Research On Powder Mixed Electrical Discharge Machining And Surface Modification Of Titanium Alloy

Ti-6Al-4V titanium alloy is a kind of dual phase alloy,which is widely used in aviation,medical equipment,ships and other fields.Titanium alloy has good comprehensive properties in many aspects,such as low density,high specific strength,high temperature deformation resistance and so on,it creates a huge economic benefits,plays an important role in the national defense.But at the same time,titanium alloy has some problems,such as low hardness,poor wear resistance and thermal conductivity.In order to overcome the disadvantages of titanium alloy,this paper uses PMEDM(Powder Mixed Electrical Discharge Machining)to achieve the purpose of surface modification of titanium alloy.The main contents of this paper are as follows:1.Research the influence under different discharge parameters law of the removal rate and surface roughness of Ti-6Al-4V Titanium alloy material between EDM and PMEDM technology.Under certain discharge parameters,change the size of the peak current found that under the condition of EDM and PMEDM,with the increase of peak current,the material removal rate and surface roughness are all increased,and under the condition of low current,the material removal rate with the PMEDM is higher than the EDM,And under the condition of high current,the material removal rate with EDM is relatively higher.The surface roughness of workpiece with PMEDM is always lower than the surface roughness with EDM.Under certain discharge parameters,change the size of the pulse width,with the increase of pulse width,the tendency of the material removal rate is broadly similar between the two different technologies,The trend of increasing first and then decreasing,the material removal rate with the PMEDM is higher than it with the EDM,The surface roughness increases,and the surface roughness of the PMEDM is lower than that of the EDM.2.Analyze the surface morphology,section organization and alloy composition of the Ti-6Al-4V titanium alloy which was after processed,the workpiece surface with EDM is composed of innumerable small pit discharge,it shows the surface of workpiece with PMEDM has large and shallow discharge pit,the surface roughness is reduced,after processing the surface of Ti-6Al-4V titanium alloy presents a layer of "white bright layer",namely strengthening layer.The thickness of strengthened layer changes with the change of pulse energy,and the thickness of the strengthened layer is smaller when the pulse energy is small,the study found that when the peak current of 9A,pulse width of 30 s strengthening layer to achieve the optimization,the enhancement layer is relatively thick and uniform,when the pulse energy will continue to increase,strengthening layer appearance of micro cracks,has a certain effect on the surface properties of workpiece.The phase of the PMEDM surface was studied by means of X-ray diffraction.It was found that the surface of the workpiece produced a TiC strengthening phase.3.Test the hardness of machining surface,and on the surface of material with different processing methods of friction and wear test,the research appears that the surface hardness of workpiece with PMEDM technology is about twice as substrate material,and abrasion resistance is better than EDM and base material.