Effect of hardening on the machinability of C22 steel under drilling operations using twist HSS drill bit

The present work is a contribution in understanding the machinability of hardened C22 steel under drilling operations using twist high-speed steel (HSS) grade drill bits. Experimental investigation has been conducted on annealed and hardened C22 steel according to the planning experience methodology (L8). The input parameters are cutting regime elements, cutting speed, feed rate, and drill diameter; meanwhile, the output parameter is the tool wear related to tool life. Apart from the common observation that tool life decreases when the cutting speed increases, the most interesting phenomenon is the controversial effect of the cutting speed when drilling the steel in hardened condition. The latter has been assessed through exploratory chip microstructure observations.