Energetic Analysis of the Anodic Double Layer During Electrochemical Machining of 42CrMo4 Steel

In contrast to most other manufacturing technologies in ECM the electric voltage is the manufacturing tool itself. The pure material dissolution takes place without upstream transformation of electrical energy into other types of energy. Nevertheless, the overall efficiency is very low as more than ninety percent of fed energy is not used for dissolution but converted into heat. Due to this it is questionable why the efficiency is so low, although there are no necessary conversions of energy which are lossy.The dissolution of material takes place in the electrolytic double layer and depending on the electrolyte system either with or without a passive transition state. Corresponding to these mechanisms the amount of energy for transpassive dissolution is quite higher than without passivation.For this reason, in this paper the necessary amount of energy for the dissolution is exemplarily examined for 42CrMo4 steel. The voltage drop in the anodic double layer takes place within a few nanometers, thus, it cannot be measured directly. However, with help of potentiometric measurements the potential drop can be determined very precisely. As this energy drop corresponds to chemical changes of the rim zone, occurring material modifications can be measured that way. Due to this, the energy conversion can be described on different length scales and summarized to a so-called process signature. Based on this idea different processes can be compared to set up rim zone properties purposefully in advance.