Laser micro-drilling of tool steel using Nd:YAG lasers

The interaction phenomena of nanosecond time period, Q-switched, diode pumped Nd:YAG laser pulses using 1064, 532 and 355 nm wavelengths with M2 tool steel was investigated at an incident laser intensity range between 2 and 450 GW/cm2. Interaction experiments were performed on 0.2 mm thickness M2 tool steel. For each sample experiment, drilling etch rate and surface structure was determined. Analysis of the results included the use of scanning electron microscopy (SEM) methods to detect changes related to melt solidification. A maximum etch rate of over 5 μm per pulse was obtained for the drilling etch rate experiments carried out using a laser wavelength of 355 nm, and just under 5 μm using 532 nm laser wavelengths. The maximum drilling etch rate obtained using a wavelength of 1064 nm was approximately 1 μm per pulse. The decrease in the drilling etch rate as the interaction wavelength is increased, is thought to occur due to the reflective nature of tool steel and absorption of laser radiation by the plasma formed above the material during high intensity laser–material interaction.