Experimental Investigation On Electrochemical Dissolution Behaviors And Electrochemical Machining Of Ti-48Al-2Cr-2Nb

With the aero-engine thrust-weight ratio increasing,the nickel base alloys are too heavy to meet the demand of weight reduction.TiAl intermetallic has the characteristics of low density,high stiffness and strength,high temperature resistance and flame retardancy.It is thought to be the ideal structural material to replace the nickel base alloy in the aero engine components.However,TiAl intermetallic has the characteristics of low temperature plasticity at room temperature,and it is very difficult to cut.Electrochemical machining（ECM）is a non-traditional processing technology to remove materials regardless of hardness and ductility.It is an ideal processing technique for TiAl intermetallic compounds manufacture.Taking two types of typical aero-engine blades as the research object,the experimental investigations of ECM TiAl4822 blade were carried out.The research mainly includes the following aspects:（1）The electrochemical dissolution characteristics of TiAl4822 materials have been mastered.The electrochemical dissolution characteristics of TiAl4822 were analyzed by the curves of anodic polarization,EIS and current effiency in NaCl and NaNO₃ electrolytes.Single factor experiments on processing parameters such as processing voltage,feed rate,electrolyte temperature,duty cycle and frequency were carried out.The influence of processing parameters on machining quality of material removal volume,machining gap and surface roughness was explored.The viscosity of electrolysis products was studied,too.（2）The ECM characteristics of TiAl4822 blade under the condition of NaCl and NaNO₃electrolytes were preliminarily grasped.The pulse ECM experiments of TiAl4822 blade in NaCl and NaNO₃ electrolytes were carried out.The results showed that higher machining rate can be got in NaCl,and the better localization of electrochemical machining can be got in NaNO₃.Therefore,compared with the NaCl,NaNO₃ is more suitable for the machining of this kind of structure blade.（3）The experimental iof ECM large size typical blade with low frequency and small duty ratio pulse current method were carried out.With the low frequency and small duty ratio pulse current ECM method,the average processing current was reduced.The possibility of processing large size TiAl workpiece by conventional pulse power supply has been proved.The specimen processed by proposed method has approximate surface quality with conventional ECM parameters.