Study on water-assisted laser ablation mechanism based on water layer characteristics

Water-assisted laser process machining process is a promising way to cut materials with less thermal damage. An investigation of different water layer characteristics of laser ablation in low-pressure water was studied. In this study, single-crystalline silicon was selected as a work sample that was grooved by using nanosecond-pulse laser ablation in two different water-assisted conditions. Finite Element (FE) modeling technique and optical transmission technique were employed to gain a better understanding of the water layer characteristics on underwater laser machining process. The groove geometry morphology was observed and analyzed. Besides, the influences of the water layer shape and thickness on the laser beam transmission were analyzed, and the impact of the flow behaviors on the groove geometries and the groove sidewall surface were also analyzed, such as the velocity and pressure of water flow. The experimental results and numerical qualitative analysis show that the main factors affecting the groove width are the water layer shape, the total pressure of the water layer, and the velocity of water flow. Below the threshold of the softening remove pressure, the water velocity plays a dominant role in the depth of the groove, that is, the groove depth decreases with the increase of the flow velocity. The water velocity and the total pressure of the water layer have essential effects on the surface morphology of the inner wall of the groove. This study helps to better understand the impact of water layer characteristics on water-assisted laser ablation and promote its potential application in the processing of hard and brittle materials.