Research progress on pitting mechanism of titanium alloy electrolytic processing

Electrochemical machining has more significant advantages than traditional machining in some fields such as biomedicine and aerospace, and titanium alloy is more suitable for electrochemical machining because of its own characteristics.

Titanium is one of the most abundant elements known in the Earth's crust, accounting for about 0.6%.

Titanium has a lower density, but has a similar strength to ordinary steel, and titanium and titanium alloys are favored in the aerospace field.

In recent years, due to the excellent corrosion resistance of titanium alloy, its application field has been greatly extended.

Electrolytic machining is the use of metal in a specific electrolyte electrochemical anodic dissolution of the principle of the workpiece processing forming a special processing means, compared with ordinary machining has many advantages, such as high processing efficiency, high molding accuracy, a wide range of applicable materials, processing tools without wear, the workpiece does not produce stress.

Ecm titanium alloy workpiece is not only used in the manufacturing process of precision parts such as integral blade disc, but also in the main load-bearing parts such as load enclosure frame, aircraft casing, landing gear beam and aircraft engine casing.

In the process of electrolytic machining of titanium alloy in the electrolyte, the passivation film formed by itself will hinder the smooth progress of the electrolytic machining, and with the titanium exposed in the electrolyte, the metal will continue to produce new passivation film to hinder the anode dissolution.

Therefore, the voltage U processing applied by ECM needs to be able to stably breakdown the passivation film, that is, to form an overpotential of electrochemical processing on the surface of the metal anode. For titanium alloys, the process of ECM is a process in which the local passivation film breaks to form pitting, and then pitting pits are superimposed until the matrix is exposed, and the matrix metal continues to dissolve and alternately form pitting and passivation on the surface.

Titanium alloy pitting is not only related to the smooth progress of the ECM process, but also affects the surface quality of the manufactured parts, which is the key in the ECM process of titanium and titanium alloy.