Increasing Wear Resistance of Copper Electrode in Electrical Discharge Machining by Using Ultra-Fine-Grained Structure
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ORIGINAL ARTICLE
Increasing Wear Resistance of Copper Electrode in Electrical Discharge Machining by Using Ultra-Fine-Grained Structure Shahin Heidari1 • Ahmad Afsari2 • Mohammad Amin Ranaei3
Received: 27 April 2020 / Accepted: 11 September 2020 Ó The Indian Institute of Metals - IIM 2020
Abstract Tool electrode wear is a severe problem in electrical discharge machining (EDM) which significantly affects the efficiency of the machining process and dimensional accuracy. In this paper, ultra-fine-grained (UFG) structures due to their unique and unusual properties are used to alleviate the wear problem of tool electrode. Equal-channel angular pressing (ECAP) is a novel severe plastic deformation metal forming process which can produce ultra-fine to nanoscale grains in bulk materials. Commercially pure copper was ECAP-ed to produce UFG microstructures and then used as tool electrode in EDM. The performance parameters in the EDM process, which have been studied, are material removal rate (MRR), volumetric electrode wear (VEW) and electrode wear ratio (EWR). For UFG and coarse-grained electrodes, the MRR, VEW and EWR obtained in EDM process have been compared. The results show that VEW and EWR decrease when UFG copper tool electrodes are used. But with increasing machining time, VEW and EWR of UFG copper electrodes approach those of the coarse-grained copper electrode. Keywords Electrical discharge machining (EDM) Tool electrode wear Machining performance Ultra-fine-grained materials Non-ferrous metals & Ahmad Afsari [email protected] 1
Department of Mechanical Engineering, Shiraz Branch, Islamic Azad University, Shiraz, Iran
2
Bone and Joint Diseases Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
3
Young Researchers and Elites Club, Birjand Branch, Islamic Azad University, Birjand, Iran
1 Introduction Electrical discharge machining (EDM), more commonly known as spark machining, removes electrically conductive materials via series discrete high-frequency electrical discharges (sparks) from electric pulse generators between the tool and workpiece [1]. In this machining process, the workpiece and the tool are flushed by (or immersed in) a dielectric liquid. The dielectric medium acts as a deionizing medium between the electrode and the workpiece, thus providing the optimal conditions for spark generation, and also flushes the debris formed in the spark gap [1–3]. The material removal mechanism in EDM is primarily an electro-thermal mechanism through a series of discharges, and it is a very complex phenomenon which involves many physical processes [4, 5]. A necessary condition for producing a spark is the ionization of dielectric which splits up its molecules into ions and electrons. During the spark, a discharge channel is created where the temperature reaches approximately 40,000°K [6], removing material by vaporization and bubble explosion of superheated metal from both the tool electrode and the workpiece [7]. Materials like graphite, copper, copper alloys, brass, cemented carb
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