# Optimization of the Surface Roughness Parameters of Ti–Al Intermetallic Based Composite Machined by Wire Electrical Discharge Machining

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## Abstract

**:**

## 1. Introduction

_{2}+ γ) Ti–Al intermetallics and revealed binary parts in structure composed of α

_{2}+ Ti

_{3}Al and γ + TiAl. In their work, a detailed fracture mechanism was interpreted with different plastic incompatibilities between the two phases [5]. However, the evolution of this intermetallic and its composition is still not fully understood.

## 2. Materials and Experimental Conditions

#### 2.1. Microstructural Assessment of the Intermetallic Composite

_{2}-Ti

_{3}Al”. Finally, the major microstructure is a substantially equiaxed lamellar structure made up of lamellar platelets containing platelets of the γ phase of the structure of the face-centred cubic lattice (fcc) (111) type L10 and a very fine α

_{2}-(0001) hexagonal structure (Figure 3).

#### 2.2. WEDM Cutting Process and Cutting Parameters

- Workpiece: Ti–Al intermetallic based composite.
- Electrode (tool): 250 μm diameter of brass wire.
- Dielectric: deionized water.

_{9}“ orthogonal array (OA) for the current study is presented in Table 3. An integrated method was used to optimize the process which brings together the Taguchi method and the response surface methodology (RSM).

- Pulse-on-time (Ton): The time duration in which the spark (electron discharge) occurs between the electrode (wire) and the workpiece once the breakdown voltage of the dielectric is reached.
- Start-up voltage (U): The minimum input voltage value.
- Feed rate or speed advance (S): Feed rate of wire into the workpiece in mm/min.
- Flushing pressure (p): the pressure of injection of the dielectric.

## 3. Experimental of WEDM: Influence of Machining Parameters on the Surface Roughness

#### 3.1. Impact of Flushing Pressure and Tension on the Surface Quality

#### 3.2. Impact of Speed Advance and Pulse-On-Time on the Surface Quality

## 4. The Integrated Method

_{9}” was used in this study and is presented in Table 3. This basic design uses up to four control factors, with three levels each of which are presented in Table 2.

_{i}is the value of the Ra.

_{on}: pulse time, U: start-up a voltage or servo voltage, S is feed rate or speed advance and p is the flushing pressure or dielectric injection pressure), β

_{ij}is the coefficients of each term and ε is a residual error.

## 5. Analysis of the Results and General Discussion

_{3}= 10 bar corresponds to the smallest roughness value compared with p

_{1}and p

_{2}. Additionally, the speed advance S

_{3}corresponds to the smallest roughness value regarding the values, S

_{1}and S

_{2}, the T

_{on}

_{2}and U

_{3}corresponds the smallest roughness value compared with T

_{on}

_{1}and T

_{on}

_{3}, U

_{1}and U

_{2}respectively.

_{j}

_{,pred}, is compared with the experimental value of the response, Y

_{j}

_{,exp}. Figure 18 illustrates this comparison between the experimental and predictive response values, relating the predictive and the experimental surface roughness values. As observed from Figure 18, the predictive results with RSM are very close to the experimental results.

## 6. Conclusion

^{2}ratios, the validity of regression equations found with the RSM analysis for the prediction of roughness value was quite high (R

^{2}

_{Ra}(adj) = 98.58%). From this consequence, these predicted functions can reliably be used for similar applications.

- Several WEDM cutting tests were identified on the Ti–Al intermetallic composite on the orthogonal plane of Taguchi, “L9”, by changing the cutting parameters (pulse time Ton (μs), voltage U (V), speed advance S (mm/min) and flushing pressure p (bar)). This means that three tests were considered for each factor, so many combinations were executed in this work.
- The optimum WEDM cutting conditions of (Ti–Al) titanium–aluminium intermetallic based composite is determined from the results of the signal-to-noise ratio in a Taguchi plane of different inputs on the surface roughness performance.
- The best surface roughness obtained were for the conditions below: a voltage of U = 120 V, a pulse time Ton = 0.9 μs, a wire feed speed S = 43 mm/min and a pressure p = 10 bar.

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## Nomenclature

EDM | Electrical Discharge Machining |

WEDM | Wire electric discharge machining |

Ton | Pulse on time (µs) |

p | dielectric Pressure (bar) |

U | Servo voltage (V) |

S | Speed advance (mm/min) |

Ra | Parameter of Surface Roughness (µm) |

Sa | Parameter of3D Surface Roughness (µm) |

RSM | Response Surface Methodology |

ANOVA | Analysis of Variance |

S/N ratio | Signal-to-Noise Ratio |

L9 | Taguchi design |

GRA | Grey Relational Analysis |

ANN | Artificial Neural Network |

## References

- Appel, F.; Paul, J.D.H.; Oehring, M. Gamma Titanium Aluminide Alloys: Science and Technology; Wiley-VCH: Weinheim, Germany, 2011. [Google Scholar]
- Clemens, H.; Mayer, S. Design, processing, microstructure, properties, and applications of advanced intermetallic TiAl Alloys. Adv. Eng. Mater.
**2012**, 15, 191–215. [Google Scholar] [CrossRef] - Wu, X. Review of alloy and process development of TiAl alloys. Intermetallics
**2006**, 14, 1114–1122. [Google Scholar] [CrossRef] - Tchoupé Ngnekou, P.E.; Lafont, M.C.; Senocq, F.; Laffont, L.; Lacaze, J. Structural characterization of the scale formed on a Ti–46Al–8Nb alloy oxidized in air at 700 °C. Intermetallics
**2010**, 18, 226–232. [Google Scholar] [CrossRef] [Green Version] - Bayraktar, E.; Bathias, C.; Xuehongquian, T.H. On the Giga cycle fatigue behavior of two-phase (α
_{2}+ γ) TiAl alloy. Int. J. Fatigue**2004**, 26, 1263–1275. [Google Scholar] [CrossRef] - Baraskar, S.S.; Banwait, S.S.; Laroiya, S.C. Multiobjective optimization of electrical discharge machining process using a hybrid method. Mater. Manuf. Process.
**2013**, 28, 348–354. [Google Scholar] [CrossRef] - Saedon, J.; Jaafar, N.; Jaafar, R.; Saad, N.H.; Kasim, M.S. Modeling and multi-response optimization on WEDM Ti6Al4V. Appl. Mech. Mater.
**2014**, 510, 123–129. [Google Scholar] [CrossRef] - Atasoy, E.; Kahraman, N. Diffusion bonding of commercially pure titanium to low carbon steel using a silver interlayer. Mater. Charact.
**2008**, 59, 1481–1490. [Google Scholar] [CrossRef] - Shabgard, M.; Khosrozadeh, B. Investigation of carbon nanotube added dielectric on the surface characteristics and machining performance of Ti–6Al–4V alloy in EDM process. J. Manuf. Process.
**2017**, 25, 212–219. [Google Scholar] [CrossRef] - Li, L.; Feng, L.; Bai, X.; Li, Z. Surface characteristics of Ti–6Al–4V alloy by EDM with Cu–SiC composite electrode. Appl. Surf. Sci.
**2016**, 388, 546–550. [Google Scholar] [CrossRef] - Gnanavelbabu, A.; Saravanan, P.; Rajkumar, K.; Karthikeyan, S.; Baskaran, R. Optimization of WEDM process parameters on multiple responses in cutting of Ti–6Al–4V. Mater. Today Proc.
**2018**, 5, 27072–27080. [Google Scholar] [CrossRef] - Kumar, R.; Roy, S.; Gunjan, P.; Sahoo, A.; Sarkar, D.D.; Das, R.K. Analysis of MRR and surface roughness in machining Ti–6Al–4V ELI titanium alloy using EDM process. Procedia Manuf.
**2018**, 20, 358–364. [Google Scholar] [CrossRef] - Khundrakpam, N.S.; Brar, G.S.; Deepak, D. Grey-Taguchi optimization of near dry EDM process parameters on the surface roughness. Mater. Today Proc.
**2018**, 5, 4445–4451. [Google Scholar] - Mazarbhuiya, R.M.; Choudhury, P.K.; Patowari, P.K. An experimental study on parametric optimization for material removal rate and surface roughness on EDM by using taguchi method. Mater. Today Proc.
**2018**, 5, 4621–4628. [Google Scholar] [CrossRef] - Kumar, S.; Singh, R.; Singh, T.P.; Sethi, B.L. Surface modification by electrical discharge machining: A review. J. Mater. Process. Technol.
**2009**, 209, 3675–3687. [Google Scholar] [CrossRef] - Suresh Kumar, S.; Uthayakumar, M.; Kumaran, S.T.; Varol, T.; Canakci, A. Investigating the surface integrity of aluminium based composites machined by EDM. Def. Technol.
**2019**, 15, 338–343. [Google Scholar] [CrossRef] - Antar, M.; Hayward, P.; Dunleavey, J.; Butler-Smith, P. Surface integrity evaluation of modified EDM surface structure. Procedia CIRP
**2018**, 68, 308–312. [Google Scholar] [CrossRef] - Kirby, M.E.D.; Zhang, M.Z.; Joseph, C.; Chen. Development of an accelerometer-based surface roughness prediction system in turning operations using multiple regression techniques. J. Ind. Technol.
**2004**, 20, 1–8. [Google Scholar] - Mahapatra, S.S.; Patnaik, A. Optimization of wire electrical discharge machining (WEDM) process parameters using Taguchi method. Int. J. Adv. Manuf. Technol.
**2007**, 34, 911–925. [Google Scholar] [CrossRef] - Chalisgaonkar, R.; Kumar, J. Optimization of WEDM process of pure titanium with multiple performance characteristics using Taguchi’s DOE approach and utility concept. Front. Mech. Eng.
**2013**, 8, 201–214. [Google Scholar] [CrossRef] - Kanagarajan, D.; Karthikeyan, R.; Palanikumar, K.; Sivaraj, P. Influence of process parameters on electric discharge machining of WC/30%Co composite. Proc. Inst. Mech. Eng. Part B J. Eng. Manuf.
**2009**, 222, 807–815. [Google Scholar] [CrossRef] - Pandey, A.B.; Brahmankar, P.K. A method to predict possibility of arcing in EDM of TiB
_{2p}reinforced ferrous matrix composite. Int. J. Adv. Manuf. Technol.**2016**, 86, 2837–2849. [Google Scholar] [CrossRef] - Goswami, A.; Kumar, J. Investigation of surface integrity, material removal rate and wire wear ratio for WEDM of Nimonic 80A alloy using GRA and Taguchi method. Eng. Sci. Technol. Int. J.
**2014**, 17, 173–184. [Google Scholar] [CrossRef] [Green Version] - Benardos, P.G.; Vosniakos, G.-C. Predicting surface roughness in machining: A review. Int. J. Mach. Tools Manuf.
**2003**, 43, 833–844. [Google Scholar] [CrossRef] - Enginsoy, H.; Gatamorta, F.; Bayraktar, E.; Robert, M.; Miskioglu, I. Experimental and numerical study of Al-Nb2Al composites via associated procedure of powder metallurgy and thixoforming. Compos. Part B Eng.
**2019**, 162, 397–410. [Google Scholar] [CrossRef] - Bayraktar, E.; Miskioglu, I.; Katundi, D.; Gatamorta, F. Manufacturing of Recycled Aluminum Matrix Composites Reinforced of TiC/MoS
_{2}/Al_{2}O_{3}Fiber Through Combined Method: Sintered + Forging. In Mechanics of Composite and Multi-functional Materials; Springer: Cham, Switzerland, 2019; Volume 5, pp. 15–26. [Google Scholar] - Tosun, N.; Cogun, C.; Tosun, G. A study on kerf and material removal rate in wire electrical discharge machining based on Taguchi method. J. Mater. Process. Technol.
**2004**, 152, 316–322. [Google Scholar] [CrossRef] - Galindo-Fernandez, M.; Diver, C.; Leahy, W. The prediction of surface finish and cutting speed for wire electro-discharge machining of polycrystalline diamond. Procedia CIRP
**2016**, 42, 297–304. [Google Scholar] [CrossRef] - Ezeddini, S.; Bayraktar, E.; Boujelbene, M.; Salem, S.B. Optimization of Surface Integrity of Titanium-Aluminum Intermetallic Composite Machined by Wire EDM. In Mechanics of Composite, Hybrid and Multifunctional Materials; Springer: Cham, Switzerland, 2019; Volume 5, pp. 47–57. [Google Scholar]
- Wong, Y.S.; Lim, L.C.; Lee, L.C. Effect of flushing on electro discharge machined surface. J. Mater. Process. Technol.
**1995**, 48, 299–305. [Google Scholar] [CrossRef] - Nourbakhsh, F.; Rajurkar, K.P.; Malshe, A.P.; Cao, J. Wire electro-discharge machining of titanium alloy. Procedia CIRP
**2013**, 5, 13–18. [Google Scholar] [CrossRef] [Green Version] - Ulutan, D.; Ozel, T. Machining induced surface integrity in titanium and nickel alloys: A review. Int. J. Mach. Tools Manuf.
**2011**, 51, 250–280. [Google Scholar] [CrossRef] - Ezeddini, S.; Boujelbene, M.; Bayraktar, E.; Salem, S.B. Recycled Ti-17 Based Composite Design; Optimization Process Parameters in Wire Cut Electrical Discharge Machining (WEDM). In Mechanics of Composite, Hybrid and Multifunctional Materials; Springer: Cham, Switzerland, 2019; Volume 5, pp. 109–125. [Google Scholar]
- Rajesh, R.; Dev Anand, M. The optimization of electro-discharge machining process using response surface methodology and genetic algorithms. Procedia Eng.
**2012**, 38, 3941–3950. [Google Scholar] [CrossRef] [Green Version]

**Figure 2.**Microstructural evaluation of the titanium–aluminium (Ti–Al) intermetallic composite at the surface.

**Figure 3.**General microstructure of Ti–Al intermetallic composite at the thickness (transversal direction).

**Figure 5.**Effects of injection pressure on the surface topography: (

**a**) S = 36 mm/min, p = 10 bar; Sa = 2.32 µm; (

**b**) S = 36 mm/min, p = 6 bar, Sa = 3.40 µm.

**Figure 6.**Effects of injection pressure on the profile of roughness: (

**a**) S = 36 mm/min, p =10 bar; Ra = 1.96 µm; (

**b**) S = 36 mm/min, p = 6 bar, Ra = 2.84 µm.

**Figure 7.**SEM observation of surface after wire electrical discharge machining (WEDM) as function of the cutting parameters; S = 36 mm/min: (

**a**) p = 10 bars, (

**b**) p = 6 bars. Scale bar = 20 μm.

**Figure 11.**SEM observation of surface after wire electric discharge machining at cutting parameters; p = 6 bar; (

**a**) Speed S = 29 mm/min; (

**b**) Speed S = 43 mm/min. Scale bar = 20 μm.

**Figure 12.**SEM observations of the cut surface after WEDM process at a pressure level of p = 8 bar under two different cutting speeds, (

**a**) S = 29 mm/min and (

**b**) S = 43 mm/min.

**Figure 13.**Diagram of the value of the surface roughness Ra at p = 8 bar; S = 29 mm/min and S = 43 mm/min.

Composition | Ti | Al | Nb_{2}Al | Nb | Yttrium-Doped-Zirconia (Y-ZrO_{2}) | Mo | B | Zn–St |
---|---|---|---|---|---|---|---|---|

t% | 53 | 27 | 4 | 15 | 1 | 0.1 | 0.15 | 1 |

Levels | Pulse-On-Time Ton (µs) | Servo Voltage U (V) | Speed Advance S (mm/min) | Flushing Pressure p (bar) |
---|---|---|---|---|

1 | 0.8 | 80 | 29 | 6 |

2 | 0.9 | 100 | 36 | 8 |

3 | 1 | 120 | 43 | 10 |

Run | Control Factors and Levels | Results | |||
---|---|---|---|---|---|

U (V) | Ton (µs) | S (mm/min) | p (bar) | Ra (µm) | |

1 | 80 | 0.8 | 29 | 6 | 2.46 |

2 | 80 | 0.9 | 36 | 8 | 1.92 |

3 | 80 | 1 | 43 | 10 | 1.8 |

4 | 100 | 0.8 | 36 | 10 | 1.7 |

5 | 100 | 0.9 | 43 | 6 | 2.53 |

6 | 100 | 1 | 29 | 8 | 2.01 |

7 | 120 | 0.8 | 43 | 8 | 1.74 |

8 | 120 | 0.9 | 29 | 10 | 1.74 |

9 | 120 | 1 | 36 | 6 | 2.96 |

Process Parameters | Level | Means | S/N Ratio | ||||||
---|---|---|---|---|---|---|---|---|---|

U(V) | Ton(µs) | S(mm/min) | P (bar) | U (V) | Ton (µs) | S (mm/min) | P (bar) | ||

Average value | L1 | 2.197 | 2.240 | 2.243 | 2.747 | −6.610 | −6.816 | −6.826 | −8.754 |

L2 | 2.150 | 2.070 | 2.243 | 1.927 | −6.599 | −6.235 | −6.874 | −5.690 | |

L3 | 2.160 | 2.197 | 2.020 | 1.833 | −6.489 | −6.647 | −5.999 | −5.254 | |

Delta | 0.047 | 0.170 | 0.223 | 0.913 | 0.121 | 0.581 | 0.875 | 3.501 | |

Rank | 4 | 3 | 2 | 1 | 3 | 2 | 4 | 1 |

Source | DF | Adj SS | Cont% | Adj MS | F-Value | P-Value | Remarks |
---|---|---|---|---|---|---|---|

Model | 8 | 2.32511 | 99.47 | 0.290639 | 148.62 | 0.000 | – |

U (V) | 1 | 0.01170 | 0.12 | 0.011697 | 5.98 | 0.037 | – |

Ton (µs) | 1 | 0.01881 | 0.17 | 0.018811 | 9.62 | 0.013 | Significant |

S (mm/min) | 1 | 0.13637 | 4.47 | 0.136368 | 69.73 | 0.000 | Significant |

p (bar) | 1 | 0.44436 | 74.73 | 0.444355 | 227.23 | 0.000 | Significant |

U^{2} (V) | 1 | 0.00934 | 0.10 | 0.009344 | 4.78 | 0.057 | – |

Ton^{2} (µs) | 1 | 0.02054 | 2,63 | 0.020544 | 10.51 | 0.000 | Significant |

S^{2} (mm/min) | 1 | 0.14188 | 1.49 | 0.141878 | 72.55 | 0.000 | Significant |

p^{2} (bar) | 1 | 0.32871 | 15.77 | 0.328711 | 168.09 | 0.010 | Significant |

Error | 9 | 0.01760 | 0.62 | 0.001956 | – | – | – |

Total | 17 | 2.34271 | 100.00 | – | – | – | – |

Parameter | |||||||

S = 0.0442217; R-sq = 99.25%; R-sq (adj) = 98.58%; R-sq (pred) = 96.99% |

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**MDPI and ACS Style**

Ezeddini, S.; Boujelbene, M.; Bayraktar, E.; Ben Salem, S.
Optimization of the Surface Roughness Parameters of Ti–Al Intermetallic Based Composite Machined by Wire Electrical Discharge Machining. *Coatings* **2020**, *10*, 900.
https://doi.org/10.3390/coatings10090900

**AMA Style**

Ezeddini S, Boujelbene M, Bayraktar E, Ben Salem S.
Optimization of the Surface Roughness Parameters of Ti–Al Intermetallic Based Composite Machined by Wire Electrical Discharge Machining. *Coatings*. 2020; 10(9):900.
https://doi.org/10.3390/coatings10090900

**Chicago/Turabian Style**

Ezeddini, Sonia, Mohamed Boujelbene, Emin Bayraktar, and Sahbi Ben Salem.
2020. "Optimization of the Surface Roughness Parameters of Ti–Al Intermetallic Based Composite Machined by Wire Electrical Discharge Machining" *Coatings* 10, no. 9: 900.
https://doi.org/10.3390/coatings10090900