Machinability of titanium alloy (Ti-6Al-4V) by abrasive waterjets

Titanium alloy is known as one of the difficult-to-machine materials using conventional machining processes, although it has superior formability. In the present study, a widely used aircraft structural titanium alloy (Ti-6Al-4V) was machined with an abrasive waterjet (AWJ) to investigate its machinability under varying cutting conditions. Machinability was evaluated in terms of kerf geometry, cut surface quality and microstructural integrity. Quality of the machined surface and microstructure features were examined using surface profilometry, scanning electron microscopy and energy dispersive X-ray (EDX) analysis. The surface roughness was ranged several micrometres near the jet entrance region and was observed to increase at the jet exit of the workpiece. Scanning electron microscopy (SEM) analysis of the surface microstructure revealed that the mechanism of material removal was a combination of scooping induced ductile shear and ploughing actions of the abrasive particles. EDX analysis showed garnet particle embedment in titanium throughout the cutting depth, and the particle size was estimated to be several tens of micrometres.