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Electrical discharge alloying was performed on AISI-D2 steel using Ni-Wp owder mixed dielectrici no rder to improve the hardness and to reduce the specific wear rate. The alloyed layer was characterized using optical microscopy,s canning electron microscopy, X-ray diffraction analysis and energy-dispersive spectroscopy. Wear tests were conducted based on L9 orthogonalarray in apin-ondisc tribometer and the alloying parameters were optimized using Taguchi's technique. Hard intermetallics based on Fe 7 C 3 ,C r 3 C 2 and Ni 2 W 4 Cw ere formed by electric discharge alloying, which primarilyc ontributed to the improvementi nh ardness up to 600 HV 0.5 .T he specific wear rate of the alloyed layer was subsequently reduced by around afactor of eightcompared to that of the base material. The pulse off-time was found to be predominant in obtaining higher hardness and lower specific wear rate among the alloyingp arameters, peak current, pulse on-time and off-time.

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Electrical discharge alloying was performed on AISI D2 tool steel with addition of nickel powder. Taguchi method has been used to plan and analysis the experiment.The major parameters like Peak current, pulse on time, and pulse off are taken for this study for formation of alloyed layer. The influences of these process parameters have been identified by Signal to noise ratio (S/N) and analysis of variance (ANOVA) and their results are within the limits of predicted and experimental values. The experiments were conducted on a specially designed apparatus in laboratory itself. The layer thickness varies from 70 to 140 μm and the highest hardness value of 1788 HV0.3 with a lower specific wear rate.

Electric discharge coating is an alternative process for surface modification/alloying/coating requirements to improve mechanical and metallurgical properties of the materials. The high-pressure compacted electrode is made of the semi-sintered nickel and tungsten during the electric discharging process which influences the material migration towards substrate. In this proecess addtiton of pyrolysis carbon from dielectric togeather with the alloying elements and substrate material results in formation of metal matrix composite coating. It depended on the stabilization pressure of spark which increases the deposition rate of alloying materials and reduces the carbon, brittleness, cracks, voids, blowhole on the surface and made the layer to be desired metallurgical properties. Modified layer shows higher in hardness value of 1100 HV0.5 and reduction in specific wear to 0.082 × 10 −5 mm 3 /Nm compared with uncoated substrate material. Inclusion of the alloying material and reduction of the carbon percentage consequences in self-lubricant properties which alter the wear rate and coefficient of friction. Surfaces topography obtained during alloying, material migration and the mechanism have been characterized through scanning electron microscopy and energy-dispersive X-ray spectroscopy. The wear behaviour has been analysed by using pin-on-disc tribometer.

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In present exploration, Electric Discharge Alloying/Coating (EDA/C) is made over duplex stainless steel as alloying elements of nickel, graphite, copper (electrode) and pyrolysis carbon from oil together with substrate material results in metal matrix composite coating. Coating possess average hardness value of 1018 HV 0.5 four times higher and lowered specific wear rate of 1.18 × 10−5 mm3/N m with an improved average friction coefficient of 0.3 through Pin on Disc (POD) wear tester. Metallurgical properties of the coating are analysed through surface topography by 3D optical profilometer, coating microstructure over and across with elemental distribution are identified by electron microscope (SEM) attached with Energy-Dispersive X-Ray Spectroscopy (EDS). Phase transform from δ and γ of cementite with meta stable iron carbide appeared as austenitic structure are identified through Electron Probe Micro Analyser (EPMA) and by X-ray diffraction. This meta stable carbides together with alloying elements provides improved tensile and bonding strength at room temperature were else copper controls further phase transformation. Copper shows stick slip at lower loading up to 40 N then restores in temperature arises during frictional contacts makes carbon and carbide to plasticity state under room temperature provides self-lubricant properties.