Performance assessment of hybrid lubricating conditions on machining-induced surface/subsurface characteristics during a novel heat assisted machining Hastelloy C4

Nickel-based superalloys are widely used in important applications in various industries, including aerospace, defence, chemical processing, and marine. However, the difficulties encountered in machining these alloys pose specific challenges regarding the efficiency and quality of the parts. Thus, adopting economical and environmentally friendly cutting strategies during machining is essential for the environment and performance. For this purpose, silicon dioxide (SiO<inf>2</inf>) and aluminium oxide (Al<inf>2</inf>O<inf>3</inf>) nanoparticles were added to a base-cutting fluid to develop a novel hybrid nanofluid MQL (HNFMQL) cutting fluid, which is then applied during turning experiments. The thermo-physical characteristics, namely pH, thermal conductivity, and coefficient of friction of different fluid mixtures, are studied. The machining experiments are performed on Hastelloy C4 under conventional (dry, MQL, HNFMQL) and heat-assisted (HA) machining (HA dry, HA MQL, HA HNFMQL), and the cooling-lubrication ability is analyzed by measuring machining responses. Compared to HNFMQL and dry conditions, heat-assisted machining with HNFMQL reduced surface roughness by 20 % and 55.56 % and decreased tool wear by 14 % and 41.47 %. The SEM and EDX analysis of worn cutting tools revealed the efficacy of HNFMQL and HA HNFMQL with lower abrasive wear. Whereas, abrasion, adhesion, and chipping are observed under dry machining. The study of the material's microstructural behaviour using Electron Backscatter Diffraction (EBSD) revealed important details about its behaviour under various machining conditions. The EBSD investigation revealed a well-aligned microstructure, proving that heat impacts a limited region in heat-assisted machining.