Green Laser Drilling Assisted with Neutral Salt Solution

Recast layer is an inherent defect commonly associated with holes produced with laser drilling. The defect is likely to limit the extent of aero industrial application. In order to solve the problem, a new processing of laser drilling assisted with neutral salt solution (SALD) has been developed to improve the overall quality of laser-drilled holes. The process bases on the application of a fluid neutral salt solution, which is being on the workpiece surface with the focused laser beam at the same time. The effects of the neutral salt solution during the process mostly consist of thermal chemical reaction and continuing cooling effect of materials. Because of green laser being weakly absorbed underwater, the experiments of SALD have been performed on 0.5mm thickness 321 stainless steel with pulsed Nd: YAG laser at second harmonic wavelength. The optical microscope is used to detect the experimental results. It is found that the recast layer has been effectively removed during the SALD compared with laser drilling in ambient atmosphere conditions. It is confirmed that the principle of SALD is right and the new process can obtain good hole quality without recast layer.