Cathode Reverse Copying Method And Its Applications On ECM Of Ti-Al Blade

TiAl intermetallic has been widely used in aero engine blades because of its excellent properties,such as light weight,high temperature resistance and so on.But TiAl intermetallic is difficult to be machined by conventional machining methods because of its low temperature ductility and high hardness.ECM is a non-traditional machining technology which removes material via the anode dissolution phenomenon in electrochemical reaction.ECM is suitable to machine TiAl intermetallic blades.But the forming process of ECM is so complex that it is too difficult to design its cathode accurately.And repeated processes of amending the cathode also extend the ECM preparation period.By using anti-copy ECM method,the workpiece can be anti-copied by the cathode which is copied by a standard blade.The anti-copy ECM is a rapid way to manufacture tool electrode.However,the process of ECM is not reversible and contains two ECM errors.So the accuracy of anti-copy ECM cannot satisfy the requirements of aero engine blade.This paper aimed to improve the accuracy of anti-copy ECM in TiAl intermetallic blades manufacture.The anti-copy ECM experiments were carried out to machine TiAl intermetallic blades.This paper mainly studies these aspects:(1)The anti-copy method with adjusting parameters for same and small machining gap was put forward.The characteristics and compositions of anti-copy ECM errors were analyzed.Through the finite element analysis of electric field,flow field and anode dynamic forming process of the two reverse ECM processes,the size and consistency of gaps were considered as key elements which mainly influence the machining accuracy of anti-copy ECM.So the anti-copy ECM method with adjusting parameters for same and small machining gap was proposed.(2)Anti-copy ECM experiments of the blades' surface were carried out.Anti-copy ECM experiments on the 1Cr18Ni9 Ti blade's surface were carried out.The results show that the accuracy of anti-copy ECM can be improved by reducing the size of machining gaps and improving the consistency of the two ECM processes.The validity of the proposed method was verified.Anti-copy ECM experiments on the TiAl intermetallic blade were also carried out by " adjusting parameters for same and small machining gap" method,and the results showed that the accuracy of TiAl intermetallic blades' surface reached 0.071 mm.It has been verified that the anti-copy ECM method is suitable for TiAl intermetallic blades manufacture.(3)End feed's direction was used in this paper when anti-copying the edges of a blade.Based on the profile of a real blade's leading and trailing edges,the anti-copy experiments of the 1Cr18Ni9 Ti blade's edges were carried out.The cylindrical surface of the leading and trailing edges has been successfully processed.The results showed that profile accuracy of the blade's edges was up to 0.062 mm.Therefore,the feasibility of machining leading and trailing edges in blades by using anticopy ECM with end feed's direction was proved.