The study on the chip formation and wear behavior for drilling forged steel S48CS1V with TiAlN-coated gun drill

The solid carbide gun drill was coated with TiAlN, and a comprehensive evaluation on the wear behavior and chip formation had been performed on it for machining forged steel S48CS1V at a cutting speed of 12.66 mm/s (4400 rpm) with a continuous Minimum Quantity Lubrication (MQL). Cutting torque had been measured versus with the quantity of the machined crankshaft. The cutting torque curves revealed the three wear stages that were the initial stage, the semi-steady stage and the disastrous stage. Gun drill with TiAlN coating suffered from adhesive wear on the wear pad and chemical diffusion wear on flank face. Additionally, sliding wear and chipping were the wear forms. The high temperature and stress played the important roles in the adhesive and chemical diffusion wears. The high alternative stress produced the plastic deformation and cold welding for the atomic absorption and thus it made the grains of carbide substrate tearing-off from deforming cobalt bond, therefore adhesive wear took place.

► The gun drill coated with TiAlN has a sufficient cutting life for the depth hole drilling due to the longer initial and semi-steady stages of wear.
► Tool wear accelerates as the Co diffusion from the solid carbide and reduce the bond strength of the carbide in substrate material.
► Chip morphology always reflects the wear progress, and the chip morphology becomes difference at different wear stages.