Experimental study on fabricating micro-holes in DD5 single-crystal nickel-based superalloy using electrical discharge d
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(2020) 20:87
ORIGINAL ARTICLE
Experimental study on fabricating micro‑holes in DD5 single‑crystal nickel‑based superalloy using electrical discharge drilling Siqian Gong1 · Yao Sun2 · Liya Jin2 · Zhipeng Su2 Received: 7 March 2020 / Revised: 22 June 2020 / Accepted: 29 June 2020 © Wroclaw University of Science and Technology 2020
Abstract The single-crystal superalloy materials have been rapidly developed and widely used in advanced thermal structural components due to their excellent comprehensive physical and chemical properties under high-temperature service conditions. However, conventional micro-hole making results in defects such as edge breakage and burr. In this study, the electrical discharge drilling (EDD) combined with helical microelectrode is first adopted to fabricate DD5 single-crystal nickel-based superalloy. The effects of tool geometry and machining parameters on subsurface damage layer, micro-hole taper, surface morphology, surface roughness and machining time were investigated in detail. Experimental results indicated that helical microelectrode can obtained smoother surface without debris deposition and thinner subsurface damage layer depth lack of micro-cracks compared with cylindrical microelectrodes. Additionally, the computational fluid dynamics model was developed to analyze working fluid movement and reveal effective debris removal mechanism of helical microelectrode. The vortices will be generated in lateral gap fluid between micro-hole and helical microelectrode and have a certain delay time. The surface roughness and dimensional precision of micro-holes fabricated by helical micro-electrodes are greatly improved and machining efficiency is also improved by 30.94% compared to cylindrical microelectrodes. This work could provide theoretical and process guidance to assist in realizing high surface quality and low subsurface damage of micro-holes obtained with EDD process. Keywords Electrical discharge drilling · Micro-holes · Single-crystal nickel-based superalloy · Subsurface damage · Surface quality
1 Introduction Single-crystal superalloy materials completely eliminate grain boundaries and have better comprehensive physical and chemical properties under high-temperature service conditions, which allow it to be rapidly developed and widely used in the preparation of turbine blades and other advanced thermal structural components [1–3]. To balance the effects * Siqian Gong [email protected] * Yao Sun [email protected] 1
School of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, No. 3 Shangyuancun, Haidian Distrct, Beijing 100044, People’s Republic of China
School of Mechanical Engineering and Automation, Northeastern University, Shenyang 110819, People’s Republic of China
2
of inlet high temperature on single-crystal superalloy components, large amounts of micro-holes are fabricated to reduce the temperature, but the surface quality and subsurface damage of these micro-holes will significantly affect the service life of these components [4].
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