Test And Technology Research On Electrochemical And Discharge Hybrid Machining For Micro Hole Of Difficult-to-machining Material

The film cooling holes on aero-engine turbine blade are large in number and small in diameter,and the surfaces are required no micro cracks and no recast layer.The materials are difficult to process superalloys.It is difficult to satisfy the processing requirements with traditional machining.Electrochemical and discharge hybrid machining include not only the advantage of high efficiency of EDM hole drilling but also the good surface machined by ECM,and could satisfy the high processing requirements.It is expected to achieve the fabrication of film cooling holes on turbine blade at high speeds and without recast layer.In this study,more attentions have been paid to technology researches on electrochemical and discharge hybrid machining for micro hole at high speeds and without recast layers.The main studies and contributions in this dissertation are as followings:(1)The reduce length of tube electrode could improve the machining quality of electrochemical and discharge machining.The hybrid machining experiments were carried out to explore the effect of length of the tube electrode.The experimental results show that using a short tube electrode could improve the machining efficiency,stability,morphology accuracy and surface quality.(2)In order to improve the surface quality of the hole wall and remove recast layer,the methods of increasing the bottom pause time and using the high & low voltage pulse power were used.The experiments were carried out to find whether these methods could improve the surface quality of the hole wall and remove recast layer.The results show the recast layer can be completely removed when the bottom pause time is set to 4s or more.Using high & low voltage pulse power could significantly reduce the residual recast layer,but there is still a small amount of residue.(3)According to the characteristics of turbine blades and film cooling holes,the experiments of electrochemical and discharge machining for slant hole were carried out,and the processing of film cooling holes on turbine blade was carried out.The experimental results show that the electrochemical and discharge hybrid machining of the oblique holes could get a better morphology,but it has a larger diameter with lower efficiency.When the bottom pause time is set to 4s,the recast layer on the walls of the holds could be completely removed.The fabrication of film cooling holes on turbine blade at high speeds and without recast layer was implemented initially by the optimizing processing parameters.