Material Response at Tool-Chip Interface and Its Effects on Tool Wear in Turning Inconel718

Because nickel-based alloy Inconel718 has poor thermal conductivity and serious work hardening, it is identified as a difficult-to-process material. The serious tool wear leads to short tool life. In this study, physical vapor deposition-coated carbide tools were used to machine Inconel718. The material response for different cutting speeds at the tool-chip interface and its effect on tool wear were studied. The results showed that at low cutting speed (v (c)=20m/min), cold welding and adhesion occurred at the tool-chip interface under high stress, and then the built-up edge (BUE) formed. The peeling off of BUE led to chipping. When the cutting speed (v (c)) was 45m/min, diffusion and oxidation occurred at the tool-chip interface. The new generated material reduced tool hardness and bond strength of Co. The wear debris was generated in tool rake face. Flakes of wear debris fell from the tool substrate, which increased tool wear. When the cutting speed was 32m/min, the softer oxides generated at the tool-chip interface served as a boundary lubrication layer. They can effectively weaken the adhesion between tool and chip, which made the chemical wear and adhesive wear reach equilibrium. Furthermore, the friction coefficient is reduced. Tool wear is reduced under this cutting condition.