Wear behavior of novel CVD-coated wiper inserts’ with various chip-breakers and resulting surface integrity during dry drilling of Ti-6Al-4V

In this paper, a comprehensive investigation in terms of tool wear/life, chip morphology, surface roughness/damage, diametric error, burr height, and microstructure is conducted by using an innovative integration of peripheral wiper and central stepped inserts when drilling Ti-6Al-4V alloy in a dry-cutting environment. Two geometries of peripheral wiper inserts termed as LM (groove width-1000 mm, groove depth-65 mm) and GT (groove width-720 mm, groove depth-20 mm) are evaluated at two levels of cutting speeds (50 m/min and 60 m/min) and three levels of feed rates (0.10 mm/rev, 0.15 mm/rev, and 0.20 mm/rev) while keeping the geometry of central stepped insert constant. The GT wiper configuration is found to be more suitable in terms of tool life, drilling maximum number of holes (75) at a cutting speed of 50 m/min and feed rate of 0.10 mm/rev which is ∼3-fold higher than that of the LM geometry. With respect to majority of the drilled hole attributes, better performance of LM geometry is observed in comparison to its GT counterpart due to its improved chip breakability. In addition, all holes are oversized ranging from 30 µm to100 µm. Minor plastic deformation of grain boundaries in the machined sub-surface is noticed to a depth of 10–15 µm in the direction of cutting.