Investigation of nanosecond laser micro-drilling of titanium under different processing environments

In this research work, the nanosecond fiber laser micro-drilling process on titanium was performed and investigated. Micro-drilling using the trepanning method is a preferred way to overcome hole taperness and create holes of desired dimensions. This study was focused on determining the effects of different processing environments on laser micro-drilled holes while keeping all other laser-related parameters constant. Experiments were performed to drill through holes of four different target diameters of 50, 100, 150, and 200 μ m in the 0.5 mm thick titanium sheet. Scanning speed, laser power, pulse width, and pulse frequency of the laser were kept constant during the micro-drilling experiments. The number of passes was varied at three different levels viz, 50 passes, 75 passes, and 100 passes to determine the effect of the number of scans on hole dimensions and other output parameters. Experiments were performed under four different processing conditions, namely open air, under static water, under surfactant mix static water, and under flowing water conditions. Output hole diameter, heat affected zone, circularity, and taperness were measured for all the drilled holes. The mechanism of laser ablation under different processing conditions has been outlined. While the processing under flowing water conditions resulted in a minimum heat affected zone, processing with surfactant was observed to be delivering the drill hole diameter closest to the desired dimensions with the highest circularity and lowest taperness.