Anodic Dissolution Localization under Pulsed Electrochemical Machining of Heat-Resistant Nickel-Chromium Alloys

It is shown that anodic dissolution of heat-resistant nickel-chromium alloys using microsecond pulses (20 µs) with a maximum current density per pulse, up to 100 A/cm², allows to increase anodic dissolution localization due to increasing the current efficiency versus the current density relationship. Such dependence was observed only for nickel-chromium steel and with a duty ratio of not less than 4. It has been hypothesized that the cause of the observed dependence is thermokinetic effects (positive feedback: the electrochemical process rate (current density) – surface temperature – the electrochemical process rate), leading to the achievement of certain critical conditions for thermokinetic instability and destruction of surface passivating layers.