Study Of Ultrasonic Assisted EDM On IN718

IN718 is one of the most widely used superalloys in aviation engines,gas turbines and nuclear reactors.But it also has the large cutting force,high cutting temperature,strong metal affinity,work hardening,cutting tool wearing and so on during the work.It is regarded as a typical hard working material.When the traditional processing,tool and workpiece wear produced a lot of heat that can not be lost in time,resulting in tool damage.In this paper,IN718 nickel base alloy was processed by Electrical Discharge Machining(EDM)and Ultrasonic assisted Electrical Discharge Machining(USEDM)respectively.The surface and cross section microstructure,surface roughness,material removal rate and relative loss of tool electrode were analyzed.The main research contents and conclusions are as follows:(1)Set up ultrasonic vibration assisted EDM device and The ultrasonic vibration system is loaded into the EDM machine?In order to realize the effective vibration of the workpiece,we designed the clamping device of the ultrasonic vibration system with the function of fine adjustmen and the clamping device of the workpiece with insulation function which can disassemble the workpiece conveniently.The fixture is fixed on the end face of the ultrasonic amplitude transformer by means of threaded connection.(2)The influence of peak current,pulse width and other main electrical parameters as well as ultrasonic vibration on the removal rate,surface roughness and surface microstructure were systematically studied.The experimental results show that EDM and USEDM show the same trend.The peak current is kept unchanged,the pulse width is increased,the diameter of the etched pits is increased,and the surface microscopic crack defects are increased.If the pulse width is kept unchanged and the value of peak current is increased,the area of the electroerosion pit formed on the machining surface will also become larger and the cracks will become more and more.When the electrical parameters are small,the surface quality will be good,and there are less microcracks.When the pulse width is small,but the peak current is large,the surface quality can be better.(3)In USEDM processing,the additional axial ultrasonic vibration of the workpiece makes the surface pitting bigger and shallower,and the surface roughness reduces by more than 13%.Surface microcracks were reduced or even disappeared.With the introduction of ultrasonic vibration,the machining speed of EDM is greatly improved.At the same time,ultrasonic vibration can effectively reduce the relative loss of electrode.Especially under large discharge energy,the relative loss of electrode can be reduced by10.8%.The vibration can also effectively reduce the thickness of the recasting layer and limit the fine cracks in the depth direction,which has a positive effect on improving the surface quality of the workpiece.