Modelling and analysis of pulsed Nd:YAG laser machining characteristics during micro-drilling of zirconia (ZrO2)

Pulsed Nd: YAG laser beam has great ability for micro-machining of ceramic materials because of high laser beam intensity at low mean beam power, good focusing characteristics due to very small pulse duration, small kerf widths and narrow heat effected zones. In the paper, experimental investigations into CNC pulsed Nd:YAG laser micro-drilling of zirconium oxide (ZrO2) have been carried out. Influence of laser machining parameters on the HAZ thickness and phenomena of tapering of the machined micro-holes has been experimentally investigated. Response Surface Methodology-based optimal parametric analysis has been performed to determine the optimal setting of process parameters such as pulse frequency and pulse width, lamp current, assist air pressure for achieving minimum HAZ thickness and taper of the micro-hole machined by pulsed Nd:YAG laser. Minimum HAZ thickness has been obtained as 0.0675 mm when the lamp current, pulse frequency, assisted air pressure and pulse width are set at optimal parametric setting i.e. 17 amp, 2.0 kHz, 2.0 kg/cm2 and 2% of the duty cycle, respectively. Minimum taper has been achieved as 0.0319 at optimal parametric setting i.e. the lamp current of 17 amp, pulse frequency of 2.0 kHz, assisted air pressure of 0.6 kg/cm2 and pulse width of 2% of the duty cycle. Analysis has also been carried out for multi-optimisation of both the responses i.e. HAZ thickness and taper during pulsed Nd:YAG laser micro-drilling on ZrO2.