为了提高纳秒激光成孔质量, 改善成孔时孔口熔融物、孔口再铸层、孔的锥度等缺陷, 利用超声振动辅助321不锈钢表面纳秒激光成孔, 观察孔口微观形貌及上下孔口直径, 分析超声振动功率、激光脉冲能量、离焦量以及辅助气体气压对纳秒激光成孔质量的影响。结果表明, 在不同工艺参数下的打通孔实验中, 超声振动辅助成孔深径比大、再铸层较小、孔壁波纹细密、喷溅物减少, 成孔质量得到改善。随着超声功率增大, 上下孔口圆度提高、锥度减小, 且打孔效率提升;激光脉冲能量对成孔的上下孔口直径、孔口熔渣溅射影响显著;离焦量为1 mm时获得锥度最小的孔, 且熔渣较少、热影响区面积小, 离焦量过大或过小, 易造成熔融物聚集, 辅助气体压力增大, 热影响区减小。

To improve the hole-quality such as melt orifices, orifice recast layer, hole taper and other defects caused by nanosecond laser drilling, nanosecond laser was used to drilling the hole assisted by ultrasonic vibration on the surface of 321 stainless steel. Microstructure including the upper and lower diameter of orifice was observed and effects of power ultrasonic vibration, laser pulse energy, the defocus amount and auxiliary gas pressure on holes quality was analized. The results show that: assisted by ultrasonic vibration, depth to diameter ratio of the hole gets down and recast layer is small, hole-wall corrugated is fine, splashes and quality improve under different process parameters. With the increases of ultrasound power, the upper and lower orifice roundness and drilling efficiency improve, taper decreases; laser pulse energy has a great influence on diameter of the upper and lower orifice and orifice slag sputtering; The smallest hole taper, with less slag, insuffcient heat-affected area is obtained when the defocus amount is 1 mm. Melt aggregation may happen during the excessive or insuffcient defocus,the heat affected zone is reduced when the auxiliary gas pressure increases.