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Research Paper EXPERIMENTAL INVESTIGATION ON MACHINABILITY OF AL/VC COMPOSITES DURING ELECTROCHEMICAL MACHINING 1 V.Sivabharathi, 2 P.Marimuthu, 3 S.

1 Research Paper EXPERIMENTAL INVESTIGATION ON MACHINABILITY OF AL/VC COMPOSITES DURING ELECTROCHEMICAL MACHINING 1 V.Sivabharathi, 2 P.Marimuthu, 3 S.Ayyappan Address for Correspondence 1* Associate Professor, Department of Mechanical Engineering, Gnanamani College of Technology, Namakkal , Tamilnadu, India. 2 Principal and Professor, Department of Mechanical Engineering, Syed Ammal Engineering College, Ramanathapuram , Tamilnadu, India. 3 Assistant Professor, Department of Mechanical Engineering, Government College of Engineering, Salem , Tamilnadu, India ABSTRACT: This paper explicates the experimental investigation on the electrochemical machining characteristics of vanadium carbide (VC) particles reinforced aluminium metal matrix composites (Al-MMCs). These aluminium composites contain weight fractions of 1 %, 2 % and 3 % reinforcements of VC particles. The electrochemical machining was carried out at different combinations of voltage and electrolyte concentration. The design of experiment (DOE) method adopted in this work is central composite (CCD) of response surface methodology (RSM). The material removal rate (MRR) and surface roughness (R a ) were measured to comprehend the machinability of this composite materials. Experimental models and the contour plots were developed to establish a relationship between performance measures and machining and product parameters. The scanning electron microscopy (SEM) pictures of the surface of the test specimen were analyzed to understand the effect of machining parameters. 1 INTRODUCTION Aluminium metal matrix composites (Al-MMCs) finds its applications in transportation, aerospace and sports equipment due to their high strength-to-weight ratio. Since the vanadium carbide (VC) reinforced Al-MMCs exhibit promising mechanical properties especially high strength and hardness, it is imperative to develop suitable machining methods. Several machining techniques have been reported in the literature. Muller et al. [1] studied the machining issues of Al-SiC metal matrix composites using electrical discharge machining (EDM) method. This machining is suffered from severe electrode wear, which increases the machining cost. Patil Nilesh et al. [2] conducted the experimental investigation on electro discharge machining to study the machinability of Al/Al 2 O 3 composites. Haq et al. [3] studied the drilling characteristics of Al/SiC particle reinforced composites. The machinability issues of Al/SiC composites using turning operation were extensively investigated [4, 5]. Another nontraditional technique of laser machining creates heating on the surface of the workpiece, which increases slightly reduced surface quality [6]. Electrochemical machining (ECM), a non-traditional machining process can overcome the difficulties discussed in the other machining techniques. The ceramic particles in the metallic matrix will abrade the tool there by reducing the life of the tool. ECM is a controlled anodic dissolution process that does not wear the tool. In ECM, work piece is the anode, and the tool is the cathode, and the electrolyte is pumped through the gap between tool and work piece, while direct current (DC) is passed to dissolve metal from the work piece. ECM finds its applications in aerospace, auto, mould and dies, roller and gear industries. Few works have been reported in electrochemical machining issues of Al-MMCs. The electrochemical machining characteristics of Al/SiC p composites were experimentally analyzed [7, 8]. Electrochemical machining suitability of Al/B 4 C composites was also studied in the earlier investigations [9, 10]. Taweel [11] combined electrochemical turning (ECT) with magnetic abrasive finishing (MAF) to analyze the machining suitability of Al/Al 2 O 3 composites. Ayyappan et al. [12] optimized process parameters for electrochemical machining of 6061Al/ 10%Wt Al O / 5%Wt SiC Composites. However, the 2 3 investigation on the electrochemical machining of Al/VC composites is not available. Therefore, in this paper, experimental research on the machinability issues in electrochemical machining of Al/VC composites was conducted. To gain a better understanding of the influence of parameters such as an applied voltage (V), electrolyte concentration (EC) and wt % of VC in aluminium matrix on the machining performances (MRR and R a ) is attempted. The central composite design (CCD) of response surface methodology (RSM) is employed to plan and analyze the experiments. RSM was implemented as an effective experimental strategy in electrochemical machining by several researchers [13-16]. 2 Experimental procedure 2.1 Experimental setup Figure 1 Schematic diagram of ECM apparatus (Ayyappan et.al, 2014[13]) 1. Electrolyte tank 2.Motor 3.Pump 4.Flow control 5. Pressure gauge 6.Flow meter 7.Filter 8.Feed mechanism and tool holder 9. Tool holder 10.Tool 11.Workpiece 12. Workholding 13.Machining chamber 14.Low voltage high current DC supply. The schematic diagram of electrochemical machining setup used in this investigation is shown in Figure 1. It consists of a power supply, electrolyte supply and filtering system, tool feed mechanism, work holding system and control panel. A 5-30V DC with current adjustable up to 280A is applied across the interelectrode gap (IEG) between a copper tool and an anode work piece. A copper tool with a circular end

is used. Aqueous sodium chloride (NaCl) solution was used as an electrolyte. Voltage (V) was controlled in the control panel. Sufficient electrolyte concentration mixed in electrolyte tank.

$µm as the reinforcement. The two materials with desired weight fractions were mixed and fabricated as composites using stir casting technique.$ Uniform distribution of VC particles within Al matrix was ensured. Figure 3 shows the VC particles distribution in the aluminium matrix.

Uniform distribution of VC particles within Al matrix was ensured. Figure 3 shows the VC particles distribution in the aluminium matrix.

2 is used. Aqueous sodium chloride (NaCl) solution was used as an electrolyte. Voltage (V) was controlled in the control panel. Sufficient electrolyte concentration mixed in electrolyte tank. The METATECH ECM used in this experiments is shown in Figure 2. Figure 2 Experimental set up 2.2 Material preparation To fabricate the SiC reinforced Al-MMCs, aluminium chips of 99% purity was used as the matrix material, and vanadium carbide (VC) particles with a mean diameter of less than 2 µm as the reinforcement. The two materials with desired weight fractions were mixed and fabricated as composites using stir casting technique. Uniform distribution of VC particles within Al matrix was ensured. Figure 3 shows the VC particles distribution in the aluminium matrix. Symbol VC Figure 3 Scanning electron microscope (SEM) images of different grades of Al/VC 2.3 Experimentation The design of experiments (DOE) based on central composite design (CCD) of response surface methodology (RSM) was used to develop the experimental conditions [13-15]. The main process parameters governing the ECM process are voltage (V) and electrolyte concentration (EC) according to the literature. Different grades of composites i.e. Al/ 1 % wt.vc, Al/ 2 % wt.vc, and Al/ 3 % wt. were considered as the parameter in DOE. The process and product parameters and its levels are shown in Table 1. Table 1 The process parameters and their values at different levels Process parameter Weight fraction of vanadium carbide in aluminium matrix Level V Voltage (volts) EC Electrolyte concentration (g of NaCl / L of water) In this work, MRR was measured based on weight loss during machining time. Weights were measured using a weighing machine with least count of 1 mg and maximum weight of 1 kg. The surface roughness (R a ) was measured with the Mitutoyo surface roughness tester with the Sl. No. Voltage(V) V Material removal rate (MRR) = Machining g/min (1) Table 2 Experimental results Weight fraction of VC in Al (VC) % Electrolyte concentration(ec) g/l sampling length of 10 mm. The results are the average of the three measurements. Table 2 shows the experimental outcomes of this investigation. Material removal rate(mrr) g/min Surface roughness(ra) µm

3 Analysis of variance (ANOVA) and mathematical modelling The analysis of variance (ANOVA) and the Fisher s test (F-ratio) have been performed to justify the goodness of fit of the mathematical models. A second order polynomial model is fitted with the following equation. Table 3 and 4 refers the ANOVA analysis results for models MRR and R a. Where, Y u -response, n -number of parameters, b o,b 1 etc., -second order regression coefficients, e u -regression error Table 3 Analysis of variance for MRR Source DF Sum of Mean sum of squares(ss) squares(ms) F-value P Regression Linear Square Interaction Residual Error Lack-of-Fit Pure Error Total = (3) (2) The MRR model F-ratio value of implies that model is statistically significant. In this case, square and interaction terms are important. The value of R 2 =93% means that the regression model provides an excellent explanation of the relationship between the variables and the response MRR. The model is fit as shown in Equation.(3). The R a model F-value of implies that the model is significant. In this case, linear, square and interaction terms are significant. The value of R 2 =91 % means that the regression model provides an excellent explanation of the relationship between the variables and the response R a. Thus the developed model equation.(4) can be used for the further analysis. Table 4 Analysis of variance for R a Sum of Mean sum of Source DF F-value P squares(ss) squares(ms) Regression Linear Square Interaction Residual Error Lack-of-Fit Pure Error Total = (4) 4 Results and discussion According to the ANOVA results, the interaction effect of parameters is playing a significant role in the ECM performance i.e. MRR and R a. Therefore, the contour plots were drawn as shown in Figures 4 and 5 to understand the effects thoroughly.

4 EC*V VC*V 1 1 VC*EC MRR < > Hold Values V 15 EC VC 2 High voltage leads to high machining current that increases the MRR. This situation could be seen in the first and third plot of Figure 4. It is clearly shown in the second and third plot, the proportion of VC particles presence in the specimen does not affect the MRR. Since vanadium carbide is an inert particle, it is not affected by an electrolytic reaction. But its surrounding aluminium metal is dissolved when the current is supplied to the inter-electrode gap. These suspended particles were flushed away by the highvelocity electrolyte jet. It can be observed that the increase in electrolyte concentration (EC) increases MRR. It is attributed to the rise in the conductance of EC*V Figure 4 Contour plots for MRR the electrolyte with the increase of concentration. But concentration above certain limit disturbs the mobility of ions which in return reduces MRR. The concentration up to g/l is sufficient to get good MRR according to the first and third plot of Figure 4. Three grades of Al/VC composite specimen machined under the condition of g/l of electrolyte concentration and voltage of 20 V were chosen for scanning electron microscopy (SEM) study. Figures 6-8 shows SEM images of different grades of Al/VC composites machined by ECM. Figure 6 demonstrates the effect of parameters on surface roughness (R a ). VC*V 1 1 VC*EC Ra < > 9 Hold Values V 15 EC VC 2 An increase in both voltage (V) and EC increases the surface roughness (R a ) enormously. As the percentage of VC increases, surface roughness also increases. Good erosive can be seen in the images of Figure 5 Contour plots for R a Figures 6-8 because of high voltage (20 V) and electrolyte concentration ( g/l). More vanadium carbide spread can be seen in Figure 8.

Figure 6 SEM images of ECM machined Al/VC 1% wt at V= 20 V and EC= g/l Figure 7 SEM images of ECM machined Al/VC 2 % wt at V= 20 V and EC= g/l Figure 8 SEM images of ECM machined Al/VC 1% wt at V= 20

$The different parameters in the analysis included voltage and electrolyte concentration and weight fraction of vanadium carbide reinforcement in aluminium.$ The results from SEM show an erosive structure at the voltage of 20 V and electrolyte concentration of g/l.

The results from SEM show an erosive structure at the voltage of 20 V and electrolyte concentration of g/l.

5 Figure 6 SEM images of ECM machined Al/VC 1% wt at V= 20 V and EC= g/l Figure 7 SEM images of ECM machined Al/VC 2 % wt at V= 20 V and EC= g/l Figure 8 SEM images of ECM machined Al/VC 1% wt at V= 20 V and EC= g/l 5 CONCLUSIONS Experiments were conducted to investigate the machining behaviour of Al/VC composites using electrochemical machining. The different parameters in the analysis included voltage and electrolyte concentration and weight fraction of vanadium carbide reinforcement in aluminium. The VC particles weight fraction has a considerable effect on surface roughness. The influence of VC particles on material removal rate is not apparent. The results from SEM show an erosive structure at the voltage of 20 V and electrolyte concentration of g/l. The experimental models derived by RSM can be used to predict the MRR and surface roughness (R a ) with different ECM process and product parameters. The contour plots were drawn to understand the effects of process parameters on MRR and R a. REFERENCES [1] F. Muller and J. Monaghan (2000) Non-conventional machining of particle reinforced metal matrix composite, International Journal of Machine Tools and Manufacture, Vol. 40, No. 9, pp [2] G. Patil Nilesh and P. K. Brahmankar (2009) Some studies into wire electro-discharge machining of alumina particulate-reinforced aluminum matrix composites, International Journal of Advanced Manufacturing Technology. [3] A. Noorul Haq, P. Marimuthu and R. Jeyapaul (2008) Multi response optimization of machining parameters of drilling Al/SiC metal matrix composite using grey relational analysis in the Taguchi method, International Journal of Advanced Manufacturing Technology 37, pp [4] A. Manna and B. Bhattacharayya (2003) A study on machinability of Al/SiC-MMC, Journal of Materials Processing Technology, Proceedings of the 6th Asia Pacific Conference on Materials Processing, Vol., Nos. 1 3, pp [5] N. Muthukrishnan, M. Murugan and K. Prahlada Rao (2008) Machinability issues in turning of Al-SiC (10p) metal matrix composites, International Journal of Advanced Manufacturing Technology 39, pp [6] Y. Yao, D. Li and Z. Yuan (2004) Mill-grinding machining for particle reinforced aluminium matrix composites, Paper presented at the 7th ICPMT International Conference on Progress of Machining Technology, Beijing, China. [7] C. Senthilkumar, G. Ganesan and R. Karthikeyan (2009) Study of electrochemical machining characteristics of Al/SiC p Composites, International Journal of Advanced Manufacturing Technology 43, pp [8] K.L.Senthil Kumar, R.Sivasubramanian and K.Kalaiselvan (2009), Selection of Optimum Parameters in Non Conventional Machining of Metal Matrix Composite, Portugaliae Electrochimica Acta, 27(4), pp [9] S.Rama Rao and G. Padmanabhan (2012), Effect of process variables on metal removal rate in electrochemical machining of Al-B4C composites, Archives of Applied Science Research, 4 (4), pp [10] S.Rama Rao and G. Padmanabhan (2013), Linear Modeling of the Electrochemical Machining Process Using Full Factorial Design of Experiments, Journal of Advanced Mechanical Engineering, 1, pp

6 [11] T. A. El-Taweel (2008), Modeling and analysis of hybrid electrochemical turning magnetic abrasive finishing of 6061 Al/Al2O3 composite, International Journal of Advanced Manufacturing Technology 37, pp [12] S. Ayyappan, M. Kalaimathi and G.Venkatachalam (2014), Multi-Objective Optimization of Process Parameters for Electrochemical Machining of 6061Al/ 10%Wt Al 2 O / 5%Wt SiC Composite using Hybrid 3 Fuzzy-Artificial Bee Colony Algorithm, Jordan Journal of Mechanical and Industrial Engineering, 8(5), pp [13] S. Ayyappan and K. Sivakumar (2014), Investigation of electrochemical machining characteristics of 20MnCr5 alloy steel using potassium dichromate mixed aqueous NaCl electrolyte and optimization of process parameters, Proc I MechE Part B:J Engineering Manufacture. pp [14] M. Kalaimathi, G. Venkatachalam, Neil Makhijani and Ankit Agrawal (2014), Investigations on Machining of Monel 400 alloys using Electrochemical Machining with Sodium Nitrate as Electrolyte, Applied Machanics and Materials,Vols , pp , Trans Tech Publications, Switzerland. [15] M. Kalaimathi, G. Venkatachalam and M. Sivakumar (2014), Experimental Investigations on the Electrochemical Machining Characteristics of Monel 400 Alloys and Optimization of Process Parameters Jordan Journal of Mechanical and Industrial Engineering, Vol.8, No.3, pp [16] S.Ayyappan and K.Sivakumar (2015), Enhancing the performance of electrochemical machining of 20MnCr5 alloy steel and optimization of process parameters by PSO-DF optimizer, International Journal of Advanced Manufacturing Technology, pp DOI: /s

Investigation of Electro Chemical Micro Machining process parameters on Al- SiCp - Gr Composites using Taguchi Methodology

International Journal of ChemTech Research CODEN (USA): IJCRGG ISSN: 0974-4290 Vol.8, No.8, pp 278-285, 2015 Investigation of Electro Chemical Micro Machining process parameters on Al- SiCp - Gr Composites