Tribological performance of hBN and graphene-enriched hybrid nanofluids on tool wear and hole surface quality in drilling: A comparative study on WAAM and wrought Inconel 625

Machining Inconel alloys presents considerable challenges due to their high strength, hardness, and heat resistance, which often results in faster tool wear, poor surface polish, higher cutting temperature, and energy consumption. These challenges are exacerbated by additively manufactured Inconel 625, as its anisotropic properties make machining more difficult. This study focuses on drilling Inconel 625, a widely used nickel-based superalloy, owing to its critical role in various industrial applications. Drilling operations are essential in areas such as aerospace manufacturing, where precision, hole quality, and efficiency are of utmost importance. The study aims to enhance the machinability of wire-arc additively manufactured (WAAMed) Inconel 625 by employing sustainable nanofluids strategies. Hexagonal boron nitride (hBN), graphene-based mono nanofluids, and hybrid nanofluids were synthesised. Further, the nanofluids were thoroughly characterized for their volumetric specific heat capacity, wettability, and dynamic viscosity. A hybrid nanofluid with (hBN to graphene) exhibited excellent lubricating and cooling performance. The machinability of both WAAM IN625 and wrought IN625 was evaluated under dry conditions, hBN and graphene mono nanofluids, and hybrid nanofluid-assisted drilling, focusing on metrics such as surface cutting temperature, surface roughness, hole circularity deviation, and tool wear and morphology. Results demonstrated that the hybrid nanofluid environment offered substantial advantages over dry machining, including a 37–41 % reduction in cutting surface temperature, a 41–45 % improvement in surface quality and a 53–54 % decrease in circularity deviation for both WAAM and wrought IN625. Furthermore, tool wear was minimised, with less adhesion and abrasive wear, resulting in a much longer tool life.