Investigation of Pulsating Electrochemical Dissolution of Nickel in Rotating Processes

Abstract

In counter-rotating electrochemical machining, the current density at a certain point on the workpiece surface presents a pulse characteristic due to the rotation of the workpiece. The waveform and the period of the current for material dissolution are different from that in conventional pulse ECM, resulting in different dissolution performances. In this paper, the pulsating dissolution behaviors of nickel in rotating processes are investigated. Nickel sheets are particularly used to investigate the dissolution processes during one rotation cycle and at different rotational speeds. The machined nickel surfaces are examined by using scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The results indicate that the pulsating dissolution of nickel depends strongly on the rotational speed. Passivation, pitting, high rate dissolution and selective dissolution occur successively during one cycle at low rotational speeds. While, when the rotational speed is over 50 rpm, passivation and pitting alternately happen due to the shortening of the pulse period, which results in rapid decrease in material removal weight. Based on the above research, it can be concluded that the low rotational speeds are more favorable for the effective machining of nickel in CRECM.