Surface improvement o f SKD61 die steel material after electrical discharge machining with graphite electrode

Available online www.jocpr.com

Journal of Chemical and Pharmaceutical Research, 2015, 7(7):1204-1211

Research Article ISSN : C O D E N ( U S A ) ; J C p R C 5 0975-7384

Surface improvement of SKD61 die steel material after electrical discharge

machining with graphite electrode

B anh Tien L o n g 1, N go C uong2, N guyen H uu P h an 2* and V ijay K um ar S. Jatti3

1H anoi U niversity o f Science and Technology, H anoi, Vietnam

2 College o f Econom ics and Technology, Thai Nguyen University, Vietnam

M echanical E ngineering Departm ent, Sym biosis Institute o f Technology (SIT), Sym biosis International University

(S1U), Lavale, Pune, M aharashtra State, India

A B S T R A C T

Electric discharge m achining (EDM ) is w idely used fo r m achining difficult to cut materials, com plex shapes and

products requiring high precision work. The limitations o f this process are the low productivity and low surface

quality after m achining. Therefore, to overcom e these lim itations o f E D M process is an utm ost concern o f the

present study. This p a p e r p resen ts the study o f the influence o f titanium p o w d er m ixed in dielectric flu id on the

surface quality o f SKD61 steel m achined by E D M process. The m achined surface was characterized fo r surface

roughness, thickness o f heat-affected zone, chem ical composition, m icrohardness and topography. R esults o f the

characterization show s that pow der m ixed in dielectric medium can be a solution to im prove the quality o f m achined

surface.

K eyw ords: PM ED M , Surface roughness, H eat affected zone, Topography, M icrohardness.

IN T R O D U C T IO N

EDM is one o f the non-traditional m achining processes which find applications to m achine com plex geom etries, and

sm all size holes w ith high precision requirem ents. Basically m aterial rem oval in EDM process takes place by precise

control o f spark generated in gap betw een the tool electrode and the w orkpiece im m ersed in a dielectric fluid. EDM

process uses therm al energy to m elt the material and evaporate the m achined m aterial. D uring the process the

tem perature is raised in the range o f 10000 to 12000 °C. EDM process has advantages over traditional m ethod that,

this process does not have negative affect on the quality o f processed products due to vibration, deform ation and

mechanical stresses. H ow ever, the use o f therm al energy during m achining leads to the changes in the m etallurgical

properties o f the surface o f the material com pared to the base material. The past research studies show ed that the

surface layer after ED M m achining consists o f large num ber o f m icroscopic cracks, w hite layer thickness and high

surface roughness values. This affects the perform ance characteristics o f the EM D process. Therefore, there is a lot

o f scope in im proving quality o f m achined surface after EDM process.

The results o f past research have shown that, pow der m ixed electrical discharge m achining (PM ED M ) is very

effective to im prove the productivity, quality and precision m achining o f workpiece. Pecas and H enriques m achined

SK.D61 steel by EDM w ith silicon pow der mixed in oil dielectric fluid. They found that the surface roughness values

and structure o f the m achined surface gets affect by silicon pow der [1]. Pecas and H enriques developed a

m athem atical m odel to predict the thickness o f the white layer, shape and depth o f surface roughness [2], Furutani et

al. used Ti pow der (<36p.m) m ixed in oil dielectric fluid for m achining AISI 1049 steel in EDM process. They found

that a TiC layer o f thickness 150 jim was created and the layer has a m icrohardness value o f 1 600 HV [3], Simao et

al. obtained a coating form ation conditions on the steel surface after PM ED M [4], Furutani et al. used PM ED M and

deposited tungsten carbide coating on the m achined surface o f the steel m ould m ade o f materials nam ely, OHNS,

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