Electrochemical Discharge Drilling of Inclined Micro Holes with Step Feeding Method
Electrochemical Discharge Drilling of Inclined Micro Holes with Step Feeding Method
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DOI：
10.20964/2020.03.13
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发表时间：
2020-03
影响因子：
1.5
通讯作者：
Hang Yusen;N. Astronautics
中科院分区：
文献类型：
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作者：
Hang Yusen;N. Astronautics
气膜冷却孔主要分布在涡轮叶片表面，中心线与切线方向成一定角度。这些“倾斜微孔”（IMH）因其直径极小、切削金属材料的挑战以及对加工质量/效率的高要求而难以加工。为了实现 IMH 的加工，我们采用了电化学放电钻孔方法。然而，由于出口处的湍流场和短电解时间，重铸层保留在IMHs的出口处。为了进一步提高IMHs的加工质量，采用了电极步进送料的方式来延长电解时间（即工具电极在穿透工件后短暂停止）。改变进给速率并增加电极的暂停时间 (PToE) 导致电极穿透 IMH 后电解继续进行。 IMH 周围的电化学溶解足以改善重铸层的去除。因此，获得了没有重铸层的IMH。进行了不同PToE的实验，并对电压波形、电流波形、平均直径、IMH形貌以及IMH壁上重铸层的消除进行了分析。结果表明，分步补料法会腐蚀IMH出口处残留的重铸层。
Film cooling holes are distributed mainly on the surface of turbine blades, with center lines at angles to the tangential direction. These “inclined micro holes” (IMHs) are difficult to machine because of their extremely small diameters, the challenge of cutting metal materials, and the high requirements for machining quality/efficiency. To achieve machining of IMHs, we employed an electrochemical discharge drilling method. The recast layer, however, remained at the outlet of IMHs due to the turbulent flow field and short electrolysis time at the outlet. To improve further the processing quality of IMHs, step feedinging of electrode was used to prolong the electrolysis time (i.e., the tool electrode was stopped for a short time after penetrating the workpiece). Changing the feed rate and increasing the pause time of electrode (PToE) led to continuation of electrolysis after penetration of the electrode out of the IMH. Electrochemical dissolution around the IMH was sufficient to improve removal of the recast layer. Therefore, IMHs without a recast layer were obtained. Experiments with different PToE were carried out, and analyses of voltage waveforms, current waveforms, average diameter, IMH morphology, and elimination of the recast layer on IMH walls undertaken. Results showed that step feeding method could corrode the residual recast layer at the outlet of IMHs.