Reducing tool wear in high-speed milling of Inconel 718 by optimizing flank-face coolant direction: A CFD-supported approach toward sustainable machining

This study investigates the impact of flank face coolant nozzle orientation on tool wear suppression in the high-speed milling of Inconel 718. Preliminary dry milling of Ti-6Al-4V with a Tool-Nose-Aimed (TNA) tool revealed severe flank wear at the bolt side edge. This failure mode persisted in Inconel 718, where the TNA tool suffered from severe adhesion and brittle fracture at this location under dry, flood and all high-pressure coolant (HPC) conditions except ultra-high pressure coolant (UHPC) at 20 MPa. Thermal and Computational Fluid Dynamics (CFD) simulations diagnosed the cause: the bolt side edge is a thermal throttling zone, and the TNA's coolant jet core deviates from this critical spot. Guided by this analysis, a novel Bolt-Side-Edge-Flank-Aimed (BSEFA) tool was designed. Its nozzle orientation was optimized to ensure the jet core directly impinges on the flank face of the bolt side edge, enhancing convective heat transfer through higher liquidity, velocity, and Turbulence Kinetic Energy (TKE). Experimentally, the BSEFA tool suppressed catastrophic failure, massive adhesion and reduced maximum flank wear (VB max ) within the wear land by 40–56% compared to the TNA tool. CFD results confirmed the mechanism, showing the optimized nozzle delivered superior coolant coverage (liquidity >0.95), higher velocity (>110 m/s), and drastically intensified turbulence (TKE increase >150%) at the target. This work establishes that strategic coolant orientation surpasses indiscriminate pressure increase. The BSEFA strategy enables high performance with minimal flow rate (<1.0 L/min), representing a > 95% reduction versus flood cooling, offering a highly efficient and sustainable machining strategy.