Drilling of Ti-6Al-4V alloy

Titanium have chemical reactivity, high affinity and low heat conductivity. These properties are responsible for the poor machinability of tiatanium alloys. In the drilling of titanium alloys the suitable materials, shape of cutting portion and cutting conditions have not found out nowadays. The cutting forces on TiN coated cobalt high speed steel drills and oxide-treated nitridized cobalt high speed steel drills in the drilling Ti-6Al-4V alloy and effect of the step feed on the performance of both drill types with respect to cutting characteristics (cutting force, tool wear, tool life and burr shape) were investigated. In the conventional drilling the cutting forces on TiN drills increase as cutting speed increases and at a cutting speed of 900rpm the torque on TiN drills rapidly attains a value twice that on COHS drills. In step feed drilling, cutting forces on TiN drills are generally lower than in conventional drilling and are also lower as compared to the forces acting on COHS drills.