Effect of using SiC powder-added dielectric media during electro-
discharge machining of Inconel 718 superalloys
Santosh Kumar Sahu
Received: 5 July 2017 / Accepted: 3 October 2017
Ó The Brazilian Society of Mechanical Sciences and Engineering 2018
Inconel 718 is a nickel-based superalloy widely applied in aerospace, automotive and defense applications. Low thermal
conductivity, extreme high temperature strength, high work-hardening characteristics make them ‘difﬁcult-to-machine.’ In
order to improve EDM performance on Inconel 718, powder-mixed electro-discharge machining is reported herein.
PMEDM is carried out by mixing SiC powder in the dielectric media in consideration with varied peak discharge current.
As compared to conventional EDM, the morphology and topographical features of the machined surface including surface
roughness, crack density, white layer thickness, metallurgical aspects (phase transformation, crystallite size, micro-strain
and dislocation density), material migration, residual stress as well as micro-indentation hardness, etc., are studied.
Additionally, effects of peak discharge on PMEDM performance features, namely material removal rate, tool wear rate,
surface roughness, surface crack density, white layer thickness, are discussed and compared with conventional EDM.
Keywords Inconel 718 Á Superalloy Á Powder-mixed electro-discharge machining
Inconel 718 belongs to the nickel–chromium-based super-
alloy family; because of the presence of nickel ([ 50%), it
is called as Inconel. It contains mainly Ni, Cr, Fe, Nb, and
Mo in its chemical composition. Minor amounts of Al, Ti,
Co, and C are also present therein. Inconel 718 exhibits
high corrosion, oxidation resistance at elevated tempera-
tures due to the presence of Ni and Cr . Niobium (Nb)
alloying element plays crucial role in retaining strength in
both of the c
phases for Inconel 718 . Salient
properties of Inconel 718 are delineated below.
• Inconel 718 has age hardening property; it maintains
strength at both high and low temperatures.
• At extreme temperatures, it possesses magniﬁcent
mechanical properties such as high tensile, creep
rupture, and fatigue strength.
• Inconel 718 has high resistance to corrosion in aqueous
environment. Due to this reason, it extended applica-
tions in marine industry also.
• It has magniﬁcent weldability characteristics [25, 39].
It ﬁnds numerous applications in distinct ﬁelds like
aerospace, chemical, marine, and nuclear industries due to
its outstanding mechanical and chemical properties at
extreme temperatures. Inconel 718 is widely used in
manufacturing of gas turbine engine components, viz.
blades, turbine disk, outer casings, and combustors. .
However, machining of Inconel 718 seems difﬁcult due to
the following reasons [8, 20, 29, 33]:
• It retains higher strength during machining.
• Due to its poor thermal conductivity, thermal effects
appear adversely predominant during machining (rise
of temperature at the tool tip) .
• Due to tendency of work hardening, it increases tool
• Due to the presence of carbides and hard abrasive
particles, it increases tool wear.
Technical Editor: Ma
rcio Bacci da Silva.
& Saurav Datta
Department of Mechanical Engineering, Jadavpur University,
Kolkata 700032, India
Department of Mechanical Engineering, National Institute of
Technology, Rourkela, Odisha 769008, India
Journal of the Brazilian Society of Mechanical Sciences and Engineering (2018) 40:330