Simulation Study On Edm Combined Machining Of Directional Crystallization Cobalt-Based Superalloy Gas Film Holes

Directional crystalline superalloys have good heat resistance and creep resistance,and are widely used in aeroengine turbine blades.In order to better improve the high temperature resistance of the blades,the gas film holes are processed on the turbine blades to reduce the surface temperature of the turbine blades.It is a better method.However,the commonly used method of EDM machining gas film holes will leave a layer of resolidification on the inner wall of the gas film holes.There are micro cracks and pores inside the resolidified layer,which will greatly reduce the service life of the turbine blades.In view of the above problems,this paper studies the method of EDM combined machining of gas film holes.From the EDM temperature field simulation,the formation process and influencing factors of the resolidified layer are analyzed.From the perspective of the flow field,the EDM gas film is analyzed.The factors affecting the hole expansion performance of holes and electrolytic machining,and finally through electrochemical simulation research and improvement of electrolytic hole expansion machining,this study laid the foundation for the directional crystallization superalloy EDM,combining the high precision of EDM and electrolysis The advantages of the processed non-stressed and non-solidified layer provide an effective basis for processing the turbine blade gas film holes without the re-solidified layer,and have important research significance.Based on the analysis of the current research status at home and abroad,this paper uses the TRANSIENT THERMAL software to establish the heat source model of EDM and analyzes the problems that the discharge process is difficult to observe during the EDM process and the shape is not easy to observe after multiple pulse machining.simulation.The results show that when the second discharge point is on the flanging of the first discharge,the size of the pit generated by the second discharge point is slightly larger than the size of the pit generated by the first discharge point.When tangent to the first discharge pit,the size of the two discharge pits is basically the same,and the thickness of the re-solidified layer is the same.As the current and pulse width increase,the pit diameter,pit depth and thickness of the resolidified layer gradually increase,but too small current and pulse width will affect the machining efficiency.The overall preferred electric discharge machining current is 2A and the pulse width is 20?s.Aiming at the difficulty of observing the flow field of EDM and electrolytic machining,FLUENT software was used to simulate the flow field of the two machining methods.The analysis shows that the internal absorption EDM method can improve the flow field conditions in the gap compared with the internal punching EDM method,which is more conducive to the discharge of electrical corrosion products in the processing gap and better guarantees the smooth processing of the electrolyte;Compared with the inlet of the electrolyte in the axial direction and the radial direction of the electrolyte,there is no negative pressure area at the inlet of the machining gap,and the dead point area of the machining speed is smaller,which is more conducive to the electrolytic processing.In order to provide processing parameters and processing methods for electrolytic machining,COMSOL software was used to perform electrochemical simulation on electrolytic machining.The analysis and simulation results show that when the tool cathode is insulated to 0.0125 mm below the hole,the shape of the hole obtained by the reaming process is the best,the optimal processing voltage for electrolytic reaming is 7V,and the optimal electrolyte concentration is 15% by mass %NaNO₃ solution,and using this parameter to simulate the hole reaming time was 2.3s,which laid a foundation for subsequent experiments.