Investigation On Electrochemical Machining Of Blades With Independent Electrolyte Supply At The Leading/Trailing Edges

As the core part of the aeroengine,the blade plays a crucial role in the performance of the engine.Because of the twisted shapes and difficult-to-machine materials of blades,it is a great challenge to manufacture them.Electrochemical machining(ECM)has unique advantages such as no tool wear,high efficiency,good surface quality,and being independent of mechanical properties of metal materials.It has gradually become one of the main methods for the manufacture of aeroengine blades.Electrochemical dissolution characteristics of workpiece materials and flow field design in machining are two basic issues in the research of ECM technology.In this paper,the dissolution characteristics of 1Cr11Ni2W2Mo V heat-resistant steel and flow field design in ECM of blades were studied as follows:1.The research focused on the electrochemical dissolution characteristics of 1Cr11Ni2W2Mo V heat-resistant steel.Bases on the analysis of the polarization curves and the current efficiency curve of the material in 20 wt%Na NO₃solution,the decomposition voltage was 1.35 V,the linear polarization curve changed smoothly and the cyclic polarization curve reflected the good self-passivation ability of the material.The current efficiency curve was nonlinear,and the maximum current efficiency in the experiments was 59.1%.The inhomogeneous microstructure was found by observing the metallographic structure of the material.2.The ECM experiments of 1Cr11Ni2W2Mo V blades under different current densities were carried out,and the different morphologies and textures of the machined surfaces were found.When the current density j?15 A/cm²,the surface of the specimen was flat substrate.When 15<j?40A/cm²,the surface presented a black-and-white water wave morphology.When j>40 A/cm²,the surface is completely covered by black oxides.Based on the experimental results,a qualitative dissolution model of 1Cr11Ni2W2Mo V in Na NO₃ solution was established.It has been proved that the machining current density of 30?40 A/cm² is conducive to better surface integrity of the specimen.3.Under the condition of the closed machining area,a new flow field model with four inlets for independent electrolyte supply at the leading and trailing edges was proposed.The flow field simulation of the whole blade ECM process was carried out.The results showed that,in the machining areas of leading and trailing edges,the pressure and velocity distribution in the four-inlet flow field was more uniform and the variation along the flow path was gentler than in traditional two-inlet flow model.4.According to the independent electrolyte supply channels at the leading and trailing edges,the optimal design of the size of inlets and the supply pressure was carried out.Through the simulation studies,the optimal parameters of the auxiliary inlets section size of 14 mm×3 mm and the electrolyte supply pressure of 0.9 MPa were obtained,which were conducive to a good uniformity of flow field in the machining process.5.For a certain type of aeroengine blades,the cross-structural cathodes and corresponding fixtures were developed,the process parameters were optimized,and the ECM experiments were carried out.The results showed that,the contour dimension deviation of concave surface was-13.2?51.4?m,the convex surface was-19.8?37.1?m,the leading edge was-73.9?53.1?m,the trailing edge was-54.6?40.7?m,and the transition of the leading and trailing edges of the blade was smooth.The surface roughnesses(Ra)of the blades were within 0.531?m.