Study on rotary ultrasonic-assisted drilling of titanium alloys (Ti6Al4V) using 8-facet drill under no cooling condition

Titanium alloys (Ti6Al4V) have been widely applied in modern aerospace industry as structural components due to their excellent mechanical and physical properties. Meanwhile, the drilling process is essential for machining the assembly holes of Ti6Al4V. However, Ti6Al4V is also a difficult-to-cut material owing to their low thermal conductivity and high chemical reactivity with many tool materials during machining, which easily lead to rapid tool wear, premature tool failure, and poor machining quality. This has attracted wide attention of researchers. In recent years, the rotary ultrasonic-assisted drilling (RUAD) technology, as a novel machining method, has been found to be very effective in the machining of difficult-to-cut materials like nickel alloys and titanium alloys. This paper first introduced an 8-facet drill tool and combined the advantages of RUAD to carry out a study on the drilling of Ti6Al4V under no cooling condition. The experimental results indicated that compared with the common drilling (CD) of Ti6Al4V, in RUAD process with the vibration amplitude of 10 mu m, the thrust force, torque, cutting temperature near the drilled hole exit, surface roughness of drilled hole, expansion increment of hole diameter, and burr height of drilled hole exit decreased by 16.79 to 20.2 %, 31.5 to 33.6 %, 18.54 to 21.68 %, 24.87 to 25.36 %, 46.75 to 57.63 %, and 82.27 to 89.18 %, respectively; the excellent chip breakability and removal effect of chip evacuation, superior surface integrity of drilled hole, enhanced tool cutting ability, and prolonged tool life were obtained in RUAD. Furthermore, the experimental results also proved that the drilling technology of RUAD of Ti6Al4V using the 8-facet drill was feasible and the cutting effects were superior.