Experimental Investigation on Effect of Heat Treatment and Nanoparticle Suspension in Dielectric Fluid on EDM of Ti-6Al-4V

This study investigates how heat treatments (annealing and quenching) and nanoparticle-mixed dielectric fluids (NPMDF) affect the electrical discharge machining (EDM) performance of Ti-6Al-4V alloy. Machining characteristics such as material removal rate (MRR), tool wear rate (TWR), and surface roughness (SR) were evaluated, alongside microstructural analysis and micro Vickers hardness (MVH) validation. EDM experiments were conducted using three dielectric fluids: base transformer oil (non-NPMDF), Al 2 O 3 -NPMDF, and TiO 2 -NPMDF. Results show that annealed samples achieved the highest MRR, followed by the quenched and untreated samples, due to material softening and grain coarsening, while TiO 2 -NPMDF enhanced MRR by retaining thermal energy in the spark channel, followed by Al 2 O 3 -NPMDF and non-NPMDF. Quenched samples exhibited the highest TWR and SR, followed by the annealed and untreated samples, attributed to their hardened structure and uneven erosion, with TiO 2 -NPMDF further accelerating tool degradation and surface roughness. Specifically, TiO 2 -NPMDF improved MRR by ~74% compared to non-NPMDF and ~37% compared to Al 2 O 3 -NPMDF, while Al 2 O 3 -NPMDF showed ~28% improvement over non-NPMDF. Quenched samples exhibited ~42% higher TWR and ~35% higher SR than annealed samples, confirming statistical significance. Microhardness validation confirmed that quenched samples had the highest MVH, followed by the untreated and annealed samples, supported by microstructural evidence of finer grains and martensitic refinement than annealed and untreated samples. However, the grain structure in the annealed sample was observed to be coarser compared to the untreated sample. The novelty of this study lies in systematically investigating the combined influence of heat treatment conditions and nanoparticle-mixed dielectric fluids on the EDM characteristics of Ti-6Al-4V alloy and establishing their correlation with microstructural evolution and hardness, an area that has received limited attention in the existing literature. Overall, the combined influence of heat treatment and NPMDF significantly impacts EDM performance, offering new insights into optimizing machining of Ti-6Al-4V alloys.