| With the continuous development of aviation technology,the requirement of thtust weight ratio performance of aero-engine is constantly improving.To achieve this,the most effective way is to replace the original parts with light materials to reduce the weight of the aero-engine.Moreover,it has become the main method for the design of new high thrust weight ratio aero-engine.The titanium aluminum(TiAl)intermetallic,as a high-temperature lightweight alloy,has the characteristics of low density,high modulus of elasticity,good flame retardant and high temperature oxidation resistance,it has become an ideal material to replace nickel base alloy in the aero-engine components.However,due to the low plasticity at room temperature and high hardness of TiAl material,it is easy to produce micro-cracks and chippings on the machined surface.The problem is especially prominent when machining the thin-walled and sharp edge areas such as the leading and trailing edges of the blade.So the machining of TiAl is very difficult.Electrochemical machining(ECM)is a non-traditional machining technology to remove materials through controlled electrochemical anodic dissolution reaction.It has become one of the main manufacturing methods of TiAl blades at present because the advantages of non-contact,no tool wear,good surface integrity and high processing efficiency.Tool vibration-assisted pulsed ECM(VPECM)is an important method to reduce the machining gap and improve the machining accuracy.Tt is also an important measure to improve the precision of electrochemical machining of the leading and trailing edges of the blade.In this paper,the electrochemical dissolution characteristics of TiAl in VPECM were studied.Taking the typical TiAl blade as the research object,the precision VPECM of its leading and trailing edge technology is studied.The main research contents includes the following aspects:(1)The electrochemical dissolution characteristics of TiAl intermetallics under VPECM were revealed.Based on the study of the anodic polarization curve and current efficiency curve of TiAl in different electrolytes,the dissolution characteristics of TiAl are preliminarily mastered.In order to grasp the influence of processing parameters on machined quality,the orthogonal experiment on parameter optimization of VPECM were carried out with the evaluation index of surface roughness,replication accuracy and average current density in pulse width.the grey correlation analysis method is selected for result analysis to determine the optimal combination of electrical machining parameters.Finally,TiAl blades were processed by using the optimized parameter combination,and the machining sample has high profile accuracy and good surface quality.(2)Preliminary grasped the forming rules of anti-copy VPECM of leading and trailing edges of the blade.Based on the analysis on the characteristics of leading and trailing edges,the electric field simulation models for the anti-copy cathode surface and ECM workpiece surface of leading and trailing edges were established.The influence of different width-diameter ratio on the contour forming of the blade's leading and trailing edges in VPECM is studied by simulation analysis method.The optimal width-diameter ratio of the blade's leading and trailing edge is optimized respectively.Finally,Anti-copy VPECM experiments of the leading and trailing edges were carried out.The test specimens have high contour accuracy,which verifies the simulation optimization results.(3)According to the characteristics of the anti-copy VPECM of leading and trailing edges on TiAl blades,the cathode and the fixture were designed according to the optimized width-diameter ratio.The experiments of anti-copy cathode surface and ECM workpiece surface were carried out by using VPECM of leading and trailing edges method.The TiAl blade samples were successfully processed,and the leading and trailing edges of the blade has good contour accuracy and repeatability. |
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