Investigation on the effect of cutting geometry on tool life in drilling Inconel 718

Inconel 718 is a high temperature, precipitate-hardened nickel alloy which is known for its excellent high temperature mechanical properties. It is widely applied in the aerospace, oil and gas and gas turbine industries. Inconel 718 is notoriously known as a difficult-to-machine material due to strain hardening and poor thermal conductivity properties, resulting in short tool life and surface integrity during machining operations. Machining Inconel 718 is widely recognised as a bottleneck for manufacturing parts and is often synonymous with low productivity and high manufacturing costs. Drilling is one of the final manufacturing processes which usually takes place when the part is most expensive due to the previous operations. Therefore, ensuring the quality of the drilling process is crucial in preventing costly scrappage. Review of literature indicated there is minimal research regarding the cutting tool geometry for drilling Inconel 718. This paper investigates the effect of various cutting tool geometries on tool life and surface roughness when drilling age hardened Inconel 718 using uncoated solid carbide drills. A robust methodology is developed to assess the significance of various cutting geometries on tool life and surface finish. A series of drills are manufactured and used for machining experiments. Rigorous analysis of the results indicated optimum cutting tool has a 30° helix angle, 130° drill point angle, 0° cutting angle and a 10° relief angle. The manufactured drill is capable of extending tool life to 69 holes before reaching the tool wear criterion.