Research on the mechanism of laser drilling alumina ceramics in shallow water

Underwater laser drilling of alumina ceramics is an effective means to improve the quality of holes in the material. In the process of underwater laser drilling, not only water plays a great role in improving the quality of the hole, but also bubbles (generated by ceramic melting explosions in water) play an important effect in reducing the recast layer of the hole wall. In this paper, the influence mechanism of water and bubbles on the surface quality of the hole of laser drilling in water was studied. Two sets of experiments were performed for the laser drilling of alumina ceramics in air and in water, respectively. The results showed that water and bubbles effectively reduced the thickness of the recast layer and the amount of spatter. Moreover, by comparing the width of cracks on the hole wall of the alumina ceramic drilled by the laser in air and in water, it was found that water significantly reduced the thermal effect of the laser. The collapse and rupture of the bubbles produced shock and vibration, causing the recast layer on the inner wall of the hole to fall off. However, the cooling time of the recast layer was reduced due to the cooling effect of water. If the bubbles cannot be broken in time, it will cause the formation of a blowhole on the hole wall. When the input current of the laser machine was 160 A, both water and bubbles were helpful to improve the quality of laser drilling alumina ceramics. The research in this article supplements the mechanism of underwater laser drilling. And it has important reference value in engineering application.