Influence of parameters on performance characteristics and defects during laser micro drilling of titanium alloys using RSM

Abstract

Abstract Titanium (Ti) and its alloys have received significant attention in recent years, particularly for applications in the medical science, automobile, and aerospace sectors. Drilling is used for around 40 percent to 60 percent of an aeronautical product's material removal processes. Non-conventional machining can be considered to obtain an optimal quality of drilled holes. The present study has employed a pulsed Nd:YAG laser having 250 W average power to perform the micro-drilling on titanium alloy of 0.45 mm thick sheet. The study focuses on determining the impact of laser parameters (gas pressure (4 ~ 8 bar), laser input current (200 ~ 260 A), pulse width (4 ~ 8 ms), and pulse repetition rate (1 ~ 7 Hz)) on performance characteristics during micro drilling on a thin foil of titanium alloy having 0.45 mm thickness. To evaluate the quality of micro-drilled holes, aspects, e.g., circularity, spatter area, and taper, have been considered. The response surface methodology based on the design of experiment technique was employed to estimate the influence of parameters on performance characteristics with the least number of experiments. The study indicates that assistant gas pressure, pulse width, and laser input current are the essential parameters in taper formation and spatter deposition. The study suggests that the increase in pulse repetition rate and pulse width improves the circularity of the hole. The electron micrography of the drilled holes helps to determine the development of the heat-affected zone (HAZ) and micro-crack near drilled holes. The presented research provides a new understanding of how the process parameters contribute to HAZ development, crack occurrence and intensity.