Performance Optimization of Ti-6Al-4V in Electrical Discharge Machining Using Graphene-Modified Dielectric Medium

Technical Summary: Performance Optimization of Ti-6Al-4V in EDM Using Graphene-Modified Dielectric

Problem Statement
Electrical Discharge Machining (EDM) is a critical non-conventional process for manufacturing complex components from high-strength, wear-resistant materials like the Ti-6Al-4V titanium alloy, widely used in aerospace, biomedical, and defense sectors. However, conventional EDM of Ti-6Al-4V faces significant limitations, including excessive Tool Wear Rate (TWR), spark instability, low Material Removal Rate (MRR), and compromised surface integrity. The study addresses these challenges by investigating the feasibility of an environmentally friendly modification to the EDM process: the addition of graphene nanoparticles (NPs) to the dielectric medium.

Methodology
The research employed a structured Design of Experiments (DOE) based on the Taguchi method using an L16 orthogonal array to optimize machining parameters.

• Materials: The workpiece was Ti-6Al-4V (Titanium Grade 5). The tool electrode was Aluminum. The dielectric fluid was modified by dispersing graphene nanoparticles, synthesized via a chemical oxidation method using graphite, sulfuric acid, phosphoric acid, potassium permanganate, and hydrogen peroxide.
• Process Parameters: Three input variables were varied across four levels each: Peak Current (15, 25, 35, 45 A), Gap Voltage (40, 45, 50, 55 V), and Pulse On Time (100, 200, 300, 400 µs).
• Analysis: Performance was evaluated based on MRR and TWR. Statistical significance was determined using Analysis of Variance (ANOVA). Surface morphology was analyzed using Scanning Electron Microscopy (SEM).

Key Results

• Optimization of Parameters: The ANOVA results indicated that Pulse On Time was the most dominant factor influencing both MRR (63% contribution) and TWR. Current was the second most significant factor for MRR (24% contribution), while Gap Voltage showed minimal statistical influence on MRR.
• Optimal Conditions: The study identified the optimal parameter combination for maximizing MRR as a Peak Current of 35 A, a Gap Voltage of 40 V, and a Pulse On Time of 400 µs.
• Performance Metrics: The integration of graphene nanoparticles into the dielectric fluid, combined with the aluminum electrode, resulted in enhanced spark stability and improved material removal. The SEM analysis revealed that the graphene-modified process produced surfaces with fewer microcracks, smaller craters, and a thinner recast layer compared to conventional methods. The graphene facilitated better debris flushing and heat dissipation, reducing thermal stress on the workpiece.
• Regression Models: The study established regression equations to predict TWR and MRR based on the input parameters, highlighting non-linear relationships, particularly regarding current and pulse duration.

Significance and Claims
The paper claims that the proposed method offers a sustainable route for high-quality EDM of Ti-6Al-4V. The primary significance lies in the demonstration that graphene-based nanofluids, when paired with aluminum electrodes, can simultaneously enhance MRR and reduce TWR while improving surface integrity. The authors attribute these improvements to the superior thermal and electrical conductivity of graphene, which stabilizes the discharge gap and promotes uniform spark energy distribution. The study concludes that this approach effectively mitigates the common drawbacks of machining titanium alloys, such as excessive tool wear and poor surface finish, without requiring complex machinery modifications. The authors suggest that future work could explore the use of environmentally benign dielectric media, such as vegetable oil, to further align the process with global sustainability goals.