Micro-EDM drilling of high aspect ratio micro-holes and in situ surface improvement in C17200 beryllium copper alloy

Beryllium copper alloys are the ideal materials to fabricate the supporting parts owing to their excellent physical and chemical properties. Many high aspect ratio micro-holes are often required to realize the special missions. However, they were not easily fabricated by the traditional machining methods owing to the materials' mechanical strength. Here, we presented a high efficiency method for drilling high aspect ratio micro-holes on C17200 beryllium copper alloy by combining deionized water based microEDM and in situ PMEDM with boron carbide additives. The machining parameters were systematically investigated and optimized to realize the ever high aspect ratio of 23.26 at the holes' diameter of 215 mm. The surface quality of the micro-hole was improved further by in-situ PMEDM, which was demonstrated by the decreasing of surface roughness (Ra) from 2.65 mu m to 0.92 mu m. Our method will open an avenue to fabricate high aspect ratio micro-holes on C17200 with high efficiency. (C) 2017 Elsevier B.V. All rights reserved.