Research on an EDM-based unitized drilling process of TC4 alloy
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To reduce the recast layer and cracks formed during the small hole, electrical discharge machining (EDM) of the TC4 alloy, negative polarity EDM, and electrical discharge machining/electrochemical machining combined process (EDM/ECM) were carried out. The machining efficiency, the recast layer, and the cracks were studied. The experimental results showed that when compared with common positive polarity EDM under the specific processing condition, the recast layer of the negative polarity EDM decreased by 65% in thickness but the material removal rate (MRR) decreased by 31%. In EDM/ECM, MMR was 18% higher than the positive polarity EDM, and the majority of the recast layer and the cracks were removed. However, issues including the low efficiency occur during the penetration period. The following paper analyzed the causes of these problems and proposed a novel unitized hole drilling process. In this unitized process, EDM/ECM was initially used and then converted to negative polarity EDM with external flushing water during the penetration period. The general machining efficiency of a single hole increased by 73% over conventional EDM/EDM. Furthermore, only a 7-μm thick recast layer remained at the hole’s outlet, with no obvious cracks found.
KeywordsEDM drilling EDM/ECM combined process TC4 alloy Recast layer
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The authors also extend their sincere thanks to those who contributed in the preparation of the instructions.
This work is supported by the open Research Fund of Key Laboratory of High Performance Complex Manufacturing, Central South University (Kfkt2015-04), and the National Natural Science Foundation of China (Grant No.51575271 and 51675272).
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