Optimization of machining parameters during drilling of aerospace grade Ti-6Al-4V alloy

Drilling of titanium alloy, a widely used aerospace material, remains a hard to machine material due to its low thermal conductivity, high strength-to-weight ratio, and chemical reactivity with cutting tools. These characteristics results in rapid tool wear, elevated cutting temperatures, and deterioration in surface quality— especially under dry machining conditions. In this study, drilling experiments were carried out on 7 mm thick Ti- 6Al-4V plates using uncoated 8 mm tungsten carbide (TC) drills. The machining was performed under dry environment with a machining conditions from 30 to 45 m/min and feed rates from 0.03 to 0.12 mm/rev. The experimental design was formulated using the Taguchi L16 orthogonal array to evaluate the effects of input parameters on surface quality indicators including surface roughness (Ra), hole circularity, and diameter accuracy. The outcomes revealed that feed rate had the most significant influence on surface roughness, with the minimum Ra value of 0.91 µm observed at 40 m/min speed and 0.06 mm/rev feed. Likewise, better hole circularity was achieved at moderate speed and lower feed combinations, with a minimum circularity deviation of 22 µm. Signal-to-noise (S/N) ratio analysis identified optimal machining conditions for enhanced hole quality. Additionally, chip formation was observed and analyzed to support understanding of the material’s cutting behavior, revealing segmented chips due to the alloy’s strain hardening and thermal properties. Grey Relational Analysis (GRA) was also applied to optimize all three attributes.