Characterization of Micro-Hole Quality in Alumina Ceramics by Picosecond Laser Ring-Cut Drilling

In this study, a novel picosecond laser ring-cut drilling method was employed to drill holes in alumina ceramics. The morphology, dimensions, taper angle, and heat-affected zone (HAZ) of the resultant micro-holes were systematically characterized under various laser processing parameters. The crystal structure, microstructure, and elemental composition of micro-holes processed under specific parameters were characterized. The results showed that the micro-hole entrance and exit dimensions and HAZ area increased with increasing spot-scanning number. However, the micro-hole taper angle initially decreased before stabilizing with an increasing spot-scanning number. Furthermore, the micro-hole entrance and exit dimensions and HAZ area gradually decreased with increasing spot-scanning speed. Conversely, the micro-hole taper angle increased with increasing spot-scanning speed. Additionally, the micro-hole entrance and exit dimensions and HAZ area gradually increased with increasing average power. However, the micro-hole taper angle gradually decreased with increasing average power. Under processing parameters of spot-scanning number N = 90, scanning speed v = 600 mm/s, and average power P = 24 W, the micro-holes exhibited a taper angle α of 4.32° and a HAZ width of approximately 0.207 mm2. In contrast to the large bright grains on the original substrate, fine grains were observed around the machining area. Compared to the original substrate surface, the percentage of oxygen atoms decreased, whereas the percentage of aluminum atoms increased at the micro-hole edge and HAZ surface. The results of this study have potential applications in the field of ceramic manufacturing.