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Research Papers

# Study on Machinabilty of $Al2O3$ Ceramic Composite in EDM Using Response Surface Methodology

[+] Author and Article Information
K. M. Patel1

Department of Mechanical Engineering, Institute of Technology, Nirma University, Ahmedabad 382 481, Indiakaushik.patel@nirmauni.ac.in

Pulak M. Pandey, P. Venkateswara Rao

Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi 110 016, India

1

Corresponding author.

J. Eng. Mater. Technol 133(2), 021004 (Mar 03, 2011) (10 pages) doi:10.1115/1.4003100 History: Received October 13, 2009; Revised August 25, 2010; Published March 03, 2011; Online March 03, 2011

## Abstract

Electric discharge machining (EDM) has been proven as an alternate process for machining complex and intricate shapes from the conductive ceramic composites. $Al2O3$ based electrodischarge machinable $Al2O3–SiCw–TiC$ ceramic composite is a potential substitute for traditional materials due to their high hardness, excellent chemical, and mechanical stability under a broad range of temperature, and high specific stiffness. The right selection of the machining condition is the most important aspect to take into consideration in the EDM. The present work correlates the inter-relationships of various EDM machining parameters, namely, discharge current, pulse-on time, duty cycle, and gap voltage on the metal removal rate (MRR), electrode wear ratio (EWR), and surface roughness using the response surface methodology (RSM) while EDM of $Al2O3–SiCw–TiC$ ceramic composite. Analysis of variance is used to study the significance of process variables on MRR, EWR, and surface roughness. The experimental results reveal that discharge current, pulse-on time, and duty cycle significantly affected MRR and EWR, while discharge current and pulse-on time affected the surface roughness. The validation of developed models shows that the MRR EWR and surface roughness of EDM of $Al2O3–SiCw–TiC$ ceramic can be estimated with reasonable accuracy using the second-order models. Finally, trust-region method for nonlinear minimization is used to find the optimum levels of the parameters. The surface and subsurface damage have also been assessed and characterized using scanning electron microscopy. This study reveals that EDMed material unevenness increases with discharge current and pulse-on time.

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## Figures

Figure 1

Microstructure of Al2O3 ceramic composite (Al2O3–SiCw–TiC)

Figure 2

Main effects plots: (a) main effects for MRR, (b) main effects for EWR, and (c) main effects for surface roughness

Figure 3

Response surfaces for MRR

Figure 4

Response surfaces for EWR

Figure 5

Response surface for surface roughness

Figure 6

EDMed surface characteristics of Al2O3–SiCw–TiC ceramic composite under a duty cycle of 0.72, a gap voltage of 70 V, and a pulse-on time of 50 μs: (a) discharge current of 3 A, (b) discharge current of 5 A, and (c) discharge current of 7 A

Figure 7

EDMed surface characteristics of Al2O3–SiCw–TiC ceramic composite under a duty cycle of 0.72, a gap voltage of 70 V, and a pulse-on time of 200 μs: (a) discharge current of 3 A, (b) discharge current of 5 A, and (c) discharge current of 7 A

Figure 8

SEM. Micrographs at a duty cycle of 0.72 and a gap voltage of 70 V: (a) 3 A/50 μs, (b) 7 A/50 μs, (c) 7 A/200 μs, where the micrographs (b) and (c) qualitatively show variation in the thickness of the recast layer for different values of pulse-on time

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