Study On Pulsed Laser Trepanning Drilling Of Superalloy Sheets And Analysis For Drilled Hole Morphology Quality

Laser drilling technology has the characteristics of high quality,good flexible,high efficiency and wide application.In the industrial production,it has abroad application prospect and high research value.This paper carries out the systematically theoretical analysis and experimental study of pulsed laser percussion and trepanning drilling technology on superalloy sheets using the single factor test.The classification of laser drilling technology and the basic principle of laser trepanning drilling were elaborated.Based on the basic theory of heat conduction,the temperature field model of laser percussion drilling and trepanning drilling was established by finite element software.The APDL programming language was used to simulate the process of percussion drilling and trepanning drilling.The hole shape and the temperature field distribution with the change of pulse number in laser percussion drilling and trepanning drilling were obtained.The hole depth with different pulse number and the hole diameter with different pulse energy in percussion drilling and trepanning drilling were solved.After numerical simulation,the changes of temperature,hole depth,and hole diameter between percussion drilling and trepanning drilling were compared.The results showed that the hole depth of percussion drilling and trepanning drilling all increased with the increase of pulse number,and the hole diameter of percussion drilling and trepanning drilling all increased with the increase of pulse energy.Those were consistent with experiment result.The equipment of DMG numerical control precision laser machining center was used to carry out the experiment of laser percussion drilling and trepanning drilling in superalloy GH4037.The effect of pulse energy,repetition frequency,pulse width and assistant gas pressure on the quality of laser percussion drilling and the effect of trepanning times,repetition frequency,assistant gas pressure,pulse width,pulse energy,trepanning velocity on the quality of laser trepanning drilling were studied systematically.The experimental quality evaluation indicators include: morphology of microhole surface,the size of hole diameter,the hole shape,hole taper and hole circularity,etc.The experimental results of percussion drilling showed that the laser pulse energy had the most significant effect on the hole diameter and hole circularity.When thepulse energy was 1J,the repetition frequency was 70 Hz,the pulse width was 0.3ms,the assistant gas pressure was 0.4MPa,the hole quality of percussion drilling was better.The hole circularity of entrance was better than the hole circularity of exit.The experimental results of trepanning drilling showed that trepanning times and trepanning velocity had little effect on the hole diameter.The appropriate trepanning times,smaller trepanning velocity made the quality of microhole surface better.When the pulse energy was 1J,the repetition frequency was 50 Hz ~70Hz,the pulse width was 0.3ms,the assistant gas pressure was 0.4MPa,the hole quality of trepanning drilling was better.Consistent with percussion drilling: pulse energy had the most significant effect on the hole diameter and hole circularity.In addition,the hole circularity of entrance was better than the hole circularity of exit.Finally,the experiment of angled laser trepanning drilling was carried out.The trepanning drilling and angled drilling were combined to verify the feasibility of machining holes on the inclined surface.