For the appearance of recast layer and micro-crack in laser drilled micro-holes
electrochemical machining(ECM)is considered to reprocess the holes to eliminate these defects. The experimental system of hybrid processing of laser beam machining with ECM is developed. Nickel based superalloy GH4169 is used in the ECM experiment to explore the influences of electrolytic current
concentration of sodium nitrate solution and parameters of pulse electrochemical machining(PECM)on the electrolytic rate and the removal effect of recast layer. When the current density is larger than 13.8 A/cm
2
the electrolytic rate is proportional to the current. The concentration of sodium nitrate solution has no effect on the electrolytic rat
e in constant current ECM. So the concentration can be determined by the current and the voltage. PECM with low frequency and wide pulse or with high frequency and narrow pulse is beneficial to the improvement of electrolytic rate. In particular
the electrolytic rate can get the maximum value at the frequency of 1 kHz and the duty ratio of 40%-60%. PECM is accompanied by hydrogen pressure wave
which plays a good role in stirring the electrolyte in the machining gap. As a result
it can improve the current efficiency and increase the electrolytic rate. The recast layer of laser drilled micro-holes can be removed completely by choosing appropriate ECM parameters.
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