Influence of cutting tool material on machinability of Inconel 718 superalloy

Appropriate selection of tool material is very important for effective machining of 'difficult-to-cut' aerospace superalloy Inconel 718, especially, under dry condition. Present work aims at investigating performance of physical vapor deposition (PVD) multi-layer (TiN/TiCN/TiN) coated cermet, and PVD TiAlN coated PCBN (Polycrystalline Cubic Boron Nitride) brazed tipped carbide inserts on machinability of Inconel 718. Machinability is assessed based on cutting force magnitude, maximum tool-tip temperature attained, tool wear morphology, chip macro/micro morphology, and end part surface integrity. Later includes detailed analysis on morphology of the machined surface, roughness, and depth of hardened layer. Results obtained thereof, are compared to that of conventional uncoated WC-Co tool. It is evidenced that coated cermet outperformed other two inserts in purview of lower cutting force, better surface finish, and tiny white layer. WC-Co causes extreme cutting temperature than other counterparts. Up to 86 m/min cutting velocity, PCBN tool exhibits minimal flank wear; afterwards, tool is severely affected by huge notch wear. On the contrary, cermet tool suffers from lower flank wear than WC-Co for all cutting speeds tested. Both cermet and PCBN inserts are found remarkably affected by notching, and coating dissipation. Attrition wear is evidenced only in case of WC-Co insert. Coated cermet, thus, appears as a better choice for dry turning of Inconel 718.