Background: Electrochemical machining (ECM) is a non-traditional machining method for the metal material based on the principle of anode electrochemical dissolution which has been used in micro/nano fabrication with advantages as not influenced by materials intensity and hardness, no residual stress and no heat treatment born on the surface of the workpiece. Several researches and applications have shown that the surface quality can be improved effectively during the electrochemical machining by using ultrashort pulse power supply.
Method: This paper presents a potential of electrochemical machining at the nanometer scale. First, a transient charging double layer mathematical model is developed to describe electrochemical nanostructuring of metallic materials with ultrashort (nanosecond) voltage pulses. And then, by using finite element method (FEM), the analysis model of electrochemical interface between poles is established to give a more realistic analysis of the comparison of transient currents at different separations between the tool and workpiece. Second, a nanoscale electrode is an essential tool in electrochemical nanostructuring. In this paper, electrodes with diameters of several ten to hundred nanometers are successfully prepared by the liquid membrane electrochemical etching. Finally, by using the nanometer scale electrodes above and the ultrashort pulse power supply, several nanostructures with physical dimension of several hundred nanometers are fabricated on nickelbased superalloys.
Results: Using the optimal machining parameters, a tool electrode with 230 nm in diameter is obtained from the initial tungsten rod radius of 100 μm. By using 0.05 M H2SO4 solution, the pulse generator with 1μs in period, 100 ns in pulse on-time and 4 V in voltage, a micro/nano groove with the depth of 150 nm and maximum entrance width of 3 μm is obtained.
Conclusion: Nanoscale electrodes with diameters of several ten to hundred nanometers is obtained successfully demonstrating that the liquid membrane electrochemical etching is a very effective method to fabricate nanoscale electrode. Several nanostructures with physical dimension of several hundred nanometers can be fabricated successfully demonstrating that ECM with ultrashort pulses is a highly promising nanostructuring technology.