Research On Processing Method And Experiments Of IUECDD For Micro-hole

In order to improve the performance of aero engine,large numbers of micro-holes appear on the key components of aero engine,the diameter of these micro-holes always between 0.3mm to 2mm,and the materials of these key components are always very difficult to be machined,such as super alloy,titanium alloy and intermetallic compound.Further more,the recast layer,micro-cracks,and heat affected zone should be removed form machining surface,thus single untraditional processing methods usually can not meet the demands.Researchers try to machine these micro-holes by ECDM(Electrochemical Discharge Machining),which can obtain high efficiency by EDM(Electric Discharge Machining)and remove the recast layer by ECM(Electrochemical Machining).However,the working fluid will wash away after the penetration of holes,which will cause insufficient of ECM and recast layer residual.Therefore,it is necessary to find a kind of underlay to fill at the back of workpiece.The underlay will not only provide sufficient and stable reverse flushing fluid after penetration,but also be convenient to fill in the cavity with complex structure,such as turbine blades of aero engine.Ice Underlay Electrochemical Discharge Drilling(IUECDD)is proposed in this paper,and platform of IUECDD has been designed and established.Influence of ice underlay on Electrochemical Discharge Drilling(ECDD)has been analyzed.The main studies and contributions in this paper are as followings:(1)Theory of IUECDD has been analyzed,and working fluid f low field with ice underlay after penetration was studied.The experimental platform of IUECDD was designed and fabricated,and the reverse flushing after penetration provided by ice underlay was confirmed be sufficient and stable by surveying the waveforms of voltage and current during the processing.This paper also studied the influence of bottom pause time on melting degree of ice underlay by watching the ice underlay after processing.The ultralow temperature brought by ice underlay may decrease the thickness of recast layer created by EDM.(2)The contrast experiments between normal temperature and ultralow temperature of ECDD were done,and the similar ities and differences of processing voltage and current between these two conditions were analyzed by watching the waveforms of voltage and current during processing.The time proportion of EDM,ECM and short circuit were studied,which can explain why the machining efficiency under ultralow temperature is slightly lower than normal temperature.In addition,the influence of ultralow temperature and concentration of working fluid on tool electrode were analyzed,and the results show that the ultralow temperature and higher concentration of working fluid can decrease the wear of tool electrode.(3)Experiment of IUECDD was done,and the influences of working fluid concentration,ice fluid concentration and bottom pause time on IUECDD were analyzed,such as diameters,shapes,taper and removal effect of recast layer.Finally,the 45° inclined micro-holes were processed by IUECDD,and the working fluid flow filed of 45° inclined micro-hole after penetration was studied.The rounded edge of entrance and exit was explained by electric filed simulation,and the removal effect of recast layer can be improved by increasing the bottom pause time.