Unveiling the impact of workpiece temperature on Ti6Al4V micro-drilling through a comparative analysis of cryogenic...

Titanium alloys are widely classified as difficult-to-cut materials due to their low thermal conductivity and high chemical reactivity, which present significant machining challenges. This study provides a pioneering comparative analysis of the micro-drilling machinability under cryogenic cooling (-196 °C) and thermally assisted drilling (TAD) using PID-controlled induction heating at 250 °C and 500 °C. Experimental results revealed that while cryogenic drilling increased thrust forces by approximately 38% compared to room temperature conditions, it exhibited superior performance in terms of chip morphology and surface integrity by reducing surface roughness (R_a) values to as low as 0.34 μm. Conversely, TAD at 250 °C offered no machinability benefits, representing a thermal dead zone within the experimental constraints of the present study. However, at 500 °C, thrust forces decreased by approximately 13% due to thermal softening, leading to significant improvements in burr morphology despite the increased risk of chip clogging and severe built-up layer formation due to adhesion. Additionally, regardless of the thermal environment, lower cutting speeds were found to be essential for maintaining process stability.