Abstract
Engineering ceramics have been widely used in modern industry for their excellent physical and mechanical properties, and they are difficult to machine owing to their high hardness and brittleness. Electrical discharge machining (EDM) is the appropriate process for machining engineering ceramics provided they are electrically conducting. However, the electrical resistivity of the popular engineering ceramics is higher, and there has been no research on the relationship between the EDM parameters and the electrical resistivity of the engineering ceramics. This paper investigates the effects of the electrical resistivity and EDM parameters such as tool polarity, pulse interval, and electrode material, on the ZnO/Al2O3 ceramic's EDM performance, in terms of the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR). The results show that the electrical resistivity and the EDM parameters have the great influence on the EDM performance. The ZnO/Al2O3 ceramic with the electrical resistivity up to 3410 Ω·cm can be effectively machined by EDM with the copper electrode, the negative tool polarity, and the shorter pulse interval. Under most machining conditions, the MRR increases, and the SR decreases with the decrease of electrical resistivity. Moreover, the tool polarity, and pulse interval affect the EWR, respectively, and the electrical resistivity and electrode material have a combined effect on the EWR. Furthermore, the EDM performance of ZnO/Al2O3 ceramic with the electrical resistivity higher than 687 Ω·cm is obviously different from that with the electrical resistivity lower than 687 Ω·cm, when the electrode material changes. The microstructure character analysis of the machined ZnO/Al2O3 ceramic surface shows that the ZnO/Al2O3 ceramic is removed by melting, evaporation and thermal spalling, and the material from the working fluid and the graphite electrode can transfer to the workpiece surface during electrical discharge machining ZnO/Al2O3 ceramic.
Highlights
Advances in materials engineering have led to the development of a generation of materials which present better properties for their use in different industrial sectors
Resistivity and Machining Parameters on Electrical discharge machining (EDM) Performance of Ceramics discharge occurs and the workpiece is removed by vaporization and melting, which makes the workepiece surface smooth, so the surface roughness (SR) decreases with the decrease of electrical resistivity
This study attempts to investigate the effects of the electrical resistivity and the EDM parameters on EDM performance of ZnO/Al2O3 ceramics
Summary
Advances in materials engineering have led to the development of a generation of materials which present better properties for their use in different industrial sectors. Some researches about EDM performance of engineering ceramics with different electrical resistivities have been made. W. Konig et al [10] have found that the high removal rate as compared with traditional techniques for machining ceramic materials can be obtained provided that their electrical resistivity is below of 100 V?cm. The results show that the electrical resistivity of the composites is approximately 0.01 V?cm when TiN content is higher than 30 vol.%, so that EDM can be used to machine this material. The authors have decided to investigate the effects of the electrical resistivity and machining parameters, such as tool polarity, pulse interval, and electrode material, on the process performance in terms of the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR Ra)
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