy used for making parts of extreme temperature applications. This paper is aimed at studying the effects of laser drilling parameters on accuracy and surface characteristics of the micro-holes drilled on Hastelloy-X alloy. The independent factors like power, pulse width, pulse repetition rate and gas pressure were selected as process variables. The experiments were designed using response surface methodology (RSM) with four factors at five levels. The process was evaluated in terms of exit diameter, entrance diameter, taper and entrance circularity error along with the surface topography analysis of the hole. Weighted principal component analysis (WPCA) is performed to calculate the accuracy of a hole through the geometric index (GI). It also determines the optimal combination among the alternatives. Relationship of GI with input parameters was established with RSM and analysis of the variance (ANOVA) was done to enact the significance of process parameters on the outputs. The obtained results proved that power, gas pressure and pulse width are the most influencing factors of accuracy. The desirability analysis also confirmed the optimal input sequence that has been obtained from the RSM–WPCA approach.