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Evaluation of dimensional accuracy and surface integrity of cylindrical array microelectrodes and cylindrical array microholes machined by EDM

Sun Yao, Gong Yadong, Wen Xuelong, Xin Bo, Yin Guoqiang, Meng Fantao, Tang Benjia

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e46, 2022

EN

In this study, the loss self-finishing method based on EDM reverse copy principle was proposed aiming to enhance the prepared efficiency of cylindrical array microholes. First, the effects of geometric parameters of microelectrodes on the diameter consistent error, inlet and outlet deviation, section profile, surface roughness parameters and the heat affected zone thickness were quantitatively investigated. The forming accuracy of cylindrical array microelectrodes obtained by self-finishing and multi-finishing methods were contrastively analyzed. Furthermore, 8 × 8 cylindrical array microelectrodes with diameter of about 185.18 μm and length of 2168.79 μm were fabricated by the loss self-finishing method for the first time. Besides, the size accuracy, surface morphology and surface roughness parameters of cylindrical array microholes machined using array microelectrodes prepared by loss self-finishing method were evaluated. Experimental results disclosed that the average consistent errors of inlet and outlet diameter for cylindrical array microholes, respectively, were 1.495 μm and 3.13 μm, indicating that the cylindrical array microelectrodes obtained by loss self-finishing method are capable to manufacture cylindrical array microholes with good surface quality and high dimensional accuracy.

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Experimental study of Ni-based single-crystal superalloy: Microstructure evolution and work hardening of ground subsurface

Xu Yunchao, Gong Yadong, Wang Zhongxu, Wen Xuelong, Yin Guoqiang, Zhang Huan, Qi Yang

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 2

74--84

EN

In the present study, the grinding experiment of second-generation nickel-based single-crystal superalloy DD5 was carried out under different grinding parameters. The grinding force was recorded during the grinding process, and it was found that it decreased with increasing grinding speed and increased with feed speed. The microstructure evolution of ground subsurface was obtained by optical microscope (OM) and scanning electron microscope (SEM), and the elemental distribution of γ/γ' phases was investigated by energy dispersion spectrum (EDS). The results show that there are two layers different from the bulk material beneath the ground surface: (i) a white layer (WL) with no obvious structural features under limited observation scale and (ii) a severe deformed layer (SDL) with the elongated and rotated γ' phase and the narrowed γ channel. Elements segregation behavior exists in both the white layer and severe deformed layer. The grinding parameters have a great influence on the thickness of the white layer, which is due to the elemental diffusion behavior caused by intensive thermo-mechanical load. There is work hardening in the white layer, and the hardening degree aggravates with the increase in cutting speed and feed speed.

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Analytical and experimental study on micro-grinding surface-generated mechanism of DD5 single-crystal superalloy using micro-diamond pencil grinding tool

Sun Yao, Su Zhipeng, Gong Yadong, Ba Dsechun, Yin Guoqiang, Zhang Huan, Zhou Linhu

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 1

353--374

EN

Single-crystal superalloy is characterized by no grain boundary and widely used in the aviation and aerospace industry due to its high creep strength and high thermal fatigue resistance, especially applications in aero engine necessitate numerous micro-scale structures made of single-crystal superalloy material with high-dimensional accuracy and surface quality. Micro-grinding as one of micro-precision machining technology is capable to fabricate micro-parts and structures with high machining precision and quality. In this work, a series of diamond micro-pencil grinding tool (MPGT) with diameter ranged from about 100 to 800 μm are firstly prepared by hybrid processes. The surface-generated mechanism of micro-grinding process associated with effects of length ratio of rubbing, ploughing and chip forming were explored based on analytical and experimental investigations. In addition, a novel analytical force model for the DD5 material machined by MPGT is developed considering variable size effect under different length proportion, protrusion height distribution of MPGT and material mechanical properties, which can more accurately agree well with the measured results compared with the traditional micro-grinding force model. This study enabled an in-depth understanding of mechanical behaviour characteristics, surface formation and material removal mechanism under microscopic scale of single-crystal superalloy involved in micro-grinding.