Some investigations on surface quality indicators for OHNS die steel machined with suspended powder EDM process
by Nitin K. Khedkar; Arunkumar Bongale; Satish Kumar; Vijayshri Khedkar; D. Vinay Kumar
International Journal of Machining and Machinability of Materials (IJMMM), Vol. 22, No. 3/4, 2020

Abstract: The study focuses on the evaluation of surface quality characteristics of oil hardened non shrinking die steel surface machined with suspended powder electrical discharge machining process. Pure copper metal is used as an electrode material, and tungsten powder is used as suspended medium for the purpose. Machining experiments were carried out by varying one parameter at a time. After each test, the machined surface is analysed for evaluating its surface roughness and microhardness values. It is found that combination of 4 A gap current, 12 μs pulse on span and 7 μs pulse off span will result in optimum surface quality indicators for the SPEDM process. Also, dry sliding wear experiments were carried out on the machined surface to evaluate the frictional force and coefficient of friction. Spectroscopic analysis and energy dispersive X-ray diffraction analysis on the machined surface indicate a considerable rise in carbon and tungsten content on the recast white layer of the machined surface. Scanning electron microscopic analysis of the machined surface revealed the presence of compounds of tungsten on the recast white layer. Also, micro-cracks were observed on the machined surface which is due to higher gap current setting during EDM process.

Online publication date: Fri, 01-May-2020

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