FIELD OF INVENTION
The Present Invention relates to a comparative experimental study on rough and trim cut and metal powder mixed Dielectric for WEDM of Nimonic-90
BACKGROUND OF THE INVENTION
In past, significant research work has been carried out on WEDM to evaluate the influence of process variables like discharge parameters, work height, wire electrode materials, dielectric conditions etc on machining performance like cutting speed (CS), metal removal rate (MRR), surface roughness (SR), geometrical accuracy, recast layer etc in processing of different work materials ranging from simple alloy steel, aluminium MMC andhigh strength-heat resisting alloysand composite materials (Bhuyan and Yadava, 2014; Bobbili et al., 2014; Delgado et al., 2011; Gupta and Jain, 2014; Hascalyk et al., 2004; Hewidy et al., 2005; Huang et al., 1999; Jangra and Grover, 2012; Kumar et al., 2013; Kumar et al., 2014;Prohaszka et al., 1997; Shandilya et al., 2013; Yu et al., 2011).
The majority of the research work conductedon WEDM deals with rough cut and a very limited research work have been conducted for trim cutting operation.Huang et al. (1999) unveiled the influence of various WEDM parameters on the performance characteristics of WEDM of alloy steel for trim or finish cutting operations. The performance characteristics were gap width, SR and thickness of recast layer on the machined surface.Using Taguchi method and numerical analysis; Ton and gap between wire periphery and work surface (Dww) were found significant parameters affecting the performance characteristics. Experimental results show that a medium value of Dww (about 30µm) can produce better surface finish. Feasible direction algorithm was proposed to determine the numbers of finish cutand parameters setting to obtain optimal machining performance. Sarkar et al. (2010)optimized the machining parameters of WEDMfor ?-titanium aluminide using ANN modelling. Machining parameters namely Ton, IP, dielectric flow rate (DFR) and effective wire offset were investigated on CS, SR and dimensional shift for multi pass cutting.Klink et al. (2011)presented the comparison of the surface finish, microstructure, micro hardness and residual stresses after rough and trim cuts in WEDM. Using trim cuts, very fine surface finish was obtained and white layer thickness was minimized.
Jangra et al. (2014)compared the machinability of tungsten carbide (WC-Co) composite, high carbon high chrome steel alloy, Nimonic-90 and Monel-400, for rough and trim cutting operation of WEDM using zinc coated brass wire electrode.Results has suggested that surface characteristics can be improved using single trim cut with optimal machining parameters and correct wire offset, irrespective the high discharge energy of rough cut. Jangra(2015)investigated multi trim cutting operation after a rough cut in WEDM for WC-5.3%Co composite. Using Taguchi’ design of experiment method, influence of IP, Ton, wire offset (WO) value and number of trim cuts, were evaluated on two performance measures namely SR and depth of material removed in trim cutting operation. A technological data has provided for rough and trim cut on WEDM for efficient machining of WC-5.3%Co composite.
In the field of die sinking EDM, lot of investigations have been carried out using metal powder additives in dielectricmedium to improve the MRR and surface characteristics. In EDM process, conductive metal powder reduces the dielectricstrength of the fluid and thereby increases the spark energyacross the two electrodes,thus, enhances thestability of the processand improves theperformance measures(Kansal et al., 2005; Sidhu et al., 2014).As per the authors’ knowledge, no research work has been found on powder mixed dielectric in WEDM. Therefore, theconcept of metal powder mixed dielectric has been attempted for WEDM in present work. The complete experimental plan has been discussed in section 3. In present work, comparative analysis of rough and trim cut using distilled water and trim cut with metal powder mixed distilled water has been presented.The influence of two metal powders namely Al and Si(varying concentration of 1g/L, 2g/L and 3g/L)have been evaluated on machining rate (MR) and surface characteristics of Nimonic-90; a nickel based high strength-high heat resisting super alloy.
CN201310646047.0 discloses a WEDM-based (wire-cut electric discharge machining based) twist drill rear face forming device comprising a bit clamping portion connected with an index table.
US08522900discloses is a feedrate controlling method and apparatus for controlling a wire-cutting electric discharging machine (WEDM) to operate at optimal feedrate.
CN201310562102.8 discloses a wire electrode for WEDM-LS electrical discharge machining and a preparation method of the wire electrode.
CN201010586744.8 discloses A long-life guide wheel assembly for a high-speed reciprocated WEDM (wire electrical discharge machining) machine tool comprises two guide wheel bushings (6) and a stepped shaft (2), the long-life guide wheel assembly for the high-speed reciprocated WEDM machine tool is characterized in that the stepped shaft (2) is symmetrically provided with a bearing (1), a guide wheel seat (3) is installed on the bearing (1), a middle part of the guide wheel seat (3) is adhered with a V-shaped circular groove jewel ring (4) and a metallic check ring (5), and the guide wheel seat (3) is symmetrically provided with a diversion trench (20); the bearing (1) is externally equipped with a water retaining cover (17) of which a diameter is more than an external diameter of the bearing (1), and an external surface of the water retaining cover (17) of the bearing and an inner surface of a water retaining cover installation cavity (18) forms a labyrinth seal structure there between to prevent a working liquid from entering the bearing; and a lower part of the guide wheel bushing (6) is provided with liquid draining holes (13) and (19). The invention has simple structure, good tightness and long service life.
None of the cited reference above disclosed or teach what the present invention discloses or teaches. The present invention distinguish over these cited prior art references. The present invention teaches the a process of trim cutting of work material for wire electrical discharge machining (WEDM) using Nimonic-90
SUMMARY OF THE INVENTION
In wire electrical discharge machining (WEDM), material removal takes place due to melting and evaporation of work material through the localised heating generation by the repetitive sparking between wire electrode and work material. With the availability of micro fabrication facilities and latest pulse generators for micro machining (Yeo et al., 2009), present WEDM tools are becoming more precise. Therefore, WEDM are being commercialised in various manufacturing industries (Jangra et al., 2014) and research institutes.
Through WEDM, all conductive materials can be processed irrespective of their hardness but an optimized parameters setting is always required in WEDM to avoid wire breakage and to obtain high surface finish and dimensional precision along with good cutting rate. WEDM parameters can be categorised into three major categories namely discharge parameters (pulse-on time (Ton), pulse-off time (Toff), Peak current (IP), servo voltage (SV)), wire electrode (wire material, wire diameter, wire coating, wire tension, wire feed rate etc) and dielectric conditions (dielectric conductivity, flow rate). Since the material removal takes place due to the high localised heating due to the repetitive sparks, top machined surface consists of poor surface integrity having hollow cavities and several micro-cracks (Lee and Li, 2003; Wang et al., 2009). Top machined layer consists of recast layer or white layer which is a re-solidified melted material on work surface that was not completely flushed away during the process (Jangra, 2015).
In WEDM, trim cut is a best option to improve the surface characteristics and dimensional accuracies of the machined surface. In trim cut, wire electrode traces back the rough cut path with certain value of wire offset to remove a very small layer of work surface (Jangra, 2015; Sarkar et al., 2008) as shown in Figure 1. It is clear from Figure 1, in rough cutting operation; spark zone is quite large as compared to trim cutting operation. As a result, the volume of molten metal is very high in rough cut which generates large pressure energy is spark zone that causes large size craters and cracks on work surface. In trim cutting operation, spark zone is influenced by wire offset value and discharge parameters. Therefore, using low discharge energy parameters and accurate value of wire offset in trim cutting operation, damaged surface layer can be minimized or eliminated.

BREIF DESCRIPTION OF DRAWINGS& TABLES
Figure 1 Terminology used for rough and trim cut in WEDM (modified in Jangra, 2015)
Figure 2 Experimental setup for WEDM in present work
Figure 3 Geometry of wire path for rough and trim cut
Figure 4(a) Comparison of different WEDM operations for MR
Figure 4(b) Influence of concentration of metal powder on MR for trim cut
Figure 5(a) Comparison of different WEDM operations for SR
Figure 5(b) Influence of concentration of metal powder in dielectric fluid for trim cut on SR
Figure 6 SEM photographs of machined surface after
(a) rough cut at high DE
(b) trim cut (without metal powder)
(c) trim cut using 3g/L Al powder in dielectric (d) trim cut using 3 g/L Si powder in dielectric
Figure 7 SEM photographs of transverse surface after (a) rough cut at high DE (b) trim cut (without metal powder) (c) trim cut using 3g/L Al powder in dielectric (d) trim cut using 3 g/L Si powder in dielectric
Figure 8 Comparison of different WEDM operations for TRL
Figure 9(a) EDS analysis of machined surface after rough Cut at High DE
Figure 9(b) EDS analysis of machined surface after trim Cut
Figure 9(c) EDS analysis of machined surface after trim cut using 3g/L Al powder
Figure 9(d) EDS analysis of machined surface after trim cut using 3g/L Si powder
Figure 10(a) Micro indent on transverse surface (b) Comparison of micro-hardness underneath the machined surface under different process conditions
Table 1 Composition and Mechanical Properties of Nimonic-90
Table 2 Parameters setting for rough and trim cutting operation

DETAILED DESCRIPTION
3.1 Setupfor Supplying of Powder Mixed Dielectric Fluid

In rough cutting operation of WEDM, the area covered by the spark zone around the wire electrode is large and the spark gap between wire electrode and work surface in the direction of cutting is very small and therefore, the dielectric fluid is used at high pressure to expel the eroded particles from the spark zone. If the metal powder mixed dielectric fluid is used at high pressure, the effect of powder additives on machining performance will not be justified.Also, due to the recirculation of dielectric fluid in WEDM setup, mixing of metal powder directly in dielectric tank (having large size = 400 litres) is not economical. Therefore, the use of metal powder in dielectric fluid for rough cut of WEDM is quite challenging as compared to die sinking EDM where dielectric fluid (kerosene or distilled water) mixed with metal powder is easily pumped under the electrode facing the work material. However, in trim cutting operation, work surface in contact with wire electrode periphery is small which requires a laminar dielectric flow for effective sparking. Therefore, the idea of metal powder mixed dielectric has been attempted in trim cutting operation only.
In present work, a separate tank of size 40 litres has been used to mix the additives in dielectric water and to pump the metal powder mixed dielectric in trim cutting operation. Figure 2 shows the experimental setup.To supply the metal powder mixed distilled water in trim cutting operation, small capacity water pump was connected to the upper nozzle throughaconnector pipe and the upper nozzle was disconnected from main dielectric tank.

3.2 Work Materialand Machined Geometry
Nimonic-90, a nickel-chromium-cobalt alloy, is most suitable for high temperature applications (6000C to 9000C). Due to high rupture strength and creep resistance at elevated temperature (up to 950 oC), it is mainly employed in turbine blades and combustion chamber. The machining of nickel based super alloys using conventionalprocesses like turning, milling, drilling etc, is very difficult because of the formation of built up layer on cutting tool face resulting large crater wear and poor surface integrity involving several surface defects such as surface drag, material pull-out/cracking, tearing surface etc. (Herbert et al., 2012; Kortabarri et al. 2011; Ulutan and Ozel, 2011). Wire EDM may yield better finish and accuracy while machining to generate intricate and complex parts in this hard and high heat resisting material. Table 1 shows the composition and mechanical properties of Nimonic-90.
Work material wasavailable in the form of rolled sheet of thickness 12.5 mm and the work samples were obtained in the form of rectangular punches of size 8 mm × 6 mm × 12.5 mm.Figure 3 shows the geometry or the wire path that has been followed in present work to perform rough cut followed by a single trim cut.

3.3 Machining Conditions
In present work, machine tool used for the experiments was 5 axis sprint cut (ELPUSE-40) WEDM made by Electronic M/C Tool LTD India. The present experimental work can be divided into threecategorisedas; (a) rough cutting operation correspond to rough cutting operations that were performed at different levels of discharge energy (DE); (b) rough cut at high DE followed by a single trim cut using distilled water as dielectric fluid and (c) rough cut at high DE followed by a single trim cut using metal power (Al/Si) mixed distilled water as dielectric fluid.
In present work, distilled water having conductivity 20 mho was been used as a dielectric fluid. To control the spark energy across the work material, values of discharge parameters namely Ton,Toff, IP and SV were varied.High dielectric flow rate is desirable in rough cutting operation to expel the melted debris quicklyand completely out of the spark gap. Therefore, for rough cutting operation, dielectric flow rate was kept at high value of 12 litres per minute (LM-1). To minimize the wire consumption, wire feed rate was kept at low valueof 5m/min.
According to Jangra(2015), low discharge energy along with a laminar dielectric flow is required for trim cutting operation to obtain effective spark generation for fine surface finish.Therefore, for trim cutting operation, a low dielectric supply was allowed through upper nozzle while bottom nozzle was closed. Table 2 shows the process parameters for rough and trim cutting operation.

RESULTS AND DISCUSSIONS
Experiments were conducted for rough and trim cutting operation corresponds to the parameters settings mentioned in Table 2. The influence of these parameter settings for rough cut and trim cutting operation has been compared for machining rate, surface roughness and surface morphology. Also the influence of Al and Si metal powders (mesh size of 400 for both)have been evaluated (with a concentration of 1g/L, 2g/L and 3g/L) and compared on these characteristics.
Effect on Machining Rate (MR)
MR represents the average speed of machining (mm/min.) of work material in linear direction which was observed from the monitor screen of the machine tool. Figure 4(a)compares the MR for experiments under the categories (a) and (b); that is rough cutting operations correspond to low, medium and high level of DEand a trim cutting operation followed after rough cut. High values of Ton, IP and low values of SV and Toff results into high DE per unit time and vice versa.
Figure 4(a) shows that MR increases with increasing DE across the twoelectrodes for rough cutting operation.High DE causes high heat generation across the two electrodes, thereby facilitating large melting and evaporation of work material (Li et al., 2013; Yu et al., 2011). Hence, MR increases with increase in DE for rough cut. From Figure 4(a), MR corresponds to high DE is 2.54 mm/min as compared to MR of 1.02 mm/min correspond to low DE for rough cut. But in trim cutting operation, MR reaches to 11.6 mm/min even at low values of discharge parameters. It is due to the fact that in trim cut, sparking occurs between a small fraction of wire electrode and work surface; thus, a small amount of work materialis removed as compared to rough cutting operationas represented in Figure 1. This contact area is mainly affected by wire offset value for trim cutting operation. Therefore,by selecting the accurate wire offset,spark frequency across the electrodes can be controlled.
Figure 4(b)compares the MR for the experiments for trim cutting operation using simple distilled water and using Al and Si powders mixed distilled water as dielectric fluid.Increasing the concentration of metal powder in dielectric fluid decreases the MR remarkably as shown in Figure 4(b). It isapropos that addition of both types of metal powder in distilled water resulted in improved and continuous sparking across the electrodes.In powder mixed EDM (PMEDM), material removal rate (MRR) increases due to the addition of metal powder in dielectric(Kansal et al., 2005; Singh et al., 2014)but in present work MR decreases.
In both, EDM and WEDM, addition of conductive metallic powders in dielectric fluidreduces the insulating strength of themediumand thus, increases the discharge channel for a given value of discharge parameters(Kansal et al., 2005). This widened and effect sparking increases the melting and erosion of work material in PMEDMand hence MRR increases. In case of trim cutting operation of WEDM, due to increase in spark radius and spark frequency, discharge area between wire periphery and work surface increases. This increasing discharge area reduces theservo feed as compared to trim cut without metal powder and thus MR decreases in trim cut using metal powder mixed dielectric. The addition of metal powders up to the concentration of 2g/Lshows a remarkable reduction in MR but beyond 2g/L, the reduction is very low. This is due to the fact that addition of more metal powders, do not participate in lower down the insulating strength of dielectric. As compared to Al, Si powder exhibits less discharging and hence the reduction in MR is low for Si powder.

Effect on Surface Characteristics
4.2.1. Surface Roughness
Figure 5(a) compares the surface roughness (Ra, values) for the experiments under categories (a) and (b); that is rough cutting operations correspond to low, medium and high level of DEand a trim cut followed after rough cut. The value of SR increases from 1.42 µm corresponds to the parameters of low DE to 3.1 µm correspond to the parameters of high DE for rough cut.SR is characterized by the size and depth of the craters that are developed after the melting and expulsion of work material. Increasing discharge energy increases the diameter and depth of surface craters resulting in highSR(Hewidy et al., 2005).
Figure 5(a) shows that the SR can be improved significantly using trim cutting operation irrespective of high discharge energy in rough cutting operation. Using trim cutting operation at appropriate wire offset value, a very thin layer of surface material is removed and thereby surface irregularities (peaks) areminimized to reduce the surface roughness.Wire offset (WO) has a significant impact on SRfor trim cut(Jangra, 2015; Sarkar et al., 2008). Referring Figure 1, it is well understood that decreasingWO value beyond 125µm (radius of wire), the area of contact between wire electrode and work surfaceincreases. This will increase the spark frequency and thus, melting and erosion of work material increases. Increasing WO beyond 125 µm will not be useful in generating the effective sparking because of large gap between wire electrode and work surface. Therefore, in present work, an effective wire offset of 105 µmhas been selected, that represent Dww of 20 µm.
Figure 5(b) illustrates the influence of Al and Si powders on SR for trim cutting operation. Result shows that addition of metal powder in a concentration of 1 g/L yields best surface finish of 0.90µm.Addition of 1g/L of metal powder in distilled water causes better spark generation and distribution on work surface, thus producing shallow craters on machined surface.The minimum achievable SR in WEDM is limited by the wire electrode diameter. Smaller the wire diameter, smaller will be the spark radius, and thus, smaller surface craters. Increasing the concentration of metal powders beyond 1g/L, the spark frequency and spark zone increases due to the reduction in insulating strength of dielectric, thus surface roughness increases.
The melting point and resistivity for Si is high as compared to Al powder, thus, the sparking is low in case of Si powder mixed dielectric. Therefore, SR is low for Si powder. The surface roughness corresponds to 3g/L of Aluminium powder is 1.3 µm which is equal to SR value obtained in trim cut without metal powder. But the surface morphology for two conditions is very different as discussed in subsequent section.

Surface Morphology and Recast layer
Figure 6 (a-d)and 7(a-d) shows the scanning electron microscopic (SEM) images of the machined and transverse surface of work samples after (a) rough cut at high DE, (b) trim cut (without metal powder), (c) trim cut using 3g/L Al powder, and (d) trim cut using 3 g/L Si powder in dielectric fluid. It can be seen from SEM image (figure 6a) that the machined surface after rough cut at high DE consists of deep and large size craters. The high discharge energy causes overheating and evaporation of molten metal forming high pressure energy that creates large size craters (Li et al., 2013).
Using trim cut at low discharge parameters, a thin layer of work surface is removed that completely eliminates the surface layer produced in rough cut. It can be confirmed from a fine and uniform surface texture obtained after trim cut as shown in Figure 6(b).Figure 6(c) and 6(d) shows a remarkable modification in surface textures after trim cut using metal powder mixed dielectric fluid. SEM image shows that the sparking on these surfaces is highly stable and uniformly distributed.Due to the absence of carbon in Nimonic-90 and a stable sparking, these machined surfaces are free of micro-cracks. Some nm sized impingement can be observed on these surfaces as encircled in figure 6(c-d). This impingement may be due to the Al and Si powders that werenot completely evaporated while sparking and thus, impinge at high pressure to the molten surface.
Figure 7(a-d) shows the recast layer on machined surface after rough and trim cutting operations. Figure 8 shows the thickness of recast layer (TRL) corresponds to the differentmachining conditions. The average TRL (in µm) for high DE for rough cut is found to be nearly 15 µmwhich is quite low as compared to steel alloys and WC-Co composites (Jangra, 2015).Trim cutting operation makes a remarkable reduction in TRL as noticed from Figure 7(b) and Figure 8.
Figure 7(c) and (d) shows the TRLfor metal powder mixed dielectric having the powder concentration of 3g/L for Al and Si powders respectively. Al powderresults in little increase in TRL while Si powderresults in a small reduction in TRL.As discussed in earlier section (4.2.1), addition of Al powder beyond 1g/L results inincreased discharge frequency and spark radius, thus, more melting and heating results in little increase in TRL. Due to high melting point and electrical resistivity of Si powder, less sparking occurs using Si powder as compared to Al powder mixed dielectric. Therefore, TRL is low in case of Si powder mixed dielectric.
Energy dispersive spectroscopic (EDS) analysis was done on machined surface taking a spot area of 1000 sq.µm. Figure 9(a-d)presents the EDS analysis of machined surfaces shown in figure 6. Figure 9(a) and 9(b) confirmed the presences of Ti, Cr, Co and Ni on machined surface whilethe presence of Al and Si elements have been confirmed by EDS analysis shown in figure 9(c) and 9(d) respectively.

MicroHardness
Using micro hardness test, the extent of surface damage due to thermal energy of WEDM process can be compared. Therefore, micro-hardness was measured on transverse section of the machined surfaceand micro-hardness profiles (Figure 10b) underneath the machined surface havebeen plotted for the samples under rough cut (high DE), trim cut without metal powder and trim cuts using Al and Si powder.
It is clear from the profiles that the micro-hardness is low at the machined top layer as compared to bulk material.This reduction is due to the thermal damage of machined surface which is predominately due to the pressure energy generated inside the plasma channeland transfer of heat energy to the work material underneath the machined surface causing large heat affected zone(Li et al., 2013). The top damaged layer consists of recast layer as discussed earlier while heat affected zone having longer grain size as compared to the bulk of the work material.
Using trim cut, this surface damage can be reduced as shown by the improved micro hardness profilesfor trim cutting operation. It is worth to mention that measurement of micro hardness value correspond to top machined layer is difficult because of the large surface damage at top surface thatcauses inaccurate impression of micro indent onthis region. Therefore, the reading for micro hardness is missing upto 20 µm underneath the top layer.
Using metal powder in dielectric fluid, the recast layer becomes smooth and dense as noticed from Figure 7(c-d). Therefore,the micro hardness improves using metal powder mixed dielectric fluid in trim cutting operation. In comparison to Al powder, Si powder results in densermachined surface and hence yields better machined surface.

CONCLUSIONS
In Present work, a comparative experimental study on WEDM of Nimonic-90, for rough cut and trim cutwithout any metal powder additivesand using Al and Si metal powders in dielectric fluid has been presented. Firstly, the influence of discharge energy for rough cut has been evaluated for MR and SR and then, compared with trim cut without any metal powder additives in dielectric fluid. In succeeding experiments, influence of Al and Si metal powders in dielectric fluid has been evaluated separately and compared for MR, SR, recast layer and micro hardness. The important findings of this work are summarized as follows:
• MR increases from low DE to high DE for rough cut. MR corresponds to high DE is 2.54 mm/min as compared to MR of 1.02 mm/min correspond to low DE in rough cutting operation. MR reaches to 11.6 mm/min, for trim cut performed at low values of discharge parameters without using metal powder additives. Increasing the concentration of metal powder in distilled water decreases the MR remarkably. The addition of metal powders up to the concentration of 2g/L yieldsmore than 50% reduction in MR but beyond 2g/L, the reduction is low.
• The value of SR increases from 1.42 µm corresponds to the parameters of low DE to 3.1 µm correspond to the parameters of high DE for rough cut. SR has been improved significantly using trim cut irrespective of high discharge energy for rough cut.Addition of metal powder in a concentration of 1 g/L yields best surface finish of 0.90 µm because of the better spark generation and distribution on work surface. Si powder yields better SR as compared to Al powder.
• SEM images shows that the machined surface after rough cut at high discharge energy consists of deep and large size craters whereas a fine and uniform surface texture was obtained after a trim cut. Micro hardness profiles show that the top machined layer is under high thermal damages for rough cut and the extent of this damage for low for trim cut. Al powder with a concentration of 3g/L results in little increase in TRL while Si powder with a concentration 3g/L results in a smaller TRL.
• Using Al and Si metal powders in dielectric fluid, a remarkable modification has been obtained for surface textures after trim cut. Using metal powder in dielectric fluid, the recast layer becomes smooth and dense and hence micro hardness increases. Some nm sized impingement was observed on machined surfaces after trim cut using metal powder additives. EDS analysis confirmed the presences of Al and Si elements on machined surface after trim cut.
• The present study has addedan opportunity for future research on powder mixed WEDM. In future work, WEDM parametersnamely Ton, IP, Toff, SV and WO usingdifferent concentration of metal powders can be investigated more precisely. Detailed investigation using high concentration of different metal powders can be carried out to modify themorphology of machined surface.
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CLAIMS:1. A process of trim cutting of work material and Metal Powder Mixed in Dielectric for wire electrical discharge machining (WEDM) of Nimonic-90 comprising the steps of:
(a) rough cutting operation correspond to rough cutting operations that are performed at different levels of discharge energy (DE);
(b) rough cut at high DE followed by a single trim cut using distilled water as dielectric fluid and;
(c) rough cut at high DE followed by a single trim cut using metal power (Al/Si) mixed distilled water as dielectric fluid.
2. The process as claimed in claim 1, wherein said Metal Powder Mixed in Dielectric water through a water pump whic connected to a upper nozzle through a connector pipe and the upper nozzle is disconnected from main dielectric tank.
3. The process as claimed in claim 1, wherein said Nimonic-90 is a nickel-chromium-cobalt alloy.
4. The process as claimed in claim 3, wherein said Nimonic-90 is most suitable for high temperature applications (6000C to 9000C).
5. The process as claimed in claim 3, wherein said Nimonic-90 is employed in turbine blades and combustion chamber.
6. The process as claimed in claim 1, wherein said Work material is available in the form of rolled sheet of thickness 12.5 mm and the work samples are obtained in the form of rectangular punches of size 8 mm × 6 mm × 12.5 mm.
7. The process as claimed in claim 1, wherein said dielectric water is distilled water having conductivity 20 mho.
8. The process as claimed in claim 1, wherein said trim cut at low discharge parameters, a thin layer of work surface is removed that completely eliminates the surface layer produced in rough cut.