镍基高温合金喷油孔的飞秒激光精密加工

Femtosecond laser precision machining of fuel injection holes in nickel-based superalloys

飞秒激光平面螺旋钻孔策略在灵活性、精度和工艺效率方面具有许多优势,可满足某型号航天发动机供油喷嘴直通孔的加工精度需求。因此,本研究采用飞秒激光平面螺旋钻孔方式,系统研究了激光功率、单层进给量、单层扫描时间、离焦量以及脉冲重复率之间的作用关系及对钻孔质量的影响。结果表明,离焦量对入口孔径的影响最为明显;对出口孔径和锥度影响较大的参数为功率以及进给量;对加工效率影响最大的参数为功率。根据上述影响规律进行调整,本实验成功在厚度为1.5 mm的GH3044板材上制备出孔径为390μm的通孔,出口入口孔径误差小于0.6μm、锥度小于0.5°。通过统计不同参数下微孔内壁粗糙度变化规律并以此对参数进行调整,有效地将孔壁粗糙度降低至Sa 0.6μm,满足工艺要求。孔壁形貌分析表明钻孔质量优良,随激光脉冲重复频率增加,孔壁附近组织逐渐粗化,但均无明显重铸层或热影响区,能够实现高精度微孔的相对“冷加工”。本研究为后续追求高雾化效果的异形孔的制备提供了理论依据。

Femtosecond laser planar spiral drilling strategies offer several advantages,such as flexibility,precision,and process efficiency,making it possible to achieve high machining accuracy for specific types of aerospace engine oil supply nozzle.Therefore,in this study,we adopted a femtosecond laser helical drilling method and systematically investigated the effects of laser power,single layer feed,single layer scan time,defocusing amount,and pulse repetition rate on the quality of drilling.The defocusing amount has significant influence on the inlet diameter,while power and feed are the parameters affecting the outlet diameter the most;processing efficiency heavily depends on power.Considering these aspects,throughholes with a hole size of 390μm were successfully prepared on GH3044 sheets with a thickness of 1.5 mm.The errors for inlet-outlet diameters and taper were less than 0.6μm and 0.5°,respectively.Using the statistical analysis of the variation law of hole wall roughness under different parameters,it was found that the roughness value can be effectively reduced to Sa=0.6μm,which exceeds than the process re⁃quirement,by simply adjusting parameters.Moreover,the analysis of the hole wall morphology showed that the drilling quality was excellent.By increasing the laser pulse repetition frequency,the microstruc⁃ture near the hole wall gradually coarsens.However,there is no obvious recast layer or heat-affected zone,which is necessary to realize the relatively“cold”processing for high-precision micro holes.This study provides a theoretical basis for the fabrication of special-shaped micro holes using the high atomiza⁃tion effect.