The Behaviour of carbon quantum dots and cryogenic cooling in turning of super duplex F 53 steel

Abstract

The objective of this research is to examine how various cooling and lubrication techniques affect the machinability of Duplex F53 steel when turning it, with particular attention to residual stress, surface roughness, chip morphology, tool wear, machining temperature, and crystallographic structures. According to the microstructure analysis, the presence of additional austenite grains at high temperatures during dry machining results in an increase in hardness. On the other hand, cooling techniques including liquid nitrogen (LN₂), carbon Quantum dots with SQL (CD), and oil with small quantity lubrication (OSQL) produce larger ferrite grains, which lower hardness. According to residual stress analysis, the high temperatures during dry cutting result in increased strains, which are successfully mitigated by lubrication. The two-phase microstructure has a crucial influence in mechanical characteristics, as demonstrated by X-ray diffraction (XRD) studies, wherein finer grains improve surface polish but demand more energy. Measuring surface roughness (Ra) reveals that adhesion wears during dry machining raises Ra, while OSQL and LN₂ cooling lower Ra and improve surface quality. Tool performance is negatively impacted by high machining temperatures. Cutting temperatures and friction are greatly reduced by LN₂ cooling. Dry machining increases tool wear because of the high temperatures and absence of lubrication; OSQL and CD lower wear rates, while LN₂ offers the best protection for tools. Thinner, better-separated chips are produced by effective lubrication in OSQL and LN₂, while thicker, more deformed chips are produced by dry machining, according to chip morphology and thickness analyses. The study leads to the conclusion that super duplex steel's surface quality, tool life, and machinability can all be significantly enhanced by carbon quantum dots and cryogenic cooling.