Experimental Investigation of Productivity, Specific Energy Consumption, and Hole Quality in Single-Pulse, Percussion, and Trepanning Drilling of IN 718 Superalloy

Abstract

Laser drilling is a high-speed process that is used to produce high aspect ratio holes of various sizes for critical applications, such as cooling holes in aero-engine and gas turbine components. Hole quality is always a major concern during the laser drilling process. Apart from hole quality, cost and productivity are also the key considerations for high-value manufacturing industries. Taking into account the significance of improving material removal quantity, energy efficiency, and product quality, this study is performed in the form of an experimental investigation and multi-objective optimisation for three different laser drilling processes (single-pulse, percussion, and trepanning). A Quasi-CW fibre laser was used to produce holes in a 1 mm thick IN 718 superalloy. The impacts of significant process parameters on the material removal rate (MRR), specific energy consumption (SEC), and hole taper have been discussed based on the results collected through an experimental matrix that was designed using the Taguchi method. The novelty of this work focuses on evaluating and comparing the performance of laser drilling methods in relation to MRR, SEC, and hole quality altogether. Comparative analysis revealed single-pulse drilling as the best option for MRR and SEC as the MRR value reduces with percussion and trepanning by 99.70% and 99.87% respectively; similarly, percussion resulted in 14.20% higher SEC value while trepanning yielded a six-folds increase in SEC as compared to single-pulse drilling. Trepanning, on the other hand, outperformed the rest of the drilling processes with 71.96% better hole quality. Moreover, optimum values of parameters simultaneously minimising SEC and hole taper and maximising MRR are determined using multi-objective optimisation.

An integrated analysis of productivity, hole quality and cost estimation of single-pulse laser drilling process

“…The intensity of the laser beam decreases due to diffraction as it penetrates, which increases the hole taper. Similar findings have been observed by Sarfraz et al 15 and Chatterjee et al 42 Influence of gas pressure and gas flow rate on hole taper. The effects of gas pressure and gas flow rate on hole taper are revealed in Figure 8.…”

“…These process parameters were chosen based on their influence on material removal rate, hole quality and drilling cost. 12,14,15,19,[28][29][30]34 The selection of limits and their levels was based on trial experiments and literature review. Table 2 shows the controlled parameters along with the selected levels.…”

“…The laser processing parameters which affect hole taper include laser pulse duration/ width, pulse energy, assist gas pressure, beam focal position and gas flow rate. [12][13][14][15][16][17][18][19][20] In previous research studies, several authors have explored the effects of these process parameters for single-pulse drilling. Yilbas and Yilbas 21 used the full factorial method to evaluate the impacts of focal position and material thickness on the quality of laser-drilled holes in Nimonic 75.…”

“…All process parameters were found to affect hole quality significantly. Sarfraz et al 15 evaluated the influence of process parameters (pulse duration and pulse energy) on hole taper during laser drilling of IN 718 alloy. The results revealed that hole taper is significantly influenced by pulse duration and pulse energy.…”

Energy Efficiency of Manufacturing Processes and Systems—An Introduction

“…Sarfraz et al [2] focused on the laser drilling process optimization. Through a statistical design of experiments and analysis of variance (ANOVA) they presented empirical models for predicting the material removal rate, the specific energy consumption and the hole taper for the case of single pulse drilling, percussion and trepanning.…”