Improved quality micro-hole fabrication using backside water assisted laser micro-drilling in titanium

Abstract Laser micro-drilling is an effective technique for producing micro-scale holes in different materials. However, titanium poses challenges due to its high melting point, low thermal conductivity, and oxide layer formation at elevated temperatures. This study investigates the influence of a thin water layer on the backside of titanium workpiece during laser micro-drilling to mitigate these issues. A 0.5 mm thick water layer was applied at the backside of the workpiece to assess its impact on hole characteristics such as heat-affected zone (HAZ), circularity, and taper angle. Experiments were performed with constant laser power, pulse frequency, and pulse width, while varying scanning speed, number of passes, and input diameters (50 μm, 100 μm, and 150 μm) using the trepanning method. The results revealed that backside water-assisted drilling, particularly with a thin water layer, significantly reduced thermal defects and produced nearly taperless microholes. The formation of cavitation bubbles and related phenomena at the backside enhanced material removal and minimize hole taper compared to open-air drilling. This study offers valuable insights into the mechanism of backside water assisted laser drilling compared to open air drilling and highlights the benefits of backside water layer in reducing thermal damage and enhancing the precision of micro-drilling in titanium.