| With the development of industrial technology,the requirements of surface quality of parts and components are higher.In order to improve the performance of the surface physical and mechanical properties,surface roughness and brightness of parts,a variety of precision mechanical and finishing methods came into being,such as precision grinding,polishing,honing,belt grinding.The consolidated or free abrasive is used to finish and improve the surface quality of parts.Although mechanical finishing is widely used,there are still some defects such as many processes,high requirements of personnel and equipment,spike-like microstructure on the surface,and low efficiency.Especially for the complex surface of the parts with high performance requirements,such as blades,the polishing process is mostly carried out manually,which is a time consuming and high labor intensity and easy to burn the surface.It is difficult to ensure the stability and reliability of processing.because the quality depends on the experience of labors.In order to deal with the problems of the finishing of complex profiled metal parts,the paper put forward a hybrid finishing method of electrochemical assisted by freely flowing abrasive particles.What’s more,the equipment for free-flowing abrasive electrochemical finishing was completed.Above all,the basic experimental investigations on hybrid finishing were carried out,the main contents are as follows:(1)Combining the principle of electrochemical polishing and the principle of abrasive flow polishing,a hybrid finishing method of electrochemical assisted by freely flowing abrasive particles was proposed.The mechanism of this hybrid finishing process was analyzed in detail.On the one hand,the passive film or adhesive film is produced on the surface of the parts by the action of electrode polarization and prevent anode dissolution.On the other hand,the abrasive particles can scour the surface under the drive of electrolyte and the film is removed by the micro-grinding action,and then,the material is exposed.However,the film is thicker at the concave and not easily scraped.It causes the difference of electrochemical dissolution,and the finishing process is achieved.(2)A hybrid finishing equipment system was developed,and an integrated test platform was designed and built.First,in order to ensure that the abrasive particles can be mixed in the electrolyte evenly and make them flow into the channel at a certain speed and pressure,a solid-liquid two-phase flow circulatory system is designed and built.Secondly,a test fixture for the observation abrasive particles is designed and produced to observe and study the flow state of the abrasive particles.Thirdly,the servo reversing system is adopted to ensure uniformity of micro-grinding action.Meanwhile,the temperature control system is designed and set up to ensure the temperature of the electrolyte constant.What’s more,to facilitate the operation of all the equipment,the control system is designed and built.Finally,the installation,commissioning and trial operation of platform have been completed for basic test research.(3)The research on the basic test of hybrid finishing is carried out.First of all,the influences of electrolyte concentration,current density,processing gap,inlet pressure and abrasive particle on the surface roughness were analyzed by single factor test.The results showed that the factors affecting the electrochemical action including current density,electrolyte concentration and machining gap.The factors affecting the micro grinding were abrasive particle size,electrolyte inlet pressure and machining gap.When the abrasive particle is 80#,the inlet pressure is 0.5MPa,the electrolyte concentration is15%,the machining gap is in the range of 2~4mm,and the current density is about 56A/dm~2,the better surface quality can be obtained,and the surface roughness value Ra is 0.23μm.Secondly,the comparative experiments were carried out,and the effects of three forms of pure electrolysis,pure abrasive and compound action on the finishing were analyzed.The results show that the hybrid machining can effectively improve the polishing efficiency,reduce surface roughness,improve the surface morphology and stress state of surface,with better finishing effect. |
