“Confined Etching –Electrolysis” Composite Electrochemical Machining On Superalloy GH4169

Superalloy has been widely used as constructive parts in aeronautical and spacial industry for its excellent performance in high temperature environment. However it is because of its excellent strength and hardness that leads to superalloy’s difficult to be machined with traditional machining methods, especially for complex three-dimensional shape parts machining. While electrochemical machining(ECM) has advantage in machining high-strength, high-hardness material and complex three-dimensional shape parts. But now the ECM can’t work in a fixed location stably, and always have a low machining precision and inferior surface quality. In view of the advantages of confined etchant layer technique(CELT) for machining complex three-dimensional shape with high precision, this thesis integrated CELT with the traditional ECM technology, formed a new type of electrochemical machining method, named as “confined etching – electrolysis” hybrid electrochemical machining technology, to make up for the disadvantages of low machining accuracy and poor of the surface quality of traditional ECM. A preliminary study was conducted for this new hybrid processing technology.“Confined etching – electrolysis’ ’ hybrid electrochemical machining technology using composite electrolyte system and through cleverly designed current direction controlling method(or cathode-anode constantly alternating method) in the composite electrolyte solution system, it made the ECM and the CELT work continuously. With this technology, the machining gap state and the machining accuracy can be improved.A series of orthogonal experiments and monofactor experiments were done for the composite electrolyte system. A composite electrolyte composition was obtained for superalloy GH4169 machining, which was suitable not only for ECM technique but also for CELT. Through the exploration to the processing parameters, pulse power was selected as processing power. the composite electrolyte system was confirmed Finally:20g/L NaCl+10g/L NaNO3+25g/L NaNO2+8g/L NaF+9g/L NaOH+15g/L C4H4Na2O6+0.1g/L C19H42 BrN,Under a set of optimal processing conditions such as the processing voltage 3-4 V, the duty cycle 1:13, the frequency 250 Hz, the running speed of cyclic pump is 100 r/min(control of electrolyte circulation rate and remove reactive products), a half-sphere structure was machined on the surface of superalloy GH4169. Its machining accuracy is 70 μm and roughness of surface is 0.78 μm. The advantages of hybrid machining were obviously shown from the comparing it with pure ECM.The work of this thesis was just a preliminary study. The machining accuracy was far lower than that of CELT in Micro machining field. We believe that the machining accuracy of hybrid machining would be improved markedly after in-depth research and improvement of technical equipment.