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Chinese Journal of Mechanical Engineering 2020年第4期33卷 175-184页

作者： Xiaoyun Hu ningsong qu Nanjing University of Aeronautics and Astronautics Nanjing 210016China Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology Nanjing 210016China

Nickel-cobalt/silicon carbide(Ni-Co/SiC)composite coatings were fabricated by supergravity field-enhanced *** surface morphology and the distribution of the SiC particles in the coatings were examined by scanning electron microscope and energy dispersive X-ray *** preferred orientations of the coatings were measured by X-ray *** wear resistance and microhardness were measured by a reciprocating tribometer and a microhardness instrument,*** results revealed that the use of the supergravity field enhanced the smoothness of the as-deposited Ni-Co/SiC coatings,and the SiC nanoparticles were uniformly distributed in comparison with that for conventional *** the rotation speed of the cathode,which provided the supergravity field,was 800 r/min,the SiC content in the coating reached a maximum of 8.1 wt%,which was a much higher content than the 2.2 wt%value obtained under conventional *** highest coating microhardness of 680 HV was also observed at this rotation *** addition,the wear resistance of the as-prepared Ni-Co/SiC coatings exhibited improved performance relative to that prepared under normal gravity.A minimum wear weight loss of 1.4 mg together with an average friction coefficient of 0.13 were also realized at a rotation speed of 800 r/min,values which were much lower than those for normal gravity.

关键词： Supergravity field Electrodeposition Microhardness Wear resistance

Improvements to machining surface quality by controlling the flow direction of electrolyte during electrochemical sinking and milling of titanium alloy

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Science China(Technological Sciences) 2020年第12期63卷 2698-2708页

作者： LIU Yang qu ningsong National Key Laboratory of Science and Technology on Helicopter Transmission Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Electrochemical milling is eminently suitable for machining aerospace parts(which usually have complex structures) because of its great flexibility. However,titanium alloys are particularly sensitive to changes in the flow field,which often cause severe pitting corrosion of the machined surface. Although electrochemical sinking and milling(ESM) can restrict the flow of electrolyte and reduce pitting corrosion,the quality of the machined surface is not ideal because the latter are susceptible to stray corrosion. To reduce such corrosion and improve the surface quality,the internal flow channel of the tool electrode and the cutting depth were investigated thoroughly. Extensive experiments revealed that stray corrosion could be reduced significantly and surface quality improved by controlling the electrolyte flow direction in the machining area,which was achieved by changing the style of the internal flow channel of the tool electrode. These reductions in corrosion and surface roughness were achieved using a tool electrode with a triangular internal flow channel. In addition,the main components and micro-hardness of the machined surface were close to that of the TB6 titanium alloy substrate,which helped to maintain the inherent high strength of the titanium alloy. The surface of the workpiece changed from being hydrophilic to being hydrophobic,which reduced the flow resistance.

关键词： electrochemical sinking and milling titanium alloys flow direction surface quality and characteristics

Flat jet electrochemical milling of TC4 alloy with tailoring backward parallel flow

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Chinese Journal of Aeronautics 2024年第4期37卷 574-592页

作者： Huanghai KONG ningsong qu College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

In flat jet electrochemical milling, the electrolyte forms a backward parallel flow after impacting the workpiece, resulting in a weak current density distribution on the workpiece. Poor surface quality usually occurs on the machined titanium alloy surface because it inevitably suffers from the weak current density. In this study, a method of flat jet electrochemical milling with tailoring the backward parallel flow was proposed to eliminate the negative effects caused by the weak current density. Multiphysics simulations are carried out to comprehend the mechanism of flat jetEC milling with tailoring backward parallel flow and better construct the novel tool *** on flat jet electrochemical milling of TC4 alloy with and without tailoring backward parallel flow are conducted. The results reveal that, compared with flat jet electrochemical milling without tailoring backward parallel flow, the recommended tool reduces the surface roughness by86% to 93%, and improves the material removal rate by 93% to 163% with different feed ***, the recommended tool is more conducive to maintaining the inherent hardness of the material. Finally, a surface with low Sa of 0.37 μm is obtained.

关键词： Flat jet electrochemical milling TC4 alloy Surface roughness Micro-hardness Material removal rate

Improving performance of macro electrolyte jet machining of TC4 titanium alloy:Experimental and numerical studies

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Chinese Journal of Aeronautics 2022年第8期35卷 280-294页

作者： Minglu WANG ningsong qu College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Electrolyte jet machining(EJM)is a promising method for shaping titanium alloys due to its lack of tool wear,thermal and residual stress,and cracks and ***,macro-EJM has attracted increasing attention for its high efficiency in machining wide grooves or ***,macro-EJM generates large amounts of electrolytic products,thereby increasing the difficulty of rapid product removal with a standard tool and reducing the surface ***,for enhanced product transport,a novel tool with a back inclined end face was proposed for macroEJM of TC4 titanium *** comparison,also proposed were ones with a standard flat end face,a front inclined end face,and both front and back inclined end *** flow field distributions of all proposed tools were simulated numerically,and experiments were also conducted to validate the simulation *** results show that one with a 5°back inclined end face can decrease the lowvelocity flow zone in the machining area and increase the high-velocity flow zone at the back end of tool,thereby promoting rapid product removal.A relatively smooth bright-white groove surface was *** same tool also resulted in the highest machining depth and material removal rate among the tested *** addition,rapid product removal was beneficial to the subsequent *** of its rapid product removal,the machining depth and material removal rate during deep groove machining using the tool with a 5°back inclined end face were respectively 7%and14%higher than those produced using a standard ***,the lowest bottom height difference of 0.027 mm can be obtained when the step-over value was 8.2 mm,and a plane with a depth of0.285 mm and a bottom height difference of 0.03 mm was fabricated using the tool with a 5°back inclined end face.

关键词： Electrochemical machining Macro electrolyte jet machining Product removal TC4 titanium alloy Tool end structure

Comparison of electrochemical behaviors of Ti-5Al-2Sn-4Zr-4Mo-2Cr-1Fe and Ti-6Al-4V titanium alloys in NaNO_(3) solution

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International Journal of Minerals,Metallurgy and Materials 2024年第4期31卷 750-763页

作者： Jia Liu Shuanglu Duan Xiaokang Yue ningsong qu College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

The Ti-5Al-2Sn-4Zr-4Mo-2Cr-1Fe(β-CEZ)alloy is considered as a potential structural material in the aviation industry due to its outstanding strength and corrosion *** machining(ECM)is an efficient and low-cost technology for manufacturing theβ-CEZ *** ECM,the machining parameter selection and tool design are based on the electrochemical dissolution behavior of the *** this study,the electrochemical dissolution behaviors of theβ-CEZ and Ti-6Al-4V(TC4)alloys in NaNO3solution are *** open circuit potential(OCP),Tafel polarization,potentiodynamic polarization,electrochemical impedance spectroscopy(EIS),and current efficiency curves of theβ-CEZ and TC4 alloys are *** results show that,compared to the TC4 alloy,the passivation film structure is denser and the charge transfer resistance in the dissolution process is greater for theβ-CEZ ***,the dissolved surface morphology of the two titanium-based alloys under different current densities are *** low current densities,theβ-CEZ alloy surface comprises dissolution pits and dissolved products,while the TC4 alloy surface comprises a porous honeycomb *** high current densities,the surface waviness of both the alloys improves and the TC4 alloy surface is flatter and smoother than theβ-CEZ alloy ***,the electrochemical dissolution models ofβ-CEZ and TC4 alloys are proposed.

关键词： electrochemical machining dissolution behavior β-CEZ titanium alloy polarization curve current efficiency

Experimental investigation of rotary sinking electrochemical discharge milling with high-conductivity salt solution and non-pulsed direct current

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Chinese Journal of Aeronautics 2023年第2期36卷 388-401页

作者： Xiaokang YUE Yuehong MA ningsong qu Hansong LI College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Electrochemical milling is a modified technique of traditional electrochemical machining(ECM)that can be used to manufacture some helicopter transmission system *** use of rotary tools and an inner-jet electrolyte supply pattern can greatly improve the material removal rate(MRR)in a single ***,the feed speed is generally limited to minimize the tool *** increase the MRR,electrical discharge machining(EDM)is introduced into the electrochemical milling *** tool rotation is employed to interrupt the discharge and the high-conductivity salt solution and non-pulsed direct current power supply are also adopted to increase ECM,eventually,a new machining method is proposed,which can be called rotary sinking electrochemical discharge milling(RSECD milling).The mechanism of it is explored in this study by analyzing the machined current,MRR,surface morphology,and tool wear at different applied voltages and feed ***,the RSECD milling using the tool with a larger diameter is also conducted to further verify the *** particular,the MRR can be increased by 742.5%when using the tool with a diameter of 20 mm at the applied voltage of 20 V.

关键词： Electrochemical discharge machining Electrochemical milling High-conductivity salt solution Material removal rate Rotary tool

Mechanical electrodeposition of bright nanocrystalline nickel

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Science China(Technological Sciences) 2008年第7期51卷 911-920页

作者： ZHU ZengWei ZHU Di qu ningsong College of Mechanical and Electrical Engineering Nanjing University of Aeronautics&AstronauticsNanjing 210016China

A new mechanical electrodeposition technology was proposed, and nanocrystalline nickel deposit with bright and smooth surface was prepared in the bath without any additive agents. Unlike traditional methods, the novel technology employed dynamical hard particles to continuously polish the cathode surface and disturb the nearby solution during electrodepositing. Experimental results showed that the polishing effect of hard particles can effectively prevent the hydrogen bubbles and impurities from adhering on the deposit surface and avoid the production of pits, pinholes and nodules. Furthermore, comparing with the deposit prepared by traditional methods, the one prepared by the novel technology was substantially refined with grain size ranging from 30 to 80 nm. Every diffraction peak's intensity of the deposit was reduced, the preferential orientation degree of (200) decreased and those of (111) and (220) increased. The microhardness notably increased. The magnetic properties were also changed with decreased saturation magnetization and increased coercive force. It was also found that variation of current density and cathode rotational speed could affect the structure and properties of the nickel deposits prepared by this technology.

关键词： electrodeposition electroforming hard particle nanocrystalline bright nickel

Electrochemical micromachining of micro-dimple arrays on cylindrical inner surfaces using a dry-film photoresist

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Chinese Journal of Aeronautics 2014年第4期27卷 1030-1036页

作者： qu ningsong Chen Xiaolei Li Hansong Zeng Yongbin College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology

The application of surface textures has been employed to improve the tribological performance of various mechanical components. Various techniques have been used for the application of surface textures such as micro-dimple arrays, but the fabrication of such arrays on cylindrical inner surfaces remains a challenge. In this study, a dry-film photoresist is used as a mask during through-mask electrochemical micromachining to successfully prepare micro-dimple arrays with dimples 94 lm in diameter and 22.7 lm deep on cylindrical inner surfaces, with a machining time of 9 s and an applied voltage of 8 V. The versatility of this method is demonstrated, as are its potential low cost and high efficiency. It is also shown that for a fixed dimple depth, a smaller dimple diameter can be obtained using a combination of lower current density and longer machining time in a passivating sodium nitrate electrolyte.

关键词： Dry-film photoresist Electrochemical machining Electrochemical micromachining Inner surface Micro-dimple arrays Texture

Electrochemical micromachining of microgroove arrays on phosphor bronze surface for improving the tribological performance

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Chinese Journal of Aeronautics 2018年第7期31卷 1609-1618页

作者： Xuan ZHOU ningsong qu Zhibao HOU Gai ZHAO College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology Nanjing 210016 China State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016 China

A high friction coefficient and a low wear rate of contacted surfaces are essential elements to friction pairs between the stator and the rotor in ultrasonic motors. It has been shown that surface textures have a significant effect on improving the tribological performance of friction *** this paper, microgroove arrays are introduced to the stator surface for improving the tribological performance of friction pairs between the stator and the rotor in ultrasonic motors. Microgrooves were fabricated on a phosphor bronze surface by through-mask electrochemical micromachining（TMEMM）. Parameters, namely, the electrolyte inlet pressure, applied voltage, pulse duty cycle,and frequency, were varied to investigate their influences on the dimensions and morphology of the microgrooves. Results showed that the width and depth of the microgrooves were strongly affected by the applied voltage and frequency, while the morphology of the microgrooves was dependent on the electrolyte inlet pressure and the pulse duty cycle. Compared with a smooth surface, the friction coefficient increased from 0.245 to 0.334 and less abrasion was obtained when a surface was textured with microgrooves of which the width and depth were 185.6 and 57.6 lm,respectively. Microgroove arrays might play an important role in enhancing the performance of ultrasonic motors.

关键词： Friction coefficient Microgrooves Through-mask electrochemical micromachining Ultrasonic motors Wear

Wire electrochemical machining with axial electrolyte flushing for titanium alloy

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Chinese Journal of Aeronautics 2013年第1期26卷 224-229页

作者： qu ningsong Fang Xiaolong Li Wei Zeng Yongbin Zhu Di College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics

Titanium and its alloys have found very wide application in aerospace due to their excellent characteristics although their processing is still a challenge. Electrochemical machining is an important issue in the fabrication of titanium and titanium alloys. Wire electrochemical machining （WECM） is mainly used for workpiece cutting under the condition of different thickness plates. It has a great advantage over wire electro-discharge machining, which is the absence of heat-affected zone around the cutting area. Moreover, the wire electrode in WECM could be used repetitively because it is not worn out. Thus, much attention has been paid to WECM. The effective way of removing electrolysis products is of importance to WECM. In this paper, the axial electrolyte flushing is presented to WECM for removing electrolysis products and renewing electrolyte. The Taguchi experiment is conducted to optimize the machining parameters, such as wire feedrate, machining voltage, electrolyte concentration, etc. Experimental results show that WECM with axial electrolyte flushing is a promising issue in the fabrication of titanium alloy （TC1）. The feasibility of multi-wire electrochemical machining is also demonstrated to improve the machining productivity of WECM.

关键词： Axial electrolyte flushing Electro machining Electrochemical machining Titanium alloy Wire electrochemical machining