An underwater femtosecond laser layered ring trepanning (FLLRT) technology is reported in this paper. The FLLRT experiments are performed in silicon carbide (SiC) ceramic sheets in air and water. The effects of water immersion and laser pulse repetition rate on laser trepanning quality and hole generation characteristics are demonstrated by altering the laser pulse repetition rate. The underwater FLLRT technology notably improves the laser hole-trepanning quality for the SiC material because of the water cooling–insulating effect, underwater bubble-cavitation effect, and water microstreaming effect. Performing FLLRT in water, the hole diameter, particularly the hole exit diameter, increased whereas the hole taper decreased when using a relatively low pulse repetition rate. Furthermore, the hole-wall formation quality and surface uniformity improved while notably reducing the hole-wall oxidation. Significantly, the redeposition of the vapourised material and the resolidification of the molten material are greatly reduced, thereby reducing the formation of the recast layer and micro cracks. When the pulse repetition rate was relatively high, the local thermal accumulation effect induced by significantly more successive laser pulses was notably enhanced for melting the SiC material despite the laser ablation-induced vapourisation.

本文报道了一种水下飞秒激光分层环形钻孔（FLLRT）技术。FLLRT 实验是在空气和水中的碳化硅 (SiC) 陶瓷片中进行的。通过改变激光脉冲重复率来证明浸水和激光脉冲重复率对激光套孔质量和孔生成特性的影响。由于水冷绝缘效应、水下气泡空化效应和水微流效应，水下 FLLRT 技术显着提高了 SiC 材料的激光开孔质量。在水中进行 FLLRT 时，当使用相对低的脉冲重复率时，孔径，尤其是孔出口直径增加，而孔锥度减小。此外，孔壁形成质量和表面均匀性得到改善，同时显着减少孔壁氧化。显着的是，汽化材料的再沉积和熔融材料的再凝固大大减少，从而减少了重铸层和微裂纹的形成。当脉冲重复率相对较高时，尽管存在激光烧蚀引起的汽化，但由显着更多连续激光脉冲引起的局部热积累效应显着增强，用于熔化 SiC 材料。