Micro-hole structures are widely used in aircraft engines, but they are difficult to fabricate because of stringent machining quality requirements. Electrochemical discharge drilling (ECDD) is a hybrid machining method for fabricating small holes in nickel-based superalloys that uses low-conductivity salt solution as the working fluid. Electrical discharge and electrochemical dissolution occur simultaneously in the ECDD process. ECDD is expected to achieve micro-holes with high machining efficiency and without any recast layer, but little research has been carried out on the surface integrity. In this study, the surface morphology, element composition, residual stress, microhardness, and recast layer properties of the ECDD machined holes were analysed. The results show that the surface integrity of the holes improves by the ECDD method, and there is no recast layer, no melted debris, and no tensile residual stress. Moreover, with an increase of the working fluid conductivity from 0.005 to 3.6 mS/cm, the residual stress of the ECDD machined hole becomes compressive, the microhardness of the wall no longer decreases significantly, and the surface roughness of the wall decreases to Ra = 1.69 μm. Furthermore, the average diameter and the taper angle of ECDD machined hole increase with the increase of machining time. In addition, the entrance of the ECDD machined hole has a round corner without a sharp edge, and its radius-of-curvature is approximately 150 μm.

微孔结构广泛用于飞机发动机中，但是由于严格的加工质量要求而难以制造。电化学放电钻孔（ECDD）是一种混合机加工方法，用于在镍基高温合金中使用低电导率盐溶液作为工作流体来制造小孔。放电和电化学溶解在ECDD过程中同时发生。ECDD有望实现具有高加工效率且没有任何重铸层的微孔，但对表面完整性的研究很少。在这项研究中，分析了ECDD加工孔的表面形态，元素组成，残余应力，显微硬度和重铸层特性。结果表明，通过ECDD方法可以改善孔的表面完整性，没有重铸层，没有熔化的碎屑，也没有拉伸残余应力。此外，随着工作流体电导率从0.005增加到3.6 mS / cm，ECDD加工孔的残余应力变为压缩状态，壁的显微硬度不再显着降低，并且壁的表面粗糙度降低至Ra = 1.69微米 此外，ECDD加工孔的平均直径和锥角随加工时间的增加而增加。另外，经ECDD加工的孔的入口具有没有尖锐边缘的圆角，并且其曲率半径为约150μm。壁的显微硬度不再显着降低，并且壁的表面粗糙度降低至Ra = 1.69μm。此外，ECDD加工孔的平均直径和锥角随加工时间的增加而增加。另外，经ECDD加工的孔的入口具有没有尖锐边缘的圆角，并且其曲率半径为约150μm。壁的显微硬度不再显着降低，并且壁的表面粗糙度降低至Ra = 1.69μm。此外，ECDD加工孔的平均直径和锥角随加工时间的增加而增加。另外，经ECDD加工的孔的入口具有没有尖锐边缘的圆角，并且其曲率半径为约150μm。