Electrochemical trepanning with an auxiliary electrode

Electrochemical trepanning(ET)is one of the main methods for processing the blisks in aero-engines.However,stray corrosion in ET has a very negative impact on the machining quality of the blades.This paper proposes an innovative ET method with an auxiliary electrode surrounding the inner wall of the cavity above the cathode.Two-dimensional electric-field models are established and simulations are carried out with the auxiliary electrode at different positions and different electric potentials.The electric-field simulations show that adding the auxiliary electrode reverses the directions of the current lines in the processed area,thereby protecting it.The results show that when the distance from the bottom of the auxiliary electrode to the top of the cathode tool is 3 mm and the potential difference between the auxiliary electrode and the anode workpiece is 5 V,the area corroded by stray current is decreased.Experiments are performed under the parameter values determined by the simulations,and they confirm that this method is effective at reducing stray corrosion.Specifically,at a feed rate of 2.5 mm/min,the blade taper angle is decreased from 1.37°to-0.09°,the thickness of the leading and trailing edges is increased from 0.307 mm to 0.704 mm,and the average surface roughness is decreased from S_(a)=8.239μm to S_(a)=7.028μm.

Optimization of flow field in electrochemical trepanning of integral cascades(Ti6Al4V)

Ti6Al4V is widely applied in the integral cascades of aero engines.As an effective machining method,electrochemical trepanning(ECTr)has unique advantages in processing surface parts made of hard-to-cut materials.In ECTr,the state of the flow field has a significant effect on processing stability and machining quality.To improve the uniformity of the flow field when ECTr is applied to Ti6Al4V,two different flow modes are designed,namely full-profile electrolyte supply(FPES)and edges electrolyte supply(EES).Different from the traditional forward flow mode,the flow directions of the electrolyte in the proposed modes are controlled by inlet channels.Simulations show that the flow field under EES is more uniform than that under FPES.To further enhance the uniformity of the flow field,the structure of EES is optimized by modifying the insulating sleeve.In the optimized configuration,the longitudinal distance between the center of the inlet hole and the center of the blade is 6.0 mm,the lateral distance between the centers of the inlet holes on both sides is 16.5 mm,the length to which the electrolyte enters the machining area is 1.5 mm,and the height of the insulating sleeve is 13.5 mm.A series of ECTr experiments are performed under the two flow modes.Compared with EES,the blade machined by FPES is less accurate and has poorer surface quality,with a surface roughness(R_(a))of 3.346μm.Under the optimized EES,the machining quality is effectively enhanced,with the surface quality improved from R_(a)=2.621μm to R_(a)=1.815μm,thus confirming the efficacy of the proposed methods.