Water-assisted laser thermal shock machining of alumina

A combined experimental and computational approach was undertaken to investigate water-assisted laser cutting of 96% pure alumina specimens through controlled thermal shock fracture mechanism. A low-power CO2 laser (<300 W) was used for localized heating and scribing of alumina samples followed by water quenching to induce thermal stress cracking. In order to elucidate the cutting mechanisms and identify the regime of processing conditions suitable for controlled fracture, laser cutting experiments were performed under two different environments: water-assisted laser cutting and dry laser cutting. Temperature profiles of the heat-affected zones were obtained using thermocouples and data acquisition system. Finite element analysis was applied to predict the temperature and thermal stress distributions developed during both water-assisted and dry laser cutting operations. Temperature histories of the samples recorded during cutting were compared with numerical model predictions to determine heat transfer parameters associated with wet and dry laser cutting of alumina samples. Both experimental data and numerical analysis indicate that water quenching makes a substantial difference in thermal stress distribution, which governs the ability to control the fracturing of alumina. This in turn, resulted in better control of cutting and higher feed rates than previously reported in laser machining of alumina.