Initial investigation on Surface Integrity when Machining Inconel 718 with conventional and Electrostatic Lubrication

Inconel 718 is largely used in high-temperature applications where high hot strength and hardness are required, such as in aerospace and oil & gas industries. The majority of parts made from Inconel 718, especially in the aerospace industries, are safety-critical components where surface quality is of significant importance. In industrial practice, the development of satisfactory surface integrity for high-performance applications of Inconel 718 is still a difficult process when machining parts with conventional cutting fluid. However, a potential alternative to conventional cooling is Minimum Quantity Lubrication (MQL), since it avoids large amounts of cutting fluid, and enhances the functional behaviour of machined components through superior surface quality. In addition, further improvements can be achieved with electrostatic lubrication (EL). With EL, the lubricant is electrosprayed increasing penetrability, atomization, deposition and wettability in the machining area. In this paper, a nozzle designed for electrostatic spraying using MQL is presented. The effects of EL on surface integrity are discussed in comparison with conventional MQL and Flood strategies. Machining experiments have been carried out in line with finishing conditions analogous to those adopted in industry for the milling of nickel-based super alloys. For these experiments, MQL and EL are supplied with the same setup, except for charging conditions. Surface integrity characteristics such as roughness, hardness and surface defects are investigated together with power consumption and tool life.