二次法激光加工小孔技术

为了提高激光加工航空发动机气膜冷却孔质量，介绍了一种采用焦耳级脉冲能量毫秒激光在镍基高温合金上快速加工初始通孔，再采用毫焦耳级脉冲能量纳秒激光扩孔的二次加工小孔方法。通过该方法试图消除毫秒激光加工小孔产生的再铸层以及解决纳秒激光直接加工几乎无再铸层小孔效率低、深度有限的问题，从而实现更高效率加工高质量气膜冷却孔。试验研究结果表明，该方法可以有效去除毫秒激光加工小孔孔壁的再铸层，改善孔壁表面质量，与纳秒激光直接加工小孔比较，在加工1 mm左右深的小孔时可以提高加工效率，但加工2 mm以上深度的小孔时，对提高加工效率的作用不明显。基于试验结果及分析，对二次法加工小孔提出了改进措施。

Sequential Laser Drilling Technology

This paper reports a new processing method that makes a hole rapidly with millisecond pulse laser in scale of joule pulse energy in nickel-based alloy at first, and enlarges the original hole with nanosecond pulse laser in scale of mJ pulse energy secondly for making higher quality cooling holes in aero-engine. In this way we attempt to eliminate the recast of holes made by millisecond pulse laser and resolve the problems of long processing time and limited processing depth caused by nanosecond pulse laser directly making holes with negligible recast,so making high quality holes with higher processing efficiency could be realized. The experimental results show that this method could remove the recast around the holes made by millisecond pulse laser effectively and improve the hole's inner surface quality; compared with nanosecond pulse laser making holes directly, it is effective in increasing the processing efficiency for holes of around 1 mm depth, but no apparent effect in shortening processing time in making holes of above 2 mm depth. Based on the research results and analysis, a few ideas for improving this kind of processing technique are proposed.