Characterization of component damage due to short circuits during electrochemical machining (Chara-Kass)

• Applicant: Dr.-Ing. Andreas Klink
• Subject Area: Metal-Cutting and Abrasive Manufacturing Engineering
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 532772852

Due to best surface qualities in combination with high material removal rates and a good energy efficiency, the electrochemical machining (ECM) is suited for manufacturing of high strength materials and therefore a relevant technology in turbomachinery business. In contrast to the numerous advantages, ECM is characterized by a challenging process control, so that short-circuits can even occur in long time established series process steps, which results in component damage. A short-circuit causes a high energy input of electrical current on a small area, resulting in a thermally damaged zone. Because of this defect in surface integrity, these parts are usually rejected without regarding the material allowance, which typically results in a great economical loss. Therefore, there is a lack of fundamental understanding of the energetic behavior of short-circuits and the resulting influence on the surface integrity of the parts in ECM. Only by analyzing and evaluating this defect, there can be a further development of the electrochemical machining process, so that the workpiece quality can be ensured. Thus, the research hypothesis of this project is the following: Using ECM process data and a detailed knowledge of the surface integrity of short circuits, a model can be derived for the nondestructive evaluation of localized edge zone damage. In this project, an experimental setup is developed to reproduce critical gap conditions in order to analyze single short-circuits on sample workpieces. By varying the electrical process parameters, the electrolyte conditioning as well as the geometrical gap parameters, different types of short-circuits are produced. The influence of these short-circuits on the surface integrity will be analyzed by using metallographic methods on the damaged area. Using electrical signal acquisition, the short-circuits will be characterized based on their energy. Furthermore, the waveforms of the signals will be interpreted. Regarding the research hypothesis, by combining the identified workpiece damage and the classification of short-circuits based on their electrical data, an empirical model regarding the non-destructive evaluation of short-circuit damage will be generated. Finally, the transferability of the model on generic short-circuit damage will be evaluated on an actual turbine blade geometry.

• DFG Programme: Research Grants