Analysis of the Effects of Water Temperature on Water-Assisted Laser Trepanning in Superalloys

The water-assisted laser trepanning method has been proven to improve the quality of laser drilling; however, the effect of water temperature on this process is currently unclear. In order to investigate the influence of water temperature on the quality of holes produced via water-assisted laser trepanning in superalloys, this study used the controlled variable method to investigate the effects of three water temperatures—low temperature (2 °C), normal temperature (20 °C), and high temperature (70 °C)—on the following factors: spatter, hole diameter, taper angle, hole sidewall morphology, and recast layer. The results show that the spatter around the hole reduced, the hole entrance/exit diameter increased, and the roughness of the hole’s sidewall decreased with an increase in single-pulse energy. However, the effect of single-pulse energy on the recast layer was not obvious. As the temperature of the water increased, the hole entrance/exit diameter increased, and the roughness of the hole’s sidewall decreased. When the single-pulse energy was 1.0–1.9 J, using a lower water temperature produced a hole with a smaller taper angle. Compared with a water temperature of 20 °C, the movement of the melt film on the hole’s sidewall accelerated when the water temperature was 70 °C; as a result, more molten material could be removed from the hole, resulting in a decrease in the thickness of the recast layer. However, when the water temperature was 2 °C, the heat-affected zone and the thickness of the recast layer decreased more significantly. The results of this study provide technical support for the optimization of water-assisted laser drilling.