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Beryllium copper alloys known as high-reliability engineered materials are widely used in many engineering fields. Micro-electrical discharge machining (micro-EDM) provides a safely and effectively machining process to machine beryllium copper alloys regardless of their toxicity and mechanical strength. During micro-EDM, the higher material removal rate and the lower electrode wear rate are observed when deionized water is used as a dielectric fluid. However, there are many stray-current corrosion pits on the end surface of holes which directly affect the performance and life span of parts. In this study, the method of auxiliary electrode was used to suppress the effects of stray-current corrosion on the end surfaces of holes on C17200 beryllium copper alloy. The end surfaces of holes were protected by sacrificing the auxiliary electrode. The feasibility of micro-EDM with an auxiliary electrode was verified by an experiment of a hole machined with half coved by the auxiliary electrode and the others without. The effects of the thickness of the auxiliary electrode on end surface quality and machining time were studied. The effects of the auxiliary electrode to suppress stray-current corrosion on C17200 beryllium copper alloy were proved under diffident pulse currents and pulse widths. Machining time and electrode wear were investigated. The results show that the electrode wear is scarcely affected by the auxiliary electrode. However, the machining time is slightly increased when the pulse current is lower than 0.55 A, and the pulse width is shorter than 20 μs. Beyond that level, the effect of the auxiliary electrode on machining time is not obvious. The end surface quality decreases when the pulse width is longer than 20 μs. In addition, the results also show that, when the thickness of the auxiliary electrode is 60 μm, a value of 0.34 A pulse current and 20 μs pulse width could be considered as ideal parameters for C17200 beryllium copper alloy machined by micro-EDM with an auxiliary electrode in deionized water. Furthermore, it is confirmed that the auxiliary electrode can be easily fixed on different radii of curvature surface and effectively protect the end surface of micro-holes from stray-current corrosion. [ABSTRACT FROM AUTHOR]

Beryllium copper alloys with excellent features are widely used in many engineering fields, and their fabrication requires high machining speed. However, the fabrication of beryllium copper alloys by traditional processes has serious problems. In this study, high-speed electrochemical discharge drilling (HSECDD), a hybrid process containing electrical discharge machining (EDM) and electrochemical machining (ECM) in deionized water, was used to machine micro-holes on C17200 beryllium copper alloy. The material removal mechanism of HSECDD was studied and compared with traditional EDM. The performance of the process was investigated under different conductivities of peak current and pulse width. The results show that HSECDD is a high-efficiency method to machine C17200 beryllium copper alloy. During HSECDD, the material removal depends mainly on EDM. And, the ECM occurs at the entrance region of micro-holes machined by EDM. The function of ECM is to expand the gap between the electrode and the hole. The machining speed and average diameter of micro-holes increase with the increasing of peak current and pulse width. Increasing the pulse width will reduce the electrode wear. However, the taper angle will increase. In addition, the results also show that a value of 0.34-A peak current and 10-μs pulse width can be considered an ideal parameter for HSECDD to machine micro-holes on C17200 beryllium copper alloy. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Superhydrophobic surfaces have a wide application prospect in the future industrial production due to its special abilities. The fabrication of superhydrophobic coating on metal surfaces can improve its performance. A one-step electrodeposition method is proposed to construct nanostructures on the surface of beryllium copper (Be-Cu) alloys, and a mixture of copper chloride and stearic acid is used as the electrolytes. The static contact angle of water on the surface can reach up to 163 ± 4°, a sliding angle of 1.7 ± 0.2°. The nanostructure and chemical composition on the surface were evaluated by scanning electron microscopy and X-ray photoelectron spectroscopy respectively. The corrosion resistance was tested through electrochemical measurement. It was found that the as-prepared superhydrophobic coating improved the corrosion resistance significantly. In addition, the coating with excellent self-cleaning performance was proved. This method solves the problems of complicated process, improves the efficiency effectively, and the electrolyte is eco-friendly. [ABSTRACT FROM AUTHOR]

Micro-liquid floated gyroscopes are widely used in nuclear submarines, intercontinental missiles, and strategic bombers. The machining accuracy of micro-ball sockets determined the motion accuracy of the rotor. However, it was not easily fabricated by micro-cutting because of the excellent physical and chemical properties of beryllium copper alloy. Here, we presented a linear compensation of tool electrode and a proportional variable thickness method for milling micro-ball sockets in C17200 beryllium copper alloy by micro-electrical discharge machining. The machining parameters were systematically investigated and optimized to achieve high-precision micro-ball sockets when the k value was 0.98 and the initial layer thickness was 0.024 mm. Our method provided a new way to fabricate micro-ball sockets in C17200 with high efficiency for micro-liquid floated gyroscopes. [ABSTRACT FROM AUTHOR]