Fundamental Experimental Research On Gas-mixed Electrochemical Machining Of Titanium Alloy TC4

Gas-mixed electrochemical machining is a method of removing material particularly by an electrochemical process in which a certain amount of gas is mixed in electrolyte.Gas-mixed electrochemical machining has the advantages of improving the degree of localized dissolution,reducing memory errors and improving the accuracy of replication compared with conventional one,so that it provides an effective alternative for manufacturing components such as blades,molds and dies benefited from lots of research since 1960 s.However,further research concerning the machining mechanism and the distribution of gas-liquid two phase flow field is still of great importance with the help of the technologically adept high-speed photography and other advancements.This paper focuses on the two major problems with a series of experimental research of machining titanium alloy TC4.Research details are as follows:(1)A gas-liquid mixing system with the function of adjusting air concentration proportion was established.In order to ensure the uniformity of mixture so as to satisfy the research requirements,a gas-liquid mixture unit based on Venturi Effect was designed to keep gas-liquid two phase flow uniform and steady enough in machining zone.(2)The distribution characteristic of gas-liquid two phase flow field was analyzed.The rectangular flow channel with different gap measurements was designed based on actual ECM condition to observe the gas-liquid two phase flow pattern and bubble moving behavior by high-speed camera in order to study the flow field characteristic of gas-mixed electrochemical machining.It was found that the regulation of flow field distribution and bubble moving behavior had strong relationship with gap measurements and then the influence of gas in the electrolyte inside the machining gap on flow field and conductivity distribution was summarized.(3)The electrochemical dissolution behavior of titanium alloy TC4 was analyzed in gas-mixed electrolyte.By comparing the anodic polarization curve and open circuit potential curve with the different environment of quiet electrolyte,conventional ECM condition and gas-mixed ECM condition,the influence of electrolyte flowing and gas mixing on electrochemical dissolution behavior of titanium alloy TC4 was obtained.The characteristic of gas-mixed electrochemical machining of titanium alloy TC4 was concluded as well.(4)The basic experimental research of gas-mixed ECM using stepped workpiece of titanium alloy TC4 was implemented.Meanwhile,the influences on the leveling ability,surface quality and stray corrosion of this material were explored when air concentration proportion was changing.Experimental results showed that an air concentration proportion of 0.55 is a relatively superior choice in gas-mixed electrochemical machining of titanium alloy TC4 under this research condition.(5)An application of gas-mixed machining of titanium alloy TC4 blade was conducted.Gas-mixed electrochemical parameters are optimized and a twisted blade,which is to be used in an aero-engine,is machined.Results showed that gas-mixed ECM revealed better leveling ability and replication accuracy when manufacturing components with small machining allowance and twisted surfaces.The equilibrium state was earlier to reach and surface precision was better than that made by conventional ECM,although the surface roughness was declined.